JPH01211696A - Compressor rotating stall prevention device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

[Prior Art] A high pressure ratio multi-stage axial flow compression system that includes a plurality of stator blade rows and rotating rotor blade rows arranged between the stator blade rows to form a compressor flow path in a casing. In an aircraft, the flow from the blade row is
Due to the separation, a partially stalled part called a cell may rotate at a speed of about half of the compressor rotational speed, resulting in so-called rotating stall.

As shown in the pressure-flow characteristic diagram of the compressor in Fig. 3, swirling stall occurs at partial speeds on the operating curve (solid line) below the design 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 cell 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 and the excitation force is large, and since the number of cells is often one, it is also unbalanced with respect to the axis. This excites a large amount of vibration not only in the blades but also in the shaft, which may lead to their breakage in some cases. Therefore, techniques for predicting and preventing rotating stalls that occur near the surge limit where the pressure ratio is high are important.

It is difficult to understand the phenomenon of rotating stall that occurs near the surge limit when the pressure ratio is high, and no complete prevention method or device has yet been developed.

Conventional general methods and devices for preventing rotating stalls are aimed at rotating stalls in regions where the pressure ratio is relatively low. The basic method is to control the rotation speed and stator blade angle so as not to enter the unstable operating range based on the pressure-flow characteristics of the compressor determined in advance through experiments. 53-77308 and those described in Japanese Utility Model Application Publication No. 51-87709 are known.

On the other hand, as a device for preventing rotational stall that occurs near the surge limit where the pressure ratio is high, there is known a device described in JP-A-62-107293.

The first invention described in the publication focuses on the fact that surging occurs prior to rotational stall in a region where the pressure ratio is high, and uses a surge sensor such as a pressure sensor installed in the compressor flow path to detect sudden surging caused by surging. It detects a pressure increase, determines the magnitude of the time differential of the pressure increase signal, and operates a blow-off valve or the like to prevent a turning stall.

In addition, the second invention provides, instead of determining the time differentiation of the pressure increase signal in the first invention, a certain time delay is generated for the pressure increase signal, and the original pressure whose sign is reversed from that signal is generated. This is to find the sum with the rising signal.

[Problems to be Solved by the Invention] In the conventional technology described in JP-A-53-77308, which targets rotational stall in a region where the pressure ratio is relatively low, the rotational stall that occurs near the surge limit where the pressure ratio is high is This was not necessarily sufficient to prevent stalling.

That is, 1) It is difficult to accurately determine the pressure-flow characteristics of the compressor near the surge limit.

2) In the high pressure ratio region, it is difficult to improve the pressure-flow characteristics of the compressor simply by controlling the rotation speed and stator vane angle.

It was insufficient in such respects.

On the other hand, when determining the magnitude of the time differential as in the first invention described in JP-A-62-107293, there is a possibility of malfunction due to pressure fluctuations due to blade row interference other than pressure increase due to surging. expensive.

Further, in the method of forcibly generating a phase difference, as in the second invention described in the same publication, there is a lot of uncertainty in how to determine the set value of the phase difference, and it is actually a cumbersome process.

As described above, the conventional techniques targeting rotational stall in a high pressure ratio region are not necessarily sufficient for practical use.

The present invention has been made to solve the above-mentioned problems in the prior art, and is capable of reliably preventing rotating stall in advance that occurs near the surge limit where the pressure ratio is high, and achieving highly reliable rotating stall of a compressor. Its purpose is to provide a preventive device.

[Means for Solving the Problems] In order to achieve the above object, the rotating stall prevention device for a compressor according to the present invention has a configuration in which a plurality of stator blade rows and a plurality of stator blade rows are arranged between the stator blade rows in a casing. a compressor comprising a row of rotor blades that rotates to form a compressor flow path; a surge sensor provided in the compressor flow path; and a control circuit that determines a signal from the surge sensor and operates an actuator. , a rotating stall prevention device for a compressor comprising a blow-off valve means provided on the discharge side of the compressor and opened and closed by the actuator, wherein the surge sensor is arranged at different axial directions in the compressor flow path. A sign inverting circuit that inverts the sign of the signal from one of the two surge sensors, and another surge sensor that does not invert the sign of the signal from the sign inverting circuit. The control circuit is composed of an adder circuit that adds the signals from the adder circuit, and an output determination circuit that determines the magnitude of the signal from the adder circuit and outputs a predetermined signal to the actuator.

[Operations] First, the rotating stall phenomenon that occurs near the surge limit where the pressure ratio is high will be explained.

FIG. 4 is a time history waveform diagram of wall pressure, stationary blade strain (stress), and shaft vibration in the casing of the compressor, showing the measurement results of a rotating stall that occurred in a multistage axial flow compressor. The characteristics of these waveforms are temporally composed of the following three stages.

In the first stage, a sudden pressure change occurs in all stages of the compressor at almost the same time, and immediately after that, high stress occurs in the blades due to the increase in static pressure, and a slight change in shaft vibration occurs.

Second stage: Although the steady pressure is high, the unsteady fluctuation component remains at a lull, and the fluctuation component gradually increases. Blade vibration also has a large steady component, with a slight fluctuation component on top of that, but there is no major change in shaft vibration.

Third stage: Periodic pressure fluctuations become considerably large.

As a result, blade and shaft vibrations increase.

Judging from the characteristics of the waveform, the pressure change in the first stage is similar to the characteristics when surging occurs, which is mainly caused by -dimensional unsteady flow, considering the operating situation at a high pressure ratio. Furthermore, in the third stage, judging from the fluctuation frequency etc.
It is a rotating stall with one cell and a propagation speed of about half the compressor rotation speed.

In other words, it can be seen that the characteristics of the rotating stall of one cell occurring at a high pressure ratio and the surging occur in advance.

On the other hand, surging is a propagation phenomenon of pressure pulsations in the axial direction. Therefore, if pressure is detected at two different points in the axial direction, the pressure waveforms will have a phase difference from each other.

From the above, it is highly likely that a rotating stall where a high pressure ratio occurs is caused by a sudden pressure change such as surging, so it is difficult to compare the sudden pressure change with the pressure change between two points in the axial direction. If a phase difference is detected and the blowoff valve is immediately opened to create a no-load state, a turning stall can be prevented.

[Example] An example of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a system diagram of a rotary stall prevention device for a compressor according to an embodiment of the present invention, and FIGS. 2(a) and 2(b).

(c) is an explanatory diagram of the operation of the circuit of FIG. 1.

In FIG. 1, although the structure is not shown, a compressor 1 includes a plurality of rows of stator blades and a row of rotating rotor blades arranged between the rows of stator blades in a casing to form a compressor flow path. This is a multi-stage axial flow compressor that sucks air through an intake pipe 2 and discharges compressed air to a discharge pipe 3.

Note that in the case of a gas turbine, the compressed air generated by the compressor is configured to serve as an air source for the combustor and the 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 is configured so that it can be suddenly opened by an actuator 6 in an emergency.

Inside the compressor 1, there is a casing that forms a compressor flow path.
Two surge sensors, for example pressure sensors 7a and 7b, are installed at intervals in the axial direction, and detect pressure fluctuations within the compressor 1. Pressure sensor 7
It is preferable that a and 7b be installed as close as possible to prevent the difference in DC components of their pressures, that is, the difference in static pressure between the two installation points, to be too large.

Pressure transducers 8a and 8b are pressure sensors 7a and 7, respectively.
The pressure from b is electrically converted and output to filter circuits 9a and 9b. Filter circuits 9a and 9b cut high frequency noise. The sign inversion circuit 10 generates a signal as shown in the solid line in FIG. 2(b) in which the sign of the signal is inverted with respect to the signal shown in the solid line in FIG. 2(a) output from the filter 9a. In the addition circuit 11, the sign inversion circuit 10
The signal from the filter 9b and the signal shown by the broken line in FIG. 2(b) from the filter 9b are added and synthesized, and a signal shown in FIG. The output discrimination circuit 12 generates and outputs a certain voltage that is above or below a preset reference voltage value depending on the magnitude of the input voltage, but is set not to output any other input voltage. ing.

The actuator 6 operates to open the blowoff valve 5 only when a signal is input from the output discrimination circuit 12 .

When the pressure sensors 7a and 7b detect a sudden pressure change immediately before a turning stall as shown in FIG. Open valve 5. By opening the blow-off valve 5, the pressure of the compressor 1 suddenly drops and the compressor 1 enters a no-load state, thereby making it possible to prevent rotational stall.

According to this embodiment, two pressure sensors 7 are provided in the compressor flow path.
a and 7b are installed, and the signals from these pressure sensors are judged to open the air discharge valve 5, so a relatively simple control circuit can prevent the rotational stall that occurs near the surge limit where the pressure ratio is high. It is possible to securely prevent damage in advance and obtain a highly reliable compressor.

Instead of the blowoff valve 5, a rupture disk may be employed in the bypass pipe 4 as the blowoff valve means. In this case, the actuator 6 destroys the rupture disk and releases air in response to the signal from the output discrimination circuit 12. When using a rupture disk, there is an advantage that air can be released more rapidly than with an air release valve.

Furthermore, the surge sensor may be a vibration sensor such as a strain gauge, an acceleration pickup, or a displacement sensor that detects blade vibration instead of the pressure sensor. In this case, in order to remove blade vibrations caused by normal fluid force, it is better to pass through a low-pass filter that removes low-frequency signals.

[Effects of the Invention] As described above, according to the present invention, a highly reliable rotating stall prevention device for a compressor is provided, which reliably prevents rotating stall that occurs near the surge limit where the pressure ratio is high. can do.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a rotary stall prevention device for a compressor according to an embodiment of the present invention, and FIGS. 2(a) and 2(b). (c) is an explanatory diagram of the operation in Fig. 1, Fig. 3 is a pressure-flow characteristic diagram of the compressor, and Fig. 4 is the wall pressure and stator blade strain (stress) in the casing of a multistage axial flow compressor. . and a time history waveform diagram of shaft vibration. 1.Compressor, 2.Suction piping, 3.Discharge piping, 4.
Bypass piping, 5...Air discharge valve, 6 Actuator, 7
a, 7b・Pressure sensor, 10・Sign inversion circuit, 11...
Addition circuit, 12...output discrimination circuit.

Claims (1)

[Claims] 1. A compressor that includes a plurality of stator blade rows and rotating rotor blade rows arranged between the stator blade rows to form a compressor flow path in a casing; A surge sensor provided in the road, a control circuit that operates an actuator based on a signal from the surge sensor, and a blow-off valve provided on the discharge side of the compressor and opened and closed by the actuator. In the rotating stall prevention device for a compressor, the surge sensor is arranged in two different axial directions in the compressor flow path.
A sign inverting circuit that inverts the sign of the signal from one of the two surge sensors, and another one that does not invert the sign of the signal from the sign inverting circuit.
an adding circuit that adds signals from two surge sensors;
A rotating stall prevention device for a compressor, characterized in that a control circuit includes an output discrimination circuit that discriminates the magnitude of a signal from the addition circuit and outputs a predetermined signal to an actuator. 2. The rotating stall prevention device for a compressor according to claim 1, wherein the two surge sensors are pressure sensors attached to a casing forming a compressor flow path. 3. The rotating stall of the compressor according to claim 1, wherein the two surge sensors are vibration sensors attached to blades of either the stator blade row or the rotor blade row. Prevention device. 4. The compressor according to claim 1, wherein the blow-off valve means is a blow-off valve connected to a bypass pipe on the discharge side of the compressor and attached to the bypass pipe. Turning speed prevention device. 5. The rotary stall device for a compressor according to claim 1, wherein the blow-off valve means is a rupture disk that can be destroyed by an actuator.