JP2019138200A - Compressor system - Google Patents

Abstract

To operate a compressor system which is composed of a plurality of constant velocity compressors by taking into consideration a variation of terminal pressure.SOLUTION: A compressor system comprises: at least two sets of compressor units; a discharge piping system composed of discharge piping, a gas tank and terminal piping; a pressure detection device for detecting discharge pressure at an upstream side from the gas tank; and a control device for controlling the compressor units by a constant velocity operation, and controlling a full-load operation or a non-load operation so as to be switchable on the basis of prescribed changeover pressure. The control device acquires a total discharge gas amount from an operation state of each compressor unit, and when one set is in the full-load operation, acquires a first pressure loss up to an air tank from the compressor units of the discharge piping system by taking into consideration a pressure difference before and after the changeover of the other set between the full-load operation and the non-load operation, calculates a use gas amount on the basis of a change rate of the discharge pressure which is detected by the pressure detection device, a capacity of the discharge piping system, and each operation state, also calculates a second pressure loss up to a terminal end from the gas tank on the basis of the use gas amount, and adds the second pressure loss to the prescribed changeover pressure of the non-load operation and the full-load operation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a compressor system including a plurality of constant speed compressors that are switched to full load operation or no load operation in accordance with a discharge side pressure of a compressor body.

  In a compressor system consisting of a plurality of compressors that compress gas, the operation method of each compressor includes load operation, unload operation, and start / stop control. In load operation, full speed load and variable speed compression of a constant speed compressor are performed. In unload operation, there are suction throttle control for finely adjusting the suction throttle valve and purge control for releasing the pressure in the compressor to the atmosphere. The operation of the compressor is generally controlled by pressure detection means built in the compressor unit. These controls are basically performed by each compressor and the discharge detected upstream of the discharge gas system. This is performed based on the pressure and power reduction (energy saving) is achieved.

  In the previous gas piping system from the gas discharge port of the compressor, the pressure loss increases as it approaches the end, but the pressure loss also changes depending on the change in the amount of discharge gas from the compressor and the amount of compressed gas used at the end. For such pressure loss, in order to keep the pressure above a certain level at the end of the gas piping system, set the compressor discharge pressure set value high and fixed in anticipation of the maximum pressure loss of the gas piping system. The terminal pressure of the gas piping system can be kept above a certain level, but when the amount of compressed gas used is small, the discharge pressure set excessively consumes extra power (for example, electric power). It becomes useless.

  Patent Document 1 and Patent Document 2 calculate the end pressure and pressure loss of the discharge piping system by switching the full load operation or no-load operation of the compressor body so that the end pressure of the discharge piping system falls within a predetermined setting range. Disclosed is a compressed air production apparatus provided with a control device that continuously calculates the amount of compressed air used as a basis from the rate of change in discharge side pressure.

  In order to stabilize the supply pressure while obtaining an energy saving effect, Patent Document 3 discloses a pressure sensor that detects the discharge pressure of the compressor at a position upstream of the discharge air system connected to the discharge side of the compressor, The pressure loss of the discharge air system is calculated according to the number of rotations of the electric motor, and based on this, the compressor pressure at the upstream position of the discharge air system is adjusted so that the end pressure at the downstream position of the discharge air system is within a predetermined range. Compressed air comprising a control device that changes the control range of the discharge pressure, and controls the rotational speed of the motor via an inverter so that the discharge pressure of the compressor detected by the pressure sensor becomes the changed control range. A manufacturing apparatus is disclosed.

  Patent Document 4 discloses an air discharge air system installed in a compressor, an upstream first pressure detection means close to the compressor side, and a second pressure detection means on the end side away from the compressor side. And a control device, and the control device performs a PI or PID calculation based on the pressure value detected by the pressure detection means, and detects the first and second pressure detection means. A function for calculating the pressure difference between the respective pressure values, a function for calculating a value obtained by subtracting the pressure difference from the first pressure value, and a second pressure corresponding to the PI or PID calculated value or the compressor rotational speed Disclosed is a compressor manufacturing apparatus having a function of setting and storing a relationship of a target pressure set value for keeping a value within a certain value.

Japanese Patent No. 4425768 Japanese Patent No. 4756081 Japanese Patent No. 4778643 Japanese Patent No. 5091787

Here, in Patent Documents 1 and 2, by changing between full-load operation or no-load operation by one constant speed compressor, the amount of air used as the basis for calculating the end pressure and pressure loss of the discharge piping system is changed. It is possible to calculate continuously from the rate.
In Patent Documents 3 and 4, it is possible to continuously calculate the terminal pressure of the discharge piping system in accordance with the number of rotations of the motor by two or three or more variable speed compressors.

However, there is no disclosure of simple and detailed means for continuously calculating the end pressure of the discharge piping system in a combination of two or more constant speed compressors.
In a compressor system consisting of multiple constant speed control compressors, the pressure of each discharge gas system is detected, and the minimum pressure setting and the amount of pressure difference from the compressor outlet to each end are taken into account. A technique that enables operation with a discharge air amount is desired.

In order to achieve the above object, for example, the configuration described in the claims is applied. That is, at least two compressor units that compress gas, a discharge pipe system that includes a discharge pipe, a gas tank, and a terminal pipe connected to the discharge side of the at least two compressor units, and at least the upstream side from the gas tank And a pressure detection device that detects the discharge pressure of the discharge piping system and controls the constant speed operation of the at least two compressor units and switches to full load operation or no load operation based on a predetermined switching pressure. A control device for controlling, wherein the control device calculates a total discharge gas amount from an operating state of each of the at least two compressor units and a maximum discharge gas amount of each, and the at least two compressors When one of the units is in full load operation or stopped, only the other one is switched between full load operation and no load operation. Obtained for each compressor unit as the first pressure loss from the compressor unit to the air tank in the outlet piping system, continuously calculating the rate of change of the discharge pressure detected by the pressure detector, the rate of change, Based on the capacity of the discharge piping system and the operating state of the at least two compressor units, the amount of gas used is calculated over time. Based on the amount of gas used, the amount of gas used from the gas tank to the end is calculated. 2 When calculating the pressure loss and switching between the no-load operation and the full load operation of the at least two compressor units, the second pressure loss is controlled based on the pressure value added to the predetermined switching pressure. is there.

  According to the present invention, in a compressor system composed of a plurality of constant speed compressors, the pressure of each discharge gas system is detected, and the fluctuation of the pressure difference from the outlet of the compressor to each end is immediately calculated. It is possible to operate with a minimum pressure setting and discharge gas amount.

It is a block diagram showing typically the composition of the compressor system by the embodiment to which the present invention is applied. It is a figure which shows typically the relationship between the discharge pressure and terminal pressure by a comparative example. It is a figure which shows typically the relationship between the discharge pressure by this embodiment, and a terminal pressure.

  Embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a block diagram schematically showing a configuration of a compressor system 100 according to an embodiment to which the present invention is applied. In the figure, a solid arrow indicates a gas flow, and a dotted arrow indicates a control signal flow. In this example, air is used as the compressed gas. However, the present invention is not limited to this, and can be applied to a system that compresses various gases.

  The compressor system 100 includes compressor units 14A and 14B, discharge pipes 16A and 16B, a supply pipe 17, an air tank 10, a system controller 20, a pressure sensor 21, an air tank 10, and a discharge air system. 18 is mainly provided. The compressed air discharged from the compressor units 14A and 14B joins the supply pipe 17 via the discharge pipes 16A and 16B, respectively, and flows into the air tank 10 which is a compressed gas storage part. The downstream side of the air tank 10 is connected to a terminal device (not shown) that uses compressed air via an air filter 11 or the like.

  The compressor system 100 is a system that generates compressed air by driving one or both of the compressor units 14 </ b> A and 14 </ b> B under the control of the system controller 20. Note that the number of compressor units may be three or more. In the present embodiment, the compressor system 100 is composed of a plurality of compressor units. However, the present invention is not limited to this, and a plurality of compressor units are arranged in one package housing. It may be a configuration.

  The system control device 20 is a control device that controls the operation of the compressor units 14A and 14B, and has a function of controlling a plurality of units to control each compressor unit via a wired or wireless communication network. In the present embodiment, the system controller 20 is described as a configuration arranged outside each compressor unit. However, a functional unit is included in a configuration stored in any unit, or in the control devices 4A and 4B of each unit described later. (It may be a configuration arranged in either one or both).

Hereinafter, each element constituting the compressor system 100 will be described in detail.
The compressor units 14A and 14B are compressors having a compressor body 1A (1B) as a compression mechanism. In this embodiment, the compressor units 14A and 14B each have a constant speed control and the same specifications (equivalent discharge air amount, etc.). Although applied, compressors with different rated discharge air amounts and discharge pressures may be applied to the compressor units 14A and 14B.

  The compressor unit 14A (same for 14B) includes a compressor body 1A that sucks and compresses air, an electric motor 2A that is a drive source for driving the compressor, and an electromagnetic switch that switches between energization and de-energization of electric power supplied to the electric motor 2A. 3A, a control device 4A that performs switching control of the electromagnetic switch 3A and various operation controls, a suction throttle valve 5A that is disposed in the suction port of the compressor body 1A and adjusts the suction amount, and the compressor body 1A discharges A check valve 8A arranged on the internal pipe for guiding the compressed air to the discharge pipe 16A, a pressure sensor 9A for detecting the pressure of the discharge pipe 16A arranged downstream from the check valve 8A, and a branch from the internal pipe A control pipe for guiding the compressed air for operation to the suction throttle valve 5A and an electromagnetic valve 13A for controlling the flow of the compressed air for operation are mainly provided, and these are housed in a package housing. .

  The compressor body 1A is, for example, a screw compressor that constitutes a compression chamber by meshing teeth of a plurality of rotors as a compression mechanism. In the present invention, various types of compression mechanisms such as a positive displacement type and a turbo type can be applied, and either a liquid supply type or a non-liquid supply type for supplying a liquid such as water or oil to the compression chamber can be applied. it can.

  The suction throttle valve 5A is a valve body that opens and closes the suction port of the compressor body 1A, and is a piston-type valve body that operates in accordance with a control command of the control device 4A. The flow of the compressed air discharged from the compressor main body 1A is controlled by the electromagnetic valve 13A to open and close. Specifically, based on the detection value of the pressure sensor 9A, the control device 4A outputs an opening / closing command for the electromagnetic valve 13A, thereby realizing opening / closing of the suction throttle valve 5A. By closing the suction throttle valve 5A, the compression load is reduced, and a no-load operation described later is realized. In addition, as a driving force of the suction throttle valve 5A, an electromagnetic valve body may be used instead of compressed air.

  The electromagnetic switch 3A is a switch that switches electric power supplied to the electric motor 2A. The electromagnetic switch 3A is configured to stop or operate the compressor main body 1A at full speed by energizing or de-energizing the motor 2A in accordance with a command from the control device 4A. The present invention is not limited to the electromagnetic switch 3A. If electric power is supplied at a constant speed, the variable speed device such as a power converter (inverter) can be used for full speed operation instead of the electromagnetic on / off valve 3A. The structure which implement | achieves a stop may be sufficient. In this case, the control device 4A outputs an operation and stop command to the variable speed device and a rotation speed command for setting the maximum rotation speed, and the variable speed device turns the electric motor 2A in accordance with the operation and stop command and the maximum rotation speed command. Rotate at maximum speed.

  The control device 4A is a functional unit realized by the cooperation of the program and the arithmetic device. A storage device that stores various control information such as a set value of the discharge pressure is provided to perform various controls. For example, the input of the detected pressure from the pressure sensor 9A is received, and a switching command for the electromagnetic switch 3A is output in comparison with the discharge pressure set value. Further, no-load operation control is executed according to the detected pressure. Note that the control device 4A may be configured by an analog circuit configuration.

  Here, no-load operation will be described. The no-load operation is an operation control for reducing the power of the compressor. If the amount of compressed air used decreases, the operating power of the compressor is wasted accordingly. Therefore, when the discharge pressure detected by the pressure sensor 9A reaches a predetermined pressure, the compressor unit 1A reduces the pressure applied to the compressor body by closing the suction throttle valve 5A to reduce power consumption. Yes. The predetermined pressure (upper limit pressure) is preferably higher than the discharge set pressure that is the target pressure. Further, when the amount of compressed air used increases during no-load operation and the upper limit pressure is lowered to a predetermined lower limit pressure, the control device 4A performs the normal compression operation again by opening the suction throttle valve 5A. . The lower limit pressure is preferably in a range lower than the upper limit pressure and higher than the target pressure, but may be slightly lower than the target pressure.

  In this embodiment, the no-load operation is performed using the suction throttle valve 5A. However, a method (purge method) using an air discharge valve may be applied together with or instead of this. . In the purge method, for example, an electromagnetic (or mechanical) air release valve that can be opened and closed is disposed on the internal piping downstream of the compressor main body 1A and upstream of the check valve 8A, and the control device 4A discharges. When the upper limit pressure is detected as the pressure, the pressure applied to the compressor main body 1A is reduced by opening the air release valve to lower the internal piping pressure, thereby reducing power.

  The air tank 10 has a function of storing the compressed air discharged from the compressor units 14 </ b> A and 14 </ b> B via the discharge pipes 16 </ b> A and 16 </ b> B and the supply pipe 17. An air filter 11 that removes dust and the like in the compressed air is disposed on the downstream side of the air tank 10. The discharge pipes 16 </ b> A and 16 </ b> B, the supply pipe 17, the air tank 10, and the piping system to the end side constitute a discharge air system 18. The air filter 11 is not an essential component of the present invention.

  The discharge air system 18 includes a pressure loss from the detection position 19a (upstream position) of the pressure sensor 9A of the compressor unit 14A to the downstream position 19c, and a detection position 19b (upstream position of the pressure sensor 9B of the compressor unit 14B). ) To the downstream position 19c is substantially equal. Hereinafter, these pressure losses are collectively referred to as a pressure loss ΔP of the discharge air system 18.

  The pressure sensor 21 is arranged in the air tank 10, detects the pressure of the discharge air system 18, and outputs it to the system control device 20. The system control device 20 can input the detection values of the pressure sensors 9A and 9B arranged in the compressor units 14A and 14B via the control device 4 and input the pressure value from the pressure sensor 21 arranged in the air tank 10. It is supposed to be. Note that the pressure detection means of the system control device 20 may be constituted by only the pressure sensor 9 or the pressure sensor 21.

  The system control device 20 outputs a control command for operating any one of the compressor units 14A and 14B to full load operation, no load operation, or a stopped state. For example, when one compressor unit is a base unit and the other is a capacity adjustment unit, the system control device 20 switches the capacity adjustment unit to full load operation when it cannot be compensated only by the discharge air amount of the base unit. When the discharge air amount can be compensated only, the capacity adjustment unit is operated by switching to a no-load operation or a stopped state.

  Further, the system control device 20 performs control so that the capacity adjustment unit and the base unit are replaced at predetermined intervals. As a result, for example, even when the capacity adjustment unit is frequently operated, the operation time of the compressor units 14A and 14B is leveled. Further, for example, when one of the compressor units 14A and 14B fails for some reason, the failed compressor unit is regarded as a failure stop and separated from the central control, and the central control is continued with the remaining compressor units. Yes.

  The system control device 20 and the control device 4A (4B) include all of the discharge pipes 16A, 16B, 17, 18, all the capacity of the compressor unit including the air tank and the air filter from the check valve 8 to the downstream position 19c. The pipe capacity C is stored. When the total pipe capacity C is clear, it is stored in the storage device in advance. However, when the total pipe capacity C is not clear, before the control of the number of the plurality of compressor units 14A and 14B is started. In addition, a control mode for calculating this is executed.

  As an example of calculating the total pipe capacity C in the control mode, when the compressor unit 14B is in a stopped state, the total piping capacity C is obtained from various values when the compressor unit 14A executes full load operation or no load operation. Specifically, the maximum discharge air amount of the compressor unit 14A set and stored in advance, the load ratio based on the ratio between the full load operation time and the no load operation time, that is, the use air amount ratio, and the use air amount ratio are 100%. That is, the compressor unit 14A calculates and stores the total pipe capacity C from the pressure sensor 9A and the maximum pressure difference between the downstream positions 19c during full load operation.

  The total pipe capacity C calculated here is the same as the total pipe capacity C calculated by the same method when the compressor unit 14A is in a stopped state and the compressor unit 14B performs full load operation or no load operation. It may be stored in the control device 4B, the system control device 20, or both. Either the total pipe capacity C calculated by any one of the compressor units or the average of the total pipe capacity C calculated in both cases may be used.

  In addition, the system controller 20 includes the maximum discharge air amount QsN and the total Qs of all the compressor units, the total pipe capacity C, and the pressure sensor 9 or pressure per unit time Δt (for example, 0.1 second). Based on the pressure change amount (change rate) ΔPt of the sensor 21 or both and the total discharge air amount QsALL of the compressor unit during full load operation, the used air amount Qs ′ is calculated and stored.

Further, the system controller 20 calculates the air flow rate Qs ′ and, when one compressor unit is switched from full load operation to no load operation, the detected value of the pressure sensor 9 and the air tank 10 (that is, The pressure difference ΔP1 of the detected value of the pressure sensor 21 is calculated and stored. This ΔP1 is an example of the primary pressure loss between the compressor unit and the air tank in the discharge piping system 18.
When one compressor unit is switched from full-load operation to no-load operation, the pressure value of the pressure sensor 9 and the pressure of the air tank 10 (detected value of the pressure sensor 21) that are different are almost the same. Therefore, either the value detected by the pressure sensor 9 or the pressure sensor 21 may be regarded as the pressure difference ΔP1 and stored.

  Next, the system controller 20 sets the maximum pressure loss ΔPMAX between the pressure sensor 9A (9B) and the downstream position 19c, the pressure difference ΔP1, the used air amount Qs ′, and all the compressor units. , The pressure difference ΔP2 between the air tank 10 and the downstream position 19c is calculated and stored. This ΔP2 is an example of the secondary pressure loss between the air tank and the downstream position 19c in the discharge piping system 18.

  In the specification for switching between full load operation and no load operation based on the pressure of the pressure sensor 9 or the pressure sensor 21, when the set pressure for switching to the no load operation is H and the set pressure for switching to the full load operation is L, the downstream side The switching set pressures H ′ and L ′ on the premise that the pressure at the position 19c is kept within a certain range are obtained as follows. That is, the set pressure L ′ for switching to the full load operation is obtained from the set pressure L and the pressure difference ΔP2, and the set pressure H ′ for switching to the no load operation can be obtained from the set pressure L ′, the set pressure H, and the set pressure L. it can.

  The system control device 20 calculates and stores L ′ and H ′, and uses them to control all compressor units 14A and 14B by switching between full-load operation, no-load operation and stop state, It is possible to keep the pressure at the downstream position 19c within a certain level and to keep the minimum pressure PMIN or more that is obtained by subtracting the maximum pressure loss ΔPMAX from the set pressure L, and to realize the minimum necessary power adjustment, that is, energy saving.

  The effect when using the control of this embodiment will be described using a comparative example with reference to FIGS. First, FIG. 2 shows the relationship between the detected pressure value of the pressure sensor 9A (corresponding to the discharge pressure of the compressor body) and the pressure value (terminal pressure) at the downstream point 19c when the control of this embodiment is not specified. . Specifically, FIG. 2 executes full-load operation and no-load operation based on the detected value of the outlet pressure of the compressor unit 14A (14B) such as the pressure sensor 9 or the pressure sensor 21 instead of the downstream point 19c. The pressure relationship when In the figure, the vertical axis represents the pressure value (MPa), the horizontal axis represents time (sec), the solid line represents the pressure value of the pressure sensor 9 and the like, and the dotted line represents the pressure value (terminal pressure) at the downstream point 19c.

At times A, B, and C, the compressor main body 1A is driven in the compressor unit 14A so that the value of the pressure sensor 9 becomes constant (0.69 Mpa).
At time A, when the amount of air used is 100%, the pressure of the pressure sensor 9 is 0.69 Mpa, the pressure at the downstream position 19c is 0.49 Mpa, and the differential pressure X1 is 0.20 Mpa.
At time B, when the amount of air used is 50%, the pressure of the pressure sensor 9 is 0.69 Mpa, the pressure at the downstream position 19c is 0.64 Mpa, and the differential pressure X2 is 0.05 MPa. The differential pressure X2 is a quarter of the differential pressure X1.
At time C, when the amount of air used is 0%, both the pressure sensor 9 and the downstream position 19c are 0.69 MPa.

FIG. 3 shows a case where the control according to this embodiment is applied. The axes and lines in the figure are synonymous with those in FIG.
At time A, when the amount of air used is 100%, the pressure of the pressure sensor 9 is 0.69 Mpa, the pressure at the downstream position 19c is 0.49 Mpa, and the differential pressure Y1 is 0.2 Mpa.
At time B, when the amount of air used is 50%, the pressure of the pressure sensor 9 is about 0.54 Mpa while the pressure of the pressure sensor 9 is about 0.49 Mpa, which is different from the differential pressure Y1 of time A. The pressure Y2 is a quarter.
At time C, when the amount of air used is 0%, both the pressure sensor 9 and the downstream position 19c are 0.49 Mpa.

  As can be seen from the comparison between FIG. 2 and FIG. 3, when the control of this embodiment is used, the power of the compressor system 100 can be reduced while maintaining the pressure (end pressure) at the downstream position 19 c. it can.

  While the embodiments of the present invention have been described above, the present invention is not limited to the above-described various configurations and controls, and various replacements and modifications can be made without departing from the spirit of the present invention.

1A, 1B: Compressor, 2A, 2B ... Electric motor, 3A, 3B ... Electromagnetic switch, 4A, 4B ... Control device, 5A, 5B ... Suction throttle valve, 6A, 6B ... Suction filter, 8A, 8B ... Check valve , 9A / 9B ... Pressure sensor, 10 ... Air tank, 11 ... Air filter, 13A / 13B ... Solenoid valve, 14A / 14B ... Compressor unit, 16A / 16B ... Discharge piping, 17 ... Supply piping, 18 ... Discharge air system 19a, 19b ... upstream position, 19c ... downstream position, 20 ... system controller, 21 ... pressure sensor, .DELTA.P ... maximum pressure loss, .DELTA.P1 ... first pressure loss, .DELTA.P2 ... second pressure loss.

Claims (5)

At least two compressor units for compressing gas, a discharge pipe system comprising a discharge pipe, a gas tank and a terminal pipe connected to the discharge side of the at least two compressor units; and at least upstream from the gas tank A pressure detection device arranged to detect the discharge pressure of the discharge piping system and the at least two compressor units to be controlled at a constant speed and controlled to switch to full load operation or no load operation based on a predetermined switching pressure. And a control device that
The control device is
The total discharge gas amount is calculated from the operating state of each of the at least two compressor units and the maximum discharge gas amount of each,
When one of the at least two compressor units is in full load operation or stopped, only the other one is switched between full load operation and no load operation, and the differential pressure between the discharge pressures before and after switching is set to the discharge pipe. Obtained for each compressor unit as the first pressure loss from the compressor unit to the air tank in the system,
The rate of change of the discharge pressure detected by the pressure detection device is continuously calculated, and the amount of gas used over time is calculated based on the rate of change, the capacity of the discharge piping system, and the operating state of the at least two compressor units. To
Calculate the second pressure loss from the gas tank to the terminal for the amount of gas used based on the amount of gas used;
A compressor system that controls the second pressure loss based on a pressure value obtained by adding the second pressure loss to the predetermined switching pressure when switching between no-load operation and full-load operation of the at least two compressor units. The compressor system according to claim 1,
When the control device switches between the no-load operation and the full-load operation of the at least two compressor units, the pressure value obtained by adding the second pressure loss to the predetermined switching pressure is set as a lower limit pressure before the no-load operation. A compressor system that switches to full load operation and performs no load operation with a pressure value obtained by switching to load operation and adding a predetermined pressure range to the second pressure loss as an upper limit pressure. The compressor system according to claim 1,
The compressor system in which the control device calculates the total discharge gas amount of the at least two compressor units by multiplying the maximum discharge gas amount of one compressor unit by the number of compressor units. The compressor system according to claim 1,
The gas is air;
A compressor system in which a compression mechanism of the at least two compressor units is a positive displacement or turbo compressor body. The compressor system according to claim 1,
A compressor system in which part or all of the at least two compressor units are arranged in one package housing.

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