JPH02259298A - Constant discharge control device of centrifugal compressor - Google Patents

Abstract

PURPOSE:To control discharge without surging by providing a guide vane, which varies a discharge of a compressor through changing an inlet angle of fluid with respect to an impeller of a centrifugal compressor, together with a by-pass line, which returns a part of fluid discharged from the compressor to an inlet side of a specified stage. CONSTITUTION:A three stage centrifugal compressor 1 consists of cascade compression stages 10 to 12, in which impellers 13 are rotatably assembled in a common compressor casing 14. A guide vane 2 is provided in an inlet line of a first compression stage 10 and changes an inlet air flow by changing an inlet angle of air with respect to the impeller 13. A by-pass line 16 having a by-pass valve 17 therein is connected to a part of a pressurized air passage 15 which connects a lower part of a discharge line of the third compression stage 12 to a plant in order to prevent surging by returning a part of compressed air to the middle between the first compression stage 10 and the second compression stage 11. By controlling opening of the by-pass valve 17, constant discharge control becomes possible in which discharge from the centrifugal compressor 1 is kept constant.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a centrifugal compressor that continuously supplies pressurized fluid to a plant, and in particular, the present invention relates to a centrifugal compressor that continuously supplies pressurized fluid to a plant, and in particular a flow rate value that selects a discharge flow rate while preventing surging of the centrifugal compressor. The present invention relates to a constant flow rate control device for a centrifugal compressor, which maintains the constant flow rate of a centrifugal compressor.

[Prior Art] As a compressor that efficiently and continuously supplies pressurized fluid at a constant pressure to a plant, there is a centrifugal compressor 1 configured as shown in FIG.

As shown in the figure, this centrifugal pressure 191111 is applied to the suction side of the centrifugal compressor 1 by a guide vane which changes the pressure-flow curve of the centrifugal compressor 1 by changing the inflow angle of the suction air to the impeller of the centrifugal compressor Ill. 2 is provided, and an air discharge control valve 3 is provided downstream of the discharge of the centrifugal compressor 1 to discharge a portion of the compressed air to the outside to prevent surging.

This centrifugal compressor 1 has an overload controller 4 that controls the operating load of a drive motor (not shown) that drives the centrifugal compressor.
Then, the discharge air pressure is adjusted using the pressure indicating controller 5, and the centrifugal compression al
a selector that compares an instruction from an overload controller 4 and an instruction from a pressure indicating controller 5, each of which is configured to be detected by a differential pressure transmitter 6 that measures a differential pressure downstream of l, and gives priority to one instruction; Guide vane 2 based on the analysis results of 7.
automatically adjusts the opening. The opening and closing of the air discharge control valve 3 is controlled by a flow rate indicating controller 8 based on the measured value of the differential pressure transmitter 6.

[Problems to be Solved by the Invention] By the way, as shown in FIG. 3, the above-mentioned centrifugal compressor has no problem as long as it is used at a flow rate higher than the surging flow rate, but it cannot be controlled in the flow rate range below point B. In order to do this, it is necessary to open the air discharge control valve to prevent surging and maintain a constant flow rate to the line. However, control to maintain a constant pressure while blowing air releases compressed air, resulting in a loss of energy used for compression.

[Means for Solving the Problems] The present invention aims to solve the above problems, and includes a guide vane that changes the flow rate of the compressor by changing the inflow angle of suction fluid into the impeller of a centrifugal pressure machine, and It is composed of a bypass valve that opens the bypass passage of sIl and returns the fluid downstream of the discharge to the suction side of a specific stage, and automatically controls the opening degree of the guide vane and reduces the flow rate below the limit flow rate due to guide vane throttling alone. A constant flow rate control device for a centrifugal compressor is constructed by a controller that opens a bypass valve when the flow rate is set to operate in a flow rate range.

[Function] The controller controls the opening and closing of the guide vane so that the flow rate is set by the controller. Then, the discharge flow rate of the centrifugal pressure machine a is fixed. On the other hand, when the actual weight flow rate value of the passing fluid exceeds the range that can be reduced by the guide vane and is set in the flow rate range, the controller executes correction control to open the bypass valve, so that the downstream fluid is discharged through the bypass passage. It is returned to the suction side of the specific stage, and the centrifugal compressor is operated at a constant flow rate without surging.

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

First, the configuration of a centrifugal compressor will be explained based on the flow sheet shown in FIG.

In the embodiment, the centrifugal compressor 1 is constructed by connecting three compression sections in series in the discharge direction, which suck fluid (air), compress it, and discharge it.

Each compression section 10 to 12 includes an impeller 13 and an impeller 1
The compressor casing 14 rotatably accommodates the compressor 3. The drive shafts (not shown) of each impeller 13 are connected by a drive force transmission mechanism (not shown) such as a flexible coupling or a gear coupling. i.e. one drive motor (
(not shown) so that these drive shafts are interlocked, and
A stage (multistage) centrifugal compressor 1 is configured.

In the first stage compression section 10, on the suction side, the inflow angle of the suction air with respect to the impeller 13 is changed to change the suction air flow rate.
Guide vane 2 that changes the pressure-flow curve of centrifugal compressor 1
is provided. This guide vane 2 is driven by a drive mechanism such as an actuator (not shown). In the embodiment, a portion of the compressed air is transferred downstream of the pressure fluid conveyance path 15 that connects the discharge section downstream of the three-stage compression section 12 and a plant (not shown). A bypass passage 16 is connected to the stage compression section 11 to prevent surging, and a bypass valve 17 for opening and closing the bypass passage 16 is provided in the bypass passage 16.

In this way, by providing the guide vane 2 in front of the impeller 13 of the first-stage compression section 10, the flow rate of the centrifugal compressor 1 can be adjusted. The centrifugal compressor 1 is configured so that the upstream side of the provided check valve 18 can be opened by the bypass valve 17.
Enables load/no-load switching operation.

By the way, the pressure fluid conveyance path 15 between the three-stage compression section 12 and the check valve 18 includes a differential pressure generator 24 for measuring the differential pressure downstream of the discharge of the centrifugal compressor 1, a differential pressure transmitter 6, and the discharge pressure. A pressure transmitter 25 is provided to detect the pressure, and the differential pressure transmitter 6 and the pressure transmitter 25 adjust the opening degree of the guide vane 2 and control the opening/closing of the bypass valve (such as a CPU).
The detected differential pressure value is input to the input/output section (IO boat, etc.) No. 19.

In the embodiment, the controller 19 includes an input/output section 20, a storage section 21, an arithmetic control section 22, etc., and the storage section 21 stores data according to the flow rate-discharge pressure of the centrifugal compressor 1 shown in FIG. There is a built-in program that can automatically perform the above control.

Here, the arithmetic control unit 22 controls the opening and closing of the guide vane 2 and the bypass valve 17 in accordance with switching or commands from the select switch or the remote controller 23 to keep the discharge flow rate of the centrifugal compressor 1 constant. It is configured to perform constant flow rate control that fixes the flow rate.

In other words, as shown in FIG.
Divide the flow rate section from point (1oox flow rate) to point B (50x flow rate) into multiple sections (in this example, 50.60°70...
・The opening degree of the guide vane 2 is automatically controlled to the flow rate value (X) specified by switching or commanding the select switch or remote controller 23 (separated at 10X intervals of 100X), while the detected differential pressure value The weight flow rate of the discharged fluid is calculated from the discharge pressure value, and when the calculated weight flow rate is less than a predetermined set value, the bypass valve 17 is fully opened, and when it is above the set value, the bypass valve 17 is opened properly. The configuration is such that correction control is executed to adjust the opening degree, and a portion of the fluid downstream of discharge is returned between the first-stage compression g10 and the second-stage compression section 11.

Therefore, it is possible to prevent surging that occurs due to changes in the set flow rate, and the centrifugal compressor 1 continues to operate at a specified constant discharge flow rate.

In other words, it is practically possible to move the flow rate-discharge pressure performance (■) from the high flow rate side to the low flow rate side without releasing compressed air to the atmosphere, and the range of use of the centrifugal compressor 1 can be expanded. .

However, when changing from a constant flow rate value (1) to another flow rate value (X), the calculation control unit 22 sequentially moves from the adjacent flow rate value (X) to the changed flow rate value (X). This control is configured to prevent sudden pressure fluctuations in the centrifugal compressor 1 and the plant due to sudden pressure fluctuations.

By the way, if the remote controller 23 is configured to send a control signal to the arithmetic control unit 22 to determine the select position of the select switch, the control side of the centrifugal compressor 1 and the operation side of the centrifugal compressor 1 can be controlled. Since the flow rate of the centrifugal compressor 1 can be set by simply operating the select switch on the operating side, control can be simplified.

[Effects of the Invention] As is clear from the above explanation, the present invention exhibits the following excellent effects.

The centrifugal compressor can be controlled to a flow rate value required by the plant while preventing surging of the centrifugal compressor without releasing compressed air to the atmosphere.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing a preferred embodiment of the present invention;
2 and 3 are flow rate-pressure performance diagrams of a centrifugal compressor, and FIG. 4 is a flow sheet of a conventional centrifugal compressor. In the figure, 1 is a centrifugal compressor, 2 is a guide vane, 16 is a bypass passage, 17 is a bypass valve, and 19 is a controller.

Claims (1)

[Claims] 1. A guide vane that changes the flow rate of the compressor by changing the inflow angle of the suction fluid into the impeller of the centrifugal compressor, and a bypass valve that opens the bypass passage of the compressor and returns the discharge downstream fluid to the suction side of a specific stage. and a controller that automatically controls the opening degree of the guide vane to match the set actual weight flow rate value, and opens the bypass valve when the flow rate is set to operate in a flow rate range below the limit flow rate for reduction due only to the guide vane throttle. A constant flow rate control device for a centrifugal compressor, characterized by comprising: