JPS608499A - Surging prevention of multi-stage axial flow compressor - Google Patents

Abstract

PURPOSE:To enlarge the stable operation range by employing a member to be driven by the differential pressure of the delivery section pressure and the intermediate stage pressure in an extraction/supply air system thereby performing extraction/exhaust automatically through simple structure and preventing stall in both high and low rotary regions. CONSTITUTION:Under high speed rotation of compressor, the delivery pressure will increase to increase the differential pressure between the delivery section 27 pressure and intermediate stage 26 pressure. Said differential pressure is received by a drive member 30 to expand a coil spring 29 thus to move said member 30 toward the suction port 25 as shown by dashed line. Consequently, the flow in an extraction/supply system 18 will pass through the delivery port 27 to the intermediate stage port 26 to perform suction (shown by dashed arrow). When the compressor will stop from high speed rotation, said differential pressure will drop to move the drive member 30 toward the delivery port 27 through recovery force of coil spring 29 thus to perform extraction. In such a manner, extraction/exhaust are performed automatically through quite simple structure to prevent stall in both low and high rotary regions of compressor resulting in enlargement of stable operation range.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a multistage axial flow compressor, and is particularly suitable for use in gas turbines and other applications where stable operation is important over a wide range of operating ranges. This relates to a surging prevention method.

[Background of the invention]

In recent years, as the temperature of gas turbines has increased, the pressure ratios of axial flow compressors used therein have been increasing, and as a result, some compressors with per-stage pressure ratios reaching 1.3 to 1.5 have appeared.

As a result, the stable operating range becomes narrower, which may cause problems in the startability and controllability of the gas turbine. FIG. 1 shows the general characteristics of a conventional multi-stage axial flow compressor. Song in Figure 1!
1, 2. ...6 is the flow rate when the rotation speed of the compressor is constant -
The pressure ratio characteristics are shown, and dotted lines 7 and 8.9 indicate surging lines. In a normal multi-stage axial flow compressor, the region to the right of the dotted line is the stable operating region, and the region to the left causes surging, rotational stalling, etc., so the compressor cannot operate stably. As is well known, compressor surging is caused by blade stall. The surging line 7 is based on the stall of the upstream stage, and the surging line 8 is based on the stall of all stages. Also,
A surging line 9 indicates a limit line based on stall in the downstream stage. Curve 10 shows the startup line of a gas turbine when a multi-stage axial flow compressor is used in the gas turbine.

When starting a gas turbine, the operation from a stopped state to a design point passes along the curve gio line from point A to point 0. In the case of FIG. 1, the area between point A and point B is the unstable operating area, and the area between point B and 0 is the stable operating area. In the unstable operating range, the vibration and noise of the compressor become large, and in severe cases, the blades may be damaged. Therefore, if the unstable operation range is wide and the AB interval is long, startup may not be possible. Furthermore, even when the distance between A and B is relatively short as shown in FIG. 1, it is necessary to pass between A and B in as short a time as possible.

By moving the surging line 7 at low speeds to the right side and creating a characteristic curve as shown in FIG. 2, it is possible to prevent the engine from passing through an unstable region at startup.

Furthermore, in order to widen the stable operating range at the design rotational speed (line 2) of the compressor, the surging line 9 at high rotational speeds may be moved to the upper left as shown in FIG. In this way, by preventing surging and widening the stable operating range, stable operation of the multistage axial flow compressor can be ensured, so such measures are particularly important in compressors for gas turbines.

Conventionally used methods for preventing compressor stall and delaying surging include methods such as variable stator vanes, two-shaft split compressors, air extraction, and air supply.

Among these, the variable stator vane method changes the mounting angle of the stator vane depending on the operating condition of the compressor to prevent the vane from stalling. In addition, a two-shaft split compressor divides the rotor shaft into an upstream stage and a downstream stage,
Each type can rotate at a different rotation speed, and both have the drawback of being complex, expensive, and difficult to control. On the other hand, when the compressor rotates at a low speed, a part of the airflow is bypassed to the outside through a bleed hole provided in an intermediate stage. As a result, the flow rate in the upstream stage increases compared to that in the downstream stage, so stalling in the upstream stage is prevented, and the surging line 7 moves to the upper left. The simplest method of supplying air is to supply part of the discharged airflow through the supply hole provided in the intermediate stage when the compressor rotates at high speed. As a result, the flow rate in the downstream stage increases compared to that in the upstream stage, so stalling in the downstream stage is prevented and the surging line 9 moves to the upper left. The air extraction and air supply methods are structurally simple and are often used alone in conventional compressors.

However, if an attempt is made to employ both bleed air and air supply, it is necessary to provide both a bleed air chamber and an air supply chamber in the intermediate stage of the casing of the compressor, resulting in a disadvantage that the casing structure becomes complicated.

Conventionally, air extraction and air supply are performed by having an electromagnetic pulp in an air extraction device or an air supply device, and opening and closing the electromagnetic pulp depending on the rotation speed of the compressor. Therefore, there is a drawback that many peripheral accessories are required to control the air extraction and air supply devices by the rotational speed.

[Purpose of the invention]

The present invention was created in view of the above-mentioned circumstances, and an object of the present invention is to provide a method for preventing surging in a multistage axial flow compressor that is inexpensive and has a wide stable operating range.

[Summary of the invention]

The features of the present invention include an oil-painted air chamber provided on the outer periphery of an intermediate stage casing of a multi-stage axial flow compressor, an oil-painted air chamber that connects the flow path and the oil-painted air chamber, an oil-painted air device connected to the oil-painted air chamber, and a conduit connecting the air device and the compressor suction section and discharge section, respectively;
Since we have installed a member in the oil-painting air system that is driven by the differential pressure between the discharge part and the intermediate stage pressure, it is possible to automatically perform both air extraction and air supply. In both of these areas, there is no stall and the stable operating range can be expanded.

[Embodiments of the invention]

An embodiment of the present invention will be described in more detail below with reference to FIGS. 3 to 5.

FIG. 3 shows a sectional view of a multi-stage axial flow compressor in which the present invention is implemented. A multistage axial flow compressor is configured by alternately arranging rotor blades 11 and stationary blades 12. The rotor blades 11 are attached to a rotor 13 and are driven by a separate motor, turbine, or the like. The stationary blades 12 are embedded in the casing 14. In the multi-stage axial flow compressor of the present invention, an oil-painted air chamber 15 is provided on the outer periphery of the intermediate stage of the casing, and the oil-painted air chamber 15 and the flow path are communicated by an oil-painted air chamber 16 consisting of a slit or a hole.

The oil painting air chamber 15 is connected to an oil painting air device 18 via an oil painting air pipe 17'fc. Further, the oil painting device 18 and the suction section 19 of the compressor are connected through a bleed pipe 20. An air supply pipe 22 connects the oil painting air device 18 and the discharge section 21 of the compressor.

Figure 4 is an enlarged view of the oil painting device, and Figure 5 is A in Figure 4.
-A view. The oil painting device 18 consists of two members, an upper case 23 and a lower case 24, which are fastened together with bolts (not shown) or the like. The oil air device 18 opens in three directions: a suction port 25 , an intermediate stage port 26 , and a discharge port 27 , which are connected to an air bleed pipe 20 , an oil air pipe 17 , and an air supply pipe 22 . A fixing member 28 is fixed to the inner surface of the lower case 24. A coil spring 29 is engaged with the fixing member 28 on the suction port 25 side. More carp. A driving member 30 is installed on the suction port 25 side of the spring 29 to drive between the suction port 25 and the discharge port 27 by expansion and contraction of the coil spring. Further, a labyrinth 31 is installed on the inner circumferences of the upper case 23 and the lower case 24 of the oil painting apparatus, extending beyond the range in which the driving member moves.

This embodiment has the configuration described above.

Next, the operation of this embodiment will be described based on FIG.

When the compressor rotates at low speed, the discharge pressure is lower than the design pressure, so the differential pressure between the discharge pressure and the intermediate stage pressure is small. Therefore, the force that the drive member 30 receives due to the differential pressure is small, and as shown by the solid line, it stops at the initial position due to the force of the coil spring or moves only a small distance toward the suction port 25 side. As a result, conduction occurs between the intermediate stage 26 and the suction port 25. On the other hand, the flow from the discharge port is Labyrinth 3.
It is sealed with 1. Therefore, the flow of the intermediate stage port 25 is directed toward the suction port 25, and air is extracted (solid line arrow 32
). At this time, some leakage flow occurs from the discharge port 25 through the gap between the drive member 3o and the labyrinth 31, but it is not considered to have a sufficient influence to degrade performance.

On the other hand, when the compressor rotates at high speed, as the discharge pressure increases,
The differential pressure between the discharge part pressure and the intermediate stage pressure increases.

When the drive member 30 receives this large pressure difference, the coil spring 29 expands due to the pressure difference, and the drive member 3o moves toward the suction port 25 as shown by the broken line. As a result, the flow inside the oil painting air device is directed from the discharge port 27 to the intermediate stage port 26, and air is supplied (dashed line arrow 33).

Furthermore, when the compressor stops from high rotation, the drive member 30 moves toward the discharge port 27 due to the restoring force of the coil spring 29 as the differential pressure between the discharge portion pressure and the intermediate stage pressure decreases. Bleeding is performed as described above.

〔Effect of the invention〕

As described above, in a multi-stage axial flow compressor according to the present invention, by using a driving member that is driven by the differential pressure between the discharge part pressure and the intermediate stage pressure in the oil painting device, there is no need for external peripheral parts. With a very simple structure, air extraction and air supply can be performed automatically, and it has the effect of providing a surging prevention method for multistage axial flow compressors with a wide stable operation range. - Also, since no external peripheral parts are required, the number of parts can be reduced and the reliability of the equipment can be improved.

[Brief explanation of drawings]

Figures 1 and 2 are explanatory diagrams showing the aerodynamic characteristics of a multistage axial compressor, Figure 3 is a sectional view of a multistage axial compressor according to an embodiment of the present invention, and Figures 4 and 5 are oil paintings. It is a sectional view of an air chamber. 15...Oil painting air chamber, 16...Oil painting air chamber, 17...
Oil painting trachea, 18... Oil painting air device, 20... Air bleed pipe,
22... Figure 1"'° Name 7, 7 ---◆711 Shiri 30

Claims (1)

[Claims] 1. In a multi-stage axial flow compressor consisting of alternating rows of rotor blades and stator blades, from the oil-painted air chamber provided on the outer periphery of the casing of the intermediate stage, and the slit or hole that connects the flow path and the oil-painted air chamber. an oil-painting air section, an oil-painting air device connected to the oil-painting air chamber via a conduit, a conduit connecting the oil-painting air device to a compressor suction section and a discharge section, respectively, and a discharge section pressure inside the oil-painting air device. A surging prevention method for a multi-stage axial flow compressor, which is characterized by disposing a drive member driven by the differential pressure between the intermediate stage pressure and the intermediate stage pressure, and automatically controlling air extraction and air supply.