JPS62126296A - Bleeder of axial-flow compressor - Google Patents

Abstract

PURPOSE:To remove the possibility of unstable flow through a bleed part by making the sectional area of an open port variable through which bleed air flows into a main current passage when a multi-stage axial-flow compressor is operated. CONSTITUTION:A movable ring 12 which can be slided axially is disposed on the internal face of a bleed chamber 6 located downstream from the bleed port 5 of a compressor. The movable ring 12 is moved by an actuator 13, that is, slided downstream to enlarge the sectional area of the bleed port when a compressor runs at a low speed with a large amount of bleed air and oppositely, slided to reduce the sectional area of the bleed port when the compressor rung at a high speed. Hence, the compressor can operate in a stable state throughout the range from the low speed range to the high speed range, whereby preventing unstable flow through the bleed part.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a multi-stage axial flow compressor, particularly to startup.

This invention relates to an air bleed system for an axial flow compressor that ensures stable operation over the entire operating range during stoppage and full load operation.

[Conventional technology]

For multi-stage axial flow compressors, low rotational speed (starting, stopping, etc.)
There is a significant difference in the internal flow between high-speed rotation and high-speed rotation (rated operation), resulting in unstable flow during low-speed rotation. Therefore, if no flow stabilization measures are taken during low-speed rotation,
When starting up, the wings may be damaged or the aircraft may not be able to start up.

The three main methods that have been conventionally adopted as flow stabilization measures at low speeds are i) variable stator vanes, it) two-shaft type, and in) bleed air. The above-mentioned conventional method is discussed in the literature "Blowers and Compressors" by Gyudon, pages 230-231. Figure 3 shows the structure of a conventional axial flow compressor with bleed. In the case of Figure 0, there are 13 stages. This is an example of an axial flow compressor.Rotor 1
The rotor blades 2 are arranged on the outer periphery of the casing 3, and the stator blades 4 are arranged on the inner periphery of the casing 3. , an air bleed port 5 is installed on the inner wall of the casing between the 6th stage stator vane and the 7th stage stator vane. In this case, the air bleed port is in the form of a continuous slit in the circumferential direction, but a multi-hole type air bleed port in which a large number of holes are disposed intermittently in the circumferential direction may be used. An air bleed chamber 6 having a donut-shaped space is provided around the outer periphery of the air bleed 5.

Collects incoming airflow from the bleed port. Around the periphery of the bleed chamber,
Furthermore, a plurality of exhaust pipes 7 are provided and configured to discharge the bleed air flow to the outside via a bleed valve 8.

[Problem that the invention seeks to solve]

In the conventional example above, the ratio of the exhaust airflow from the bleed port to the main flow is at low speed rotation (for example, below 80% of the rated rotation speed)
It is large (for example, about 20%), but it becomes zero or very small (several % for cooling or sealing) during high-speed rotation. During low-speed rotation, pressure does not rise in the rear stage, so the volumetric flow rate becomes excessive and a choke condition occurs. For this reason,
The upstream stage suffers from insufficient flow, causing the blade row to stall. Therefore, by discharging the airflow from the air bleed port provided at the intermediate stage, a large flow rate can be sent to the upstream stage, making it possible to avoid stalling. A more detailed explanation of the effect of bleed air is given in the above-mentioned article by Gyudon entitled "Blowers and Compressors".

In recent years, the pressure ratio of compressors has been increased, but as the pressure ratio is increased, the difference between the flow at low speed and high speed increases.
It becomes noticeable. Therefore, as high pressure ratio compressors become
The amount of extracted air tends to increase.

In order to increase the amount of bleed air, the area of the bleed port must be increased. Therefore, in recent years, high pressure ratio compressors have come to have a significantly larger bleed port area than conventional compressors. In such a multi-stage axial flow compressor with a large bleed area, there has recently been an accident in which a blade was damaged due to stable flow in the bleed section during rotation of the rated rotary plate. Two phenomena are thought to be the cause of this. One is the case where large pressure fluctuations occur due to air column resonance in the bleed chamber during rated operation when the mainstream flow rate is large, giving excessive vibration stress to the blades. The second phenomenon will be explained using FIG. 4. FIG. 4 shows a cross section taken along the line - in FIG. 3. As mentioned above, during rated operation, the bleed air flow rate is almost zero, but because the bleed port area and the bleed chamber volume are large, there is a flow 9 in which the air flows around the bleed chamber in the circumferential direction, and a flow 1 flowing into the main stream.
0 or, conversely, a flow 11 flowing from the mainstream to the bleed port.

When there is such a flow, the rotor blade is subjected to several excitation forces during one rotation, and in severe cases, the blade may be damaged.

As mentioned above, in the conventional bleed structure with a high pressure ratio, large bleed port area, and large bleed chamber volume, the flow in the bleed section becomes unstable when rotating at high speeds such as the rated M@, and when the rotation becomes extreme, the blades may be damaged. It had some flaws.

The purpose of the present invention is to eliminate the instability of the flow in the bleed section that occurs during high-speed operation such as rated operation in a high pressure ratio axial flow compressor with a large bleed port area and bleed chamber volume, and to An object of the present invention is to provide a bleed structure for an axial flow compressor that can ensure stable operation in all operating ranges.

[Means for solving problems]

As mentioned earlier, there are two reasons for stable flow in the bleed section (
There is air column resonance and flow flowing in and out of the bleed port), but both of these are caused by the bleed port area and bleed chamber volume being too large. A large bleed port area and volume are necessary during low-speed operation, but are not only unnecessary but harmful during high-speed operation.

The present invention was developed based on the above considerations, and aims to eliminate unstable flow in the bleed section by changing the area of the axial air port between low speed and high speed.

[Effect]

Sufficient air bleed port area is ensured at low speeds.

It is kept fully open, but the area of the bleed port is closed during high-speed operation when no bleed air is required.6 If the bleed port is fully open or small, two phenomena (air column resonance and Since there is no flow in and out of the air bleed port, stable operation is ensured over the entire operating range.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. A movable ring 12 that is slidable in the axial direction is provided on the inner surface of the bleed chamber 6 at a position downstream of the bleed port 5.

The movable ring 12 is connected to a reciprocating drive 13 (such as an actuator). According to the above configuration, during low speed rotation with a large amount of bleed air, the movable ring 12 can be slid downstream to expand the bleed port area. In addition, during high-speed operation when air bleed is not required, the movable ring 12 can be slid upstream to keep the bleed port closed or close to closed, eliminating the cause of stable flow in the bleed part and ensuring stable operation. becomes possible.

Next, another embodiment of the present invention will be described with reference to FIG.

A movable ring 14 with a collar that is slidable in the axial direction is provided on the inner surface of the bleed chamber 6 at a position downstream of the bleed port 5. A disc-shaped collar 15 is provided on the inner surface of the movable collar 14, and has a space between it and the casing 3 for a high pressure chamber 16 and a low pressure chamber 17.

A spring 18 is provided inside the low pressure chamber 17. A vent hole 19 is provided in the outer wall of the flow path downstream of the stationary blade after the air bleed port, and is communicated with the high pressure chamber 16 .

In the case of such a configuration, when the rotation speed is low, the movable collared ring 17 is pushed downstream by the action of the spring 18, and the area of the air bleed port becomes large. At high speeds where pressure increases, there is a pressure difference between the pressure downstream of the stator blade and the bleed chamber pressure.

It acts on the collar 15, overcomes the spring force, and slides the movable collar 17 toward the upstream side. Therefore, the bleed port area is closed or nearly closed during high rotation, and stable operation of the compressor is ensured.

〔Effect of the invention〕

As explained above, according to the present invention, the bleed port area can be changed between low rotation and high rotation of the compressor, so the bleed port can be closed or close to closed during high rotation. I can do it. Therefore, it is possible to eliminate the cause of the stable flow in the bleed part that occurs at high rotation speeds, and to provide a bleed device for an axial flow compressor with bleed air that can operate stably over the entire range from low rotation speeds to high rotation speeds. There is an effect that can be done.

[Brief explanation of drawings]

Figures 1 and 2 are longitudinal sectional views of the bleed section of an embodiment of the present invention, Figure 3 is a longitudinal sectional view of a conventional axial flow compressor with bleed, and Figure 4 is a cross-sectional view of Figure 3. It is. 5... Air extraction port, 6... Extraction chamber, 12... Movable ring. 13... Reciprocating motion drive device, 14... Movable ring with collar, 18... Spring, 19... Ventilation hole. ] 'f, 1 Figure ↑ VJ Z Figure ↑ Not 3 Figure

Claims (1)

[Scope of Claims] 1. In a multi-stage axial flow compressor in which rows of moving blades and rows of stationary blades are arranged alternately and a bleed port is provided in an intermediate stage, the area of the bleed opening to the main flow path is reduced during compressor operation. Variable axial flow compressor extraction device. 2. An axial flow compressor bleed device characterized in that the variable bleed device according to claim 1 uses a movable ring and a reciprocating drive device. 3. In the variable air bleed device according to claim 1, a movable ring with a collar is provided on the outer periphery of the bleed chamber downstream of the bleed port position, with a high pressure chamber and a low pressure chamber arranged in the front and rear, and a movable ring with a collar is provided at the rear stage of the bleed port. An air bleed device for an axial flow compressor, characterized in that a vent hole is provided in the outer wall of the flow path downstream of the stator blade, communicating with the high pressure chamber, and a spring is provided in the low pressure chamber.