CN116202256B

CN116202256B - Monitoring and control method of adjustable single screw compressor regenerative cascade low temperature refrigeration system

Info

Publication number: CN116202256B
Application number: CN202310199385.8A
Authority: CN
Inventors: 吴玉庭; 封旭; 雷标; 鹿院卫
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2023-03-03
Filing date: 2023-03-03
Publication date: 2025-05-06
Anticipated expiration: 2043-03-03
Also published as: CN116202256A

Abstract

The monitoring and control method of an adjustable single-screw compressor regenerative cascade low-temperature refrigeration system belongs to the field of monitoring or testing devices for regulating systems. The system includes a refrigerant circuit and a monitoring-control circuit. The refrigerant circuit connects the high-temperature and low-temperature circuits by a condenser evaporator, and the controller is simultaneously connected to the compressor motor, compressor slide valve power device, throttling element, bypass element, liquid injection control element, pressure sensor and temperature sensor. After setting the target refrigeration temperature and refrigeration capacity, the controller is guided by the monitoring data of each sensor to adjust the compressor motor, compressor slide valve power device, throttling element, bypass element, and liquid injection control element of each level of the system to achieve functions such as variable refrigeration temperature, variable refrigeration capacity, variable motor frequency, variable compressor content ratio, variable overheat/undercooling temperature, liquid injection, and air replenishment, so that the system operation is more stable and the performance is improved.

Description

Monitoring and control method for adjustable single-screw compressor regenerative cascade low-temperature refrigerating system

Technical Field

The invention relates to the field of monitoring or testing devices of general regulating systems, in particular to a monitoring and control method of an adjustable single-screw compressor regenerative cascade low-temperature refrigerating system.

Background

The energy saving and emission reduction and energy utilization efficiency improvement become important research points, the low-temperature refrigeration system consumes significant electric energy in the process of preparing lower temperature, the system stability is obviously affected when the variable environment temperature, the refrigeration temperature and the refrigeration capacity work condition are operated, the system performance is poor, the energy utilization rate is not high, the stable operation of the system is monitored and precisely controlled when the system is not separated, the cascade refrigeration system is used as a common system for preparing low temperature of-50 ℃ to-100 ℃, the cascade refrigeration system has reliability and safety, but the cascade refrigeration system consists of a high-temperature-level and low-temperature-level two-stage system, the two-stage systems complement and mutually influence, the fluctuation of the two-stage system is caused by one operation parameter change, the variable working condition operation brings more problems of inter-stage matching unbalance and the like, the long-time stable operation of the cascade refrigeration system is adversely affected, and the reasonable monitoring and control of the system are effective means for improving the system performance, the system operation life and the energy utilization rate.

Disclosure of Invention

The invention aims to provide an adjustable monitoring and control method of a single-screw compressor regenerative cascade low-temperature refrigerating system, which is used for improving the performance and operation regulation stability of the regenerative cascade low-temperature refrigerating system and providing an energy-saving and efficient monitoring and control method for the system to cope with different operation conditions.

In order to achieve the above purpose, the present invention adopts the following technical scheme.

An adjustable single screw compressor regenerative cascade low temperature refrigeration system is composed of a refrigerant loop and a monitoring-control circuit.

The adjustable single-screw compressor regenerative cascade low-temperature refrigerating system is used for preparing low temperature of 0 ℃ to-80 ℃, and the refrigerant loop comprises a high-low-temperature-level refrigerating main loop, a high-temperature-level primary throttling branch, a high-temperature-level heat regenerator branch, a high-temperature-level liquid spraying branch, a low-temperature-level primary throttling branch, a low-temperature-level heat returning branch and a low-temperature-level liquid spraying branch which are connected by a condensing evaporator (13).

The high-low temperature level refrigeration main circuit comprises a high-temperature level secondary flowmeter (12), a high-temperature level compressor (1), a condenser (2), a high-temperature level refrigerant liquid storage tank (3), a high-temperature level subcooler (5), a high-temperature level heat regenerator (8), a high-Wen Jier secondary throttling element (10), a condensation evaporator (13), a low-temperature level refrigerant liquid storage tank (14), a low-temperature level subcooler (16), a low-temperature level heat regenerator (20), a low-temperature level secondary throttling element (22), an evaporator (23), a high-temperature level secondary flowmeter (25) and a low-temperature level compressor (18).

The high-low temperature level refrigerating main circuit operation logic is that the high-temperature level compressor (1) is started up according to the working conditions corresponding to the ambient temperature and the refrigerating temperature by calculating and adjusting the corresponding internal volume ratio gear, the high-temperature level refrigerant (29) flows into the condenser (2) from the outlet a of the high-temperature level compressor (1) to exchange heat with the ambient, then flows through the high-temperature level refrigerant liquid storage tank (3), the inlet a of the high-temperature level subcooler (5), the outlet c of the high-temperature level subcooler (5), the inlet a of the high-temperature level regenerator (8), the outlet b of the high-temperature level regenerator (8) flows into the high-Wen Jier secondary throttling element (10), the opening degree is adjusted by the high-Wen Jier secondary throttling element (10), the high-temperature level refrigerant pressure flowing into the inlet a of the condensing evaporator (13) is controlled, flows out of the outlet b of the condensing evaporator (13) after exchanging heat with the low-temperature level refrigerant in the condensing evaporator (13), flows through the inlet c of the high-temperature level regenerator (8), the outlet d of the high-temperature level refrigerant (8), the high-temperature level refrigerant flows into the high-temperature level evaporator (12) from the corresponding to the high-temperature level compressor (1) to the high-temperature level compressor (18) according to the working conditions corresponding to the temperature of the low-temperature level compressor (13) and the high-temperature level refrigerant (13) and flows out of the condensing evaporator (13) to the corresponding to the high-temperature level compressor (13) according to the working conditions, the low-temperature-level refrigerant flows through a low-temperature-level refrigerant liquid storage tank (14), an inlet a of a low-temperature-level subcooler (16), an outlet c of the low-temperature-level subcooler (16), an inlet a of a low-temperature-level heat regenerator (20) and an outlet b of the low-temperature-level heat regenerator (20) to flow into a low-temperature-level secondary throttling element (22), the opening degree of the low-temperature-level secondary throttling element (22) is adjusted, the temperature of the low-temperature-level refrigerant flowing out of an outlet of an evaporator (23) is controlled to flow out of the outlet of the evaporator (23), and flows through an inlet c of the low-temperature-level heat regenerator (20), an outlet d of the low-temperature-level heat regenerator (20) and an inlet d of the low-temperature-level secondary flowmeter (25) to flow into an inlet of a low-temperature-level compressor (18), and meanwhile, a high-low-temperature-level refrigeration main loop can adjust the refrigerating capacity by adjusting the motor speed of the high-temperature-level compressor (1) and the motor speed of the low-temperature-level compressor (18).

The high-temperature-stage primary throttling branch is divided into a branch and is connected with an inlet of a high-temperature-stage primary throttling element (4) after an outlet of a high-temperature-stage refrigerant liquid storage tank (3), an outlet of the high-temperature-stage primary throttling element (4) is connected with an inlet b of a high-temperature-stage subcooler (5), and the high-temperature-stage primary throttling branch flows into an inlet b of a high-temperature-stage compressor (1) through a high-temperature-stage primary flowmeter (6) after flowing out of an outlet d of the high-temperature-stage subcooler (5).

And when the temperature of the outlet a of the high-temperature-stage compressor (1) is higher, the opening degree of the high-temperature-stage primary throttling element (4) is adjusted, so that part of high-temperature-stage refrigerant at the outlet of the high-temperature-stage refrigerant liquid storage tank (3) flows through the high-temperature-stage primary throttling element (4) and then flows into the inlet b of the high-temperature-stage subcooler (5), exchanges heat with high-temperature-stage refrigerant in the high-temperature-stage subcooler (5) and flows out from the outlet d of the high-temperature-stage subcooler (5), and flows into the inlet b of the high-temperature-stage compressor (1) through the high-temperature-stage primary flowmeter (6).

The high-temperature-stage heat regenerator branch comprises two ends of a high-temperature-stage heat regenerator liquid bypass element (7) which are respectively connected with an inlet a of a high-temperature-stage heat regenerator (8) and an outlet b of the high-temperature-stage heat regenerator (8), wherein the high-temperature-stage heat regenerator liquid bypass element (7) is connected with the inlet a of the high-temperature-stage heat regenerator (8) and the outlet b of the high-temperature-stage heat regenerator (8) in parallel, and two ends of a high-temperature-stage heat regenerator gas bypass element (11) are respectively connected with an inlet c of the high-temperature-stage heat regenerator (8) and an outlet d of the high-temperature-stage heat regenerator (8) so that the high-temperature-stage heat regenerator gas bypass element (11) is connected with the inlet c of the high-temperature-stage heat regenerator (8) and the outlet d of the high-temperature-stage heat regenerator (8) in parallel.

Further, the high-temperature-stage regenerator branch operation logic is to adjust the opening of the high-temperature-stage regenerator liquid bypass element (7) when the supercooling temperature of the high-temperature-stage regenerator is not satisfied, so that part of high-temperature-stage refrigerant at the outlet c of the high-temperature-stage regenerator (5) flows through the high-temperature-stage regenerator liquid bypass element (7), then is mixed with high-temperature-stage refrigerant flowing through the inlet a of the high-temperature-stage regenerator (8) and the outlet b of the high-temperature-stage regenerator (8), then flows into the high-Wen Jier secondary throttling element (10) to adjust the supercooling temperature of the high-temperature-stage regenerator, and adjust the opening of the high-temperature-stage regenerator gas bypass element (11) when the superheating temperature of the high-temperature-stage regenerator is not satisfied, so that part of high-temperature-stage refrigerant at the outlet b of the condensing evaporator (13) flows through the high-temperature-stage regenerator gas bypass element (11), then is mixed with high-temperature-stage refrigerant flowing through the inlet c of the high-temperature-stage regenerator (8) and the outlet d of the high-temperature-stage regenerator (8), then flows into the high-temperature-stage secondary flowmeter (12) to adjust the superheating temperature of the high-stage regenerator (1).

The high-temperature-stage spray branch is connected with the inlet of the high-temperature-stage spray control element (9) by a branch which is arranged in front of the inlet of the high Wen Jier times throttling element (10), and the outlet of the high-temperature-stage spray control element (9) is connected with the inlet c of the high-temperature-stage compressor (1).

Further, the high-temperature-stage spray branch operation logic is that when the temperature of the outlet a of the high-temperature-stage compressor (1) is higher, the opening degree of the high-temperature-stage spray control element (9) is adjusted, so that part of high-temperature-stage refrigerant before the high-Wen Jier times of throttling elements (10) flows through the high-temperature-stage spray control element (9) and then flows into the inlet c of the high-temperature-stage compressor (1).

The low-temperature-stage primary throttling branch is characterized in that a branch is divided into a branch after the outlet of a low-temperature-stage refrigerant liquid storage tank (14) and is connected with the inlet of a low-temperature-stage primary throttling element (15), the outlet of the low-temperature-stage primary throttling element (15) is connected with the inlet b of a low-temperature-stage subcooler (16), and the low-temperature-stage primary throttling branch flows out of the outlet d of the low-temperature-stage subcooler (16) and flows into the inlet b of a low-temperature-stage compressor (18) through a low-temperature-stage primary flowmeter (17).

Further, the low-temperature-stage primary throttling branch operation logic is that when the temperature of an outlet a of the low-temperature-stage compressor (18) is higher, the opening degree of the low-temperature-stage primary throttling element (15) is adjusted, so that part of low-temperature-stage refrigerant at the outlet of the low-temperature-stage refrigerant storage tank (14) flows through the low-temperature-stage primary throttling element (15) and then flows into an inlet b of the low-temperature-stage subcooler (16), exchanges heat with low-temperature-stage refrigerant in the high-low-temperature-stage refrigeration main circuit in the low-temperature-stage subcooler (16), flows out from an outlet d of the low-temperature-stage subcooler (16), and flows into an inlet b of the low-temperature-stage compressor (18) through the low-temperature-stage primary flowmeter (17).

The low-temperature-level heat regenerator branch comprises two ends of a low-temperature-level heat regenerator liquid bypass element (19) which are respectively connected with an inlet a of a low-temperature-level heat regenerator (20) and an outlet b of the low-temperature-level heat regenerator (20), wherein the low-temperature-level heat regenerator liquid bypass element (19) is connected with the inlet a of the low-temperature-level heat regenerator (20) and the outlet b of the low-temperature-level heat regenerator (20) in parallel, two ends of a low-temperature-level heat regenerator gas bypass element (24) are respectively connected with an inlet c of the low-temperature-level heat regenerator (20) and an outlet d of the low-temperature-level heat regenerator (20), and the low-temperature-level heat regenerator gas bypass element (24) is connected with the inlet c of the low-temperature-level heat regenerator (20) and the outlet d in parallel.

Further, the low-temperature-stage regenerator bypass operation logic is to adjust the opening of the low-temperature-stage regenerator liquid bypass element (19) when the supercooling temperature of the low-temperature-stage regenerator is not satisfied, so that a part of low-temperature-stage refrigerant at the outlet c of the low-temperature-stage regenerator (16) flows through the low-temperature-stage regenerator liquid bypass element (19), then mixes with low-temperature-stage refrigerant flowing through the inlet a of the low-temperature-stage regenerator (20) and the outlet b of the low-temperature-stage regenerator (20), then flows into the low-temperature-stage secondary throttling element (22) to adjust the supercooling temperature of the low-temperature-stage regenerator, and adjust the opening of the low-temperature-stage regenerator gas bypass element (24) when the superheating temperature of the low-temperature-stage regenerator is not satisfied, so that a part of low-temperature-stage refrigerant at the outlet of the evaporator (23) flows through the low-temperature-stage regenerator gas bypass element (24), then mixes with low-temperature-stage refrigerant flowing through the inlet c of the low-temperature-stage regenerator (20) and the outlet d of the low-temperature-stage regenerator (20), then flows into the low-temperature-stage secondary throttling element (25), and flows into the low-temperature-stage regenerator compressor (18) to adjust the superheating temperature of the low-stage regenerator.

The low-temperature-stage spray branch is connected with the inlet of a low-temperature-stage spray control element (21) by a branch before the inlet of a low-temperature-stage secondary throttling element (22), and the outlet of the low-temperature-stage spray control element (21) is connected with the inlet c of a low-temperature-stage compressor (18).

Further, the low-temperature-stage spray branch operation logic is that when the temperature of the outlet a of the low-temperature-stage compressor (18) is higher, the opening degree of the low-temperature-stage spray control element (21) is adjusted, so that part of low-temperature-stage refrigerant before the low-temperature-stage secondary throttling element (22) flows through the low-temperature-stage spray control element (21) and then flows into the inlet c of the low-temperature-stage compressor (18).

The monitoring-control circuit is connected with an inlet e of a high-temperature-stage compressor (1) and an inlet e of a low-temperature-stage compressor (18) in the system by a controller (26) and is used for controlling the internal volume ratio gear adjustment of the high-temperature-stage compressor (1) and the low-temperature-stage compressor (18), the controller (26) is connected with an inlet f of the high-temperature-stage compressor (1) and an inlet f of the low-temperature-stage compressor (18) in the system and is used for controlling the motor rotation speed adjustment of the high-temperature-stage compressor (1) and the low-temperature-stage compressor (18), the controller (26) is connected with a high-temperature-stage primary throttling element (4), a high-Wen Jier secondary throttling element (10), a high-temperature-stage regenerator liquid bypass element (7), a high-temperature-stage regenerator gas bypass element (11), a high-temperature-stage liquid spray control element (9), a low-temperature-stage primary throttling element (15), a low-temperature-stage secondary throttling element (22), a low-stage regenerator liquid bypass element (19), a low-temperature-stage gas bypass element (24) and a low-stage control element (21) in the system and is used for controlling the rotation speed adjustment of motors of the high-temperature-stage compressors (1), the high-stage liquid flow meters (6), the high-stage liquid flow meters (17) and the high-temperature-stage liquid flow meters (17) and the high-stage liquid flow meters (17) respectively, and the high-temperature-stage liquid flow meters (17) and the high-stage flow meters (6) and the high-stage flow meter and the high-temperature-stage and the low-stage flow meters (respectively The flow of the low-temperature-stage primary flow branch is monitored, and a controller (26) is connected with each pressure sensor and each temperature sensor in the system and is used for monitoring the system.

The controller (26) is internally provided with a monitoring module, a calculating module and a control module to realize the monitoring and control method, the monitoring module is connected with each pressure sensor, each temperature sensor, each level of primary flowmeter and each level of secondary flowmeter to monitor the front and rear pressure, temperature, ambient temperature, refrigeration temperature and flow of the refrigerant of main components in the system, the calculating module is used for protecting the pressure, protecting the temperature value, the refrigerant saturation temperature-pressure database, the calculating formula, the empirical formula, the calculation tool such as characteristic curve and the like to process the data and guide the control module to regulate, and the control module is used for realizing the control function of the system by connecting each level of compressor slide valve device, each level of compressor motor, each level of primary throttling element, each level of secondary throttling element, each level of regenerator liquid bypass element, each level of regenerator gas bypass element and the like.

Further, the controller (26) calculates the temperature difference in the module to be ΔT ₁, calculates the target condensation temperature according to the measured ambient temperature, and the temperature difference to be ΔT ₂, calculates the target evaporation temperature according to the target refrigeration temperature, and sets the protection condensation pressure P _con,b, the protection condensation evaporation high-temperature side pressure P _c-e,l,b, the protection condensation evaporation low-temperature side pressure P _c-e,h,b, and the protection evaporation pressure P _eva,b, and sets the target compressor outlet a temperature T _pq,m and the protection compressor outlet a temperature T _pq,b.

The adjustable single-screw compressor regenerative cascade low-temperature refrigerating system is set with a target refrigerating temperature T _c,m and a target refrigerating capacity W _c,m before starting.

Further, according to the target refrigerating temperature T _c,m and the target refrigerating capacity W _c,m and the measured ambient temperature T ₁, a built-in calculation module of the controller (26) calls a calculation formula to obtain the target condensation temperature T _con,m(T_con,m＝T₁-ΔT₁), target evaporation temperature T _eva,m(T_eva,m＝T_c,m-ΔT₂), and the calculation module calls a refrigerant saturation temperature-pressure database to obtain target condensation pressure P _con,m corresponding to T _con,m, Obtaining target evaporating pressure P _eva,m corresponding to T _eva,m, obtaining target condensing evaporating temperature T _c-e,m by a calculation module by calling an empirical formula, obtaining target condensing evaporating high-temperature side pressure P _c-e,h,m corresponding to T _c-e,m by a calculation module by calling a refrigerant saturation temperature-pressure database, Obtaining a target condensing evaporation low-temperature side pressure P _c-e,l,m corresponding to T _c-e,m, and calling a calculation formula by a calculation module to obtain a volume ratio V _h,m of the target high-temperature stage compressor according to P _con,m/P_c-e,h,m, Obtaining the volume ratio V _l,m of the target low-temperature-stage compressor according to P _c-e,l,m/P_eva,m, and calling an empirical formula by a calculation module to obtain the target high-temperature-stage overheat temperature T _h,gr,m, the target high-temperature-stage supercooling temperature T _h,gl,m, the target low-temperature-stage overheat temperature T _l,gr,m, Target low-temperature-stage supercooling temperature T _l,gl,m, target high-temperature-stage primary throttle opening temperature T _bq,h,m, target high-temperature-stage primary throttle pressure P _bq,h,m, target low-temperature-stage primary throttle opening temperature T _bq,l,m, the target low temperature stage primary throttle pressure P _bq,l,m.

Further, the target values are used as adjusting basis of a control module of the controller (26), a monitoring module of the controller (26) monitors each temperature and each pressure sensor in the system, the monitored values are used as actual measurement values, when errors of the corresponding measuring point target values and the actual measurement values accord with a certain range, the system is considered to run stably, the control module of the controller (26) pauses the system adjustment, and when the actual measurement values of the corresponding measuring points exceed a protection value, the control module of the controller (26) immediately stops the system and cuts off the power of the system.

The monitoring module monitors data including:

The system comprises a high-temperature-stage compressor (1) inlet d pressure sensor (101) real-time pressure value P ₁₀₁, a high-temperature-stage compressor (1) inlet d temperature sensor (102) real-time temperature value T ₁₀₂, a high-temperature-stage compressor (1) outlet a temperature sensor (103) real-time temperature value T ₁₀₃, a high-temperature-stage compressor (1) outlet a pressure sensor (104) real-time pressure value P ₁₀₄, a high-temperature-stage compressor (1) inlet b temperature sensor (107) real-time pressure value T ₁₀₇, a high-temperature-stage compressor (1) inlet b pressure sensor (108) real-time pressure value P ₁₀₈, a low-temperature-stage compressor (18) inlet d pressure sensor (1801) real-time pressure value P ₁₈₀₁, a low-temperature-stage compressor (18) inlet d temperature sensor (1802) real-time temperature value T ₁₈₀₂, a low-temperature-stage compressor (18) outlet a temperature sensor (1803) real-time temperature value T ₁₈₀₃, a low-temperature-stage compressor (18) outlet a pressure sensor (₁₈₀₄) real-time pressure value P ₁₈₀₄, a low-temperature-stage compressor (180) inlet 180) low-temperature sensor (180) real-time pressure value P348 and a low-temperature sensor (180) real-time pressure value P28;

The high-temperature-stage primary throttling element (4) inlet pressure sensor (401) real-time pressure value P ₄₀₁, the high-temperature-stage primary throttling element (4) inlet temperature sensor (402) real-time temperature value T ₄₀₂, the high-temperature-stage primary throttling element (4) outlet temperature sensor (403) real-time temperature value T ₄₀₃, the high-temperature-stage primary throttling element (4) outlet pressure sensor (404) real-time pressure value P ₄₀₄, the high-temperature-stage subcooler (5) outlet d temperature sensor (501) real-time temperature value T ₅₀₁, the high-temperature-stage subcooler (5) outlet d pressure sensor (502) real-time pressure value P ₅₀₂, the low-temperature-stage primary throttling element (15) inlet pressure sensor (1501) real-time pressure value P ₁₅₀₁, the low-temperature-stage primary throttling element (15) inlet temperature sensor (1502) real-time temperature value T ₁₅₀₂, the low-temperature-stage primary throttling element (15) outlet temperature value T ₁₅₀₃, the low-temperature-stage primary throttling element (15) outlet pressure sensor (1503) outlet pressure value P ₁₅₀₄), the low-temperature-stage subcooler (3416) outlet pressure value P3416 d (16) real-time pressure value P1602;

the high-temperature-stage regenerator liquid bypass element (7) inlet pressure sensor (701) real-time pressure value P ₇₀₁, the high-temperature-stage regenerator liquid bypass element (7) inlet temperature sensor (702) real-time temperature value T ₇₀₂, the high-temperature-stage regenerator liquid bypass element (7) outlet temperature sensor (703) real-time temperature value T ₇₀₃, the high-temperature-stage regenerator liquid bypass element (7) outlet pressure sensor (704) real-time pressure value P ₇₀₄, the high-temperature-stage regenerator (8) inlet a pressure sensor (801) real-time pressure value P ₈₀₁, the high-temperature-stage regenerator (8) inlet a temperature sensor (802) real-time temperature value T ₈₀₂, the high-temperature-stage regenerator (8) outlet b temperature sensor (802) real-time temperature value T ₈₀₃, the high-temperature-stage regenerator (8) outlet pressure sensor (804) real-time pressure value P ₈₀₄, the high-temperature-stage regenerator (8) inlet c pressure sensor (805) real-time pressure value P ₈₀₅, the high-temperature-stage regenerator (8) inlet c temperature sensor (806) temperature value T ₈₀₆, the high-stage regenerator (37) pressure sensor (803) real-time temperature value T5698, the high-stage regenerator (803) outlet pressure value T heat regenerator (803) real-time temperature value T688) real-time pressure value (803) and the high-stage regenerator pressure sensor (803) real-time pressure value P688, real-time temperature value T ₁₁₀₂ of an inlet temperature sensor (1102) of the high-temperature-stage regenerator gas bypass element (11), real-time temperature value T ₁₁₀₃ of an outlet temperature sensor (1103) of the high-temperature-stage regenerator gas bypass element (11), and real-time pressure value P ₁₁₀₄ of an outlet pressure sensor (1104) of the high-temperature-stage regenerator gas bypass element (11); a low-temperature-stage regenerator liquid bypass element (19) inlet pressure sensor (1901) real-time pressure value P ₁₉₀₁, a low-temperature-stage regenerator liquid bypass element (19) inlet temperature sensor (1902) real-time temperature value T ₁₉₀₂, a low-temperature-stage regenerator liquid bypass element (19) outlet temperature sensor (1903) real-time temperature value T ₁₉₀₃, a low-temperature-stage regenerator liquid bypass element (19) outlet pressure sensor (1904) real-time pressure value P ₁₉₀₄, a low-temperature-stage regenerator (20) inlet a pressure sensor (2001) real-time pressure value P ₂₀₀₁, a low-temperature-stage regenerator (20) inlet a temperature sensor (2002) real-time temperature value T ₂₀₀₂, a low-temperature-stage regenerator (20) outlet b temperature sensor (2003) real-time temperature value T ₂₀₀₃, a low-temperature-stage regenerator (20) outlet pressure sensor (2004) real-time pressure value P ₂₀₀₄, a low-temperature-stage regenerator (20) inlet c pressure sensor (2005) real-time pressure value P ₂₀₀₅, a low-temperature-stage regenerator (20) inlet c temperature sensor (2006) real-time temperature value T ₂₀₀₆), real-time temperature value T of outlet d temperature sensor (2007) of low-temperature-stage regenerator (20) ₂₀₀₇ A real-time pressure value P ₂₀₀₈ of an outlet pressure sensor (2008) of the low-temperature-level heat regenerator (20);

A real-time pressure value P ₂₀₁ of an inlet pressure sensor (201) of the condenser (2), a real-time temperature value T ₂₀₂ of an inlet temperature sensor (202) of the condenser (2), a real-time pressure value P ₂₀₃ of an outlet temperature sensor (203) of the condenser (2), a real-time pressure value P ₂₀₄ of an outlet pressure sensor (204) of the condenser (2), a real-time pressure value P ₁₃₀₁ of an inlet a pressure sensor (1301) of the condenser (13), a real-time temperature value T ₁₃₀₂ of an inlet a pressure sensor (1302) of the condenser (13), a real-time pressure value T ₁₃₀₂ of an outlet b temperature sensor (1303) of the condenser (13), a real-time pressure value P ₁₃₀₄ of an outlet b pressure sensor (1304) of the condenser (13), a real-time pressure value P ₁₃₀₅ of an inlet c pressure sensor (1305) of the condenser (13), a real-time temperature value T ₁₃₀₆ of an inlet c pressure sensor (1306) of the condenser (13), a real-time temperature value T ₁₃₀₇ of an outlet d pressure sensor (7) of the condenser (13), a real-time temperature value P23038 of an outlet b pressure sensor (1305) of the condenser (13), a real-time pressure value P ₂₃₀₂ of an inlet (1305) of the condenser (13) and a real-time pressure value P3823 of the condenser (1305) of the pressure sensor (1305) of the condenser (13), a real-time temperature value T ₂₃₀₃ of an outlet temperature sensor (2303) of the evaporator (23), a real-time pressure value P ₂₃₀₄ of an outlet pressure sensor (2304) of the evaporator (23);

Real-time flow value V ₆ of the high-temperature-stage primary flowmeter, real-time flow value V ₁₂ of the high-temperature-stage secondary flowmeter, real-time flow value V ₁₇ of the low-temperature-stage primary flowmeter, and real-time flow value V ₂₅ of the low-temperature-stage secondary flowmeter;

Ambient temperature sensor (27) real-time temperature value T ₁, and refrigeration temperature sensor (28) real-time temperature value T ₂.

When the adjustable single-screw compressor regenerative cascade low-temperature refrigerating system is started, a high-temperature and low-temperature stage refrigerating main circuit firstly operates, a controller (26) control module controls a motor (106) of a high-temperature stage compressor (1) to rotate, a controller (26) control module adjusts a slide valve power device (105) of the high-temperature stage compressor (1) to move to a compressor internal volume ratio gear closest to V _h,m, and meanwhile, the controller (26) control module controls the opening of a high-temperature stage secondary throttling element (10).

Further, the control logic of the opening degree of the high Wen Jier-order throttling element (10) is that the monitoring module monitors the value of P ₂₀₄, takes P _con,m as a target, and simultaneously, the monitoring module monitors the value of P ₁₃₀₄, takes P _c-e,h,m as a target, and adjusts the opening degree of the high Wen Jier-order throttling element (10).

After the high-temperature-stage compressor runs for a period of time, a motor (1806) of the low-temperature-stage compressor (18) is controlled by a control module of the controller (26) to rotate, a slide valve power device (1805) of the low-temperature-stage compressor (18) is adjusted by the control module of the controller (26) to move to a compressor internal volume ratio gear closest to V _l,m, and meanwhile, the opening of the low-temperature-stage secondary throttling element (22) is controlled by the control module of the controller (26).

Further, the control logic of the opening degree of the low-temperature-stage secondary throttling element (22) is that the monitoring module monitors the value of P ₂₃₀₄, takes P _eva,m as a target, and simultaneously, the monitoring module monitors the value of P ₁₃₀₈, takes P _c-e,l,m as a target, and adjusts the opening degree of the low-temperature-stage secondary throttling element (21).

And when the monitoring module monitors T ₂＝T_c,m, the real-time refrigerating capacity W _L is calculated, the real-time refrigerating capacity W _c,m is used as a target, and the controller adjusts the motor rotation speeds of the high-temperature-stage compressor (1) and the low-temperature-stage compressor (18).

Further, the controller adjusts the high temperature stage compressor (1), The control logic of the motor rotating speed of the low-temperature-level compressor (18) comprises a monitoring module monitoring P ₁₀₁、T₁₀₂, a calculating module calling a refrigerant saturation temperature-pressure database to obtain a density rho _1,d corresponding to P ₁₀₁、T₁₀₂, a monitoring module monitoring P ₁₃₀₁、T₁₃₀₂, a calculating module calling the refrigerant saturation temperature-pressure database to obtain an enthalpy h _13,b corresponding to P ₁₃₀₁、T₁₃₀₂, a monitoring module monitoring P ₁₃₀₄、T₁₃₀₃, a calculating module calling the refrigerant saturation temperature-pressure database to obtain an enthalpy h _13,a corresponding to P ₁₃₀₄、T₁₃₀₃, a calculating module calling the calculating formula to calculate the real-time high-temperature-level refrigerating capacity W _H, a monitoring module monitoring P ₁₈₀₁、T₁₈₀₂, a calculating module calling the refrigerant saturation temperature-pressure database to obtain a density rho _18,d corresponding to P ₁₈₀₁、T₁₈₀₂, a monitoring module monitoring P ₂₃₀₁、T₂₃₀₂, a calculating module calling the refrigerant saturation temperature-pressure database to obtain an enthalpy h _23,in corresponding to P ₂₃₀₁、T₂₃₀₂, a monitoring module monitoring P ₂₃₀₄、T₂₃₀₃, a calculating module calling the refrigerant saturation temperature-pressure database to obtain an enthalpy h _23,out corresponding to P ₂₃₀₄、T₂₃₀₃, a calculating formula calling the real-time refrigerating capacity W _L, and controlling the high-temperature-level compressor (1) when W _L is smaller than W _c,m When the rotation speed of the motor of the low-temperature-stage compressor (18) is properly increased, when W _L is larger than W _c,m, the control module controls the rotation speeds of the motor of the high-temperature-stage compressor (1) and the motor of the low-temperature-stage compressor (18) to be properly reduced, and the W _L is always kept smaller than W _H in the adjustment process.

After the adjustable single-screw compressor regenerative cascade low-temperature refrigerating system is started to operate, the high-temperature-stage primary throttling branch, the high-temperature-stage heat regenerator branch, the high-temperature-stage liquid spraying branch, the low-temperature-stage primary throttling branch, the low-temperature-stage heat regeneration branch and the low-temperature-stage liquid spraying branch can be operated according to requirements.

Further, the high-temperature-stage primary throttling branch is used for reducing the temperature of an outlet a of the high-temperature-stage compressor (1), the monitoring system monitors T ₁₀₃, when T _bq,h,m is taken as a target, and when T ₁₀₃ is more than or equal to T _bq,h,m, the control module controls the opening of the high-temperature-stage primary throttling element (4), the monitoring module monitors P ₄₀₄, takes P _bq,h,m as a target, the opening of the high-temperature-stage primary throttling element (4) is adjusted, and the monitoring system monitors P₁₀₁、T₁₀₂、T₂₀₃、P₂₀₄、T₁₀₇、P₁₀₈、P₈₀₁、T₈₀₂、V₆、V₁₂, to check the opening of the high-temperature-stage primary throttling element (4) through calculation.

Further, the high-temperature-stage regenerator branch is used for adjusting the high-temperature-stage circulation overheat temperature and the high-temperature-stage circulation supercooling temperature, the monitoring system monitors T ₇₀₂、T₇₀₃、T₈₀₂、T₈₀₃、T₈₀₆、T₈₀₇、T₁₁₀₂、T₁₁₀₃, T _h,gl,m is used as a target, the opening of the high-temperature-stage regenerator liquid bypass element (7) and the opening of the high-temperature-stage regenerator gas bypass element (11) are adjusted, the control module controls the opening of the high-temperature-stage regenerator liquid bypass element (7) when (T ₈₀₂-T₈₀₃) is larger than T _h,gl,m, the opening of the high-temperature-stage regenerator liquid bypass element (7) is reduced when (T ₈₀₂-T₈₀₃) is smaller than T _h,gl,m, the opening of the high-temperature-stage regenerator liquid bypass element (7) is kept when (T ₇₀₂-T₇₀₃) is equal to T _h,gl,m, T _h,gr,m is used as a target, the controller controls the opening of the high-temperature-stage regenerator gas bypass element (11) when (T ₈₀₇-T₈₀₆) is larger than T _h,gr,m, the opening of the high-stage regenerator gas bypass element (11) is reduced when (T ₈₀₇-T₈₀₆) is smaller than T _h,gr,m, and the opening of the high-temperature-stage regenerator gas bypass element (11) is kept when (T ₁₁₀₃-T₁₁₀₂) is equal to T _h,gr,m.

Further, the high-temperature-stage spray branch is used for reducing the temperature of the outlet a of the high-temperature-stage compressor, the monitoring system monitors T ₁₀₃, T _pq,m is taken as a target, and when T ₁₀₃ is greater than or equal to T _pq,m, the control module controls the high-temperature-stage spray control element (9) to be opened.

Further, the low-temperature-stage primary throttling branch is used for reducing the temperature of an outlet a of the low-temperature-stage compressor, the monitoring system monitors T ₁₈₀₃, when T ₁₈₀₃ is larger than or equal to T _bq,l,m with the aim of T _bq,l,m, the control module controls the opening of the low-temperature-stage primary throttling element (15), the monitoring module monitors P ₁₅₀₄, with the aim of P _bq,l,m, the opening of the low-temperature-stage primary throttling element (15) is adjusted, and the monitoring system monitors P₁₈₀₁、T₁₈₀₂、T₁₃₀₇、P₁₃₀₈、T₁₈₀₇、P₁₈₀₈、P₂₀₀₁、T₂₀₀₂、V₁₇、V₂₅, to check the opening of the low-temperature-stage primary throttling element (15) through calculation.

Further, the low-temperature-stage regenerator branch is used for adjusting low-temperature-stage circulation overheat temperature and low-temperature-stage circulation supercooling temperature, a monitoring system monitors T ₁₉₀₂、T₁₉₀₃、T₂₀₀₂、T₂₀₀₃、T₂₀₀₆、T₂₀₀₇、T₂₄₀₂、T₂₄₀₃, T _l,gl,m is used as a target, the opening of the low-temperature-stage regenerator liquid bypass element (19) and the opening of the low-temperature-stage regenerator gas bypass element (24) are adjusted, when (T ₂₀₀₂-T₂₀₀₃) is larger than T _l,gl,m, the control module controls the opening of the low-temperature-stage regenerator liquid bypass element (19) to be opened, when (T ₂₀₀₂-T₂₀₀₃) is smaller than T _l,gl,m, the opening of the low-temperature-stage regenerator liquid bypass element (19) is reduced, when (T ₁₉₀₂-T₁₉₀₃) is equal to T _l,gl,m, the opening of the low-temperature-stage regenerator liquid bypass element (19) is kept, T _l,gr,m is used as a target, when (T ₂₀₀₇-T₂₀₀₆) is larger than T _l,gr,m, the controller controls the opening of the low-temperature-stage regenerator gas bypass element (24) to be opened, when (T ₂₀₀₇-T₂₀₀₆) is smaller than T _l,gr,m, and when (T ₂₄₀₃-T₂₄₀₂) is equal to T _l,gl,m, the opening of the low-temperature-stage regenerator gas bypass element (24) is kept.

Further, the low-temperature-stage spray branch is used for reducing the temperature of the outlet a of the low-temperature-stage compressor, the monitoring system monitors T ₁₈₀₃, T _pq,m is taken as a target, and when T ₁₈₀₃ is larger than T _pq,m, the control module controls the low-temperature-stage spray control element (21) to be opened.

Further, in the running process of the system, the monitoring system monitors T ₁₀₃、T₁₈₀₃, when T ₁₀₃ is more than or equal to T _pq,b or T ₁₈₀₃ is more than or equal to T _pq,b or both, the control module immediately controls the system to stop and power off, the monitoring system monitors P ₂₀₄, when P ₂₀₄ is more than or equal to P _con,b, the control module immediately controls the system to stop and power off, the monitoring system monitors P ₁₃₀₄, when P ₁₃₀₄ is more than or equal to P _c-e,b, the control module immediately controls the system to stop and power off, the monitoring system monitors P ₂₃₀₄, and when P ₂₃₀₄ is more than or equal to P _eva,b, the control module immediately controls the system to stop and power off so as to ensure safety.

The system comprises a refrigerant loop and a monitoring-control circuit, wherein the refrigerant loop connects a high-temperature level loop and a low-temperature level loop through a condensing evaporator, the controller is simultaneously connected with a compressor motor, a compressor slide valve power device, a throttling element, a bypass element, a spray control element, a pressure sensor and a temperature sensor, after target refrigeration temperature and refrigeration capacity are set, the controller is guided to regulate the compressor motor, the compressor slide valve power device, the throttling element, the bypass element and the spray control element of each level system through monitoring data of each sensor, the functions of variable refrigeration temperature, variable refrigeration capacity, motor frequency, the internal volume ratio of the compressor, variable overheat/supercooling temperature, spray liquid, air supplementing and the like are realized, accurate judgment and adjustment are carried out, the matching degree of the loop of the high-temperature and low-temperature two-stage system is improved, the various environment temperatures and refrigeration temperature and refrigeration capacity requirements are more effectively adapted, the system operation is more stable, the performance is improved, the problem that the system cannot be operated stably and efficiently under the conditions of variable environment temperature operation working condition and variable refrigeration temperature and refrigeration capacity is solved, and the service life of the system is greatly prolonged is helped.

Drawings

FIG. 1 is a flow chart of a method for controlling an adjustable single screw compressor regenerative cascade cryogenic refrigeration system;

FIG. 2 is a schematic diagram of an adjustable single screw compressor regenerative cascade cryogenic refrigeration system;

FIG. 3 is a schematic diagram of the inlet and outlet temperature and pressure sensor measurement points of the high-temperature-stage compressor;

FIG. 4 is a schematic diagram of low temperature stage compressor inlet and outlet temperature and pressure sensor measurement points;

FIG. 5 is a schematic diagram of the measurement points of the high-temperature primary throttle inlet and outlet temperature and the pressure sensor;

FIG. 6 is a schematic diagram of the low-temperature stage primary throttle inlet and outlet temperature and pressure sensor measurement points;

FIG. 7 is a schematic diagram of high temperature stage backheating and bypass inlet and outlet temperatures and pressure sensor measurement points;

FIG. 8 is a schematic diagram of low temperature stage backheating and bypass inlet and outlet temperature and pressure sensor measurement point control;

FIG. 9 is a schematic diagram of the condenser, condensing evaporator, evaporator inlet and outlet temperatures and pressure sensor stations;

reference numerals illustrate:

The high-temperature-stage compressor (1), a high-temperature-stage compressor inlet d pressure sensor (101), a high-temperature-stage compressor inlet d temperature sensor (102), a high-temperature-stage compressor outlet a temperature sensor (103), a high-temperature-stage compressor outlet a pressure sensor (104), a high-temperature-stage compressor slide valve power device (105), a high-temperature-stage compressor motor (106), a high-temperature-stage compressor inlet b temperature sensor (107), a high-temperature-stage compressor inlet b pressure sensor (108), a condenser (2), a condenser inlet pressure sensor (201), a condenser inlet temperature sensor (202), A condenser outlet temperature sensor (203), a condenser outlet pressure sensor (204), a high-temperature-stage refrigerant liquid storage tank (3), a high-temperature-stage primary throttling element (4), a high-temperature-stage primary throttling element inlet pressure sensor (401), a high-temperature-stage primary throttling element inlet temperature sensor (402), a high-temperature-stage primary throttling element outlet temperature sensor (403), a high-temperature-stage primary throttling element outlet pressure sensor (404), a high-temperature-stage subcooler (5), a high-temperature-stage subcooler outlet d sensor (501), a high-temperature-stage subcooler outlet d pressure sensor (502), a high-temperature-stage primary flowmeter (6), a high-temperature-stage regenerator liquid bypass element (7), A high temperature stage regenerator liquid bypass element inlet pressure sensor (701), a high temperature stage regenerator liquid bypass element inlet temperature sensor (702), a high temperature stage regenerator liquid bypass element outlet temperature sensor (703), a high temperature stage regenerator liquid bypass element outlet pressure sensor (704), a high temperature stage regenerator (8), a high temperature stage regenerator inlet a pressure sensor (801), a high temperature stage regenerator inlet a temperature sensor (802), a high temperature stage regenerator outlet b pressure sensor (803), a high temperature stage regenerator outlet b pressure sensor (804), a high temperature stage regenerator inlet c pressure sensor (805), A high-temperature-stage regenerator inlet c temperature sensor (806), a high-temperature-stage regenerator outlet d temperature sensor (807), a high-temperature-stage regenerator outlet d pressure sensor (808), a high-temperature-stage spray control element (9), a high-Wen Jier secondary throttling element (10), a high-temperature-stage regenerator gas bypass element (11), a high-temperature-stage regenerator gas bypass element inlet pressure sensor (1101), a high-temperature-stage regenerator gas bypass element inlet temperature sensor (1102), a high-temperature-stage regenerator gas bypass element outlet temperature sensor (1103), a high-temperature-stage regenerator gas bypass element outlet pressure sensor (1104), a high-temperature-stage secondary flowmeter (12), a condensing evaporator (13), A condensing evaporator inlet a pressure sensor (1301), a condensing evaporator inlet a temperature sensor (1302), a condensing evaporator outlet b temperature sensor (1303), a condensing evaporator outlet b pressure sensor (1304), a condensing evaporator inlet c pressure sensor (1305), a condensing evaporator inlet c temperature sensor (1306), a condensing evaporator outlet d temperature sensor (1307), and a condensing evaporator outlet d pressure sensor (1308).

A low-temperature-stage refrigerant liquid storage tank (14), a low-temperature-stage primary throttling element (15), a low-temperature-stage primary throttling element inlet pressure sensor (1501), a low-temperature-stage primary throttling element inlet temperature sensor (1502), a low-temperature-stage primary throttling element outlet temperature sensor (1503), a low-temperature-stage primary throttling element outlet pressure sensor (1504), a low-temperature-stage subcooler (16), a low-temperature-stage subcooler outlet d temperature sensor (1601), a low-temperature-stage subcooler outlet d pressure sensor (1602), a low-temperature-stage primary flowmeter (17), a low temperature stage compressor (18), a low temperature stage compressor inlet d pressure sensor (1801), a low temperature stage compressor inlet d temperature sensor (1802), a low temperature stage compressor outlet a temperature sensor (1803), a low temperature stage compressor outlet a pressure sensor (1804), a low temperature stage compressor slide valve power device (1805), a low temperature stage compressor motor (1806), a low temperature stage compressor inlet b temperature sensor (1807), a low temperature stage compressor inlet d pressure sensor (1808), a low temperature stage regenerator liquid bypass element (19), a low temperature stage regenerator liquid bypass element inlet pressure sensor (1901), a low temperature stage regenerator liquid bypass element inlet temperature sensor (1902), a low temperature stage regenerator liquid bypass element outlet temperature sensor (1903), a low temperature stage regenerator liquid bypass element outlet pressure sensor (1904), a low-temperature-stage regenerator (20), a low-temperature-stage regenerator inlet a pressure sensor (2001), a low-temperature-stage regenerator inlet a temperature sensor (2002), a low-temperature-stage regenerator outlet b temperature sensor (2003), a low-temperature-stage regenerator outlet b pressure sensor (2004), a low-temperature-stage regenerator inlet c pressure sensor (2005), a low-temperature-stage regenerator inlet c temperature sensor (2006), a low-temperature-stage regenerator outlet d temperature sensor (2007), a low-temperature-stage regenerator outlet d pressure sensor (2008), a low-temperature-stage spray control element (21), a low-temperature-stage secondary throttling element (22), an evaporator (23), an evaporator inlet pressure sensor (2301), an evaporator inlet temperature sensor (2302), an evaporator outlet temperature sensor (2303), an evaporator outlet pressure sensor (2304), a low-stage regenerator gas bypass element (24), a low-stage regenerator gas bypass element inlet pressure sensor (2401), a low-temperature-stage regenerator gas bypass element inlet temperature sensor (2402), a low-stage regenerator gas bypass element outlet temperature sensor (25), a low-stage regenerator gas bypass element (24029), a low-stage regenerator temperature sensor (24026), a low-stage regenerator temperature sensor (2404), a low-stage refrigerant temperature sensor (28), a low-stage regenerator temperature sensor (2404), low temperature stage refrigerant (30).

Detailed Description

The present invention will be further described with reference to examples, but the present invention is not limited to the following examples, and the structures of the high temperature stage compressor (1) and the low temperature stage compressor (18) can be seen in the related patent No. ZL 2016 10729709.4

For the purposes of clarity, technical solutions and advantages of embodiments of the present invention, it should be described in detail below that the described embodiments are some but not all embodiments of the present invention and that other embodiments obtained by a person skilled in the art based on the embodiments of the present invention without making creative efforts are within the protection scope of the present invention.

In the description of the present invention, it will be understood that when one element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may be present, and when one element is referred to as being "disposed" to the other element, it can be directly disposed on the other element or intervening elements may be present.

Furthermore, the terms "long," "short," "inner," "outer," and the like, as used herein, refer to an orientation or positional relationship based on that shown in the drawings, for convenience of description of the present invention, and are not intended to indicate or imply that the apparatus or elements referred to must have this particular orientation, operate in a particular orientation configuration, and thus should not be construed as limiting the invention.

Pressure sensors and temperature sensor monitoring points not mentioned in the following embodiments also play an important role in the system, and provide measurement support for the monitoring and control methods of other embodiments.

The technical scheme of the invention is specifically described below by the specific embodiments with reference to the accompanying drawings.

Referring to fig. 2-9, the invention is based on an adjustable single screw compressor regenerative cascade cryogenic refrigeration system monitoring and control method, the arrangement positions of sensor measuring points for implementing the monitoring are shown in fig. 3-9, and the refrigerant loop and circuit connection for implementing the control method are shown in fig. 2.

In order to efficiently realize the target refrigeration temperature T _c,m and the target refrigeration capacity W _c,m, an adjustable single-screw compressor regenerative cascade low-temperature refrigeration system monitoring and control method is used.

The adjustable single-screw compressor regenerative cascade low-temperature refrigeration system is characterized in that a built-in monitoring module of a controller monitors that the ambient temperature is T ₁ before the controller is started, a built-in calculating module of the controller 26 calls a calculating formula to obtain a target condensing temperature T _con,m(T_con,m＝T₁-ΔT₁) and a target evaporating temperature T _eva,m(T_eva,m＝T_c,m-ΔT₂), and the calculating module calls a high-temperature-level refrigerant 29 saturated temperature-pressure database to obtain a target condensing pressure P _con,m corresponding to T _con,m, The target evaporating pressure P _eva,m corresponding to T _eva,m is obtained by calling a low-temperature-level refrigerant 30 saturated temperature-pressure database, the target condensing evaporating temperature T _c-e,m is obtained by calling an intermediate pressure empirical formula by a calculation module, and the target condensing evaporating high-temperature side pressure P _c-e,h,m corresponding to T _c-e,m is obtained by calling a high-temperature-level refrigerant 29 saturated temperature-pressure database by the calculation module, The calculation module calls a volume ratio-pressure ratio calculation formula to obtain the volume ratio V _h,m of the target temperature-stage compressor according to P _con,m/P_c-e,h,m, Obtaining the volume ratio V _l,m of the target low-temperature-stage compressor according to P _c-e,l,m/P_eva,m, and calling an overheat-supercooling temperature empirical formula by a calculation module to obtain the target high-temperature-stage overheat temperature T _h,gr,m, the target high-temperature-stage supercooling temperature T _h,gl,m, the target low-temperature-stage overheat temperature T _l,gr,m, The calculation module calls the air supplementing pressure empirical formula to obtain the target low-temperature-level primary throttling pressure P _bq,h,m and the target low-temperature-level primary throttling pressure P _bq,l,m.

When the adjustable single-screw compressor regenerative cascade low-temperature refrigerating system is started, a high-temperature and low-temperature stage refrigerating main circuit firstly operates, a controller 26 control module controls a motor 106 of a high-temperature stage compressor 1 to rotate, a controller 26 control module adjusts a slide valve power device 105 of the high-temperature stage compressor 1 to move to a compressor internal volume ratio gear closest to V _h,m, and simultaneously, the controller 26 control module controls the opening of a high-temperature stage secondary throttling element 10; the monitoring module monitors the P ₂₀₄ value, takes P _con,m as a target, simultaneously monitors the P ₁₃₀₄ value, takes P _c-e,h,m as a target, adjusts the opening of the high Wen Jier secondary throttling element 10, controls the module to control the low-temperature-stage compressor 18 motor 1806 to rotate after the high-temperature-stage compressor 1 operates for a period of time, controls the module to adjust the low-temperature-stage compressor 18 slide valve power device 1805 to move to the internal volume ratio gear closest to V _l,m by the controller 26, simultaneously controls the module to control the opening of the low-temperature-stage secondary throttling element 22 by the controller 26, monitors the P ₂₃₀₄ value, takes P _eva,m as a target, simultaneously monitors the P ₁₃₀₈ value, takes P _c-e,l,m as a target, adjusts the opening of the low-temperature-stage secondary throttling element 22, monitors the difference between the real-time pressure of the pressure and the target pressure in the adjusting process, keeps the opening of the secondary throttling element basically unchanged when the difference is smaller than 5%, maintains the stable operation of the system, and controls the module to control the system to stabilize the opening of the system when the difference between the measured pressure and the target pressure increases to reach the stable operation after the system exceeds the difference between the measured pressure and the target pressure, and the second throttling element 26 controls the opening of the secondary throttling element 10 again when the second throttling element is controlled to be more than the high-stage throttling element 76 for a period of time The low temperature secondary throttling element 22 is a common technology in the industry, and therefore, the control module controls the system to stop when P ₂₀₄ is greater than the protection condensing pressure P _con,b (i.e., P ₂₀₄ is greater than P _con,b), or when P ₁₃₀₄ is less than the protection condensing high-temperature side pressure P _c-e,l,b (i.e., P ₁₃₀₄ is less than P _c-e,l,b), or when P ₁₃₀₈ is greater than the protection condensing low-temperature side pressure P _c-e,h,b (i.e., P ₁₃₀₈ is greater than P _c-e,h,b), or when P ₂₃₀₄ is less than the protection evaporating pressure P _eva,b (i.e., P ₂₃₀₄ is less than P _eva,b), so as to ensure safe operation of the system.

The adjustable single screw compressor regenerative cascade low-temperature refrigerating system is continuously operated with T _c,m as a target after being started, wherein when the monitoring module monitors that T ₂ is equal to T _c,m, the real-time refrigerating capacity W _L is calculated, the monitoring module monitors P ₁₀₁、T₁₀₂, the calculating module calls a high-temperature-level refrigerant 29 saturated temperature-pressure database to obtain the density rho ₁₀₁、T₁₀₂ corresponding to P ₁₀₁、T₁₀₂, the monitoring module monitors P ₁₀₁、T₁₀₂, the calculating module calls the high-temperature-level refrigerant 29 saturated temperature-pressure database to obtain the enthalpy value h ₁₀₁、T₁₀₂ corresponding to P ₁₀₁、T₁₀₂, the monitoring module monitors V ₁₀₁、T₁₀₂, the calculating module calculates the real-time high-temperature-level refrigerating capacity W ₁₀₁、T₁₀₂, the monitoring module monitors P ₁₀₁、T₁₀₂, the calculating module calls the low-temperature-level refrigerant 30 saturated temperature-pressure database to obtain the density rho 2 corresponding to P ₁₀₁、T₁₀₂, the calculating module P ₁₀₁、T₁₀₂ calls the low-temperature-level refrigerant 30 saturated temperature-pressure database to obtain the enthalpy value W ₁₀₁、T₁₀₂ corresponding to the enthalpy value h ₁₀₁、T₁₀₂ corresponding to the low-temperature-level refrigerant ₁₀₁、T₁₀₂, the calculating module calls the low-temperature-level refrigerant 30 saturated temperature-pressure database to obtain the enthalpy value W ₁₀₁、T₁₀₂ corresponding to the enthalpy value of the low- ₁₀₁、T₁₀₂ is calculated to be ₁₀₁、T₁₀₂, when the enthalpy value of the low-level refrigerant is calculated to be ₁₀₁、T₁₀₂ is less than the real-time is calculated and the enthalpy value is calculated to be ₁₀₁、T₁₀₂, the calculation module calculates the real-time high-temperature-level refrigerating capacity W _H, When the real-time refrigerating capacity W _L,|W_L-W_c,m is calculated to be less than 5%, the motor rotating speed of each stage of compressor is kept basically unchanged, the stable operation of the system is maintained, W _L is always kept to be less than W _H in the adjusting process, and when W _L is less than W _H and less than W _c,m, the control module controls the high-temperature stage compressor 1 to be increased, The motor rotating speed of the low-temperature-level compressor 18 is monitored by a monitoring module, P ₁₀₁、T₁₀₂、P₁₃₀₁、T₁₃₀₂、P₁₈₀₁、T₁₈₀₂、P₂₃₀₄、T₂₃₀₃ is monitored by a calculating module, and the real-time high-temperature-level refrigerating capacity W _H is calculated by a calculating module, When the real-time refrigerating capacity W _L,|W_L-W_c,m is calculated to be less than 5%, the motor rotation speed of each compressor is kept basically unchanged, the stable operation of the system is maintained, W _L is always kept to be less than W _H in the adjustment process, and when W _c,m campus W _L is used, the control module controls the high-temperature-stage compressor to be reduced, The motor rotating speed of the low-temperature-level compressor is monitored by a monitoring module, P ₁₀₁、T₁₀₂、P₁₃₀₁、T₁₃₀₂、P₁₈₀₁、T₁₈₀₂、P₂₃₀₄、T₂₃₀₃ is monitored by a calculating module, and the real-time high-temperature-level refrigerating capacity W _H is calculated by a calculating module, when the real-time refrigerating capacity W _L,|W_L-W_c,m | is calculated to be smaller than 5%, the motor rotating speed of each stage of compressor is kept basically unchanged, the stable operation of the system is maintained, and W _L is always kept smaller than W _H in the adjustment process; the monitoring module monitors P ₂₀₁、T₂₀₂, the calculating module calls a high-temperature-level refrigerant 29 saturated temperature-pressure database to obtain an enthalpy value h _2,out corresponding to P ₂₀₁、T₂₀₂ and is used for calculating a system COP, the monitoring module monitors P ₈₀₁、T₈₀₂, the calculating module calls a high-temperature-level refrigerant 29 saturated temperature-pressure database to obtain an enthalpy value h _8,a corresponding to P ₈₀₁、T₈₀₂, the monitoring module monitors P ₈₀₄、T₈₀₃, the calculating module calls a high-temperature-level refrigerant 29 saturated temperature-pressure database to obtain an enthalpy value h _8,b corresponding to P ₈₀₄、T₈₀₃, the monitoring module monitors P ₈₀₅、T₈₀₆, the calculating module calls a high-temperature-level refrigerant 29 saturated temperature-pressure database to obtain an enthalpy value h _8,c corresponding to P ₈₀₅、T₈₀₆, the monitoring module monitors P ₈₀₈、T₈₀₇, the calculating module calls a high-temperature-level refrigerant 29 saturated temperature-pressure database to obtain an enthalpy value h 2 corresponding to P ₈₀₈、T₈₀₇, the calculating module calls calculation formulas (h ₈₀₈、T₈₀₇) and (h ₈₀₈、T₈₀₇) to check the heat balance in the high-temperature-level regenerator (3938), the calculating module calls a low-temperature-level refrigerant 30 saturated temperature-pressure database to obtain an enthalpy value h ₈₀₈、T₈₀₇ corresponding to P ₈₀₈、T₈₀₇ and a calculating module calls a calculation formula (₈₀₈、T₈₀₇), the system comprises a monitoring module, a calculation module, a P ₂₀₀₄、T₂₀₀₃ and a calculation module, wherein the monitoring module is used for checking heat balance in the condensation evaporator 13, the monitoring module is used for monitoring P ₂₀₀₁、T₂₀₀₂, the calculation module is used for calling a low-temperature-level refrigerant 30 saturated temperature-pressure database to obtain an enthalpy h _20,a corresponding to P ₂₀₀₁、T₂₀₀₂, the monitoring module is used for monitoring P ₂₀₀₄、T₂₀₀₃, and the calculation module is used for calling the low-temperature-level refrigerant 30 saturated temperature-pressure database to obtain an enthalpy h _20,b corresponding to P ₂₀₀₄、T₂₀₀₃; The monitoring module monitors P ₂₀₀₅、T₂₀₀₆, the calculating module calls the low-temperature-level refrigerant 30 saturated temperature-pressure database to obtain an enthalpy value h _20,c corresponding to P ₂₀₀₅、T₂₀₀₆, the monitoring module monitors P ₂₀₀₈、T₂₀₀₇, the calculating module calls the low-temperature-level refrigerant 30 saturated temperature-pressure database to obtain an enthalpy value h _20,d corresponding to P ₂₀₀₈、T₂₀₀₇, and the calculating module calls calculation formulas (h _20,a-h_20,b) and (h _20,d-h_20,c) for checking heat balance in the low-temperature-level regenerator 20.

The adjustable single screw compressor regenerative cascade low-temperature refrigerating system is characterized in that after the system is started and operated for a period of time, a monitoring module monitors T ₁₀₃, takes T _bq,h,m as a target, when T ₁₀₃ is more than or equal to T _bq,h,m, a control module controls a high-temperature-stage primary throttling element 4 to be opened, a high-temperature-stage primary throttling branch is opened, a monitoring module monitors P ₄₀₄, takes P _bq,h,s as a target, adjusts the opening of the high-temperature-stage primary throttling element 4, when |P ₄₀₄-P_bq,h,m | is less than 5%, the opening of the high-temperature-stage primary throttling element 4 is kept unchanged basically, the opening of the high-temperature-stage primary throttling element is checked, a monitoring module monitors P ₁₀₈、T₁₀₇, and a calculation module calls a high-temperature-stage refrigerant 29 saturated temperature-pressure database to obtain density ρ _1,b corresponding to P ₁₀₈、T₁₀₇, Enthalpy h _1b, monitoring P ₁₀₁、T₁₀₂ by a monitoring module, and calling a high-temperature-level refrigerant 29 saturated temperature-pressure database by a calculating module to obtain density ρ _1,d corresponding to P ₁₀₁、T₁₀₂, Enthalpy h _1,d; the monitoring module monitors P ₂₀₄、T₂₀₃, and the calculation module calls a saturation temperature-pressure database of the high-temperature-level refrigerant 29 to obtain an enthalpy value h _2,out corresponding to P ₂₀₄、T₂₀₃; the monitoring module monitors P ₈₀₁、T₈₀₂, and the calculation module calls a high-temperature-level refrigerant 29 saturated temperature-pressure database to obtain an enthalpy value h _8,a corresponding to P ₈₀₁、T₈₀₂; the monitoring module monitors V ₆、V₁₂, the calculating module calls a relative air supplementing amount calculation formula to calculate the relative air supplementing amount a _1,h＝(ρ_1,b*V₆)/(ρ_1,d*V₁₂ of the high-temperature-stage compressor, the calculating module calls a circulating air supplementing amount calculation formula to calculate the circulating air supplementing amount a _2,h＝(h_2,out-h_8,a)/(h_1,d-h_2,out of the high-temperature-stage compressor, when a _1,h is larger than a _2,h, the control module controls the opening degree of the high-temperature-stage primary throttling element 4 to be properly reduced, when a _1,h is smaller than a _2,h, the control module controls the opening degree of the high-temperature-stage primary throttling element 4 to be properly increased, when a _1,h＝a_2,h is reached, the opening degree of the high-temperature-stage primary throttling element 4 is kept unchanged, the stable operation of the system is maintained, the monitoring module monitors P ₄₀₁、T₄₀₂, the calculating module calls a saturated temperature-pressure database of the high-temperature-stage refrigerant 29 to obtain an enthalpy value h _4,in corresponding to P ₄₀₁、T₄₀₂, the monitoring module monitors P ₈₀₁、T₈₀₂, the calculating module calls a saturated temperature-pressure database of the high-temperature-stage refrigerant 29 to obtain an enthalpy value h _8,a corresponding to P ₈₀₁、T₈₀₂, the monitoring module monitors P ₄₀₄、T₄₀₃, the calculating module calls a saturated temperature-pressure database of the high-temperature-stage refrigerant 29 to obtain an enthalpy value h _4,out corresponding to P ₄₀₄、T₄₀₃, the monitoring module monitors P2, the calculation module calls the saturated temperature-pressure database of the high-temperature-level refrigerant 29 to obtain an enthalpy value h _5,out corresponding to P ₅₀₂、T₅₀₁, and the calculation module calls calculation formulas (h _4,in-h_8,a) and (h _5,out-h_4,out) for checking the heat balance of the high-temperature-level subcooler 5.

The adjustable single-screw compressor regenerative cascade low-temperature refrigerating system is started and operated for a period of time, a monitoring system monitors T ₇₀₂、T₇₀₃、T₈₀₂、T₈₀₃、T₈₀₆、T₈₀₇、T₁₁₀₂、T₁₁₀₃, and aims at T _h,gl,m, when (T ₈₀₂-T₈₀₃) is larger than T _h,gl,m, a control module controls the opening of the high-temperature-stage regenerator liquid bypass element 7, when (T ₈₀₂-T₈₀₃) is smaller than T _h,gl,m, the opening of the high-temperature-stage regenerator liquid bypass element is reduced, when (T ₇₀₂-T₇₀₃) is equal to T _h,gl,m, the opening of the high-temperature-stage regenerator liquid bypass element is kept, when (T _h,gr,m) is equal to T _h,gl,m, and aims at T _h,gr,m, when (T ₈₀₇-T₈₀₆) is larger than T _h,gr,m, the control module controls the opening of the high-temperature-stage regenerator gas bypass element 11, when (T ₈₀₇-T₈₀₆) is smaller than T _h,gr,m, the opening of the high-temperature-stage regenerator gas bypass element is reduced, and when (T ₁₁₀₃-T₁₁₀₂) is equal to T _h,gr,m.

After the adjustable single-screw compressor regenerative cascade low-temperature refrigerating system is started and operated for a period of time, the monitoring module monitors T ₁₀₃, and takes T _pq,m as a target, when T ₁₀₃ is more than or equal to T _pq,m, the control module controls the high-temperature-stage liquid spraying control element 9 to be opened, the high-temperature-stage liquid spraying branch is opened, when T ₁₀₃ is less than T _pq,m, the control module controls the high-temperature-stage liquid spraying control element to be closed, and when T ₁₀₃ is more than or equal to T _pq,b, the control module controls the system to stop so as to ensure the safe operation of the system.

After the adjustable single screw compressor regenerative cascade low-temperature refrigerating system is started and operated for a period of time, a monitoring module monitors T ₁₈₀₃, takes T _bq,l,m as a target, when T ₁₈₀₃ is more than or equal to T _bq,l,m, a control module controls the opening of a low-temperature-stage primary throttling element 15, a low-temperature-stage primary throttling branch is opened, a monitoring module monitors P ₁₅₀₄, takes P _bq,l,m as a target, adjusts the opening of the low-temperature-stage primary throttling element 15, when P ₁₅₀₄ is smaller than P _bq,l,m, the control module controls the opening of the low-temperature-stage primary throttling element 15 to be increased, when P ₁₅₀₄ is larger than P _bq,l,m, the control module controls the opening of the low-temperature-stage primary throttling element 15 to be reduced, when |P ₁₅₀₄-P_bq,l,m | is smaller than 5%, the opening of the low-temperature-stage primary throttling element 15 is kept basically unchanged, the opening of the low-temperature-stage primary throttling element is checked, the monitoring module monitors P ₁₈₀₈、T₁₈₀₇, and a calculation module calls a low-temperature-stage refrigerant 30 saturated temperature-pressure database to obtain density ρ _18,b corresponding to P ₁₈₀₈、T₁₈₀₇, The enthalpy value h _18,b, the monitoring module monitors P ₁₈₀₁、T₁₈₀₂, and the calculating module calls a low-temperature-level refrigerant 30 saturated temperature-pressure database to obtain density ρ _18,d corresponding to P ₁₈₀₁、T₁₈₀₂, Enthalpy h _18,d; the monitoring module monitors P ₁₃₀₈、T₁₃₀₇, the calculating module calls a low-temperature-level refrigerant 30 saturated temperature-pressure database to obtain an enthalpy value h _13,d corresponding to P ₁₃₀₈、T₁₃₀₇, the monitoring module monitors P ₂₀₀₁、T₂₀₀₂, the calculating module calls a low-temperature-level refrigerant 30 saturated temperature-pressure database to obtain an enthalpy value h _20,a corresponding to P ₂₀₀₁、T₂₀₀₂, the monitoring module monitors V ₁₇、V₂₅, the calculating module calls a relative air supplementing amount calculation formula to calculate a relative air supplementing amount a _1,l＝(ρ_18,b*V₁₇)/(ρ_18,d*V₂₅ of a low-temperature-level compressor, the calculating module calls a circulating air supplementing amount calculation formula to calculate a circulating air supplementing amount a _2,l＝(h_13,d-h_20,a)/(h_18,d-h_13,d of the low-temperature-level compressor, when a _1,l is larger than a _2,l, the control module controls the opening of the low-temperature-level primary throttling element 15 to be properly reduced, when a _1,l is smaller than a _2,l, the opening of the low-temperature-level primary throttling element 15 is properly increased, when a _1,l is equal to a 82348, the opening of the low-temperature-level primary throttling element 15 is kept unchanged, the system is maintained to stably operate, the monitoring module calls a low-temperature-level refrigerant 30 saturated temperature-pressure database to obtain an enthalpy value h _15,in corresponding to P ₁₅₀₁、T₁₅₀₂, the calculating module calls a circulating air supplementing amount calculation formula to calculate a circulating air supplementing amount a _2,l＝(h_13,d-h_20,a)/(h_18,d-h_13,d of the low-level compressor, when a _1,l is larger than a _20,a, the monitoring module calls a low-temperature-level refrigerant 30 to monitor P _20,a to monitor the enthalpy value corresponding to obtain an enthalpy value of the low-level saturated temperature-level 30, and the low-level saturated temperature-level data is calculated by the control module to obtain _20,a, when the low-level is equal to _20,a, the calculation module calls the saturated temperature-pressure database of the low-temperature-level refrigerant 30 to obtain an enthalpy value h _16,out corresponding to P ₁₆₀₂、T₁₆₀₁, and the calculation module calls calculation formulas (h _15,in-h_20,a) and (h _16,out-h_15,out) for checking the heat balance of the low-temperature-level subcooler 16.

The adjustable single-screw compressor regenerative cascade low-temperature refrigerating system is started and operated for a period of time, the monitoring system monitors T ₁₉₀₂、T₁₉₀₃、T₂₀₀₂、T₂₀₀₃、T₂₀₀₆、T₂₀₀₇、T₂₄₀₂、T₂₄₀₃, and aims at T _l,gl,m, when (T ₂₀₀₂-T₂₀₀₃) is larger than T _l,gl,m, the control module controls the low-temperature-stage regenerator liquid bypass element 19 to be opened, when (T ₂₀₀₂-T₂₀₀₃) is smaller than T _l,gl,m, the opening of the low-temperature-stage regenerator liquid bypass element is reduced, when (T ₁₉₀₂-T₁₉₀₃) is equal to T _l,gl,m, the opening of the low-temperature-stage regenerator liquid bypass element is kept, when (T ₂₀₀₇-T₂₀₀₆) is larger than T _l,gr,m, the control module controls the low-temperature-stage regenerator gas bypass element 24 to be opened, when (T ₂₀₀₇-T₂₀₀₆) is smaller than T _l,gr,m, the opening of the low-temperature-stage regenerator gas bypass element is kept when (T _l,gr,m) is equal to T ₁₉₀₂-T₁₉₀₃.

After the adjustable single-screw compressor regenerative cascade low-temperature refrigerating system is started and operated for a period of time, the monitoring module monitors T ₁₈₀₃, and takes T _pq,m as a target, when T ₁₈₀₃ is more than or equal to T _pq,m, the control module controls the low-temperature-stage liquid spraying control element 21 to be opened, the low-temperature-stage liquid spraying branch is opened, when T ₁₈₀₃ is less than T _pq,m, the control module controls the low-temperature-stage liquid spraying control element to be closed, and when T ₁₈₀₃ is more than or equal to T _pq,b, the control module controls the system to stop so as to ensure the safe operation of the system.

It should be noted that the above-mentioned embodiments are merely for illustrating the technical solution of the present invention, and not for limiting the same, and although the present invention has been described in detail with reference to the above-mentioned embodiments, it should be understood by those skilled in the art that the technical solution described in the above-mentioned embodiments may be modified or some technical features may be equivalently replaced, and these modifications or substitutions do not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solution of the embodiments of the present invention.

Claims

1. The method is used for monitoring and controlling the system to reach the set refrigeration temperature and the refrigeration capacity under different environment temperatures, and is characterized in that the adjustable single-screw compressor regenerative cascade low-temperature refrigeration system consists of a refrigerant loop and a monitoring-controlling circuit;

The refrigerant loop comprises a high-low temperature grade refrigeration main loop, a high-temperature grade primary throttling branch, a high-temperature grade heat regenerator branch, a high-temperature grade spray branch, a low-temperature grade primary throttling branch, a low-temperature grade heat regenerator branch and a low-temperature grade spray branch which are connected by a condensing evaporator (13);

The high-low temperature level refrigeration main circuit comprises a high-temperature level secondary flowmeter (12), a high-temperature level compressor (1), a condenser (2), a high-temperature level refrigerant liquid storage tank (3), a high-temperature level subcooler (5), a high-temperature level heat regenerator (8), a high-Wen Jier secondary throttling element (10), a condensation evaporator (13), a low-temperature level refrigerant liquid storage tank (14), a low-temperature level subcooler (16), a low-temperature level heat regenerator (20), a low-temperature level secondary throttling element (22), an evaporator (23), a low-temperature level secondary flowmeter (25) and a low-temperature level compressor (18);

The high-temperature-stage compressor (1) is started up through calculating and adjusting to a corresponding internal volume ratio gear according to the working conditions corresponding to the ambient temperature and the refrigeration temperature, high-temperature-stage refrigerant (29) flows into a condenser (2) from an outlet a of the high-temperature-stage compressor (1) to exchange heat with the environment, flows through an inlet a of a high-temperature-stage refrigerant liquid storage tank (3), an outlet c of the high-temperature-stage subcooler (5), an inlet a of a high-temperature-stage heat regenerator (8) and an outlet b of the high-temperature-stage heat regenerator (8) to flow into a high-Wen Jier secondary throttling element (10), the opening degree is adjusted by the high-Wen Jier secondary throttling element (10), the pressure of the high-temperature-stage refrigerant flowing into the inlet a of a condensing evaporator (13) is controlled, and flows out of an outlet b of the condensing evaporator (13) after exchanging heat with the low-temperature-stage refrigerant in the condensing evaporator (13) to flow into the high-temperature-stage evaporator (1) inlet d; the low-temperature-level compressor (18) is started up by calculating and adjusting to a corresponding internal volume ratio gear according to working conditions corresponding to the ambient temperature and the refrigeration temperature, low-temperature-level refrigerant (30) flows into the condensing evaporator (13) from the outlet a of the low-temperature-level compressor (18) to exchange heat with high-temperature-level refrigerant, flows out from the outlet d of the condensing evaporator (13) and flows through the low-temperature-level refrigerant liquid storage tank (14), the low-temperature-stage subcooler (16) inlet a, the low-temperature-stage subcooler (16) outlet c, the low-temperature-stage regenerator (20) inlet a and the low-temperature-stage regenerator (20) outlet b flow into the low-temperature-stage secondary throttling element (22), the opening degree of the low-temperature-stage secondary throttling element (22) is adjusted, the low-temperature-stage refrigerant temperature flowing out of the outlet of the evaporator (23) is controlled, the low-temperature-stage refrigerant flows out of the outlet of the evaporator (23) and flows into the low-temperature-stage compressor (18) inlet d through the low-temperature-stage regenerator (20) inlet c, the low-temperature-stage regenerator (20) outlet d and the low-temperature-stage secondary flowmeter (25);

The high-temperature-stage primary throttling branch is divided into a branch and is connected with the inlet of a high-temperature-stage primary throttling element (4) after the outlet of a high-temperature-stage refrigerant liquid storage tank (3), the outlet of the high-temperature-stage primary throttling element (4) is connected with the inlet b of a high-temperature-stage subcooler (5), and the high-temperature-stage primary throttling branch flows into the inlet b of a high-temperature-stage compressor (1) through a high-temperature-stage primary flowmeter (6) after flowing out of the outlet d of the high-temperature-stage subcooler (5);

When the temperature of an outlet a of the high-temperature-stage compressor (1) is higher, the opening degree of the high-temperature-stage primary throttling element (4) is adjusted, so that part of high-temperature-stage refrigerant at the outlet of the high-temperature-stage refrigerant liquid storage tank (3) flows through the high-temperature-stage primary throttling element (4) and then flows into an inlet b of the high-temperature-stage subcooler (5), exchanges heat with high-temperature-stage refrigerant in the high-temperature-stage subcooler (5) and flows out from an outlet d of the high-temperature-stage subcooler (5), and flows into an inlet b of the high-temperature-stage compressor (1) through the high-temperature-stage primary flowmeter (6);

The high-temperature-stage heat regenerator branch comprises two ends of a high-temperature-stage heat regenerator liquid bypass element (7) which are respectively connected with an inlet a of a high-temperature-stage heat regenerator (8) and an outlet b of the high-temperature-stage heat regenerator (8), so that the high-temperature-stage heat regenerator liquid bypass element (7) is connected with the inlet a of the high-temperature-stage heat regenerator (8) and the outlet b of the high-temperature-stage heat regenerator (8) in parallel, and two ends of a high-temperature-stage heat regenerator gas bypass element (11) are respectively connected with an inlet c of the high-temperature-stage heat regenerator (8) and an outlet d of the high-temperature-stage heat regenerator (8) so that the high-temperature-stage heat regenerator gas bypass element (11) is connected with the inlet c of the high-temperature-stage heat regenerator (8) and the outlet d of the high-temperature-stage heat regenerator (8) in parallel;

The high-temperature-stage heat regenerator branch operation logic is used for adjusting the opening of a high-temperature-stage heat regenerator liquid bypass element (7) when the supercooling temperature of the high-temperature-stage heat regenerator is not satisfied, so that part of high-temperature-stage refrigerant at an outlet c of a high-temperature-stage heat regenerator (5) flows through the high-temperature-stage heat regenerator liquid bypass element (7), is mixed with high-temperature-stage refrigerant flowing through an inlet a of the high-temperature-stage heat regenerator (8) and an outlet b of the high-temperature-stage heat regenerator (8), flows into a high-Wen Jier secondary throttling element (10) after being mixed, and adjusts the supercooling temperature of the high-temperature-stage heat regenerator;

A high-temperature-stage spray branch is divided into a branch before the inlet of a high Wen Jier times throttling element (10) and is connected with the inlet of a high-temperature-stage spray control element (9), and the outlet of the high-temperature-stage spray control element (9) is connected with the inlet c of a high-temperature-stage compressor (1);

When the temperature of an outlet a of the high-temperature-stage compressor (1) is higher, the opening degree of the high-temperature-stage spray control element (9) is adjusted, so that part of high-temperature-stage refrigerant before a high Wen Jier times throttling element (10) flows through the high-temperature-stage spray control element (9) and then flows into an inlet c of the high-temperature-stage compressor (1);

a low-temperature-stage primary throttling branch is divided into a branch after the outlet of a low-temperature-stage refrigerant liquid storage tank (14) and is connected with the inlet of a low-temperature-stage primary throttling element (15), the outlet of the low-temperature-stage primary throttling element (15) is connected with the inlet b of a low-temperature-stage subcooler (16), and the low-temperature-stage refrigerant flows out of the outlet d of the low-temperature-stage subcooler (16) and flows into the inlet b of a low-temperature-stage compressor (18) through a low-temperature-stage primary flowmeter (17);

The low-temperature-stage primary throttling branch operation logic is that when the temperature of an outlet a of a low-temperature-stage compressor (18) is higher, a low-temperature-stage primary throttling element (15) adjusts the opening degree, so that part of low-temperature-stage refrigerant at the outlet of a low-temperature-stage refrigerant storage tank (14) flows through the low-temperature-stage primary throttling element (15) and then flows into an inlet b of a low-temperature-stage subcooler (16), exchanges heat with low-temperature-stage refrigerant in a high-low-temperature-stage refrigeration main loop in the low-temperature-stage subcooler (16), flows out from an outlet d of the low-temperature-stage subcooler (16), flows into an inlet b of the low-temperature-stage compressor (18) through a low-temperature-stage primary flowmeter (17);

The low-temperature-level heat regenerator branch comprises two ends of a low-temperature-level heat regenerator liquid bypass element (19) which are respectively connected with an inlet a of a low-temperature-level heat regenerator (20) and an outlet b of the low-temperature-level heat regenerator (20), so that the low-temperature-level heat regenerator liquid bypass element (19) is connected with the inlet a of the low-temperature-level heat regenerator (20) and the outlet b of the low-temperature-level heat regenerator (20) in parallel, two ends of a low-temperature-level heat regenerator gas bypass element (24) are respectively connected with an inlet c of the low-temperature-level heat regenerator (20) and an outlet d of the low-temperature-level heat regenerator (20), and the low-temperature-level heat regenerator gas bypass element (24) is connected with the inlet c of the low-temperature-level heat regenerator (20) and the outlet d in parallel;

The low-temperature-stage regenerator bypass operation logic is used for adjusting the opening degree of a low-temperature-stage regenerator liquid bypass element (19) when the supercooling temperature of the low-temperature-stage regenerator is not met, so that part of low-temperature-stage refrigerant at an outlet c of a low-temperature-stage subcooler (16) flows through the low-temperature-stage regenerator liquid bypass element (19), is mixed with low-temperature-stage refrigerant flowing through an inlet a of a low-temperature-stage regenerator (20) and an outlet b of the low-temperature-stage regenerator (20), flows into a low-temperature-stage secondary throttling element (22) and adjusts the supercooling temperature of the low-temperature-stage regenerator, and when the superheating temperature of the low-temperature-stage regenerator is not met, adjusts the opening degree of a low-temperature-stage regenerator gas bypass element (24) so that part of low-temperature-stage refrigerant at an outlet of an evaporator (23) flows through the low-temperature-stage regenerator gas bypass element (24), flows into a low-temperature-stage secondary flowmeter (25) after being mixed with low-temperature-stage refrigerant flowing through an inlet c of the low-temperature-stage regenerator (20) and an outlet d of the low-temperature-stage regenerator (20), and flows into a low-temperature-stage compressor (18) and the low-temperature-stage regenerator is adjusted;

the low-temperature-stage spray branch is connected with the inlet of a low-temperature-stage spray control element (21) by a branch before the inlet of a low-temperature-stage secondary throttling element (22), and the outlet of the low-temperature-stage spray control element (21) is connected with the inlet c of a low-temperature-stage compressor (18);

the low-temperature-stage spray branch operation logic comprises that when the temperature of an outlet a of a low-temperature-stage compressor (18) is higher, a low-temperature-stage spray control element (21) adjusts the opening degree, so that part of low-temperature-stage refrigerant before a low-temperature-stage secondary throttling element (22) flows through the low-temperature-stage spray control element (21) and then flows into an inlet c of the low-temperature-stage compressor (18);

The monitoring-control circuit is connected with an inlet e of a high-temperature-stage compressor (1) and an inlet e of a low-temperature-stage compressor (18) in the system by a controller (26) and is used for controlling the internal volume ratio gear adjustment of the high-temperature-stage compressor (1) and the low-temperature-stage compressor (18), the controller (26) is connected with an inlet f of the high-temperature-stage compressor (1) and an inlet f of the low-temperature-stage compressor (18) in the system and is used for controlling the motor rotation speed adjustment of the high-temperature-stage compressor (1) and the low-temperature-stage compressor (18), the controller (26) is connected with a high-temperature-stage primary throttling element (4), a high-Wen Jier secondary throttling element (10), a high-temperature-stage regenerator liquid bypass element (7), a high-temperature-stage regenerator gas bypass element (11), a high-temperature-stage liquid spray control element (9), a low-temperature-stage primary throttling element (15), a low-temperature-stage secondary throttling element (22), a low-stage regenerator liquid bypass element (19), a low-temperature-stage gas bypass element (24) and a low-stage control element (21) in the system and is used for controlling the rotation speed adjustment of motors of the high-temperature-stage compressors (1), the high-stage liquid flow meters (6), the high-stage liquid flow meters (17) and the high-temperature-stage liquid flow meters (17) and the high-stage liquid flow meters (17) respectively, and the high-temperature-stage liquid flow meters (17) and the high-stage flow meters (6) and the high-stage flow meter and the high-temperature-stage and the low-stage flow meters (respectively The controller (26) is connected with each pressure sensor and each temperature sensor in the system and is used for monitoring the system;

The controller (26) is internally provided with a monitoring module, a calculating module and a control module to realize the monitoring and control method, wherein the monitoring module monitors the front and rear pressure, the temperature, the ambient temperature, the refrigeration temperature and the flow of the refrigerant of main components in the system by being connected with each pressure sensor, each temperature sensor, each level of primary flowmeter and each level of secondary flowmeter;

The controller (26) calculates the temperature difference in the module to be delta T ₁, is used for calculating the target condensation temperature according to the actual measured ambient temperature, and is used for calculating the target evaporation temperature according to the target refrigeration temperature, and is set to be delta T ₂, and is set to be a protection condensation pressure P _con,b, a protection condensation evaporation high-temperature side pressure P _c-e,l,b, a protection condensation evaporation low-temperature side pressure P _c-e,h,b and a protection evaporation pressure P _eva,b, and is set to be a target compressor outlet a temperature T _pq,m and a protection compressor outlet a temperature T _pq,b;

Setting a target refrigeration temperature T _c,m and a target refrigeration capacity W _c,m of the adjustable single-screw compressor regenerative cascade low-temperature refrigeration system before starting;

according to the target refrigerating temperature T _c,m and the target refrigerating capacity W _c,m, the measured ambient temperature T ₁, a built-in calculation module of the controller (26) calls a calculation formula to obtain the target condensation temperature T _con,m(T_con,m＝T₁-ΔT₁), target evaporation temperature T _eva,m(T_eva,m＝T_c,m-ΔT₂), and the calculation module calls a refrigerant saturation temperature-pressure database to obtain target condensation pressure P _con,m corresponding to T _con,m, Obtaining target evaporating pressure P _eva,m corresponding to T _eva,m, obtaining target condensing evaporating temperature T _c-e,m by a calculation module by calling an empirical formula, obtaining target condensing evaporating high-temperature side pressure P _c-e,h,m corresponding to T _c-e,m by a calculation module by calling a refrigerant saturation temperature-pressure database, Obtaining a target condensing evaporation low-temperature side pressure P _c-e,l,m corresponding to T _c-e,m, and calling a calculation formula by a calculation module to obtain a volume ratio V _h,m of the target high-temperature stage compressor according to P _con,m/P_c-e,h,m, Obtaining the volume ratio V _l,m of the target low-temperature-stage compressor according to P _c-e,l,m/P_eva,m, and calling an empirical formula by a calculation module to obtain the target high-temperature-stage overheat temperature T _h,gr,m, the target high-temperature-stage supercooling temperature T _h,gl,m, the target low-temperature-stage overheat temperature T _l,gr,m, Target low-temperature-stage supercooling temperature T _l,gl,m, target high-temperature-stage primary throttle opening temperature T _bq,h,m, target high-temperature-stage primary throttle pressure P _bq,h,m, target low-temperature-stage primary throttle opening temperature T _bq,l,m, Target low temperature stage primary throttle pressure P _bq,l,m;

the system is characterized in that the system comprises a controller (26) and a controller (26), wherein the controller (26) is used for controlling a module to regulate, the controller (26) is used for monitoring each temperature and each pressure sensor in the system, the monitored value is used as an actual measurement value, when the error between the corresponding measuring point target value and the actual measurement value accords with a certain range, the system is considered to be stably operated, the controller (26) is used for controlling the module to suspend the system to regulate, when the actual measurement value of the corresponding measuring point exceeds a protection value, the controller (26) is used for controlling the module to immediately stop the system and controlling the system to be powered off;

The monitoring module monitors data including:

An ambient temperature sensor (27) real-time temperature value T ₁, a refrigeration temperature sensor (28) real-time temperature value T ₂;

When the adjustable single-screw compressor regenerative cascade low-temperature refrigerating system is started, a high-low temperature stage refrigerating main loop firstly operates, a controller (26) control module controls a motor (106) of a high-temperature stage compressor (1) to rotate, a controller (26) control module adjusts a slide valve power device (105) of the high-temperature stage compressor (1) to move to a compressor internal volume ratio gear closest to V _h,m, and meanwhile, the controller (26) control module controls the opening of a high-temperature stage secondary throttling element (10);

the monitoring module monitors the P ₂₀₄ value, takes P _con,m as a target, and simultaneously, the monitoring module monitors the P ₁₃₀₄ value, takes P _c-e,h,m as a target, and adjusts the opening of the high Wen Jier throttling element (10);

after the high-temperature-level compressor runs for a period of time, a motor (1806) of the low-temperature-level compressor (18) is controlled by a control module of the controller (26), a slide valve power device (1805) of the low-temperature-level compressor (18) is regulated by the control module of the controller (26) to move to a compressor internal volume ratio gear closest to V _l,m, and meanwhile, the opening of the low-temperature-level secondary throttling element (22) is controlled by the control module of the controller (26);

The monitoring module monitors the P ₂₃₀₄ value, takes P _eva,m as a target, and simultaneously, the monitoring module monitors the P ₁₃₀₈ value, takes P _c-e,l,m as a target, and adjusts the opening of the low-temperature secondary throttling element (22);

When the monitoring module monitors T ₂＝T_c,m, the real-time refrigerating capacity W _L is calculated, the real-time refrigerating capacity W _c,m is used as a target, and the controller adjusts the motor rotation speeds of the high-temperature-stage compressor (1) and the low-temperature-stage compressor (18);

The controller adjusts the high-temperature-stage compressor (1), The control logic of the motor rotating speed of the low-temperature-level compressor (18) comprises a monitoring module monitoring P ₁₀₁、T₁₀₂, a calculating module calling a refrigerant saturation temperature-pressure database to obtain a density rho _1,d corresponding to P ₁₀₁、T₁₀₂, a monitoring module monitoring P ₁₃₀₁、T₁₃₀₂, a calculating module calling the refrigerant saturation temperature-pressure database to obtain an enthalpy h _13,b corresponding to P ₁₃₀₁、T₁₃₀₂, a monitoring module monitoring P ₁₃₀₄、T₁₃₀₃, a calculating module calling the refrigerant saturation temperature-pressure database to obtain an enthalpy h _13,a corresponding to P ₁₃₀₄、T₁₃₀₃, a calculating module calling the calculating formula to calculate the real-time high-temperature-level refrigerating capacity W _H, a monitoring module monitoring P ₁₈₀₁、T₁₈₀₂, a calculating module calling the refrigerant saturation temperature-pressure database to obtain a density rho _18,d corresponding to P ₁₈₀₁、T₁₈₀₂, a monitoring module monitoring P ₂₃₀₁、T₂₃₀₂, a calculating module calling the refrigerant saturation temperature-pressure database to obtain an enthalpy h _23,in corresponding to P ₂₃₀₁、T₂₃₀₂, a monitoring module monitoring P ₂₃₀₄、T₂₃₀₃, a calculating module calling the refrigerant saturation temperature-pressure database to obtain an enthalpy h _23,out corresponding to P ₂₃₀₄、T₂₃₀₃, a calculating formula calling the real-time refrigerating capacity W _L, and controlling the high-temperature-level compressor (1) when W _L is smaller than W _c,m When W _L is larger than W _c,m, the control module controls the motor rotation speed of the high-temperature-level compressor (1) and the motor rotation speed of the low-temperature-level compressor (18) to be reduced properly, and the W _L is kept smaller than W _H all the time in the adjustment process;

After the adjustable single-screw compressor regenerative cascade low-temperature refrigerating system is started and operated, the high-temperature-stage primary throttling branch, the high-temperature-stage heat regenerator branch, the high-temperature-stage liquid spraying branch, the low-temperature-stage primary throttling branch, the low-temperature-stage heat regeneration branch and the low-temperature-stage liquid spraying branch can be operated according to requirements;

The high-temperature-stage primary throttling branch is used for reducing the temperature of an outlet a of the high-temperature-stage compressor (1), the monitoring system monitors T ₁₀₃, and when T ₁₀₃ is more than or equal to T _bq,h,m, the control module controls the opening of the high-temperature-stage primary throttling element (4), the monitoring module monitors P ₄₀₄, and the P _bq,h,m is used for adjusting the opening of the high-temperature-stage primary throttling element (4);

The high-temperature-stage heat regenerator branch is used for adjusting the high-temperature-stage circulation overheat temperature and the high-temperature-stage circulation supercooling temperature, a monitoring system monitors T ₇₀₂、T₇₀₃、T₈₀₂、T₈₀₃、T₈₀₆、T₈₀₇、T₁₁₀₂、T₁₁₀₃, aims at T _h,gl,m, adjusts the opening of the high-temperature-stage heat regenerator liquid bypass element (7) and the opening of the high-temperature-stage heat regenerator gas bypass element (11), controls the opening of the high-temperature-stage heat regenerator liquid bypass element (7) when (T ₈₀₂-T₈₀₃) is larger than T _h,gl,m, reduces the opening of the high-temperature-stage heat regenerator liquid bypass element (7) when (T ₈₀₂-T₈₀₃) is smaller than T _h,gl,m, keeps the opening of the high-temperature-stage heat regenerator liquid bypass element (7) when (T ₇₀₂-T₇₀₃) is equal to T _h,gl,m, aims at T _h,gr,m, controls the opening of the high-temperature-stage heat regenerator gas bypass element (11) when (T ₈₀₇-T₈₀₆) is larger than T _h,gr,m, reduces the opening of the high-temperature-stage heat regenerator gas bypass element (11) when (T ₈₀₇-T₈₀₆) is smaller than T _h,gr,m, and keeps the opening of the high-temperature-stage heat regenerator gas bypass element (11) when (T ₁₁₀₃-T₁₁₀₂) is equal to T _h,gr,m;

The high-temperature-stage spray branch is used for reducing the temperature of an outlet a of the high-temperature-stage compressor, the monitoring system monitors T ₁₀₃, and when T ₁₀₃ is greater than or equal to T _pq,m with T _pq,m as a target, the control module controls the high-temperature-stage spray control element (9) to be opened;

The low-temperature-stage primary throttling branch is used for reducing the temperature of an outlet a of the low-temperature-stage compressor, a monitoring system monitors T ₁₈₀₃, takes T _bq,l,m as a target, controls the low-temperature-stage primary throttling element (15) to be opened when T ₁₈₀₃ is larger than or equal to T _bq,l,m, monitors P ₁₅₀₄ and takes P _bq,l,m as a target to adjust the opening of the low-temperature-stage primary throttling element (15), monitors P₁₈₀₁、T₁₈₀₂、T₁₃₀₇、P₁₃₀₈、T₁₈₀₇、P₁₈₀₈、P₂₀₀₁、T₂₀₀₂、V₁₇、V₂₅, and checks the opening of the low-temperature-stage primary throttling element (15) through calculation;

The low-temperature-stage heat regenerator branch is used for adjusting low-temperature-stage circulation overheat temperature and low-temperature-stage circulation supercooling temperature, a monitoring system monitors T ₁₉₀₂、T₁₉₀₃、T₂₀₀₂、T₂₀₀₃、T₂₀₀₆、T₂₀₀₇、T₂₄₀₂、T₂₄₀₃, aims at T _l,gl,m, adjusts the opening of a low-temperature-stage heat regenerator liquid bypass element (19) and a low-temperature-stage heat regenerator gas bypass element (24), controls the opening of the low-temperature-stage heat regenerator liquid bypass element (19) when (T ₂₀₀₂-T₂₀₀₃) is larger than T _l,gl,m, reduces the opening of the low-temperature-stage heat regenerator liquid bypass element (19) when (T ₂₀₀₂-T₂₀₀₃) is smaller than T _l,gl,m, keeps the opening of the low-temperature-stage heat regenerator liquid bypass element (19) when (T ₁₉₀₂-T₁₉₀₃) is equal to T _l,gl,m, aims at T _l,gr,m, controls the opening of the low-temperature-stage heat regenerator gas bypass element (24) when (T ₂₀₀₇-T₂₀₀₆) is larger than T _l,gr,m, reduces the opening of the low-temperature-stage heat regenerator gas bypass element (24) when (T ₂₀₀₇-T₂₀₀₆) is smaller than T _l,gr,m, and keeps the opening of the low-temperature-stage heat regenerator gas bypass element (24) when (T ₂₄₀₃-T₂₄₀₂) is equal to T _l,gl,m;

The low-temperature-stage spray branch is used for reducing the temperature of an outlet a of the low-temperature-stage compressor, the monitoring system monitors T ₁₈₀₃, and aims at T _pq,m, and when T ₁₈₀₃ is larger than T _pq,m, the control module controls the low-temperature-stage spray control element (21) to be opened;

In the running process of the system, the monitoring system monitors T ₁₀₃、T₁₈₀₃, when T ₁₀₃ is greater than or equal to T _pq,b or T ₁₈₀₃ is greater than or equal to T _pq,b or both, the control module immediately controls the system to stop and power off, the monitoring system monitors P ₂₀₄, when P ₂₀₄ is greater than or equal to P _con,b, the control module immediately controls the system to stop and power off, the monitoring system monitors P ₁₃₀₄, when P ₁₃₀₄ is greater than or equal to P _c-e,b, the control module immediately controls the system to stop and power off, the monitoring system monitors P ₂₃₀₄, and when P ₂₃₀₄ is greater than or equal to P _eva,b, the control module immediately controls the system to stop and power off so as to ensure safety.

2. The method according to claim 1, wherein the low temperature of 0 ℃ to-80 ℃ is obtained.