JPH063327B2 - Expander control device - Google Patents

Description

The present invention relates to a control device for an expander such as an expansion turbine used in, for example, a helium liquefaction refrigeration system.

[Conventional technology]

Expansion machines such as expansion turbines used in helium liquefaction refrigeration equipment, etc. must be operated under conditions where the inlet pressure is not too high and the inlet or outlet temperature is not too low. A method of operating or controlling the pressure in a single loop has been adopted.

As a prior art document describing the control of the expander, there is JP-A-57-108557.

[Problems to be solved by the invention]

In the conventional control method, when the amount of cold heat generated by the expander is larger than the refrigeration load, the temperature of the expander is abnormally lowered, and the process gas of the expander is liquefied in the expander, resulting in damage to the expander. The efficiency of the refrigeration system is significantly reduced due to clogging or insufficient gas flow to the expander, and conversely, the inlet pressure of the expander abnormally rises due to excessive gas flow and the expander becomes overloaded. However, in an extreme case, there is a drawback that the economical efficiency and reliability of operation are low, such as the necessity of stopping the expander due to overspeed.

The object of the present invention is to eliminate the drawbacks of the prior art, to automatically prevent the temperature of the expander from decreasing and the pressure of the expander to always rise in accordance with changes in operating conditions, enabling stable operation without lowering efficiency. The purpose is to provide an expander control device that is highly economical and reliable.

[Means for solving problems]

In the expander having the expander inlet valve, the above-mentioned object is to detect the expander outlet pressure, and if the detected pressure is out of a set value, a cascade-controllable pressure controller that increases or decreases the opening of the expansion inlet valve. And, the expander outlet temperature is detected, a signal is transmitted when the detected temperature is out of a set value, a temperature controller for changing the established value of the pressure controller through a control signal limiter is provided, and the control signal limiter is If the output signal from the temperature controller is within the signal setting width, it is output as it is to the pressure controller side, and if it exceeds the signal setting width, the signal pressed within the signal setting is output to the pressure controller side. Achieved by being equipped.

[Work]

The pressure controller 3 can control the gas cage, and when the detected pressure rises above the set value, the expander inlet valve 2
When the detected pressure is lower than the set value, the opening of the expander inlet valve 2 is increased, so that the inlet pressure of the expander 10 matches the set value of the pressure controller 3. It will be controlled automatically.

On the other hand, the temperature controller 1 raises the set value of the pressure controller 3 when the detected temperature rises above the set value to expand the expander.
On the contrary, when the detected temperature falls below the set value so as to increase the load of 10, the set value of the pressure controller 3 is lowered to act to reduce the load of the expander 10, and the inlet temperature of the expander 10 becomes It is automatically controlled so as to match the set value of the controller 3.

The control signal limiter 4 provided between the output signal of the temperature controller 1 and the setting signal input side of the pressure controller 3 has a signal from the temperature control design 1 that rises or falls below the signal setting width. However, since the pressure controller 3 is used so that it can be automatically pressed within the signal setting width, it is possible to prevent the setting value of the pressure regulator 3 from changing extremely and adversely affecting the process.

〔Example〕

Hereinafter, an embodiment in which the present invention is applied to an expansion turbine for a helium liquefaction refrigeration system will be described with reference to the drawings.

In FIG. 1, reference numeral 3 denotes a pressure controller capable of cascade control. When the detected pressure rises above the set value, the detected pressure falls below the set value so that the opening of the expander inlet valve 2 is reduced. In such a case, it acts so as to increase the opening degree of the expander inlet valve 2.

Reference numeral 1 is a temperature controller, which raises the established value of the pressure controller 3 through the control signal limiter 4 when the detected temperature rises above the set value, and conversely when the detected temperature falls below the set value. The control signal limiter 4 acts to lower the set value of the total 3.

Reference numeral 4 is a control signal limiter, which is provided between the output signal of the temperature controller 1 and the setting signal input side of the pressure controller 3 so that the signal from the temperature controller 1 can be set to a preset signal setting width. If it is within the signal setting width, the pressure controller 3 outputs the signal as it is. If the signal from the temperature controller 1 exceeds the signal setting width, the signal held within the signal setting width is pressed by the pressure controller 3 It works like outputting to the side.

Compressed gas from the compressor (not shown) is supplied from the pipe 5 to the refrigerator 6
Low-pressure recycled gas from the refrigerator 6 is supplied to the pipe 7
To the compressor. Reference numeral 8 is a refrigerating load such as a superconducting magnet. 11 to 15 are heat exchangers, 16 is J
-T valve, 9 and 10 are expanders such as expansion turbines.

The operation of each control device in the above configuration will be described with reference to FIGS. 1 and 2.

When the refrigeration load 8 and the amount of cold heat generation are in equilibrium, the set value of the temperature controller 1 and the detected temperature match, so that the output of the temperature controller 1 does not change, as shown in step 100 of FIG.

When the refrigeration load 8 increases and the cold heat becomes insufficient, the inlet temperature of the expander 10 rises and the detected temperature rises above the set value of the temperature controller 1, so this is determined in step 110, After performing a predetermined control calculation such as PID calculation in step 120, the output is output to the input side of the control signal limiter 4.

In this case, the output of the temperature controller 1 is configured to increase.

The control signal limiter 4 determines in step 130 whether or not the signal is larger than a preset upper limit signal, and if larger, processes it in step 140 into the upper limit signal,
On the contrary, when it is less than the upper limit signal, the signal from the temperature controller 1 is directly output to the cascade setting input side of the pressure controller 3 (step 150).

When the set value given from the control signal limiter 4 and the detected pressure match, the pressure controller 3 makes a step 160.
Although the output of the pressure regulator 3 does not change as shown in, if the detected pressure rises, it is judged in step 170 and necessary control calculation such as PID calculation is performed in step 180. In step 190, the opening degree of the expander inlet valve 2 is continuously reduced until the set value and the detected pressure match.

Conversely, when the detected pressure drops below the set value, step 2
This is judged at 00, and predetermined control calculation such as PID calculation is performed at step 210, and step 2 is performed based on the result.
At 20, the opening of the expander artificial valve 2 is continuously increased until the set value and the detected pressure match.

Since the pressure regulator 3 operates in this way, the inlet pressure of the expander 10 is automatically controlled so as to match the set pressure from the pressure regulator 3 provided by the control signal limiter 4.

On the other hand, when the refrigeration load 8 decreases and the cold heat becomes surplus,
Since the inlet temperature of the expander 10 becomes lower than the set value of the temperature controller 1, this is judged in step 230 and step 2
After performing a predetermined control calculation such as PID calculation at 40, the output is output to the input side of the control signal limiter 4.

In this case, the output of the temperature controller 1 is configured to decrease.

The control signal limiter 4 determines in step 250 whether or not the signal is smaller than a preset lower limit signal, and if smaller, processes it in step 260 into the lower limit signal,
On the contrary, when the signal is equal to or more than the lower limit signal, the signal from the temperature controller 1 is output as it is to the cascade setting input side of the pressure controller 3 (step 270).

Also in this case, the operation of the pressure regulator 3 is the same as in step 1 above.
It is the same as from 60 to step 220.

That is, in the present invention, the temperature controller 1 is used as a master controller,
Since the pressure controller 3 constitutes a control loop using a minor controller, both the artificial temperature and the pressure of the expander 10 are automatically controlled. The control signal limiter 4 operates so as to prevent the set value of the pressure regulator 3 from changing extremely.

〔The invention's effect〕

According to the present invention, it is possible to automatically follow changes in operating conditions that eliminate the drawbacks of the prior art, and always prevent excessive temperature fluctuations of the expander and excessive fluctuations of the expander inlet pressure. It is possible to obtain a control device for an expander that has both high economical efficiency and high reliability.

[Brief description of drawings]

FIG. 1 is a system diagram of a helium liquefaction refrigerating apparatus showing an embodiment of the present invention, and FIG. 2 is a flow chart showing a control flow. 1 ... Temperature controller, 2 ... Expander inlet valve, 3 ... Pressure controller, 4 ... Control signal limiter, 5, 7 ... Pipe, 6 ... Refrigerator, 8 ... Refrigeration load, 9, 10 ... ... expander, 11-15 ...... heat exchanger, 16 ...... J-T valve, PV _T ...... measurement temperature, SV _T ...
… Set temperature, MV… manipulated variable, MVS… control signal limiter set value, PV _P …… measured pressure, SV _P …… set pressure

Claims (1)

[Claims] Claims: 1. An expander equipped with an expander inlet valve, wherein the expander outlet pressure is detected, and when the detected pressure deviates from a set value, a cascade controllable pressure for increasing or decreasing the opening of the expander inlet valve. A controller and a temperature controller that detects the expander outlet temperature, sends a signal when the detected temperature is out of the set value, and changes the set value of the pressure controller through a control signal limiter, the control signal limiter Will output to the pressure controller as it is if the output signal from the temperature controller is within the signal setting width, and if it exceeds the signal setting width, the signal pressed within the signal setting width is output to the pressure controller side. A control device for an expander, which is provided with a function to perform.