JPH01271700A - Centrifugal compressor - Google Patents

Abstract

PURPOSE:To suppress the reduction of discharge pressure and prevent the generation of surging by setting an upper limit value of the discharge pressure to that on a line for surging prevention by means of a pressure adjustor, while providing an aperture detecting means for an inlet guide blade. CONSTITUTION:Pressure signals according to a detection of a pressure detector 19 are input to a pressure adjustor 22, while aperture signals according to a detection of an aperture detector 1 which detects an aperture of an inlet guide blade 13 are input through a computer 2. The pressure adjustor 22 is preset such that a surging preventing pressure against an optional aperture of the inlet guide blade 13 is an upper limit value of a discharge pressure for switching a volume control to a blow-off control of a compressor main body 11, and when the detected discharge pressure is exceeding the preset pressure, the blow- off control is performed.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a centrifugal compressor which is used in, for example, a chemical plant and whose flow rate and discharge pressure are adjusted by an inlet guide vane and a blow-off valve or a bypass valve. It's about machines.

(Prior Art) Conventionally, a centrifugal compressor shown in FIG. The opening degree is adjusted as appropriate by an operating device 15 operated by the following. On the other hand, a flowmeter orifice 17 is interposed in the discharge passage 16 of the compressor main body 11, and a differential pressure detector 18 is attached to this orifice 17.
A pressure detector 19 is attached to the discharge passage 16 on the side of the compressor main body 11, and an air discharge flow is provided with an air discharge valve (or bypass valve) 20 branched from the discharge passage 16 on the downstream side of the orifice 17. Route 2.1 is provided.

Then, the pressure signal detected by the pressure detector 19 is input to the pressure regulator 22, and the differential pressure signal detected by the differential pressure detector l8 is input to the pressure regulator 22 via the calculator 23 to adjust the pressure. The air discharge valve 20 is controlled by a total of 22.

Specifically, in the compressor performance curve shown in Fig. 2 (horizontal axis: discharge gas flow rate Q, vertical axis: discharge pressure P), straight line l is the surge line, straight line ■ is the surge sig prevention line, and each of the curve group ■ is Opening degree θ1 of the inlet guide vane 13. In the curve showing the state inside the discharge flow path 16 at θ, . . . , when point A is set as the normal operating point, the following control is performed.

That is, the differential pressure detected by the differential pressure detector 18 is converted into a signal corresponding to the flow rate Q by the calculator 23, and this signal is used as an input signal for automatic setting of the pressure regulator 22. The set pressure of the pressure regulator 22 is set in proportion to this input signal. For example, when the opening degree of the inlet guide vane 13 is 08, if the flow rate is Q, the set pressure is P, and the detected discharge The pressure is P.

If the pressure is on the rise, the air discharge valve 20 is opened to suppress the discharge pressure to the PI value to prevent surge sig from occurring.

, Similarly, when the opening degree is θ,, θ,..., the discharge pressure is P,, P when the flow rate is Q,, Q,..., respectively.
s... becomes the set pressure of the pressure regulator 22.

In addition, in the region below the set pressure, the capacity and pressure of the compressor main body are controlled by adjusting the opening degree of the inlet guide vanes 13.

(Problems to be Solved by the Invention) In the conventional device described above, flow measurement is required and the orifice 17 is used, which causes pressure loss in this part and reduces the discharge pressure from the compressor main body 11. There is a problem with getting bigger. Furthermore, in order to improve the accuracy of flow rate measurement, straight piping sections of a certain value or more are required before and after the orifice 17, and there are problems such as a large installation requiring space.

The present invention has been made to address these conventional problems, and aims to provide a centrifugal compressor that can reduce the drop in discharge pressure and can be installed in a small space.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides an inlet guide vane which is a flow rate = pressure regulating means on the suction side of the compressor main body, and a pressure detection vane on the discharge side of the compressor main body. means.

Comprising a pressure regulating means and a discharge valve or a bypass valve for releasing part or all of the discharged gas from the discharge flow path,
In a centrifugal compressor that uses both the capacity control of the main body and the blow-off valve control or the bypass valve control, the opening degree of the inlet guide vane is detected, and this opening degree signal is sent to the Inlet guide vane opening detection means is provided for inputting input to the adjustment means, and the pressure adjustment means switches from capacity control of the main body to blow-off valve control or bypass valve control. The upper limit value of the discharge pressure was set to the discharge pressure on the surge sig prevention line for a preset arbitrary opening degree of the inlet guide vane.

(Example) Next, an example of the present invention will be explained according to the drawings. Fig. 1 shows a centrifugal compressor according to a first example of the present invention,
The centrifugal compressor shown in FIG. 4 is substantially the same except for a part of the control system of the blow-off valve 20, and corresponding parts are given the same reference numerals and a description thereof will be omitted.

As shown in the figure, in this centrifugal compressor, a pressure signal detected by a pressure detector 19 is input to a pressure regulator 22, and an opening signal detected by an opening detector l that detects the opening of the inlet guide vane 13 is input. is inputted via the arithmetic unit 2. Then, as shown in FIG. 2, the entrance guide vane 1
3, each opening degree θ,.

At θt..., the inherent surge sig prevention pressure is PI
+Pt... is present, so the pressure regulator 22 is used as the upper limit of the discharge pressure to switch the surge prevention pressure for any opening degree from the capacity control of the compressor main body 11 to the blow-off valve control.
is set in advance, and when the detected discharge pressure is about to exceed the set pressure, the air discharge valve is controlled. For example, by adjusting the opening degree of the inlet guide vanes 13 as appropriate,
When the capacity control operation is continued, if the discharge pressure detected when the opening degree of the inlet guide vanes 13 is 01 is about to exceed the set pressure P, the opening degree of the inlet guide vanes 13 is not changed, While keeping the capacity of the compressor body constant, the air discharge valve 2
By opening 0 and letting some of the discharged gas escape to the atmosphere,
The flow rate of the discharged gas pumped through the discharge flow path can be adjusted without causing a surge signal.

Next, FIG. 3 shows a centrifugal compressor according to a second embodiment of the present invention, which is adapted to handle the case where the temperature of the suction gas changes depending on the time or season. are given the same number and the explanation will be omitted.

In this centrifugal compressor, a temperature detector 3 is attached to the suction flow path 12, and a suction gas temperature signal detected thereby is sent to a calculator 4.
is inputted to correct the change in the compressor performance curve due to temperature, so that the setting pressure value in the pressure regulator 22 is determined without the influence of temperature.

In addition, although the above-mentioned example showed what was branched from the discharge flow path 16 and provided the flow path 21 for blowing air, the present invention is not limited to this, and the flow path 21 for blowing air is branched from the discharge flow path 16. Instead, the suction flow path branches off from the discharge flow path 16 and passes through a bypass valve that is an on-off valve!
2 may be provided with a bypass flow path. In this case, bypass valve control similar to that described above is performed instead of the above-mentioned blow-off valve control.

Further, although the above embodiment uses a pressure regulator 22 that continuously controls the opening degree of the blow-off valve 20 based on the input pressure signal, the present invention is not limited to this. In addition, as shown in FIG. 4, it also includes a pressure switch 2 that only opens and closes a blow-off valve 20.

That is, FIG. 4 is different from the pressure regulator 22 shown in FIG.
In place of the pressure switch 23. Except for the provision of a two-way solenoid valve, the other parts are substantially the same, and corresponding parts are given the same numbers.

This pressure switch 23 has a function of automatically changing the set pressure according to the input signal from the calculator 2,
On the other hand, the three-way solenoid valve 24 has a diaphragm actuator, and when the discharge pressure exceeds the set pressure, the pressure switch 2
Based on the signal from 3, the air from the diaphragm actuator is released in a short time to switch the blow-off valve 20 from fully closed to fully open.

(Effects of the Invention) As is clear from the above description, according to the present invention, the inlet guide vane detects the opening degree of the inlet guide vane and inputs this opening degree signal to the pressure regulating means via the calculator. In addition to providing an opening detection means, the upper limit of the discharge pressure for switching from compressor main body capacity control to blow-off valve control or bypass valve control is set in advance by the pressure regulating means to prevent surge sig for any opening of the inlet guide vane. Set the discharge pressure on the line. Therefore, there is no need to install an orifice in the discharge flow path that causes pressure loss and requires a straight pipe section of a certain value or more before and after the orifice, which reduces the drop in discharge pressure and allows for a small installation. This has the effect that the discharge gas flow rate can be adjusted in a space without causing a surge signal.

[Brief explanation of the drawing]

FIG. 1 shows a gas compressor of a centrifugal compressor according to a first embodiment of the present invention.
A control system diagram, FIG. 2 is a compressor performance curve diagram, and FIG. 3 is a gas/control system diagram of a centrifugal compressor according to the second embodiment of the present invention.
FIG. 4 shows a gas compressor of a centrifugal compressor according to a third embodiment of the present invention.
Control System Diagram FIG. 5 is a gas/control system diagram of a conventional centrifugal compressor. l... Opening degree detector, 2... Arithmetic unit, Il... Compressor main body, 18... Inlet guide vane, 19... Pressure detector, 20... Air discharge valve, 2 tons・・Air flow channel, 22...
Pressure regulator 23...pressure switch. Patent applicant: Agent of Kobe Steel, Ltd.
Patent attorney Aobai Ao and 1 other person Figure 1 Figure 2 yi 0 01 Q@Qs 040s, i Quantity. Figure 5

Claims (1)

[Claims] (1) An inlet guide vane serving as a flow rate and pressure adjustment means on the suction side of the compressor body, a pressure detection means and a pressure adjustment means on the discharge side of the compressor body, and a part or all of the discharge gas from the discharge flow path. In a centrifugal compressor that is equipped with a blowoff valve or a bypass valve for air relief, and that uses both the capacity control of the main body and the blowoff valve control or bypass valve control, the opening degree of the inlet guide vane is detected. , an inlet guide vane opening detecting means is provided for inputting this opening signal to the pressure regulating means via a computing unit, and the pressure regulating means switches from capacity control of the main body to blow-off valve control or bypass valve control. A centrifugal compressor characterized in that an upper limit value of discharge pressure is set to a discharge pressure on a surge sig prevention line for an arbitrary opening degree of an inlet guide vane set in advance.