JPH07103871B2 - Water pressure control method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for controlling a water supply pressure (discharge pressure) from a pump group used in an air conditioning control device or the like.

[Conventional technology]

In the air-conditioning control device, a pump is used to feed the water supply for air-conditioning, but in order to cope with fluctuations in the air-conditioning load, multiple pumps are connected in parallel, and for example, one of them can be variably rotated. The number of rotations is controlled according to the load fluctuation within a certain range, and the number of other pumps operating in a row is controlled when the load fluctuation exceeds the coping range.

Figure 4 is a instrumentation diagram showing a pump unit of the conventional air conditioning system, the pump 1 ₂ to 1 _n of the variable rotational speed of the pump 1 ₁ and the fixed speed in parallel through a header 2 ₁ and 2 ₂ It is connected and returns the return water from the input side pipe 3 and pressure-feeds it to the air conditioner (not shown) via the output side pipe 4.

Maximum capacity of pump 1 ₁ is a pump 1 ₂ to 1 _n the same capacity, that is, is set equal to the maximum rotation speed and the pump 1 ₂ to 1 _n fixed rotational speed of the pump 1 _1, the control device 9 may perform the control operation according to the data of the air conditioning status provided by routes drawing omitted (discharge pressure value and correction data), this results in consideration, the rotational speed of the pump 1 ₁ via the control panel 10 and controls, for the pump 1 ₂ to 1 _n transmits a command for start and stop, performs controlling the number of parallel operations for these.

That is, the operation now, when it is assumed that is performing the water supply by the operation of only the pump 1 _1, when the operation of only the pump 1 ₁ determines that it is unable to cope with the air conditioning load increases, the pump 1 ₂ In addition to the pump 1 ₁ (Add). For example, determine the current required flow rate F as an amount corresponding to the air-conditioning load, if it exceeds the maximum flow F1 can be supplied when the required flow rate F rotates the pump 1 ₁ at maximum capacity (maximum rotation speed) , to operate the pump 1 ₂ in addition to the pump 1 _1.

In contrast, pump 1 ₁ and pumps 1 ₂ and 1 ₃ (not shown)
If it is determined that uneconomical to decrease the air-conditioning load in parallel operation with, stops the operation of the pump 1 ₃ (reduction stages) to. For example, determine the current required flow rate F as an amount corresponding to the air-conditioning load, if it is below the maximum flow F2 can be supplied when the required flow rate F rotates the pump 1 ₁ and 1 ₂ at maximum capacity, Stop operation of pump 1 ₃ .

[Problems to be solved by the invention]

However, according to such a unit count control method, such as a pump 1 ₁ and when parallel operation of the pumps 1 _2, pump 1 ₁ of the outlet of the water supply pressure P1 ₁ against water pressure P1 ₂ of the pump 1 _second outlet
If drops significantly, that is, when the rotational speed of the pump 1 ₁ is the water supply pressure P1 ₁ is low rotation control is greatly reduced relative to P1 _2, water is suppressed retention of the header 2 ₂ from the pump 1 ₁ However, the kinetic energy of the accumulated water is changed to thermal energy, and the pipe 12 ₁ is damaged, or the pump ₁₁ is damaged under the worst conditions.

Therefore, when the parallel operation is established a lower limit value of the rotational speed to the pump 1 _1, it is considered so as not to stay the water to the header 2 _2.

However, in this method, in a state in which the pump 1 ₁ has reached a rotational speed lower limit value, when the air conditioner 2-way valve opening is restricted by a separate controller (not shown) in accordance with the reduction of fine air conditioning load ,
Flow rate of Kaemizu is reduced, the discharge pressure P _T is increased in the header 2 _2. When the discharge pressure P _T rises excessively, it is suppressed and the water sent from the pump 1 ₁ to the header 2 ₂ accumulates, and the pipe 12
₁ is damaged, problems arise such as the pump 1 ₁ may be damaged.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention comprises the following means.

That is, in the above-mentioned pump group, a bypass valve is provided between the output side and the input side of this pump group, and the number of rotations of the variable rotation speed pump increases as the number of parallel operation pumps of fixed rotation speed increases. The lower limit value is set and the opening of the bypass valve is controlled according to the pressure difference between the output side and the input side of the pump group, and the differential pressure at which the bypass valve starts to open increases the number of parallel pumps operating at fixed speed. I try to make it smaller as I do.

[Action]

Therefore, according to the present invention, the lower limit value of the rotational speed of the variable speed pump increases as the number of parallel operating pumps of the fixed rotational speed increases, and as the number of parallel operating pumps of the fixed rotational speed increases. The differential pressure at which the bypass valve starts to open becomes small, and the excessive increase in the discharge pressure from the pump group is bypassed by the bypass valve as soon as the number of parallel operating pumps with a fixed rotational speed increases. The discharge pressure will not excessively rise in the state where several pumps have reached the lower limit rotation speed, and the retention of the water supply from the pumps of variable rotation speed will not occur.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing examples.

FIG. 1 is an instrumentation diagram showing a pump group. In the figure,
The same reference numerals as those in FIG. 4 denote the same or equivalent components,
The description is omitted.

In the present embodiment, a bypass valve 7 is provided between the output-side and input-side pipes 4 and 3 via the branch pipes 5 and 6, and the differential pressure P'at both ends is set to the differential pressure P '. The control device 9 detects by the sensor 8 and the bypass valve 7 detects the detected output.
Is to control the opening degree of.

The minimum pressure (required minimum pressure) of the discharge pressure P _T required to flow the flow rate F is determined by the flow rate pressure specially set as the system, and increases as the flow rate F increases.

Now, P ₁ the minimum required pressure for passing the maximum flow rate F1 to comply with this when operating the only pump 1 ₁ at full capacity, the pump 1 ₁
And the other one are operated in parallel at maximum capacity, the minimum pressure required to flow the maximum flow rate F2 corresponding to this is P ₂ , ...,
When the pump 1 ₁ and the pumps 1 ₂ to 1 _n are operated in parallel at maximum capacity, the minimum pressure required to flow the maximum flow rate Fn
And P _n, the required minimum pressure P ₁ and set discharge pressure during operation of only the pump 1 _1, and set ejection pressure required minimum pressure P ₂ at the time of parallel operation of the 1 ₁ and the other one pump, ...
·, And set ejection pressure required minimum pressure P _n at the parallel operation of the pump 1 ₁ and the pump 1 ₂ to 1 _n.

The relationship between the second figure pump 1 ₁ to 1 _n the number of operating units (or operating capacity of the apparatus) corresponding to the set discharge pressure of P ₁ to P _n and the lower limit rotation speed of the pump 1 ₁ at that R ₁ to R _n Show. That is, in this embodiment, with the increase of the set discharge pressure P, the lower limit rotational speed R of the pump 1 ₁ is also defined as being raised, the pump 1 ₁
In controlling the rotation speed R of, the rotation speed R does not decrease below the respective lower limit values.

Here, in a state in which the pump 1 ₁ has reached the lower limit revolution speed, 2-way valve opening degree of the air conditioner in accordance with the reduction of air conditioning load is squeezed, the feed water flow rate F is reduced, the discharge pressure P _T is increased Think about when you do.

In this case, the opening degree of the bypass valve 7 is controlled according to the differential pressure P ′ detected by the differential pressure sensor 8.

FIG. 3 shows the opening adjustment characteristic of the bypass valve 7 depending on the differential pressure P ′, and the set differential pressures P _S1 to P _n according to the set discharge pressures P _{1 to} P _n.
Sn is defined. That is, it is set that the set differential pressure P _{S at} which the bypass valve 7 starts to open decreases as the set discharge pressure P increases. And this set differential pressure P
Toward _S1 to P _Sn was used as a reference set pressure differential P _S0, during operation of only the pump 1 ₁ l _1, pump 1 ₂ to l parallel during operation either one of _n is l _2, all pumps 1 as l _n during parallel operation of ₂ to l _n,
The adjustment characteristic of the opening degree D of the bypass valve 7 is set individually.

Therefore, according to the present embodiment, the opening of the bypass valve 7 is started from the point where the differential pressure P'is low according to the increase in the number of parallel-operated machines, and the side flow effect of the bypass valve 7 is earlier as the number of parallel-operated machines is larger. to occur because the discharge pressure P _T is balanced lowered, the discharge pressure P _T in the state in which the pump 1 ₁ has reached the lower limit engine speed
Is an excessive increase of blocking, retention of water to the header 2 ₂ from the pump 1 ₁ is assumed to not occur.

The characteristics shown in FIG. 2 (FIG. 3) are determined depending on the situation, and are set not only in a curved shape (straight line shape) but also in a straight line shape (curve shape).

The adjustment characteristic of FIG. 3 is stored in the memory of the control unit 9, the number of operating units is judged by a processor or the like to read out a predetermined characteristic, and the bypass valve 7 is controlled according to the differential pressure P ′. The same applies to the control characteristics and the lower limit values R _{1 to} R _n in FIG.

However, a plurality of pumps with variable rotation speeds may be provided, and the characteristics of FIGS. 2 and 3 may be determined according to the situation, and not only the air conditioner but also a group of pumps having a similar configuration for various purposes. It can be applied to various modifications such as being applicable to.

〔The invention's effect〕

As is clear from the above description, according to the present invention,
The lower limit of the rotational speed of the variable speed pump increases as the number of fixed speed pumps operating in parallel increases, and the differential pressure at which the bypass valve begins to open increases as the number of parallel operating pumps of fixed speed increases. As the number of pumps with fixed rotation speed increases in parallel, the excess increase in discharge pressure from the pump group is bypassed earlier by the bypass valve, which causes the pump with variable rotation speed to rotate at the lower limit value. The discharge pressure does not rise excessively when the number of pumps reaches the maximum number, the accumulated water is not accumulated from the variable speed pump, and the pipes and variable speed pump are not damaged. A remarkable effect can be obtained in the control of the pump group including the pumps.

[Brief description of drawings]

FIG. 1 is an instrumentation diagram of a pump group in an air conditioner to which the present invention is applied, FIG. 2 is a diagram showing a relationship between a set discharge pressure and a lower limit rotation speed of the pump, and FIG. 3 is a bypass valve depending on a differential pressure. FIG. 4 is a diagram showing the opening adjustment characteristic of FIG. 4, and FIG. 4 is an instrumentation diagram showing a pump group in a conventional air conditioner. 1 ₁ …… Pump (pump whose rotation speed is controlled), 1 ₂ to 1 _n …
… Pumps (pumps whose number is controlled in parallel), 2 ₁ , 2
₂ …… Header, 3,4 …… Pipeline, 5,6 …… Branch line, 7 ……
Bypass valve, 8 ... Differential pressure sensor, 9 ... Control device, R ₁ ~
R _n …… Lower limit value, P _{1 to} P _n …… Set discharge pressure, P _{S0 to} P _Sn ……
Set differential pressure.

Claims (1)

[Claims] 1. A variable speed pump and a plurality of fixed speed pumps connected in parallel to the variable speed pump via a header, wherein the variable speed pump has a variable speed. On the other hand, when the load fluctuation cannot be dealt with by the rotation speed control of the variable rotation speed pump, in the pump group in which the number of operating pumps of the fixed rotation speed is controlled, the output side of this pump group is controlled. A bypass valve is provided between the pump group and the input side, and the lower limit of the number of rotations of the variable speed pump is increased as the number of parallel-operated pumps of the fixed number of rotations increases. The opening degree of the bypass valve according to the differential pressure between the input side and the input side, and the differential pressure at which the bypass valve starts to open is reduced as the number of parallel operating pumps with the fixed rotation speed increases. The water supply pressure control method characterized in that