JPH0447197A - Turning stall preventing device for compressor - Google Patents

Abstract

PURPOSE:To prevent turning stall generated around a surge of a high pressure ratio immediately after its generation by a simple control circuit so as to obtain a compressor of high reliability by judging a signal from a shaft vibration sensor mounted onto the body outer side of a compressor to open a blow-off valve. CONSTITUTION:A shaft vibration sensor 7 detects the shaft vibration of a compressor 1, and a filter circuit 8 cuts the high frequency noise of a signal outputted from the shaft vibration sensor 7. A rectifier circuit 9 converts an a.c. signal into a specified d.c. signal corresponding to the grade of its amplitude and outputs it into an output discriminating circuit 10. The output discriminating circuit 10 generates constant voltage exceeding the preset reference voltage value according to the grade of input voltage. On the other hand, an actuator 6 is operated only when a signal is inputted from the output discriminating circuit 10 to open a blow-off valve 5. Accordingly, when large shaft vibration due to turning stall is generated, the blow-off valve 5 is opened to lower the pressure of the compressor 1 suddenly and thereby to place the compressor 1 into the unloaded state. Turning stall can be therefore avoided immediately after its generation.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a rotating stall prevention device for a compressor, and in particular, a rotating stall prevention device for a compressor suitable for preventing rotating stall that occurs near the surge limit where the pressure ratio is high. This invention relates to a stall prevention device.

[Conventional technology]

In a high pressure ratio multi-stage axial flow compressor, which has multiple rows of stator blades and rotating rows of rotor blades arranged between the rows of stator blades to form a compressor flow path in the casing, As a result of flow separation, a partially stalled region called a cell may rotate at approximately half the speed of the compressor, causing a so-called rotating stall.

As shown in the pressure-flow characteristic diagram of the compressor in Figure 3, swirling stall occurs at partial rotation speeds on the operating curve (solid line) below the design rotation speed of the compressor, as well as when the pressure ratio Some occur near the high surge limit (-dotted chain line). In the former case, the blade excitation frequency, which is the product of the number of cells and the propagation speed, is generally lower than the primary natural frequency of the blade, and the excitation force is also small, so the blade vibration stress does not become large enough to cause a problem. On the other hand, in the latter case, the pressure is high, the excitation force is large, and the number of cells is often one, resulting in imbalance with respect to the axis. This excites a large amount of vibration not only in the blades but also in the shaft, and in some cases leads to their failure. Therefore, it is important to establish a method and a device for preventing rotational stall that occurs near the surge limit where the pressure ratio is high.

Conventional devices for preventing rotational stall that occur near the surge limit when the pressure ratio is high are known as those described in JP-A-62-107293 and JP-A-63-33978.

These inventions focus on the fact that surging occurs prior to rotational stall in areas with high pressure ratios, and use surge sensors such as pressure sensors and blade vibration sensors installed in the compressor flow path to detect sudden surges caused by surging. It detects a pressure rise and operates a blow-off valve through a control circuit to prevent rotation stalls.

[Problem to be solved by the invention]

JP-A-62-107293 and JP-A-63-33
The conventional rotating stall prevention device described in Japanese Patent No. 978 detects a pressure increase due to surging using a surge sensor such as a pressure sensor or a blade vibration sensor attached to the compressor body.

However, in these surge sensors, when the temperature in the compressor flow path increases, (1) the lead wire coating melts and the insulation resistance decreases.

(2) Sensor sensitivity changes and correction is difficult.

There were other problems.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable rotating stall prevention device for a compressor that can immediately avoid a rotating stall that occurs near the surge limit where the pressure ratio is high after it occurs.

[Means to solve the problem]

In order to achieve the above object, a rotating stall prevention device for a compressor according to the present invention includes, in a casing, a plurality of rows of stator blades and a row of rotating rotor blades arranged between the rows of stator blades. In a compressor forming a machine flow path, a shaft vibration sensor mounted on the outside of the compressor main body, a control circuit that determines a signal from the shaft vibration sensor and operates an actuator,
It consists of a blow-off valve that is installed on the discharge side of the compressor and is opened and closed by an actuator.

[Effect]

First, the rotating stall phenomenon that occurs near a surge where the pressure ratio is high will be explained.

FIG. 4 is a time history waveform diagram of wall pressure fluctuations and shaft vibrations in the casing of the compressor, showing the measurement results of a rotating stall occurring in a multistage axial flow compressor.

In the figure, the amplitudes of both wall pressure fluctuations and shaft vibrations increase rapidly with the dot-dashed line as the boundary. An increase in wall pressure fluctuations is indicative of an increase in the level of rotational stall.

In this rotating stall, the number of cells (the number of cells in the circumferential direction in the stall area) is 1, and because it is unbalanced with respect to the compressor axis,
This increases shaft vibration.

Therefore, if the shaft vibration caused by a rotating stall is detected by a shaft vibration sensor attached to the outside of the compressor body, and the blow-off valve is immediately opened to place the compressor in an unloaded state, the rotating stall can be immediately avoided. can do.

The shaft vibration sensor is installed on the outside of the compressor body, so
The above-mentioned problem is solved without being directly affected by the temperature rise in the flow path.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a system diagram of a rotating stall prevention device for a compressor according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the operation of the circuit shown in FIG. 1.

In FIG. 1, a compressor 1 is a multistage axial flow compressor that includes a plurality of rows of stator blades in a casing and rows of rotating rotor blades arranged between the rows of stator blades to form a compressor flow path. , suction pipe 2
Air is sucked in through the compressor and the compressor air is discharged to the discharge pipe 3.

Note that in the case of a gas turbine, compressed air generated by a compressor is configured to serve as an air source for a combustion machine or a turbine.

A bypass pipe 4 is connected to the discharge pipe 3, and a blowoff valve 5 is provided on the discharge side thereof.

The blowoff valve 5 is closed during normal operation of the compressor 1, but can be suddenly opened by the actuator 6 in an emergency.

A shaft vibration sensor 7 is attached to the outside of the compressor 1, and detects shaft vibration of the compressor 1. The shaft vibration sensor is not easily affected by temperature rise in the flow path, for example, the bearing is mounted in a box or the like.

The filter circuit 8 cuts high frequency noise in the signal output from the shaft vibration sensor 7. The rectifier circuit 9 converts the AC signal into a DC signal as shown in FIG. 2 according to its amplitude, and outputs it to the output discrimination circuit 10.

The output discrimination circuit 10 is set to generate and output a certain voltage when it is equal to or higher than a preset reference voltage value depending on the magnitude of the input voltage, but not to output at other input voltages.

The actuator 6 operates to open the blowoff valve 5 only when a signal is input from the output discrimination circuit 10 .

When the shaft vibration sensor 7 detects a large shaft vibration due to a rotating stall as shown in FIG. 2, the actuator 6 is operated according to the process described above to open the blow-off valve 5. By opening the blow-off valve 5, the pressure of the compressor 1 rapidly drops and the compressor 1 enters a no-load state, so that rotational stall can be immediately avoided after it occurs.

According to this embodiment, a shaft vibration sensor is attached to the outside of the compressor main body, and the signal from this shaft vibration sensor is judged to open the air discharge valve. Therefore, a simple control circuit can be used to control pressure A highly reliable compressor can be obtained by immediately preventing the rotational stall that occurs near the surge where the ratio is high. Furthermore, the shaft vibration sensor is usually mounted on the compressor body, and if the rotating stall test is utilized, there is an advantage that there is no need to install the shaft vibration sensor.

Also, instead of using the filter circuit 8 and the rectifier circuit 9,
An FFT analyzer may also be used. In that case, the blowoff valve may be controlled to open when the level of shaft vibration at the rotating stall frequency is greater than a certain set value. According to this embodiment, since the frequency component due to the rotating stall can be separated from the rotational order component, etc., it is possible to prevent the rotating stall with higher accuracy.

〔Effect of the invention〕

According to the present invention, it is possible to provide a highly reliable rotating stall prevention device for a compressor that can immediately avoid a rotating stall that occurs near a surge where the pressure ratio is high after it occurs.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a rotating stall prevention device for a compressor according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of Fig. 1, and Fig. 3 is a pressure-flow characteristic curve of the compressor. Figure 4 is
FIG. 3 is a time history waveform diagram of wall pressure fluctuations and shaft vibrations of a multistage axial flow compressor. 1... Compressor, 2... Suction piping, 3... Discharge piping, 4... Bypass piping, 5... Air discharge valve, 6...
Actuator, 7... Shaft vibration sensor, 8... Filter, 9... Rectifier circuit, 10... Output discrimination circuit. Map w: J2TZJ Kuzuzu, Kunoun LQ Kyouzu

Claims (1)

[Scope of Claims] 1. A compressor comprising, in a casing, a plurality of rows of stator blades and a row of rotating rotor blades arranged between the rows of stator blades to form a compressor flow path, the compressor comprising: A shaft vibration sensor mounted on the outside of the main body, a control circuit that judges a signal from the shaft vibration sensor and operates an actuator, and an air release valve that is opened and closed by the actuator. Rotational stall prevention device for compressors.