JPS58180798A - Surge prevention control method for compressor - Google Patents

Abstract

PURPOSE:To perform the surge prevention control without employing a flow meter, by multiplying the boosting ratio of a compressor and the measurement of the inlet pressure while operating a regulation valve such that said multiplied level and the outlet pressure of compressor will match. CONSTITUTION:The boosting ratio Po/Ps calculated by a function generator 14 and the measurement of a pressure gauge 16 for measuring the inlet pressure Ps of a centrifugal compressor are provided to a multiplier 15 and the output is employed as the setting of a pressure detection regulator 17. The outlet pressure Po from said compressor 1 is employed as the control value and a regulation valve 11 provided in a circulation piping 10 is operated to match said value with the setting. Consequently even when the rotation N of rotor or the inlet pressure Ps are varied, said compressor 1 can be operated with proper boosting ratio Po/ Ps thus to prevent the surge.

Description

[Detailed description of the invention] The present invention relates to a surge prevention control method for a compressor.

FIG. 1 is a system diagram for explaining a conventional surge prevention control method for a centrifugal compressor.

In Fig. 1, the gas flowing in from the pipe 3 is as follows.

It passes through the check valve 4, enters the inlet drum 5, and then enters the drive machine 2.
It is compressed by centrifugal compressor driven by IK & The gas whose temperature has become high after being adiabatically compressed by the centrifugal compressor 1 is cooled by a cooler 6 at the outlet of the centrifugal compressor 1, and is cooled by a check valve 7. It flows through the shutoff valve 8 into the pipe 9.

Further, a control valve 11 is provided in the middle of the circulation pipe 10 for circulating gas from the outlet of the cooler 6 to the inlet side of the inlet drum 5. By adjusting the control valve 11, the circulation pipe The flow rate flowing through 10 can be adjusted. The flow rate detection controller 12 serves to detect the flow rate of gas flowing into the centrifugal compressor 1 and to operate the control valve 11 so that the detected flow rate matches a preset value.

Figure 2 is a performance curve diagram with the rotational speed N of the centrifugal compressor shown in Figure 1 as a parameter, where the horizontal axis is the flow rate Q and the vertical axis is the boost ratio!
Io/IIg (suction pressure is Ps, discharge pressure is Pa).

As is clear from Figure 2, the performance curve of the centrifugal compressor is 9
When the rotational speed N is constant, when the flow rate Q is increased, the inlet pressure P8 and the outlet pressure P- of the centrifugal compressor.

The pressure increase ratio Po/P8, which is the ratio of , decreases, and when the flow rate Q is decreased, the pressure increase ratio P o/P a increases. If the flow rate Q is further decreased to be below a certain limit, a surging phenomenon occurs in which the pressure and flow rate become unstable, and the centrifugal compressor 1 may be damaged.

The critical flow rate at which this surging phenomenon begins to occur is the rotational speed N.
The line that connects each limit flow rate that differs depending on the rotation speed N is generally called a surge line. It is necessary to operate where the flow rate Q is higher than that of line SG.

Therefore, in the conventional surge prevention control method, the dashed line L in Fig. 2
The flow rate Q' indicated by ' is the setting value of the flow rate detection controller 12, the flow rate flowing into the centrifugal compressor 1 is the control amount, and the control valve 1 is
The surging phenomenon is prevented by controlling the flow rate flowing into the centrifugal compressor 1 to a flow rate Q' indicated by a broken line L' in FIG. 2 using the valve opening degree of 1 as a manipulated variable.

However, in the conventional flow rate detection controller 12, the flow rate is directly detected by a flow meter, and in general, a flow meter is more difficult to repair than a pressure gauge or the like.

It is expensive and has the drawback that the upper and lower values tend to fluctuate, making control unstable.

The present invention is designed to perform surge prevention control without using a flow meter with these drawbacks, and measures the rotor rotation speed of the compressor, and compares the measured value with the preset rotor rotation speed and boost ratio. Calculate the boost ratio corresponding to the measured value of the rotor rotation speed from the relationship, multiply the calculated boost ratio by the measured value of the compressor inlet pressure, and the multiplied value matches the measured value of the compression-like outlet pressure. It is an object of the present invention to provide a surge prevention control method for a compressor, which is characterized in that a control valve provided in a circulation pipe connecting an outlet pipe and an inlet pipe of the compressor is operated.

The present invention will be specifically explained below with reference to FIGS. 3 to 5. FIG. 3 is a system diagram to which the centrifugal compressor surge prevention control method according to the present invention is applied, and FIG. 4 is a performance curve diagram of the centrifugal compressor.

Gas flowing in from the pipe 3 flows through the same system as that shown in FIG. Note that in the drawings, the same reference numerals as those shown in FIG. 1 indicate the same members.

In the present invention, the rotor rotation speed N of the centrifugal compressor 1 is measured directly by the detector 13 or indirectly from the rotor rotation speed of the drive machine 2, and the measured value is input to the function generator 14.

The function generator 14 has a relationship between the rotor rotational speed N and the boost ratio Po/P@ shown in the broken line L1 shown in FIG. Therefore, it is pre-installed in analog form. Therefore, when the measured rotor rotational speed N is input to the function generator 14, the broken line L' in FIG. 4 corresponding to the rotor rotational speed N is
The step-up ratio P o/P s is calculated and output.

This is the calculated fixed value of the step-up ratio P o/P s output by the function generator 14.

The boost ratio P o corresponding to the rotor rotational speed N indicated by the broken line L'
The control valve 11 is installed in the circulation pipe 10 so that the set value and the control amount match, with the outlet pressure PO of the centrifugal compressor I being the control amount. Operate the valve opening degree.

Therefore, even if the rotor rotational speed N or inlet pressure Ps changes, the centrifugal compressor 1 can be operated at the boost ratio Po/Ps above the broken line L' in FIG. 4, and the surge line SG will not be exceeded. , it is possible to reliably prevent the occurrence of surging phenomena.

FIG. 6 is a system diagram for explaining another embodiment of the present invention.
When the control valve 19 is controlled to be constant by operating the control valve 19, the output of the function generator 14 is amplified by the amplifier 18 so that the set value of the inlet pressure control becomes the amplification rate, and the pressure detection controller 1
The setting value may be set to 7.

Although the present invention has been specifically explained based on an embodiment in which the present invention is applied to a centrifugal compressor, the present invention is not limited to this embodiment; it is also applicable to an axial flow compressor, a mixed flow compressor, etc. Applicable.

As specifically explained above, according to the present invention, it is possible to perform surge prevention control of a compressor without using a flow meter, which is difficult and expensive to repair, and which has the drawbacks that the detected value tends to fluctuate and the control becomes unstable. There are advantages to doing so.

[Brief explanation of the drawing]

Fig. 1 is a system diagram for explaining the conventional surge prevention control method for a centrifugal compressor, Fig. 2 is a performance curve diagram of the centrifugal compressor, and Fig. 3 is a diagram showing the control method according to the present invention. FIG. 4 is a diagram showing its performance curve, FIG. 5 is a diagram showing the correlation between p-Talo rotation and boost ratio, and FIG. 6 is a system diagram for explaining another embodiment of the present invention. be. 1... Centrifugal compressor, 2... Drive machine, 3, 9... Piping. 4.7...Check valve, 5...Inlet drum, 6...Cooler. 8...Shutoff valve, 10...Circulation piping, 11.19...
·Control valve. 12'...Flow rate detection controller, 17.20...Pressure detection controller. Figure 1 Figure 12 Figure U' Flow IQ Figure 3 Figure 4 Flow Q

Claims (1)

[Claims] Measure the rotor rotation speed of the compressor, and calculate the boost ratio corresponding to the measured value of the rotor rotation speed from the relationship between the measured value, the rotor rotation speed, and the boost ratio set in advance. boost ratio and compressor input. Multiply the measured value of the mouth pressure by the measured value of the compressor outlet pressure, and operate the control valve installed in the circulation pipe connecting the compressor outlet pipe and the inlet pipe so that the multiplied value matches the measured value of the compressor outlet pressure. A surge prevention control method for a compressor, characterized in that: