JP4487339B2 - Capacity control method and apparatus for gas pumping device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a capacity control method and apparatus for a gas pumping device such as a centrifugal compressor or a blower used as a gas source for a raw material such as an air source or pressurized nitrogen in a general manufacturing or assembly factory.
[0002]
[Prior art]
As an example, the capacity control of a conventional compressor in which surging is avoided when the amount of use becomes equal to or less than the surging limit air volume by performing no-load operation. As shown in FIG. 9, a centrifugal compressor is shown. A suction valve 3 is provided in the middle of the suction side pipe 2 for the gas sucked into 1, and a branch pipe 6 is connected in the middle of the discharge side pipe 5 for sending the compressed gas discharged from the compressor 1 to the receiver 4. In the configuration in which the branch pipe 6 is provided with a discharge valve (exhaust valve) 7 for exhaust, and the check valve 8 is provided in the middle of the discharge side pipe 5 after the branch pipe 6, the receiver 4 The pressure transmitter 9 for detecting the discharge pressure determined by the balance of the gas pressure, that is, the amount used in the factory on the load side and the discharge amount of the compressor, and the signal from the pressure transmitter 9 as a measurement input Acts to keep discharge pressure constant A constant wind pressure controller (pressure indicating controller with a lower limit switch) 10, a current (or power) converter 11 for detecting a current (or power) supplied to the drive motor of the compressor 1, An overload prevention controller (current or power indicating controller with a lower limit switch) 12 that acts so as to prevent the motor rating from exceeding the signal as a measurement input, and an output signal (regulation signal) from the overload prevention controller 12 A low selector 13 which compares the value with the value of the output signal (control signal) from the constant wind pressure controller 10 and always sends the opening position adjustment signal α to the intake valve 3 based on the smaller value; When the amount of compressed gas used decreases, the constant air pressure control is maintained by narrowing the suction valve 3 through the low selector 13 until it approaches the surging region, as shown in the operating characteristic curve in FIG. To make more current When it is detected that the value (or power value) has decreased to reach a predetermined lower limit value, the intake valve 3 is immediately closed and the discharge valve 7 is fully opened by a control command from the lower limit switch of the overload prevention controller 12. So that no-load operation is performed. In FIG. 10, a is a surging line in mechanical performance, b is a surging prevention line, c is an operating line, d is a load point, and e is a no-load point. SP12 is a current adjustment target setting value of the overload prevention controller 12, SP12L is a current lower limit switch setting value, SP10 is a pressure adjustment target setting value of the constant wind pressure controller 10, and SP10L is a pressure lower limit switch setting value. .
[0003]
In FIG. 9, instead of providing the branch pipe 6 and the air discharge valve 7, a bypass valve 14 is provided between the outlet side of the compressor 1 and the inlet side of the intake valve 3 as indicated by a two-dot chain line. There is also a system in which the provided bypass pipe 15 is provided so that the compressed air is returned to the suction side through the bypass pipe 15 when the current value (or power value) reaches the lower limit value.
[0004]
In the configuration shown in FIG. 9, when surging is detected at a flow rate, control is performed so that the intake valve 3 is closed and the air discharge valve 7 is opened by a control command from the lower limit switch of the overload prevention controller 12. Instead, as shown in FIG. 11, when the flow rate of the compressed gas flowing through the discharge side pipe 5 of the compressor 1 is detected by the flow rate transmitter 16 and the flow rate value reaches a predetermined lower limit value, the lower limit is reached. Control is performed such that the intake valve 3 is closed and the air discharge valve 7 is opened by a control command from a flow rate lower limit switch of the flow rate indicator 17 with switch.
[0005]
On the other hand, there is also a method in which surging is avoided by performing a wind-off operation while preventing the surging from being below the surging limit air volume. That is, in the configuration shown in FIG. 9, instead of controlling the opening and closing of the intake valve 3 and the air discharge valve 7 with a command from the overload prevention controller 12, as shown in FIG. A throttle opening limiter (a broken line function calculator) 18 that adjusts the throttle opening of the valve 3 and an opening degree controller (a broken line function calculator) that similarly adjusts the opening of the discharge valve 7 by a command from the low selector 13. 19, the throttle opening degree of the intake valve 3 is fixed to, for example, 50% in advance by the throttle opening limiter 18 so that it does not become less than the surging limit air volume, and the discharge valve 7 is increased by increasing the pressure or the like. Is used as a partial opening to prevent surging. FIG. 13 is an operating characteristic curve diagram of the apparatus shown in FIG. 12, where f is a vent valve opening region and g is a suction valve throttle region.
[0006]
[Problems to be solved by the invention]
However, in the case of the former method, which immediately enters a no-load operation and avoids surging when approaching the surging area, in a general factory where the load fluctuates rapidly, the intake valve is narrowed down by a constant wind pressure adjustment signal for loads near the surging area Because the operation is too early, even with loads that can be balanced, the lower limit of current and flow rate will be reached immediately and no load will be applied. There are many problems with points (increased opening and closing frequency).
[0007]
On the other hand, in the case of the latter method in which the throttle opening of the suction valve is fixed, the flow rate changes greatly due to the temperature change of the gas to be sucked. There is a problem from the point of view of energy saving (power loss) because it is a wind-release operation at the time when the limit is not reached.
[0008]
Therefore, the present invention makes it possible to set the balance even with a load in the vicinity of the surging region, and to ensure a surging limit air volume that is as close as possible to the surging line in mechanical performance without being affected by the temperature of the intake gas. It is something to try.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention reduces the opening degree of the suction valve provided in the suction side piping of the gas pressure feeding device with the constant wind pressure adjustment signal as the amount of gas used on the load side decreases. the gas discharge amount of the gas pumping unit in a volume control method and apparatus for a gas pumping device to ensure that fit the gas use amount, the measurement of the current or power supplied to the drive motor of the gas pumping device, measuring inputs the signal When the adjustment signal that increases the output with the approach to the surging region is calculated by the weight loss limit controller, and when the adjustment signal becomes larger than the constant wind pressure adjustment signal , the opening degree of the intake valve is calculated by the adjustment signal The capacity control method and apparatus of the gas pressure feeding device is controlled so as to prevent the throttling of the gas so as not to be less than the surging limit air volume.
[0010]
Until the operating point approaches the surging area, the control is performed to reduce the opening of the intake valve with the constant wind pressure adjustment signal, but when the operating point approaches the surging area, the intake valve is controlled by the adjustment signal from the weight loss limit controller. Further throttling is prevented, so that it is suppressed to the surging limit air volume or less.
[0011]
In addition, after the adjustment signal calculated by the reduction limit controller becomes larger than the constant wind pressure adjustment signal, the adjustment signal prevents the opening of the intake valve from being throttled so that it does not become less than the surging limit air volume. When the discharge pressure of the device rises and the amount of gas used on the load side becomes smaller than the surging limit air volume, only the remaining surplus, which is obtained by subtracting the surging limit air volume from the gas usage, is discharged or sucked. Even in the case of bypassing, it is possible to reduce the air discharge loss by expanding the constant pressure region.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 shows an embodiment of the present invention. A suction valve 3 is provided in the middle of a suction side pipe 2 for gas sucked into the compressor 1, and the compressed gas discharged from the compressor 1 is received by a receiver. A branch pipe 6 provided with a discharge valve 7 is connected in the middle of the discharge side pipe 5 to be sent to 4, and a check valve 8 is provided in the middle of the discharge side pipe 5 after the branch pipe 6. A pressure transmitter 9 that detects the discharge pressure of the compressor, a constant wind pressure controller 10 that acts to make the discharge pressure constant by using a signal from the pressure transmitter 9 as a measurement input, and a current supplied to the motor of the compressor 1 A current (or power) converter 11 for detecting (or power), and an overload prevention controller (indicating controller) 12 which acts so as not to exceed the rating of the motor using a signal from the converter 11 as a measurement input; The value of the output signal (control signal) from the overload prevention controller 12 and the above A low selector 13 that compares the value of the output signal (regulation signal) from the constant wind pressure controller 10 and always sends the opening position adjustment signal α to the intake valve 3 based on the smaller value. In the compressor capacity control apparatus having the configuration, a surging prevention line b having a minimum required margin parallel to the surging line a on the mechanical performance of the operating characteristic curve shown in FIG. 2 according to the gas pressure in the receiver 4 is provided. The ratio converter 20 to be set, and the signal from the current (or power) converter 11 are used as measurement inputs, and the output thereof becomes closer to the surging prevention line b as a set value by the ratio converter 20. A current (or power) indicating controller 21 as a weight loss limit controller that increases the signal (control signal), an output signal (control signal) β of the current indicating controller 21 and the rose And a high selector 22 which always compares the adjustment signal α sent via the Kuta 13 and outputs the signal on the larger side with priority, and surging by the adjustment signal β outputted via the high selector 22 The throttle opening of the intake valve 3 can be controlled so that it does not become less than the limit air volume.
[0014]
In FIG. 2, SP21 indicates the current adjustment target setting value of the current indicating controller 21, SP10H indicates the pressure upper limit switch setting value of the constant wind pressure controller 10, and the other components are the same as those shown in FIG.
[0015]
Now, when the amount of compressed gas used decreases, the suction valve 3 is gradually closed by the adjustment signal α selected by the low selector 13 so that the pressure is kept constant, and the operation shown in FIG. As indicated by curve C, the movement is adjusted so that the operating point matches the amount of gas used. At this time, the output signal β of the current indicating controller 21 as the weight reduction limit controller and the adjustment signal α sent via the low selector 13 are continuously compared in magnitude by the high selector 22. Since the output signal β of the indicator controller 21 increases as the operating point approaches the surging prevention line b, the adjustment signal α sent via the low selector 13 is selected at this time, and the intake valve 3 is controlled.
[0016]
In the above, when the use amount of the compressed gas further decreases, the operating point moves to the surging prevention line b on the set discharge pressure constant line (pressure adjustment target set value SP10) by the adjustment operation that is repeatedly performed. You will approach. As the surging approaches, the output signal β of the current indicating controller 21 increases and becomes larger than the adjusting signal α, so that the output signal β of the current indicating controller 21 is selected by the high selector 22, so that the intake valve 3 The diaphragm control by the adjustment signal α is blocked and is controlled by the output signal β of the current indicating controller 21. At this time, since the current indicating controller 21 operates so as to keep the operating point on the surging prevention line b, it does not fall below the surging limit air volume. From this, even if the amount of compressed gas used is further reduced, the pressure increases along the surging prevention line b. Further, when the pressure rises to the pressure upper limit switch setting value SP10H of the constant air pressure controller 10, the suction valve 3 is closed and the air discharge valve 7 is opened by the control command from the pressure upper limit switch so that no-load operation is performed. To do.
[0017]
As a result, the balance can be set even in the vicinity of the surging region, and the surging limit air volume that is as close as possible to the surging line in mechanical performance can be secured without being affected by the intake gas temperature.
[0018]
Next, FIG. 3 shows another embodiment of the present invention, and shows a case where surging detection is performed with a flow rate. That is, instead of using a current (or power) indicating controller 21 having a signal from the current (or power) converter 11 as a measurement input in the same configuration as shown in FIG. Thus, a flow rate indicating controller 23 in which a signal from the flow transmitter 16 provided in the discharge side pipe 5 of the compressor 1 is used as a measurement input is used as a reduction limit controller.
[0019]
Even with the configuration as shown in FIG. 3, the same effects as those shown in FIG. 1 can be exhibited.
[0020]
Next, FIG. 4 shows still another embodiment of the present invention, which is an example in the case where the usage amount is equal to or less than the surging limit air amount and the surging avoidance operation is performed when the pressure rises, and is shown in FIG. In the same configuration as the above, a pressure indicating controller 24 is provided as an air discharge constant pressure controller using the signal of the pressure transmitter 9 as a measurement input instead of the pressure upper limit switch, and as shown in FIG. A set value SP24 of the pressure indicating controller 24 is provided at a position having a certain pressure difference from the set value SP10, and the opening degree of the discharge valve 7 is controlled by an output signal (control signal) from the pressure indicating controller 24. It is something that can be done.
[0021]
As shown in FIG. 4, when surging avoidance at the time of pressure rise is a ventilating operation, and the amount of gas used in the factory is smaller than the surging limit air volume, the remaining surplus obtained by subtracting the surging limit air volume from the factory use amount Since the surging limit air volume is close to the surging line in mechanical performance, the air discharge loss can be reduced.
[0022]
FIG. 6 shows still another embodiment of the present invention, in which surging detection is performed at a flow rate by changing the embodiment of FIG. 4 in which surging detection is performed by current (or power). It is. That is, in the same configuration as shown in FIG. 3, a pressure indicating controller 24 as an air discharge constant pressure controller using the signal of the pressure transmitter 9 as a measurement input is provided in the same manner as in FIG. The opening degree of the air discharge valve 7 can be controlled by an output signal (regulation signal) from the total 24.
[0023]
Even if it is shown in FIG. 6, the same effect as the case of embodiment of FIG. 4 can be show | played.
[0024]
Incidentally, FIG. 7 shows the present invention shown in FIG. 1 to FIG. 3 and FIG. 9 to FIG. 11 in the case where the surging avoidance when the amount of use is below the surging limit air volume and the pressure rises is set to no-load operation. The power performance is compared with the conventional method, and FIG. 8 is shown in FIGS. 4 to 6 in the case where the surging avoidance when the amount of use is less than the surging limit air volume and the pressure rises is set as the discharge operation. The power performance is compared between the present invention and the conventional system shown in FIGS. 7 and 8, h is the suction throttle operation line from the rated point i to the weight loss limit point j in the machine performance, k is the ideal line, l is the operation line according to the present invention, and m is the case according to the conventional method. The operation line is shown.
[0025]
As apparent from FIGS. 7 and 8, the operation line l according to the present invention is closer to the ideal line k than the operation line m according to the conventional method, and it is possible to perform actual operation at the surging limit point. Recognize. In other words, it is possible to expand the constant pressure region with power reduction (□ mark → ○ mark) and to reduce the discharge loss (shaded area), especially when performing surging avoidance with no-load operation This can further reduce the air loss that occurs when the intake valve and the air release valve are switched. Furthermore, many opportunities for balance settling in the vicinity of the surging region are created, and the valve opening / closing frequency can be reduced, thereby extending the life of the valve.
[0026]
In each of the above embodiments, the case where the branch pipe 6 provided with the discharge valve 7 is connected to the discharge side pipe 5 of the compressor 1 is shown, but in FIG. 9 and FIG. In the same manner as shown, it can be applied to a line configuration in which a bypass pipe 15 having a bypass valve 14 is incorporated instead of the branch pipe 6 having the discharge valve 7. Although the case where the ratio converter 20 is provided separately from the current indicating controller 21 and the flow indicating controller 23 as limit controllers is shown, a weight loss limit controller incorporating the function of the ratio converter 20 is shown. Of course, various modifications may be made without departing from the scope of the present invention.
[0027]
【The invention's effect】
As described above, according to the present invention, as the amount of gas used on the load side decreases, the opening of the suction valve provided in the suction side piping of the gas pressure feeding device is reduced by the constant wind pressure adjustment signal. in the capacity control method and apparatus for a gas pumping device to ensure that fit the gas use amount of gas discharge amount of the pumping device, a current or power supplied to the drive motor of the gas pumping unit is measured, the measurement inputs the signal When the adjustment signal becomes larger than the constant wind pressure adjustment signal , the adjustment signal is used to calculate the opening degree of the suction valve. Since it is a capacity control method and device for a gas pumping device that controls the throttle so that it does not fall below the surging limit air flow, it is as close as possible to the surging line in mechanical performance. It is possible to expand the constant pressure region with power reduction, enabling actual operation at the surging limit point, and creating more opportunities for balance setting near the surging region. In addition, the life of the valve can be extended, and the adjustment signal calculated by the weight reduction limit controller becomes larger than the constant wind pressure adjustment signal, and the adjustment signal reduces the opening of the intake valve. After the discharge pressure of the gas pumping device rises and the usage amount on the gas load side becomes smaller than the surging limit air volume, Even when only surplus after subtracting the surging limit air volume is discharged or bypassed to the suction side, it is possible to reduce the air discharge loss by expanding the constant pressure region. It exhibits an excellent effect of.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an embodiment of a capacity control device of a gas pressure feeding device of the present invention.
FIG. 2 is an operating characteristic curve diagram when the apparatus shown in FIG. 1 is used.
FIG. 3 is a schematic view showing another embodiment of the present invention.
FIG. 4 is a schematic view showing still another embodiment of the present invention.
5 is an operating characteristic curve diagram when the apparatus shown in FIG. 4 is used. FIG.
FIG. 6 is a schematic view showing still another embodiment of the present invention.
FIG. 7 is a characteristic curve diagram comparing the present invention and a conventional method when surging avoidance is performed in a no-load operation.
FIG. 8 is a characteristic curve diagram comparing the present invention and a conventional method when the surging avoidance is set as a wind discharge operation.
FIG. 9 is a schematic view showing an example of a conventional compressor capacity control device;
10 is an operating characteristic curve diagram of the apparatus shown in FIG. 9. FIG.
FIG. 11 is a schematic view showing another example of a conventional compressor capacity control apparatus.
FIG. 12 is a schematic view showing still another example of a conventional compressor capacity control apparatus.
13 is an operating characteristic curve diagram of the apparatus shown in FIG.
[Explanation of symbols]
1 Compressor (gas pumping device)
2 Suction side piping 3 Suction valve 5 Discharge side piping 7 Air discharge valve 10 Constant air pressure controller 21 Current indicating controller (weight reduction limit controller)
22 High selector 23 Flow rate indicating controller (weight reduction limit controller)
24 Pressure indicating controller (Ventilation constant pressure controller)

Claims (4)

As the amount of gas used on the load side decreases, the amount of gas discharged from the gas pumping device is reduced to the amount of gas used by restricting the opening of the suction valve provided in the suction side piping of the gas pumping device with a constant air pressure control signal. in the capacity control method of a gas pumping device to ensure that align the current or power supplied to the drive motor of the gas pumping unit is measured, output together with access to the surging area by reduction limit controllers to measure inputs the signal When the adjustment signal becomes larger than the constant wind pressure adjustment signal, the adjustment signal prevents the opening of the intake valve from being throttled so that it does not fall below the surging limit air volume. A capacity control method for a gas pressure feeding device, characterized by controlling the capacity. After the adjustment signal calculated by the reduction limit controller becomes larger than the constant wind pressure adjustment signal, the adjustment signal prevents the opening of the intake valve from being throttled so that it does not fall below the surging limit air volume. When the discharge pressure rises and the amount of gas used on the load side becomes smaller than the surging limit air volume, only the remaining excess of the gas usage minus the surging limit air volume is bypassed to the discharge or suction side The capacity | capacitance control method of the gas pressure feeder of Claim 1 made to do. As the amount of gas used on the load side decreases, the amount of gas discharged from the gas pumping device is reduced to the amount of gas used by restricting the opening of the suction valve provided in the suction side piping of the gas pumping device with a constant air pressure control signal. the capacity control device, the gas pumping device to ensure that align the current or power supplied to the drive motor of the gas pumping unit as a measurement input, and the operating point is to increase the hand output signal as it approaches the surging area And a high selector that outputs the larger one by giving priority to comparing the output signal of the weight loss limit controller and the constant wind pressure adjustment signal, and through the high selector A capacity control device for a gas pressure feeding device, characterized in that the opening of the suction valve can be controlled by an output signal so as not to be less than a surging limit air volume. Comprises a blow-off pressure controllers with high required set value than the discharge pressure as the measurement input and the Teifuatsu Controller set value of the gas pumping unit, the blow-off pressure controllers setting under the control of the high selector When the discharge pressure of the gas pumping device rises up to this point, only the remaining surplus obtained by subtracting the surging limit air volume from the gas use amount is bypassed to the discharge or suction side by the constant air pressure adjustment. Item 4. A capacity control device for a gas pressure feeding device according to Item 3.

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