JP3290241B2 - Pressure control valve control device for cavitation prevention - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure control valve for preventing cavitation, which adjusts the opening of a plurality of pressure control valves arranged in series in a pipe extending from an upstream side to a downstream side.

[0002]

2. Description of the Related Art Conventionally, when the elevation difference between a sending pond and a receiving pond is large, the difference in pressure between the sending pond and the receiving pond is larger than the reduced pressure that can be reduced by one pressure regulating valve. In this method, two pressure regulating valves are installed in series in an inflow pipe between a sending pond and a receiving pond to reduce pressure in a step-by-step manner and to appropriately control an inflow flow rate.

[0003] In this case, the inflow flow rate control of the receiving pond requires 2
This is performed by opening and closing the opening of the pressure regulating valve of the table. For example, the inflow flow rate is reduced (decreased) by reducing (decreasing) the valve opening and increasing the pressure reduction amount (loss head caused by the pressure regulating valve) at the pressure regulating valve.
In addition, the reverse operation of the above, that is, an operation of increasing the inflow flow rate by an operation of expanding (enlarging) the valve opening is performed.

However, if the elevation difference between the sending pond and the receiving pond is large and the differential pressure between the sending pond and the receiving pond is larger than the reduced pressure that can be produced by one pressure regulating valve, it is assumed that Assuming that the first pressure regulating valve is fully opened and the pressure is reduced only by the second pressure regulating valve, the pressure received by the second pressure regulating valve exceeds the pressure reduction amount that can be reduced by the second pressure regulating valve. As a result, an accident that the second pressure regulating valve is damaged may occur.

Next, a control device of the pressure regulating valve will be described. A conventional control device for a pressure regulating valve is a first control circuit for operating a first pressure regulating valve to make a secondary pressure of the first pressure regulating valve coincide with a predetermined secondary pressure target value. And a second control circuit for operating the second pressure regulating valve to make the inflow flow rate equal to the flow rate target value.
That is, in the first control circuit, the secondary pressure target value of the first pressure regulating valve and the second pressure target value of the first pressure regulating valve measured from the process.
Using the next pressure difference, a control operation represented by PID control is performed to output a valve opening operation amount, and the first pressure regulating valve is controlled so that the valve opening becomes a predetermined value.

Similarly, the second control circuit operates the second pressure regulating valve to control the second pressure regulating valve so that the inflow rate matches the inflow rate target value.

[0007]

In the case where the above-described conventional pressure regulating valve control device is used, the inflow flow rate which is an input to the second control circuit is affected by the operation of the first pressure regulating valve. May be received. Similarly, the secondary pressure of the first pressure regulating valve may fluctuate due to the operation of the second pressure regulating valve. In this case, the first control circuit and the second control circuit Cause mutual interference. As a means for avoiding mutual interference, a technique of increasing the ratio of the control cycle of the first control circuit to the control cycle of the second control circuit to three times or more is used. The control response of the control target value controlled in the control cycle becomes slow.

As a result, the pressure reducing amount of the first pressure regulating valve and the pressure regulating amount of the second pressure regulating valve become inappropriate, and the pressure regulating valve sharing the excessive pressure reducing amount is damaged, or the pressure regulating valve due to cavitation. There is a problem that damage and noise cannot be prevented.

When the control gain is not changed,
There is a problem that the control response deteriorates depending on the valve opening. Further, when the flow rate target value is suddenly changed and the pressure regulating valve is largely operated in order to follow the sudden change, an excessive pressure reduction amount may be applied to one of the pressure regulating valves. In this case, cavitation occurs in one of the pressure regulating valves.

Such cavitation occurs when the cavitation margin becomes 1 or less. Here, the cavitation margin can be calculated by the following equation. cavk1: cavitation margin cav1: cavitation coefficient cav1 ₀ : initial cavitation coefficient In equation (1), the initial cavitation coefficient is a value at the moment when cavitation occurs.

That is, when the cavitation coefficient at that time is smaller than the initial cavitation coefficient at a certain valve opening, cavitation occurs.

The initial cavitation coefficient is a unique numerical value, and the cavitation coefficient at the valve opening can be calculated by the following equation. cav1: Cavitation coefficient at valve opening H2: Pressure [m] on the downstream side of pressure regulating valve ΔH: Differential pressure amount [m] on the upstream side and downstream side of pressure regulating valve 10: Atmospheric pressure correction value [m] It was made in consideration of the points,
To provide a pressure control valve control device for preventing cavitation, which can appropriately maintain the pressure reduction amount distribution such that cavitation does not occur, can follow the inflow rate target value well, and can prevent damage to the pressure control valve due to cavitation and noise. With the goal.

[0013]

SUMMARY OF THE INVENTION The present invention is a pressure regulating valve control device for adjusting the valve opening of a plurality of pressure regulating valves arranged in series in a pipe running from upstream to downstream. Depressurization to find a set value of the pressure reduction ratio between the pressure control valves so that the cavitation margin, which is the value obtained by dividing the cavitation coefficient of the valve drive device and the cavitation coefficient at the time when cavitation occurs, by the initial cavitation coefficient, matches. Volume ratio setting means, an adder for obtaining a deviation signal from the flow rate target value and the current flow rate, and based on the signal from the adder, the current pressure reduction amount ratio of each pressure regulating valve is brought close to the pressure reduction amount ratio set value. A pressure regulating valve selecting means for selecting a pressure regulating valve to be operated, and an operation amount of the selected pressure regulating valve is calculated based on a signal from the adder, and the calculation result is transmitted to a valve driving device of the selected pressure regulating valve. Output A valve opening calculating means, a cavitation prevention regulating valve control apparatus characterized by comprising a.

[0014]

The pressure reducing amount ratio setting means determines a pressure reducing amount set value between the pressure regulating valves so that the cavitation margins of the pressure regulating valves coincide with each other, and the pressure regulating valve selecting means determines the flow rate target value from the adder and the current flow rate. The pressure control valve to be operated is selected based on the deviation signal indicating that the current pressure reduction amount ratio approaches the pressure reduction amount ratio set value. Next, in the valve opening calculating means, the operation amount of the selected pressure regulating valve is calculated based on the deviation signal from the adder, and the calculation result is output to the valve driving device to control the pressure regulating valve.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 to FIG. 4 are views showing an embodiment of a pressure regulating valve control device for preventing cavitation according to the present invention.

In FIG. 1, the elevation difference between the sending pond 21 and the receiving pond 22 of the water distribution plant is large, and the pipe 26 between the sending pond 21 and the receiving pond 22 has No. 2 pressure regulating valve 23 and No. 2 pressure regulating valve 24 are provided. In this case, the pressure between the sending-side pond 21 and the receiving-side pond 22 is larger than the pressure reduction amount that can be reduced by one pressure regulating valve.
The pressure is reduced stepwise by the two pressure regulating valves 23 and 24, and appropriate flow rate control is performed.

Further, the pressure regulating valve control device for adjusting the valve opening of the pressure regulating valves 23, 24 is provided with a pressure reduction ratio setting value between the pressure regulating valves 23, 24 such that the cavitation margins of the pressure regulating valves 23, 24 coincide with each other. And the pressure regulating valves 23 and 2 based on a deviation signal from the adder 16 described later.
And a pressure regulating valve selecting means 5 for selecting a pressure regulating valve to be operated so that the current pressure reducing amount ratio of 4 becomes closer to the pressure reducing amount ratio set value. That is, a flow meter 25 is provided in the pipeline 26, and the flow rate target value from the inflow flow rate target value change amount limiter device 1 and the signal from the flow meter 25 are sent to the adder 16, and the deviation from the adder 16 is A signal is sent to the pressure regulating valve selection means 5.

Here, the reduced pressure ratio will be described. For example, when the primary pressure of the first pressure regulating valve 23 is 15 m, the secondary pressure of the first pressure regulating valve 23 and the primary pressure of the second pressure regulating valve 24 are 10 m, and the secondary pressure of the second pressure regulating valve 24 is 8 m. Case 1
The pressure reduction amount of the No. 2 pressure regulating valve 23 is 15 m−10 m = 5 m, and the pressure reduction amount of the No. 2 pressure regulating valve 24 is 10 m−8 m = 2 m.

The first pressure regulating valve 23 and the second pressure regulating valve 24
Is 5 m / 2 m = 5/2.

Next, a method of obtaining the reduced pressure ratio setting value performed by the reduced pressure ratio setting means 4 will be described below. The pressure reduction amount ratio set value is a pressure reduction amount ratio such that the cavitation margins of the pressure regulating valves 23 and 24 coincide with each other, and is obtained by the following equation. A: Pressure reduction ratio set value H1: Pressure [m] on the downstream (secondary) side of No. 2 pressure regulating valve H2: Pressure [m] on the downstream (secondary) side of No. 2 pressure regulating valve cav1 ₀ (u1): 1 No. 2 pressure regulating valve initial cavitation coefficient cav2 ₀ (u2): No. 2 pressure regulating valve initial cavitation coefficient u1: Opening of No. 2 pressure regulating valve u2: Opening of No. 2 pressure regulating valve Based on the signal, a pressure regulating valve to be operated is selected so that the current pressure reduction amount ratio approaches the pressure reduction amount ratio set value, and a selection signal is output to the valve opening calculating means 20. Valve opening calculating means 20
Has an auto-tuning PI control signal 2 and a valve operation amount correcting device 3. And the valve opening calculating means 20
Calculates the operation amount of the selected pressure control valve based on the deviation signal input from the adder 16 and outputs the calculation result to the valve driving device 6 that drives the pressure control valves 23 and 24. I have.

In the line 26, pressure gauges 27a, 27b, 27c are provided on the upstream side of the No. 1 pressure regulating valve 23, on the downstream side of the No. 1 pressure regulating valve 23, and on the downstream side of the No. 2 pressure regulating valve 24, respectively. ing.

Next, an embodiment of the present invention having such a configuration will be described. First, when the flow rate initial target value 14 is changed, it is determined in the inflow flow rate target value change amount limiter device 1 whether the cavitation margin of the two pressure regulating valves 23 and 24 is approaching 1, and the cavitation margin is approaching 1. In this case, the amount of change in the flow rate target value 13 is reduced, and the flow rate target value 13 is gradually increased.
Approach.

Next, the flow rate target value 13 and the flow rate 15 from the flow meter 25 are added by the adder 16 to determine the deviation between them. Thereafter, the deviation signal from the adder 16 is input to the auto-tuning PI control device 2, and the manipulated variables 7, 8 of the two pressure regulating valves are obtained using a gain scheduling type PI control arithmetic expression. Operation amount 7,
8 is input to the valve operation amount correcting device 3.

On the other hand, the pressure reduction amount ratio setting means 4 sets the pressure based on the pressure values from the pressure gauges 27a, 27b, 27c.
Using the equation (3), a set value of the pressure reduction amount ratio is determined so that the cavitation margins of the pressure regulating valves 23 and 24 coincide with each other.
In the pressure regulating valve selecting means 5, the pressure gauges 27a, 27b, 2
Based on the pressure value from 7c, the current pressure reduction amount ratio of each pressure regulating valve 23, 24 is obtained. And pressure regulating valve selecting means 5
In, based on the signal from the adder 16, the pressure regulating valves 23 and 24 to be operated so that the current pressure reducing amount ratio approaches the pressure reducing amount ratio set value are selected.

The selecting operation of the pressure regulating valve selecting means 5 will be described in detail with reference to FIG. Case 1: When the pressure-regulating valve is operated in the opening direction by the signal from the adder and the pressure-reducing amount ratio of each pressure-regulating valve> the pressure-reducing amount ratio set value.

That is, when the pressure reducing amount of the No. 1 pressure regulating valve is large and the opening direction operation is performed on the pressure regulating valve, the No. 1 pressure regulating valve is opened. Case 2: When the pressure reducing valve is operated in the closing direction by the signal from the adder and the pressure reducing amount ratio of each pressure regulating valve> the pressure reducing amount ratio set value.

In other words, when the pressure reducing amount of the first pressure regulating valve is largely shared and the closing direction operation is performed on the pressure regulating valve, the second pressure regulating valve is closed. Case 3: When the pressure reducing valve is operated in the closing direction according to the signal from the adder and the pressure reducing amount ratio of each pressure regulating valve ≦ the pressure reducing amount ratio set value.

That is, when the pressure reducing amount of the No. 2 pressure regulating valve is large and the closing direction operation is performed on the pressure regulating valve, the No. 1 pressure regulating valve is closed. Case 4: When the pressure reducing valve is operated in the opening direction according to the signal from the adder and the pressure reducing amount ratio of each pressure regulating valve ≦ the pressure reducing amount ratio set value.

That is, when the pressure reducing amount of the No. 2 pressure regulating valve is large and the opening direction operation is performed on the pressure regulating valve, the No. 2 pressure regulating valve is opened.

When the pressure control valve selection device 5 selects which pressure control valve to operate, the operation amount of the pressure control valve that is not operated in the valve operation amount correction device 3 is set to 0, and the pressure control valve to be operated is all Correct the operation amount of the pressure regulating valve so as to cover the operation amount. That is, the valve opening calculating means 20 calculates the operation amount of the pressure regulating valve selected by the pressure regulating valve selecting means 5 based on the deviation signal from the adder 16. The manipulated variables 9 and 10 from the valve manipulated variable correcting device 3 are then sent to the valve driving device 6 and the pressure regulating valve 2 is controlled by the valve driving device 6.
3, 24 are driven.

According to the above-described embodiment, as shown in FIG. 3, by selecting the pressure regulating valve to be operated based on the pressure reduction ratio setting value, the two pressure regulating valves are regulated without generating cavitation. It is possible to appropriately control the pressure reduction amount of the pressure valve, and to perform a control that favorably follows the flow rate target value. Further, it is possible to prevent noise generation of the pressure regulating valve due to an excessive amount of pressure reduction at one pressure regulating valve. In addition,
FIG. 3 is a diagram showing a received water flow rate control response (a) and a cavitation margin (b) in the cavitation preventing pressure regulating valve control device according to the present invention.

Here, for comparison, FIG. 4 shows a response (a) of the received water amount control and a cavitation margin (b) by the conventional pressure regulating valve control device. As shown in FIGS. 3 and 4, according to the present invention, the occurrence of cavitation can be reliably prevented as compared with the conventional one.

As described above, according to the present embodiment, the following effects can be obtained. (1) There is an effect that the pressure reduction valve control can be performed so that the pressure reduction amount sharing of each pressure control valve is properly maintained and the tracking of the flow rate target value is good. Further, it is possible to prevent noise generation of the pressure regulating valve due to an excessive amount of pressure reduction at one pressure regulating valve. (2) When controlling the inflow flow rate to the target value, the nonlinear characteristic of the valve opening degree-valve resistance characteristic can be corrected by using the gain scheduling type PI control operation equation, and the follow-up to the flow rate target value can be adjusted more favorably. Pressure valve control becomes possible. (3) When the cavitation allowance approaches 1, a limiter is applied to the initial flow rate target value by the inflow flow rate target value change amount limit device, so that cavitation does not occur even if the initial flow rate target value changes suddenly. Can be controlled.

In the above-described embodiment, the gain-scheduling PI
The control arithmetic expression was used. In addition, the PID control arithmetic expression, I
-PD control calculation formula, 2-DOF PID control calculation formula, etc. may be used.

[0035]

As described above, according to the present invention,
The pressure reduction amount set value between the pressure adjustment valves is determined so that the cavitation margin of each pressure adjustment valve matches, and the pressure reduction valve to be operated is selected and operated so that the current pressure reduction amount ratio approaches the pressure reduction amount set value. It is possible to adjust the flow rate without appropriately reducing the amount of pressure reduction of each pressure regulating valve without generating cavitation in the pressure regulating valve. For this reason, cavitation does not occur or noise does not occur due to an excessive amount of reduced pressure at a specific pressure regulating valve.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of a pressure control valve control device for preventing cavitation according to the present invention.

FIG. 2 is a diagram showing an operation of a pressure regulating valve selecting means.

FIG. 3 is a diagram showing a received water flow rate control response and a cavitation margin showing a control effect of the present invention.

FIG. 4 is a diagram showing a received water flow rate control response indicating a conventional control result and a margin of cavitation.

[Explanation of symbols]

 4 Decompression amount ratio setting means 5 Pressure regulating valve selecting means 6 Valve driving device 16 Adder 20 Valve opening calculating means 21 Sending pond 22 Receiving pond 23 No. 1 pressure regulating valve 24 No. 2 pressure regulating valve

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shoji Uchida 1-1-1, Shibaura, Minato-ku, Tokyo Inside the head office of Toshiba Corporation (72) Inventor Koji Yamashita 1-chome, Shibaura, Minato-ku, Tokyo No. 1-1 In the head office of Toshiba Corporation (56) References JP-A-53-129788 (JP, A) JP-A-1-219912 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ G05D 16/00-16/20 G05D 7/00-7/06 F16D 55/00 F17D 1/20 F16K 37/00

Claims (1)

(57) [Claims] 1. A pressure regulating valve control device for adjusting the valve opening of a plurality of pressure regulating valves arranged in series in a pipeline from upstream to downstream, comprising: a valve driving device for driving each pressure regulating valve; Pressure reduction ratio setting means for calculating a pressure reduction ratio setting value between the pressure regulating valves so that a cavitation margin consisting of a value obtained by dividing the cavitation coefficient of the cavitation by the initial cavitation coefficient at the time when cavitation occurs, and a flow rate target An adder for obtaining a deviation signal from the value and the current flow rate, and based on the signal from the adder, a pressure regulating valve to be operated so that the current pressure reducing amount ratio of each pressure regulating valve approaches the pressure reducing amount ratio set value. Pressure regulating valve selecting means, and a valve opening degree computing means for computing an operation amount of the selected pressure regulating valve based on a signal from the adder, and outputting a result of the computation to a valve driving device of the selected pressure regulating valve. , Cavitation for pressure regulating valve control device, characterized in that was e.