RU2582537C2 - Axial-flow compressor - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to aircraft engine construction and can be used in axial compressors for perfection of aerodynamics of their flow section owing to the flow control nearby the impeller housing. A circular chamber is arranged in the housing wall of at least one stage above the impeller blades, feed channels being uniformly made from the inner side of the housing of said chamber over the entire diameter. Said channels provide the blow-out of working fluid from said circular chamber into the axial compressor radial groove at angle φ of 1-5 degrees in vertical plane relative to the housing inner surface, in horizontal plane at angle ψ relative to the front of grates of the profiles. Working fluid is fed into said circular chamber from the compressor last stages, or from whatever other source via appropriate feeder. The location of blow-out points over the blade chord and the number of feed channels for every stage define the conditions of minimization of their quantity and of working fluid flow rate given the required magnitude and direction of absolute rate correspond to the ideal design flow. The feed channels can be arranged directly in the axial compressor housing above the impeller while the circular chamber and working fluid feeder are located above the housing via u-like adapter arranged thereat.

EFFECT: higher head, efficiency and margin of gas-dynamic stability.

2 cl, 5 dwg

Description

The invention relates to the field of aircraft engine manufacturing and can be used in axial compressors to improve their aerodynamics by controlling the flow of the impeller housing.

Closest to the technical nature of the claimed invention is the design of an axial compressor containing a housing and mounted in pairs rotating and fixed crowns of the blades. Each rotating crown of the blades forms an impeller, and each fixed crown of the blades forms a guiding apparatus. The impeller and guide vanes form the stage of the axial compressor. In the steps of the axial compressor, between the blades of the impeller and the inner surface of the casing, there is always a constructive radial clearance (see, for example, Nechaev Yu.N. Theory of aircraft engines, part 1. Textbook for high schools of the Air Force. M.: VVIA named after prof. N.E. Zhukovsky, 2005.366 pp. 57-58, 89).

A disadvantage of the known design is that in the area of the tips of the feathers of the impeller blades there are losses from overflows due to the presence of a radial clearance, which are composed of losses from leaks through the clearance in the axial direction and overflows through the end of the blade from the high pressure side (trough) to the side low pressure (back) (see, for example, Rzhavin Yu.A., Emin O.N., Karasev V.N. Axial and centrifugal compressors of aircraft engines. Theory and calculation: Textbook. - M .: MAI - PRINT 2008, 700 p. S.152-153).

The flow of air through the radial clearance leads to a decrease in peripheral effort and, consequently, to a decrease in the work transmitted to the air in the stage. The useless energy expenditures for the flow of air through the radial gap and for the creation of a vortex flow at the tip of the feathers of the blades near the radial gap cause, in addition, a drop in the efficiency of the stage. All this leads to a decrease in the pressure (adiabatic operation) of the step (see, for example, Nechaev Yu.N. Theory of aircraft engines, part 1. Textbook for high schools of the Air Force. M: VVIA named after prof. N.E. Zhukovsky, 2005 366 p. S. 90-91).

The technical result of the invention is to improve the aerodynamics of the flowing part of the axial compressor by applying the blowing of the working fluid from the impeller housing to create conditions for preventing air from flowing through the radial clearance, aligning the direction and ensuring a uniform field of flow velocities at the impeller housing and in the radial clearance.

The essence of the invention lies in the fact that when the air moves near the impeller casing of the axial compressor with respect to the ideal design flow at the i point near the casing of the impeller, represented by a velocity triangle (see Fig. 1), as a result of air friction against the casing and overflow gap is changed in radial direction and the absolute velocity at a _i c _ip, so that at equal circumferential u _i = u _ip speeds reduces the axial component of the absolute velocity with _ai through from _AIP and voltage change Lenia and values of the relative velocity w _i to w _ip, and thus increase the lag angle δ _i flow. As a result of this, stalling phenomena occur on the back of the impeller blades, leading to an increase in aerodynamic losses in the flow part near the impeller housing.

The conducted experimental studies made it possible to establish that one of the effective ways to control the flow at the impeller housing, including in the radial clearance, is the use of blowing the working fluid from the axial compressor housing over the impeller blades. The blowing speed c _iв = c _i and the blowing angle ψ of the working fluid, including at the calculated operating modes of the compressor, should provide the value and direction of the absolute speed c _i equal to the calculated one. In this case, the axial component of the absolute velocity increases to c _ai and the direction and value of the relative velocity W change; in the direction of decreasing the flow lag angle δ _i to values close to or equal to 0. In this case, continuous flow around the impeller blades is achieved and aerodynamic losses at the housing in the flow part of the axial compressor are reduced, which leads to the creation of conditions for equalizing the direction and ensuring a uniform field of flow velocities at the impeller housing and in the radial clearance.

The required speed and direction of flow are determined by the values corresponding to the calculated flow regime without taking into account friction and flow in the radial clearance. The blowing speed c _iв and the blowing angle ψ are determined by constructing a speed plan (see Fig. 1), at each i point of the interscapular channel, based on the conditions:

- the axial component of the absolute speed c _ai is determined by the air flow G through the impeller;

- the direction of the relative speed w _i coincides with the tangent to the midline of the profile of the blade at the radius r _i from the center of rotation and the location of the 1 _i i point relative to the nose of the blade along its chord b _rk ;

- peripheral speed u _i is determined by the rotational speed n of the impeller and the radius r _i from the center of rotation.

List of drawings

In the drawings:

FIG. 1 shows speed plans at the i point of the interscapular canal corresponding to:

- the operating mode of the flow, taking into account friction and flow in the radial clearance, where: the absolute velocity vector c _ip , the axial component of the absolute velocity c _aip , the _peripheral velocity vector u _ip , the relative velocity vector w _ip ;

- flow regime, taking into account the blowing of the working fluid from the axial compressor casing above the impeller blades, corresponding to the conditions for equalizing the direction and ensuring a uniform field of flow velocities at the casing and in the radial clearance and equal to the ideal design flow regime without taking into account friction and flow in the radial clearance, where: vector of absolute speed c _i , vector of axial component of absolute speed with _аi , vector of _peripheral speed u _i , vector of relative speed w _i .

FIG. 2 shows a longitudinal section of the stage of an axial compressor with a constructive blowing of the working fluid, where 1 is the compressor housing, 2 is the impeller, 3 is an annular spacer, 4 is a supply channel, 5 is an annular cavity, 6 is a pipeline for supplying a working fluid, 7 is a fitting supply of a working fluid.

FIG. 3 shows element I in FIG. 2 on a 4: 1 scale.

FIG. 4 shows a cross section AA in FIG. 2 on a 2: 1 scale.

FIG. 5 shows a longitudinal section through a stage of an axial compressor with a p-shaped extension mounted on the housing.

The specified technical result is achieved by the fact that in the compressor housing 1 (see Fig. 2) above the vanes of the impellers 2, an annular groove of a rectangular shape is made, in which an annular spacer 3 is installed, on the inside of which there are uniformly distributed over the entire diameter inlet channels 4 providing blowing of the working fluid from the annular cavity 5 formed between the housing and the annular spacer into the radial clearance of the axial compressor at an angle φ (see Fig. 3) of 1-5 degrees, in ikalnoy plane relative to the inner surface of the housing in the horizontal plane at an angle ψ (see. FIG. 4) with respect to the front grating profiles. The supply of the working fluid to the annular cavity is carried out from the last stages of the compressor or from any other source of supply of the working fluid through the supply device, which is made in the form of 4-8 fittings 7 mounted directly above the annular cavity, proportionally distributed around the circumference of the compressor casing.

The location of the blowing point along the chord of the blade l _i (see Fig. 1), the number of supply channels for each stage is determined from the condition of minimizing their number and minimizing the flow rate of the working fluid while ensuring the required magnitude and direction of the absolute speed corresponding to the ideal calculated flow.

In addition, the supply channels can be made directly in the axial compressor housing above the impeller, and the annular cavity and the working fluid supply device are made on top of the housing by installing an u-shaped extension 8 (see Fig. 5).

The application of the invention will increase the degree of pressure increase, the efficiency and the stock of gas-dynamic stability of the axial compressor.

Claims (2)

1. An axial compressor comprising a housing, a blade ring of the impeller, a guiding apparatus, characterized in that an annular cavity is made in the housing above the vanes of the impellers of at least one stage, a device for supplying the working fluid to the annular cavity is installed on the outside of the housing, and on the inside of the casing, feed channels are evenly distributed over the entire diameter of the casing, providing a blowing of the working fluid from the annular cavity into the flow part of the axial compressor at an angle of 1-5 degrees in the vertical plane relative to the inner surface of the housing, and the angle in the horizontal plane, the location of the points of blowing the working fluid and the number of supply channels for each stage is determined from the condition of minimizing the number of supply channels and minimizing the flow rate of the working fluid while ensuring flow regime, taking into account the blowing of the working fluid conditions for aligning the direction and ensuring a uniform field of air flow velocities at the impeller housing and in the radial clearance equal to ideal design flow regime without taking into account friction and flow in the radial clearance. 2. The axial compressor according to claim 1, characterized in that the supply channels are made directly in the axial compressor housing, and the annular cavity and the working fluid supply device are made on top of the housing by installing a p-shaped extension on it.

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