CN110821851B

CN110821851B - Multistage axial compressor expands steady structure based on sawtooth trailing edge blade

Info

Publication number: CN110821851B
Application number: CN201911152413.0A
Authority: CN
Inventors: 李传鹏; 王蕴源; 胡骏; 王志强; 王英锋; 屠宝锋; 阮立群
Original assignee: Nanjing University of Aeronautics and Astronautics
Current assignee: Nanjing University of Aeronautics and Astronautics
Priority date: 2019-11-22
Filing date: 2019-11-22
Publication date: 2021-03-09
Anticipated expiration: 2039-11-22
Also published as: CN110821851A

Abstract

The invention discloses a multi-stage axial flow compressor stabilization structure based on sawtooth trailing edge blades. A sawtooth trailing edge is arranged on the blade of the multistage axial flow compressor to form a sawtooth trailing edge blade, which is arranged on the multistage axial flow compressor. One or more blade rows of the machine; the tooth height H of the sawtooth trailing edge blade is 8-16% of the blade chord length, the tooth tip angle θ is 20-60°, and the number of sawtooth is 1-20; the sawtooth The trailing edge blade is provided with a sawtooth structure near the blade tip or the blade root; the sawtooth trailing edge blade is arranged symmetrically in the circumferential direction of the leaf row, or the entire blade row is set as a sawtooth trailing edge blade. The invention utilizes the sawtooth configuration and the pressure difference between the two sides of the blade to generate a flow vortex, which entrains the main flow and interacts with the wake shear layer to break up the large-scale vortex structure in the wake, improve the shape of the blade wake, and interact with the wake shear layer. The coherent flow field characteristics of the downstream blades can delay the compressor stall and widen the compressor stability margin. The serrated trailing edge blade structure of the present invention has the advantages of no additional equipment, light structure and the like.

Description

Multistage axial compressor expands steady structure based on sawtooth trailing edge blade

Technical Field

The invention belongs to the technical field of aerodynamics, and particularly relates to a multistage axial flow compressor stability augmentation structure based on sawtooth trailing edge blades, which is a novel aviation axial flow compressor stability augmentation measure.

Background

In the future, a high thrust-weight ratio engine requires a fan/compressor to have a higher stage pressure ratio, and the higher the stage load of the fan/compressor is, the more severe the requirement on the stability of the fan/compressor is. The stability is characterized by the anti-interference and anti-distortion capability of the fan/compressor and is related to the response of the fan/compressor working at a stable working point to external disturbance, and the high stability indicates that the fan/compressor can overcome disturbance factors and keep stable and normal work. When the fans/compressors are much more reserved with a stability margin, their stability is of course high. Conversely, the compressor has high stability and strong robustness, and the reserved available stability margin can be reduced, so that the compressor can work in an operating area with high efficiency and high pressure ratio closer to a stability boundary without generating pneumatic instability. Therefore, the stability of the fan/compressor is greatly improved, namely the restriction condition that the fan/compressor further improves the pressure ratio is removed, and the development of the fan/compressor with higher efficiency and higher load becomes possible.

The stability problems of fans/compressors (surge and rotating stall) occur almost simultaneously with axial compressors and have plagued the industry and academia for nearly half a century as a limit to reliable and stable operation of compressors. After decades of researches, people have clearly described the dynamic characteristics of instability of internal flow of an axial flow compressor, disclose basic conditions of instability of the compressor, and provide a theoretical model for describing instability of the compressor and corresponding stability criteria, which have remarkable effects on the aspects of predicting the instability of the compressor and further inhibiting the damage of the compressor. Researchers actively explore and develop various air compressor stability expansion methods, and the flow control technologies such as casing treatment, blade tip air injection, blowing/adsorption surface layer, plasma pneumatic excitation and the like become the current research hotspots, so that the anti-interference and anti-distortion capabilities of the fan air compressor are effectively improved, the air flow stall is delayed, and the stable working range of the air compressor is widened.

The flow in the impeller machinery is inherent unsteady flow, the blades of the impeller machinery experience unsteady fluctuation at every moment, the blades experience non-uniform flow at the outlet of the guide vane at the upper stage and unequal potential flow in the circumferential direction of the stator at the downstream in the rotating process, and the attack angle of the incoming flow of the blades also changes constantly even under the design working condition of the gas compressor. The factors influencing the fluctuation of the incoming flow attack angle are many, such as the channel vortex, the tip leakage vortex, the end wall boundary layer, the separation and other flow structures of the upstream blade all influence the incoming flow attack angle of the downstream blade to different degrees, and especially, the trailing flow formed by the confluence of the blade disc and the blade back boundary layer through the trailing edge of the blade has far difference between the flow speed and the total pressure of the trailing flow and the main flow area, and is the most obvious disturbance source for the incoming flow attack angle of the downstream blade.

Under the assumption of a critical angle of attack for compressor instability, a large separation flow occurs when the incoming flow angle of attack of some of the blades in the blade row exceeds its critical angle of attack, resulting in a compressor rotating stall or surge. When the upstream wake is swept, the transient angle of attack sensed by the blade may exceed the critical angle of attack to induce compressor stall. The invention provides a method for improving the stability of a fan/compressor by taking a sawtooth trailing edge blade as a flow control strategy and changing the wake flow characteristic of an upstream blade.

The sawtooth trailing edge can strengthen the mixing between the low-speed stream of wake district and mainstream, shortens shear layer length, and the effect in the aspect of making an uproar is showing, receives attention in a plurality of fields. Early scholars proposed the sawtooth wing trailing edge of 'resistance reduction, lift increase and noise reduction' in the field of aircraft outflow, and also successfully applied the sawtooth trailing edge to a nozzle of an exhaust system of an engine of a civil aircraft, so as to strengthen mixing between jet flow and outflow of the engine and reduce civil aircraft noise.

The university of Brinell London, UK has carried out a flat plate blowing test at the tail edge of the sawtooth, studies the influence of the tail edge of the sawtooth on the turbulent flow of the flat plate, and finds that the tail edge of the sawtooth changes the turbulent flow structure of the flat plate, thereby reducing the noise frequency. The german aachen industry university carries out the research on the airfoil wave phenomenon of the sawtooth trailing edge, finds that the sawtooth trailing edge can interfere the formation of wake vortexes, enhances the flowing three-dimensional structure and greatly reduces the amplitude in a flow field.

Chinese scholars also develop a plurality of related researches on sawtooth tail edge noise reduction in the years. In northern aviation, research on the wing profile noise is controlled by unfolding the sawtooth wing profile trailing edge through a low-speed opening wind tunnel in a full-noise-elimination environment, and the noise reduction effect is related to the tooth profile, so that the large tooth noise reduction effect is better, and particularly in the low-frequency part. When the large-scale vortex system impacts on the saw teeth, the vortex system is broken, so that the large-scale vortex system is developed to a small scale, energy is transferred from low frequency to high frequency, and low-frequency noise is reduced. Numerical simulation research on aerodynamic characteristics of a sawtooth trailing edge blade performed by engineering thermophysics shows that a row of counter-rotating vortex pairs can be formed at the trailing edge by the trailing edge sawtooth, the trailing vortex structure is changed, the spanwise correlation of a downstream wake region is weakened, and the far field radiation of noise is reduced. When the basic characteristics of a turbulence flow field at the tail edge of a sawtooth tail edge airfoil are researched by the West worker, the sawtooth widens a wake region and accelerates the breaking of a large vortex, vortex energy is diffused towards the spanwise direction and the vertical direction, and the pulsation attenuation rate of the turbulence is increased along the flowing direction.

Although the above studies have been directed to noise reduction, they have been conducted for a single airfoil or a single row fan. However, deep analysis of the wake flow field structure shows that the sawtooth can effectively change the wake vortex structure, distribution and attenuation speed. The method provides possibility and basis for utilizing the dynamic-static interference flow field which is dominant by the trailing edge of the sawtooth in the multistage compressor.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the defects in the prior art, the invention takes the remarkable effect of the sawtooth tail edge on noise elimination and reduction as a support, and provides a concept of expanding the stability of the compressor by taking the sawtooth tail edge blade as a flow control strategy. The flow direction vortex is generated by utilizing the sawtooth configuration and the pressure difference on two sides of the blade, the main flow is sucked by the flow direction vortex and interacts with the wake shearing layer, the structure of the large-scale vortex in the wake is broken, the wake form of the blade and the coherent flow field characteristic of the downstream blade are improved, and therefore the stalling of the gas compressor is delayed, and the stability margin of the gas compressor is widened. Compared with the existing stability expanding technologies such as casing treatment, blade tip air injection, blowing/adsorption surface layer and the like, the sawtooth tail edge blade has the advantages of no additional equipment, light structure weight and the like.

The technical scheme is as follows: in order to achieve the purpose, the invention adopts the technical scheme that:

the invention provides a multistage axial flow compressor stability expanding structure based on a sawtooth tail edge blade. The sawtooth structure can be triangular, trapezoidal and the like, the tooth height H of the blade at the tail edge of the sawtooth is generally controlled to be 8-16% of the chord length of the blade, the tooth crest angle theta is approximately 20-60 degrees, and the number of the sawtooth is 1-20; the blade with the sawtooth tail edge can be provided with a sawtooth structure at the tail edge of 5-50% of the blade height near the blade tip, or provided with a sawtooth structure at the tail edge of 5-50% of the blade height near the blade root, or provided with the tail edge of a full-blade high sawtooth structure; 1-5 sawtooth tail edge blades can be symmetrically arranged on 3-5 phases in the circumferential direction of the blade row, or all the blade rows (full rings) are all sawtooth tail edge blades; such serrated trailing edge blades are arranged as far upstream as possible of the stall initiation stage (stall initiation blade row), either in the stator blade row or in the rotor blade row; the sawtooth trailing edge blade can be arranged on one blade row of the multistage axial flow compressor, and can also be arranged on a plurality of blade rows.

Has the advantages that: the multistage axial flow compressor stability augmentation technology of the sawtooth trailing edge blade provided by the invention has the following advantages:

1. the saw-tooth tail edge blade increases the stable working range of the multistage axial flow compressor;

2. the sawtooth tail edge blade has the advantages of no additional equipment, light structure weight and the like;

3. the influence of the blade with the blade height and the sawtooth tail edge on the upper part of the circumferential local phase on the performance of the multistage axial flow compressor is small, and the characteristics (flow, pressure and efficiency) of the compressor are almost unchanged.

Drawings

In the figure 1, 5-50% of the blade height near the blade tip is provided with a blade with a sawtooth structure at the trailing edge.

FIG. 2 shows a blade row in which 3 sawtooth trailing edge blades are arranged on 3 circumferentially symmetrical phases.

Fig. 3 shows a multistage axial compressor in which the serrated trailing edge blades are arranged in the stator blade row.

Fig. 4 shows a multistage axial compressor with serrated trailing edge blades arranged in the rotor blade row.

Detailed Description

The invention is further described with reference to the following figures and examples.

Examples

Because a small block is lost in the chord length direction of the sawtooth tail edge structure, the processing pressurization capacity of the section is inevitably weakened. In order to reduce the performance of the multistage axial flow compressor as small as possible and widen the stable working range of the compressor, the stall characteristic of the axial flow compressor needs to be obtained through technical means such as tests, numerical calculation, theoretical analysis and the like before the stability expansion processing is carried out on the multistage axial flow compressor by adopting a sawtooth trailing edge structure. And determining a sawtooth trailing edge blade pneumatic stability augmentation strategy according to the stall characteristic of the multistage axial flow compressor.

After a stall initial stage or a stall initial blade row of a multistage axial-flow compressor with insufficient stability margin is obtained, determining that a sawtooth trailing edge blade is adopted by the stall initial stage or the blade row upstream of the stall initial blade row; (the stability margin of each compressor is required by specific values, the stability margins of engines of different models are different, and the stability margin of an aircraft engine is about 15% -25%, which is negotiated by an engine end user and an engine research party).

Determining whether the sawtooth trailing edge blade is a partial blade height sawtooth or a full blade height sawtooth according to the radial range of a stall group of a first stage/first stage of stall of the multistage axial flow compressor: partial blade high stall is provided with partial blade high sawteeth, and full blade high stall is provided with full blade high sawteeth.

Whether the part of the blade height serrations are the blade tip position or the blade root position depends on the stall mass radial position: the blade trailing edge sawtooth position corresponds to the radial position of the stall group, the blade tip stall arranges the trailing edge sawtooth near the blade tip, the blade root stall arranges the trailing edge sawtooth near the blade root, and the radial range of the blade trailing edge sawtooth is smaller than or equal to the radial range of the stall group, as shown in fig. 1.

According to the circumferential range and the propagation frequency of a stall group of a first stage/first stage of stall of the multistage axial-flow compressor, whether the sawtooth trailing edge blade is a full ring or a sawtooth trailing edge blade group is arranged in a circumferential local phase position is determined, and the sawtooth structure is adopted by the corresponding trailing edge of each group of blades:

when the circumferential range of the stall cluster is larger than 90 degrees, saw tooth trailing edge blades are arranged in a full ring;

when the circumferential range of the stall group is 45-90 degrees, two groups of sawtooth trailing edge blades are circumferentially and symmetrically arranged, and the circumferential range of each group of sawtooth trailing edge blades is 40-45 degrees;

when the circumferential range of the stall group is smaller than 45 degrees, 3-5 groups of sawtooth trailing edge blades are symmetrically arranged in the circumferential direction, and the circumferential range of each group of sawtooth trailing edge blades is 20-30 degrees. Wherein the number of sets arranged circumferentially symmetrically depends on the stall mass propagation frequency, and the lower the propagation frequency, the more the number of sets, as shown in fig. 2-4.

The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.

Claims

1. A multi-stage axial flow compressor stabilization structure based on sawtooth trailing edge blades, it is characterized in that: a sawtooth trailing edge is set on the blade of the multistage axial flow compressor, forming a sawtooth trailing edge blade, arranged on the multistage shaft on one or more blade rows of a flow compressor; the serrated trailing edge blades are arranged at the upstream position of the stall starter stage; the serrated trailing edge blades are provided with a serration structure near the blade tip or blade root; the serrated trailing edge blades are arranged in the blade row Circumferentially symmetrically arranged, or the entire blade row is set as a sawtooth trailing edge blade;

According to the circumferential range and propagation frequency of the stall cluster of the multi-stage axial compressor stall start stage, it is determined whether the serrated trailing edge blade is a full ring or a circumferential partial phase arrangement of the serrated trailing edge blade group, and the corresponding number of blades in each group The trailing edge adopts a sawtooth structure:

When the circumferential range of the stall group is greater than 90°, the serrated trailing edge blades are arranged in the whole ring;

When the circumferential range of the stall group is 45 to 90°, two sets of serrated trailing edge blades are arranged symmetrically in the circumferential direction, and the circumferential range of each set of serrated trailing edge blades is 40 to 45°;

When the circumferential range of the stall group is less than 45°, 3 to 5 groups of serrated trailing edge blades are arranged symmetrically in the circumferential direction, and the circumferential range of each group of serrated trailing edge blades is 20 to 30°.

2 . The multi-stage axial flow compressor stabilization structure based on sawtooth trailing edge blades according to claim 1 , wherein the sawtooth trailing edge blades are arranged with sawtooth structures at 5-50% of the height of the trailing edge near the blade tip, or in the 5-50% of the leaf height and trailing edge are arranged with sawtooth structure near the root of the leaf, or the entire leaf height and trailing edge are arranged with sawtooth structure.

3. The multi-stage axial flow compressor stabilization structure based on sawtooth trailing edge blades according to claim 1, wherein the tooth height H of the sawtooth trailing edge blades is 8-16% of the blade chord length, and the tooth tip The angle θ is 20-60°, and the number of saw teeth is 1-20.

4 . The multi-stage axial compressor stabilization structure based on serrated trailing edge blades according to claim 1 , wherein the serrated trailing edge blades are all arranged in a row of stator blades, or are arranged in a row of rotor blades. 5 .

5 . The multi-stage axial flow compressor stabilization structure based on serrated trailing edge blades according to claim 1 , wherein the sawtooth structure of the serrated trailing edge blades comprises a triangle or a trapezoid. 6 .

6 . The multi-stage axial compressor stabilization structure based on serrated trailing edge blades according to claim 1 , wherein when the circumferential range of the stall mass is less than 45°, the serrated trailing edge blades are symmetrical in the circumferential direction of the blade row. 7 . 1 to 5 sawtooth trailing edge blades are arranged on 3 to 5 phases respectively.

7. The multi-stage axial compressor stabilization structure based on the sawtooth trailing edge blade according to claim 1, wherein the sawtooth tail is determined according to the radial extent of the stall mass of the stall start stage of the multistage axial compressor. Whether the edge blades are partial leaf height serrations or full leaf height serrations: partial leaf height serrations are arranged for partial leaf height stalls, and full leaf height serrations are arranged for full leaf height stalls.

8. The multi-stage axial-flow compressor stabilization structure based on sawtooth trailing edge blades according to claim 7, characterized in that: whether a part of the blade height sawtooth is a blade tip position or a blade root position depends on the radial position of the stall group: The position of the sawtooth on the trailing edge corresponds to the radial position of the stall group. For the tip stall, the trailing edge sawtooth is arranged near the tip of the blade, and for the root stall, the trailing edge sawtooth is arranged near the root of the blade. The radial range of the blade trailing edge sawtooth is less than or equal to Radial extent of the stall cluster.

9. The multi-stage axial flow compressor stabilization structure based on sawtooth trailing edge blades according to claim 1, characterized in that: when the circumferential range of the stall clusters is less than 45°, the number of clusters arranged symmetrically in the circumferential direction is based on the stall clusters. Depends on the propagation frequency, the lower the propagation frequency, the greater the number of groups.