阅读说明：本技术 一种基于锯齿尾缘叶片的多级轴流压气机扩稳结构 (Multistage axial compressor expands steady structure based on sawtooth trailing edge blade ) 是由 李传鹏 王蕴源 胡骏 王志强 王英锋 屠宝锋 阮立群 于 2019-11-22 设计创作，主要内容包括：本发明公开了一种基于锯齿尾缘叶片的多级轴流压气机扩稳结构,在多级轴流压气机的叶片上设置锯齿尾缘,形成锯齿尾缘叶片,布置在多级轴流压气机的一个或多个叶排上；所述锯齿尾缘叶片的齿高H为8～16％叶片弦长,齿顶角θ为20～60°,锯齿个数1-20个；所述锯齿尾缘叶片在叶尖或叶根附近设置锯齿结构；锯齿尾缘叶片在叶排周向对称设置,或者全叶排都设置为锯齿尾缘叶片。本发明利用锯齿构型及叶片两侧压差,产生流向涡,流向涡将主流卷吸进来,并与尾迹剪切层发生相互作用,破碎掉尾迹中大尺度涡结构、改善叶片尾迹形态以及与下游叶片相干流场特性,从而延缓压气机失速,拓宽压气机稳定裕度。本发明的锯齿尾缘叶片结构具有无另加设备、结构重量轻等优点。(The invention discloses a multistage axial flow compressor stability expanding structure based on a sawtooth tail edge blade.A sawtooth tail edge is arranged on a blade of a multistage axial flow compressor to form a sawtooth tail edge blade which is arranged on one or more blade rows of the multistage axial flow compressor; the tooth height H of the blade at the tail edge of the saw tooth is 8-16% of the blade chord length, the tooth crest angle theta is 20-60 degrees, and the number of the saw teeth is 1-20; the blade with the sawtooth tail edge is provided with a sawtooth structure at the blade tip or near the blade root; the sawtooth tail edge blades are symmetrically arranged in the circumferential direction of the blade row, or all the blade rows are all arranged into the sawtooth tail edge blades. The invention utilizes the sawtooth configuration and the pressure difference at two sides of the blade to generate a flow direction vortex, the flow direction vortex sucks in main flow, and the main flow interacts with the wake shearing layer to break the large-scale vortex structure in the wake, improve the wake form of the blade and the coherent flow field characteristic of the downstream blade, thereby delaying the stalling of the compressor and widening the stability margin of the compressor. The blade structure with the sawtooth tail edge has the advantages of no additional equipment, light structure weight and the like.)

1. The utility model provides a multistage axial compressor expands steady structure based on sawtooth trailing edge blade which characterized in that: the method comprises the following steps that sawtooth trailing edges are arranged on blades of a multistage axial flow compressor to form sawtooth trailing edge blades, and the sawtooth trailing edge blades are arranged on one or more blade rows of the multistage axial flow compressor; the serrated trailing edge blade is disposed at a position upstream of a stall onset stage; the blade with the sawtooth tail edge is provided with a sawtooth structure at the blade tip or near the blade root; the sawtooth tail edge blades are symmetrically arranged in the circumferential direction of the blade row, or all the blade rows are all arranged into the sawtooth tail edge blades.

2. The multistage axial flow compressor stability augmentation structure based on the sawtooth trailing edge blade of claim 1, characterized in that: the blade with the sawtooth tail edge is characterized in that the sawtooth structure is arranged on the 5-50% blade height tail edge near the blade tip, or the sawtooth structure is arranged on the 5-50% blade height tail edge near the blade root, or the sawtooth structure is arranged on the full blade height tail edge.

3. The multistage axial flow compressor stability augmentation structure based on the sawtooth trailing edge blade of claim 1, characterized in that: the tooth height H of the blade at the tail edge of the saw tooth is 8-16% of the chord length of the blade, the tooth crest angle theta is 20-60 degrees, and the number of the saw teeth is 1-20.

4. The multistage axial flow compressor stability augmentation structure based on the sawtooth trailing edge blade of claim 1, characterized in that: the blades at the tail edges of the sawteeth are uniformly arranged in the stator blade row or the rotor blade row.

5. The multistage axial flow compressor stability augmentation structure based on the sawtooth trailing edge blade of claim 1, characterized in that: the sawtooth structure of the sawtooth tail edge blade comprises a triangle and a trapezoid.

6. The multistage axial flow compressor stability augmentation structure based on the sawtooth trailing edge blade of claim 1, characterized in that: the sawtooth trailing edge blade arranges 1 ~ 5 sawtooth trailing edge blades on the symmetrical 3 ~ 5 phase positions of blade row circumference.

7. The multistage axial flow compressor stability augmentation structure based on the sawtooth trailing edge blade of claim 1, characterized in that: 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 blade row of the 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.

8. The multistage axial flow compressor stability augmentation structure based on the sawtooth trailing edge blade of claim 7, characterized in that: 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 trailing edge sawtooth is arranged near the blade tip when the blade tip stalls, the trailing edge sawtooth is arranged near the blade root when the blade root stalls, and the radial range of the blade trailing edge sawtooth is smaller than or equal to that of the stall group.

9. The multistage axial flow compressor stability augmentation structure based on the sawtooth trailing edge blade of claim 1, characterized in that: 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.

10. The multistage axial flow compressor stability augmentation structure based on the sawtooth trailing edge blade of claim 9, characterized in that: when the circumferential extent of the stall mass is less than 45 degrees, the number of groups arranged circumferentially symmetrically depends on the stall mass propagation frequency, and the lower the propagation frequency, the more the number of groups.

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.