JPH02223694A - Operation control method for centrifugal compressor - Google Patents

Abstract

PURPOSE:To reduce the consumption power of a compressor by a method wherein the opening of a suction control valve is regulated, and load - no-load control through which a blow-off control valve is operated according to the opening and constant pressure - non-surge control are effected. CONSTITUTION:A suction control valve 2 to regulate an intake air amount is mounted on the suction side of a compressor 1. A blow-off control valve 8 to blow off a part of air in a delivery pipe to the open air is located in a blow-off passage 7 connected to a delivery pipe 3 situated between a check valve 4 and the compressor 1. A controller 11 opens and closes the suction control valve 2, and performs load - no-load control through which the blow-off control valve 8 is operated according to the opening. The opening of the suction control valve 2 is regulated so that a pressure is maintained at a set value, and constant pressure - non-surge control through which the blow-off control valve 8 is opened so that a flow rate does not enter a surging area. This constitution enables reduction of the consumption power of a compressor.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a method for controlling a centrifugal compressor that performs load-no-load control and constant-pressure-non-surge control, and particularly relates to a method for controlling a centrifugal compressor during these #I operation. It calculates the power consumption and automatically switches to the control that consumes less power to improve compressor operating efficiency.
This invention relates to a method for controlling the operation of a centrifugal compressor.

[Prior art] Centrifugal compression FI (Fig. 3) enables load-no-load control operation as an air compressor that supplies compressed air to a wide variety of products or a large number of users, and enables constant pressure and non-surge control nM rotation. A centrifugal compressor (Figure 4) is known.

A centrifugal compressor that performs load-no-load control operation is shown in Figure 3.
As shown in the figure, a suction control valve 2 is provided on the suction side of the compressor 1, and a check valve 4 is sequentially installed in the discharge pipe 3' downstream of the compression Ill.
．． A receiver tank 6 is provided, and a check valve 4 and a compression ii
A blowoff fgJ control valve 8 for blowing off a part of the compressed air is provided in the blowoff path 7 connected between the An electromagnetic three-way switching valve 21 is provided in the receiver tank 6 to control the electromagnetic three-way switching valve 2.
It is constructed by attaching a pressure switch 22 that switches between 1 and 2.

In this load-no-load control, as shown in FIG. 5, the compressor 1 is operated under load between two set pressures C and D of the capacity-pressure characteristic when the suction control valve 2 is fully open. During load operation, when the user's air consumption decreases and the receiver tank pressure rises to the set pressure C, just before the surging region,
The pressure switch 22 is turned off and the air discharge control valve 8 is automatically opened.
Switch the suction control valve 2 to close (but 12%) and switch the pressure aR1 to no-load operation, and conversely, when the pressure in the receiver tank 6 decreases below the set pressure due to an increase in air consumption by the user, the pressure switch 22 enters and automatically closes the air discharge control valve 8, opens the suction control valve 2, and switches to load operation.

In other words, the two set points C-
Load-no-load operation is automatically repeated between D. Furthermore, the power consumption of the compressor 1 at this time, that is, the shaft power, is as shown by the dotted line in the figure.

As shown in FIG. 4, the centrifugal compressor that performs constant pressure operation and non-surge operation control has the air discharge path 7 and the compression tat.
A pressure indicating controller 24 for detecting the discharge pressure is installed in the discharge pipe 3 between the
is installed, and the opening degree of the suction control valve 2 is adjusted so that the discharge pressure is constant based on the detected value of the pressure indicating controller 24, and a detection valve is installed in the discharge pipe upstream of the check valve 4. A differential pressure transmitter 9 is installed to input the differential pressure to the flow rate indicating controller 23, and the opening degree of the air discharge control valve 8 is controlled by the flow rate indicating controller 23 so that the compression at is operated at a constant pressure. In other words, as shown in FIG.
Adjust the opening degree of the suction control valve 2 so that the air consumption becomes 00% (for example, 8 atm), and perform constant pressure operation until the air consumption on the user side 15 is from a flow rate close to the surging region to a flow rate of 100% (D -A) On the other hand, when the flow rate decreases and enters the surging region, the air discharge 1tillall valve 8 is opened by the flow rate indicating controller 23 while maintaining the opening degree of the suction control valve 2 at an opening degree that does not cause surging. A non-surge operation is performed in which surplus air in the discharge pipe 3 is discharged from the air discharge path 7 to the atmosphere. In this case, as shown in the figure, the power consumption of compression IR1 is constant (approximately 65% of the rated power consumption) in the surging region (non-surge control), and 65% of the rated power consumption in the constant pressure control.
It will increase by 5-100%.

[Issue Ui to be Solved by the Invention] By the way, when comparing the power consumption of the compressors under load-no-load control and constant-pressure-non-surge control described above, it is found that when the compressor is operated at a flow rate that causes surging, the load-no-load control is Load operation is advantageous over constant pressure/non-surge control, and conversely, constant pressure/non-surge control is more advantageous at flow rates that do not cause surging.

That is, in FIGS. 5 and 6, if the shaft power of the compressor at 50% capacity (air consumption) is approximately the same power consumption for load-no-load control and constant pressure-non-surge control, then
When the flow is below the G point, the load-no-load control operation results in less shaft power, and when it is above the G point, the constant pressure-non-surge control operation results in less shaft power.

When looking at the shaft power, it is desirable to switch between the two controls depending on the amount of air used.

However, even if a centrifugal compressor is configured to perform the various controls described above, the system automatically selects the control that minimizes the power consumption of the compressor by comparing the various controls described above based on the amount of air used by the user. There was very little control over the situation.

The present invention has been made in consideration of the above circumstances, and its purpose is to provide a centrifugal compressor that performs load-no-load control and constant-pressure-non-surge control, and when the amount of air used is almost the same, The purpose of the present invention is to automatically select control that reduces the power consumption of the compressor, thereby reducing the power consumption of the compressor.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a suction control valve for adjusting the amount of intake air on the suction side of the compressor, and a check valve on the discharge pipe of the compressor. , in a method for controlling a centrifugal compressor in which a blow-off control valve is connected to a discharge pipe between a check valve and a compressor,
Load-no-load control is performed in which the suction control valve is opened and closed between two set pressures, and the air discharge control valve is opened and closed accordingly, and the valve opening of the suction control valve is adjusted to maintain the set pressure. g! i! E, perform constant pressure-non-surge control by opening the air discharge control valve so that the flow rate does not enter the surging region, and operate with the load-no-load control and constant pressure-non-surge control based on the amount of compressed air used. The power consumption of the compressor at that time is determined, and the control that consumes less power is automatically applied.

[Function] Load-no-load control that opens and closes the valve opening of the suction control valve between two set pressure points and opens and closes the air discharge control valve accordingly, and Constant pressure/non-surge control is performed by adjusting the valve opening of the suction control valve and opening the above-mentioned air discharge control valve so that the flow rate does not enter the surging region. If the power consumption of the compressor is determined at all times or at regular intervals, and control is executed to automatically switch to the control that consumes less power, the centrifugal compressor will be operated with the minimum power consumption and its operating efficiency will be improved. will improve.

[Embodiment] A preferred embodiment of the present invention will be described below based on the accompanying drawings.

As shown in FIG. 1, a suction control valve 2 for adjusting the intake air amount is provided on the suction side of the compressor 1, and a discharge pressure transmitter 10 sequentially outputs the pressure as a signal to the discharge pipe 3 downstream from the compressor 1. ．． Flow meter 25. Check valve 4. Discharge valve 5. A receiver tank 6 is provided, and an air release path 7 connecting the check valve 4 and the discharge pipe 3 of the compressor 1 is provided with an air release control valve 8 for releasing part of the air in the discharge pipe to the atmosphere. receiver tank 6,
Alternatively, a tank pressure transmitter 26 that takes out pressure as a signal is attached to the discharge pipe 3 between the check valve 4 and the receiver 6, and a discharge pipe 3 upstream of the check valve 4 is installed downstream of the discharge of the compressor 1.
Attach the flow meter 27 to. Each of the flow meters 25 and 27 is equipped with a differential pressure transmitter 9 that outputs the flow rate of compressed air as a signal.
Install. These pressure transmitters 25, 27 and differential pressure transmitters 9.9 are connected to an input/output section 12 of a controller (such as a CPU) 11, and input pressure and flow rate as signals, respectively.

As shown in FIG. 2, the controller 11 opens and closes the suction control valve 2 (opening degree 1
00% to 12%), and opens and closes the air discharge control valve 8 according to its opening and closing, that is, when the suction control valve 2 is open, the air discharge control valve 8 is closed, and when the suction control valve 2 is closed, the air discharge control valve 8 is closed. It is configured to perform load-no-load control by opening the m control valve 8,
In addition, the valve opening of the suction control valve 2 is adjusted to maintain the set pressure P, and the flow rate changes from the surging region to the set point D (100
%), and when the flow rate is below the surging range, the opening of the suction control valve 2 is kept at the opening above the surging range, and the air discharge control valve 8 is controlled by the flowmeter 25.27. It is configured to perform non-surge control to release excess compressed air.

For this purpose, the flow rate-pressure performance (FIG. 2) for executing these controls is input into the memory section 13 of the controller 11. The arithmetic control unit 14 of the controller 11 compares the input signal from the input/output unit 12 with the memory unit 13,
It is configured to calculate the shaft power (power consumption) when operating under dual control and determine its magnitude, and
Based on the determination result, it is configured to output a load-no-load control signal or a constant pressure-non-surge control signal to the suction control valve 2 and the air discharge control valve 8. However, the controller has an internal timer function. In the embodiment, the arithmetic control unit 14 calculates the amount of air used by each compressor 1 when performing the load-no-load control and constant-pressure-non-surge control from the amount of compressed air used on the user side 15. is integrated over a certain period of time, and the power consumption of the compressor 1 is calculated from the determined air usage amount and output to the calculation control section 14.

Based on the calculation result, the calculation control unit 14 selects and switches the control that consumes less power from among the load-no-load control and the constant pressure-non-surge control.

Next, switching control in this embodiment will be explained with reference to FIG.

First, in the case of load-no-load control operation, during load operation, the opening degree of the suction control valve 2 is set to 100%, and at that time, the operation is performed between C and D of the capacity-pressure characteristic as shown in FIG. During no-load control operation, the suction control valve 2 is closed and the air discharge control valve 8 is open, and the 8 points shown in the figure (capacity JL 10%, 1.1 atm (atmospheric pressure +
The switching between the load and no-load control operation performed in α)) is based on the pressure transmitter 10. The amount of compressed air used during the load-no-load M control operation is determined by the pressure transmitter on the upstream side of the receiver tank 6. 26 and flowmeter 25. That is, for the total air amount, the detected values of the flow meter 25 and pressure transmitter 10 are input to the controller 11 during load operation, and the amount of compressed air used at the rated pressure (100%) is calculated based on the load time at this time.
The shaft power (power consumption) of the compressor 1 at this time is determined.

On the other hand, in constant pressure-non-surge control operation, as shown in Figure 2, when the flow rate is below the crab point (the point where the capacity is slightly larger than surge line I), non-surge control operation is performed and K-D
At times in between, constant pressure (100% rated pressure) control is performed. In this constant pressure - non-surge control operation, the amount of compressed air used for control is determined by the two flowmeters 25 and 27 shown in Figure 1, and the amount of compressed air used at that time is The shaft power (power consumption) of the compressor is determined.

During operation, the controller 11 determines the power consumption of both controls at all times or at regular intervals, and automatically selects the operation that consumes less shaft power of both controls.

This will be explained in detail in FIG.

Now, if one of the above-mentioned controls is being performed and the air usage amount for that control operation is point A, in this case, if constant pressure control operation has already been performed, the operation will continue as it is, and the load will be lowered. If it is no-load operation, switch to constant pressure/non-surge control operation.

Moreover, if the air consumption is below point B, the operation is switched to load-no-load control operation. As explained in FIGS. 5 and 6, this switching is performed, for example, when the flow rate is 50% or more, constant pressure/non-surge control operation is performed.

In this way, the shaft power of the compressor 1 is determined for the amount of compressed air used, the power consumption in re-control operation is determined either constantly or at regular intervals, and the control that consumes less power is automatically selected based on the determined results. By switching the compressor 1, the compressor 1 can be operated more efficiently.

[Effects of the Invention] As is clear from the above explanation, the present invention provides a centrifugal compressor that performs load-no-load control and constant-pressure-non-surge control. It has the excellent effect of being able to operate a centrifugal compressor.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing a preferred embodiment of the present invention;
2nd (!I is the flow rate-pressure performance diagram of the centrifugal compressor, 3rd
Fig. 4 is a flow sheet showing a conventional centrifugal compressor.
FIGS. 5 and 6 are performance diagrams showing an example of flow rate-pressure characteristics and flow rate-shaft power performance of a conventional centrifugal compressor, respectively. In the figure, 1 is a compressor, 2 is a suction control valve, 3 is a discharge pipe, 4 is a check valve, 8 is an air discharge control valve, and 11 is a controller.

Claims (1)

[Claims] 1. A suction control valve is installed on the suction side of the compressor to adjust the amount of intake air, a check valve is installed in the discharge pipe of the compressor, and a blowout control valve is connected to the discharge pipe between the check valve and the compressor. The method for controlling the operation of a centrifugal compressor includes load-no-load control in which the suction control valve is opened and closed between two set pressure points, and the discharge control valve is opened and closed in response to this, and the pressure is maintained at the set pressure. To avoid this, the valve opening of the suction control valve should be adjusted, and the air discharge control valve should be opened so that the flow rate does not enter the surging region.Constant pressure-non-surge control should be carried out, and the amount of compressed air used should be adjusted to reduce the load-no-surge control. Operation of a centrifugal compressor characterized in that the power consumption of the compressor is determined when operating under load control and constant pressure-non-surge control, and the control is automatically switched to the control that consumes less power. Control method.