JP5379421B2 - Compression device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compression device precisely controlling discharge pressure only by the slide valve of a screw compressor. <P>SOLUTION: This compression device 1 includes: a spool valve drive means 11 periodically changing a spool valve 10 between a load position and an unload position and controlling a spool value as a ratio of time in the load position of the spool valve 10; a slide valve opening setting means 16 setting the target opening of the slide valve 3 according to a deviation between the discharge pressure of the screw compressor 2 and target pressure; and a spool valve setting means 17 setting the target value of the spool value in the spool valve drive means 11 according to a deviation between the opening of the slide valve 3 and the target opening determined by the slide valve opening setting means 16. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a compression device, and more particularly to a screw-type compression device that controls discharge pressure by a slide valve.

  Conventionally, as disclosed in Patent Document 1, a slide valve that determines the discharge position of a screw compressor and changes the discharge pressure is driven by a hydraulic cylinder whose position can be detected. Conventionally, a spool valve (three-position switching valve) for selecting a state of supply (load) / discharge (unload) / hold (neutral) of hydraulic oil in the hydraulic cylinder so that the position of the hydraulic cylinder becomes a set position. The operation is controlled and the set position of the hydraulic cylinder is adjusted according to the deviation of the discharge pressure from the target pressure.

  When adjusting the screw compressor capacity with a slide valve, when changing the opening of the slide valve, the spool valve is loaded or unloaded, and after confirming that the slide valve has reached the set position, the spool valve is neutral. I was in a state. At this time, an error occurs in the opening of the slide valve due to the detection of the opening of the slide valve and the delay in driving the spool valve. Even if a needle valve or the like is provided in the hydraulic oil supply path to limit the hydraulic oil flow rate and reduce the amount of movement during the delay time, the slide valve opening will have an error of about 1.5%. I had to accept it.

  In Patent Document 1, in order to eliminate a slight error in the discharge pressure, a bypass flow path is provided for allowing compressed gas to flow from the discharge flow path to the suction flow path via the bypass valve, and the discharge flow path is adjusted by adjusting the opening of the bypass valve. The pressure of is fine-tuned.

  Patent Document 2 describes a screw compression device that drives a slide valve by a pneumatic cylinder, but fine discharge pressure control is also performed by a bypass valve.

For example, in a LNG power generation screw compressor for boosting fuel gas, strict pressure control with an allowable error of, for example, ± 0.1% or less is required. For this reason, in the conventional screw type compression device, in order to precisely control the pressure of the discharge flow path, it is necessary to circulate about 10% of compressed gas from the discharge side to the suction side via the bypass valve. The shaft power of the machine was greatly wasted.
Japanese Patent No. 34299999 JP-A-2005-194926

  In view of the above problems, an object of the present invention is to provide a compression device capable of precise discharge pressure control only by a slide valve of a screw compressor during steady operation.

In order to solve the above-described problems, a compression device according to the present invention includes a slide valve that accommodates a pair of male and female screw rotors that rotate while meshing with each other in a rotor chamber, and changes a discharge position of the rotor chamber. A screw compressor having a fluid pressure cylinder that drives and detects the position of the slide valve, a load position that supplies a working fluid to a main chamber of the fluid pressure cylinder, and the working fluid is discharged from the main chamber. A spool valve having an unloading position; and periodically changing the spool valve between the loading position and the unloading position, and a ratio of time at which the spool valve is at the loading position, the fluid pressure a controllable spool valve driving means spools value corresponding to the expansion and contraction speed of the cylinder, in accordance with a deviation between the discharge pressure and the target pressure of the screw compressor, The slide valve opening setting means for setting the target opening of the slide valve, and the deviation between the opening of the slide valve detected by the fluid pressure cylinder and the target opening determined by the slide valve opening setting means. And a spool value setting means for setting a target value of the spool value in the spool valve driving means, wherein the spool value setting means continuously changes the target value of the spool value, When the flow rate of the working fluid determined according to the spool value is continuously changed, the expansion / contraction speed of the fluid pressure cylinder is continuously changed, and the discharge pressure of the screw compressor approaches the target pressure, The slide valve opening setting means reduces the change in the target opening of the slide valve, and the spool value setting means sets the target value of the spool value to the fluid pressure cylinder. The stretch speed was reduced to one that changes to slow the opening change of the slide valve.

  According to this configuration, if the extension amount of the fluid pressure cylinder at the load position and the contraction amount of the fluid pressure cylinder at the unload position are balanced, the fluid pressure cylinder can be regarded as substantially not expanding and contracting. By performing at high speed, the fluid pressure cylinder can be expanded and contracted at a speed corresponding to the spool value. In this way, by continuously changing the expansion / contraction speed of the fluid pressure cylinder according to the spool value, which is a continuous value, the error in the opening of the slide valve due to the delay in stopping the fluid pressure cylinder can be reduced, and the discharge pressure of the compressor Can be controlled accurately.

  The compression device according to the present invention further includes spool value detection means for detecting an actual value of the spool value, and a deviation between the actual value of the spool value and a target value of the spool value is a predetermined value. When this happens, an alarm signal may be issued.

  Since a large torque is not required for driving the spool valve, it is considered that some abnormality has occurred when the spool value deviates from the target value. For this reason, it is possible to avoid a serious accident by notifying the operator of the possibility of abnormality by an alarm signal or by making an emergency stop of the apparatus.

  Further, in the compression device according to the present invention, when the discharge side and the suction side of the screw compressor are connected via a bypass valve, and the external signal indicating a sudden decrease in the gas demand is received, the bypass valve is You may open it.

  According to this configuration, the control during steady operation can be optimized by responding to a sudden decrease in demand with a bypass valve to prevent a pressure rise, and the error in discharge pressure during steady operation can be reduced. it can.

  Further, in the compression device according to the present invention, when the discharge side and the suction side of the screw compressor are connected via a bypass valve, the bypass valve is opened when the discharge pressure of the screw compressor reaches a preset upper limit pressure. May be.

  According to this configuration, when the discharge pressure cannot be appropriately controlled by the slide valve for some reason, the increase in the discharge pressure can be eliminated by the bypass valve, which is safe.

  According to the present invention, since the spool value is controlled in accordance with the discharge pressure of the screw compressor, the opening of the slide valve can be adjusted appropriately, so that the discharge pressure of the screw compressor can be controlled with high accuracy.

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 shows a compression apparatus 1 according to one embodiment of the present invention. The compression device 1 is for compressing gas by a screw compressor 2 that houses a pair of male and female screw rotors in a rotor chamber.

  The screw compressor 2 has a slide valve 3 that can change the discharge position of the rotor chamber. The slide valve 3 is driven by a hydraulic cylinder (fluid pressure cylinder) 4. The hydraulic cylinder 4 has a main chamber 5 that receives the reaction force of the slide valve 3, and a sub chamber 6 that is in a complementary relationship with the main chamber 5, and the main chamber 5 and the sub chamber 6 are connected via a spool proportional control valve 7. The hydraulic pump 8 and the oil receiver 9 are connected. The hydraulic cylinder 4 outputs a position signal of 0 to 5 V, for example, indicating its own piston position indicating the opening degree of the slide valve 3.

  The spool proportional control valve 7 includes a spool valve 10 that switches a connection state between the main chamber 5 and the sub chamber 6, the hydraulic pump 8 and the oil receiver 9, an actuator 11 that drives the spool valve 10, and a spool valve that controls the actuator 11. And a control device 12.

  The spool valve 10 connects the main chamber 5 to the hydraulic pump 8 and connects the sub chamber 6 to the flow path to the oil receiver 9 so that hydraulic oil (working fluid) is supplied to the main chamber 5. Connecting the main chamber 5 to the flow path to the oil receiver 9, connecting the sub chamber 6 to the hydraulic pump 8, and discharging the hydraulic oil from the main chamber 5. Between the load position, the main chamber 5 and the sub chamber 6 are separated from the hydraulic pump 8 and the oil receiver 9 and have three states: a neutral position where the increase and decrease of hydraulic oil is prohibited.

  For example, the actuator 11 holds the spool valve 10 at the load position when a voltage is input from the spool valve control device 12, and holds the spool valve 10 at the unload position when no voltage is input from the spool valve control device 12. .

  The spool valve control device 12 inputs a rectangular-wave drive voltage having a predetermined frequency to the actuator 11. The spool valve control device 12 can control the ratio of the time during which the spool valve 10 is at the load position by, for example, changing the pulse width of the drive voltage (PWM) (spool valve drive means). Further, the actuator 11 can output a spool value, which is a ratio of time when the actual spool valve 10 is at the load position, as a current signal of 4 to 20 mA, for example (spool value detecting means).

  Since the frequency of the drive voltage of the spool proportional control valve 7 is sufficiently high, the hydraulic cylinder 4 has a speed substantially proportional to the difference between the time when the actual spool valve 10 is in the load position and the time when it is in the unload position. It expands and contracts with. When the spool value is 50%, the spool valve 10 is in the load position and the hydraulic oil is supplied to the main chamber 5 of the hydraulic cylinder 4, and the spool valve 10 is in the unload position and the main chamber of the hydraulic cylinder 4 is The time for discharging the hydraulic oil from 5 is equal, and the position of the piston of the hydraulic cylinder 4 is substantially unchanged.

  In the compression device 1, the discharge flow path and the suction flow path of the screw compressor 2 are connected via a bypass valve 13. Further, the compression device 1 includes a discharge pressure detector 14 that detects the pressure of the discharge flow path of the screw compressor 2 and a control device 15 that is configured by a computer.

  The control device 15 includes a slide valve opening control unit (slide valve opening setting unit) 16, a spool value control unit 17 (spool value setting unit), an alarm control unit 18, and a bypass valve, each realized as a program. And a control unit 19.

  The slide valve opening control unit 16 performs feedback control (for example, PID control) so that the deviation between the target discharge pressure of the compression device 1 input via the console 20 and the pressure detected by the discharge pressure detector 14 becomes small. To set the target opening of the slide valve 3 and input it to the spool value controller 17.

  The spool value control unit 17 performs spooling by feedback control (for example, PID control) so that the deviation between the target opening of the slide valve 3 set by the slide valve opening control unit 16 and the piston position signal of the hydraulic cylinder 4 becomes small. A target value of the spool value of the proportional control valve 7 is set and input to the spool valve control device 12.

  The alarm control unit 18 outputs an alarm signal to the outside when the deviation between the spool value target value set by the spool value control unit 17 and the spool value output from the actuator 11 exceeds a predetermined value.

  When the pressure detected by the discharge pressure detector 14 reaches a preset upper limit pressure and when a predetermined signal is input from the outside, the bypass valve control unit 19 determines the current flow rate from the opening of the slide valve 3. And the bypass valve 13 is opened at such an opening that the discharge pressure can be maintained at the target discharge pressure at the calculated flow rate.

  In the spool proportional control valve 7, the spool value of the spool valve 10 is a continuous amount of 0 to 100%, and this spool value is substantially proportional to the flow rate of hydraulic oil supplied (or discharged) to the hydraulic cylinder 4. That is, when the discharge pressure of the screw compressor 2 approaches the target discharge pressure, the flow rate of the hydraulic oil decreases and the expansion / contraction speed of the hydraulic cylinder 4 decreases, so that the opening change speed of the slide valve 3 decreases. For this reason, even if there is a slight delay in the control of the control device 15, there is almost no change in the opening of the slide valve 3 during the delay time, and the slide valve 3 can be adjusted to the optimum opening.

  As a result, in the control device 1, during steady operation where there is no sudden load fluctuation or the like, only the opening control of the slide valve 3 by the spool proportional control valve 7 is used to control the discharge pressure of the screw compressor 2 to the target discharge pressure ± 0. It can be strictly controlled within one. Further, since the bypass valve 13 is closed during steady operation, the loss of pressure energy of the discharged gas, that is, the loss of shaft power of the screw compressor 2 can be eliminated.

  Further, since the flow rate of the hydraulic oil is adjusted by the spool proportional control valve 7, a flow rate adjusting means such as a set of a needle valve and a check valve is provided in the hydraulic oil supply / discharge flow path to the hydraulic cylinder 4. There is no need to provide it.

  Further, when the control parameters of the slide valve opening control unit 16 and the spool value control unit 17 (for example, the differential time and integration time of PID control) are set to be optimal in the steady operation, the demand facility is suddenly stopped. Such a rapid decrease in demand cannot be accommodated, and the discharge pressure of the compressor 1 becomes high. Therefore, the control device 15 includes a bypass valve control unit 19 that detects a sudden change in operating conditions and opens the bypass valve 13. Thereby, since the raise of the discharge pressure of the compression apparatus 1 can be prevented, the control of the opening degree of the slide valve 3 can be optimized according to the steady operation.

  Further, it is considered that the spool proportional control valve 7 is abnormal when the spool valve 10 does not require a large torque and the spool value of the spool valve 10 deviates from the target value. For this reason, when the alarm control unit 18 outputs an alarm signal, the operator may be notified of the possibility of abnormality by turning on a warning lamp or the like, or the compressor 1 or the entire plant may be emergency stopped.

1 is a schematic view of a compression device according to one embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Compression apparatus 2 ... Screw compressor 3 ... Slide valve 4 ... Hydraulic cylinder (fluid pressure cylinder)
DESCRIPTION OF SYMBOLS 5 ... Main chamber 6 ... Sub chamber 7 ... Spool proportional control valve 8 ... Hydraulic pump 9 ... Oil receiver 10 ... Spool valve 11 ... Actuator 12 ... Spool control device 13 ... Bypass valve 14 ... Discharge pressure detector 15 ... Control device 16 ... Slide valve opening control unit (slide valve opening setting means)
17 ... Spool value control section (spool value setting means)
18 ... Alarm control unit 19 ... Bypass valve control unit 20 ... Console

Claims (4)

A screw compressor having a slide valve that rotates by meshing with each other in the rotor chamber, accommodates a pair of male and female screw rotors that compress gas, and changes the discharge position of the rotor chamber;
A fluid pressure cylinder for driving the slide valve and detecting its position;
A spool valve having a load position for supplying the working fluid to the main chamber of the fluid pressure cylinder, and an unloading position for discharging the working fluid from the main chamber;
The spool valve is periodically changed between the load position and the unload position, and the spool is a ratio of the time at which the spool valve is at the load position and is associated with the expansion / contraction speed of the fluid pressure cylinder. Spool valve drive means capable of controlling the value;
A slide valve opening setting means for setting a target opening of the slide valve according to a deviation between a discharge pressure of the screw compressor and a target pressure;
A target value of the spool value in the spool valve driving means is set according to a deviation between the opening degree of the slide valve detected by the fluid pressure cylinder and the target opening degree determined by the slide valve opening degree setting means. Spool value setting means,
The spool value setting means continuously changes the flow rate of the working fluid, which is determined according to the spool value, by continuously changing the target value of the spool value. Continuously changing
When the discharge pressure of the screw compressor approaches the target pressure, the slide valve opening setting means reduces the change in the target opening of the slide valve, and the spool value setting means sets the spool value target. The value is changed so that the expansion / contraction speed of the fluid pressure cylinder is decreased to decrease the speed of change of the opening degree of the slide valve. A spool value detecting means for detecting an actual value of the spool value;
2. The compression apparatus according to claim 1, wherein an alarm signal is generated when a deviation between an actual value of the spool value and a target value of the spool value becomes a predetermined value or more. The discharge side and suction side of the screw compressor are connected via a bypass valve,
3. The compression device according to claim 1, wherein the bypass valve is opened when an external signal indicating a rapid decrease in the gas demand is received. The discharge side and suction side of the screw compressor are connected via a bypass valve,
3. The compression device according to claim 1, wherein when the discharge pressure of the screw compressor reaches a preset upper limit pressure, the bypass valve is opened.

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