CN110821851A - A multi-stage axial flow compressor stabilization structure based on sawtooth trailing edge blades - Google Patents

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

A multi-stage axial flow compressor stabilization structure based on sawtooth trailing edge blades

technical field

The invention belongs to the technical field of aerodynamics, and in particular relates to a multi-stage axial-flow compressor stabilization structure based on sawtooth trailing edge blades, which is a novel aeronautical axial-flow compressor stabilization measure.

Background technique

In the future, the high thrust-to-weight ratio engine requires a higher pressure ratio of the fan/compressor, and the higher the stage load of the fan/compressor, the more stringent the stability requirements. Stability is the anti-interference and anti-distortion capability of the fan/compressor, which is related to the response of the fan/compressor working at a stable operating point to external disturbances. High stability indicates that the fan/compressor can overcome the disturbance factor and maintain stable and normal operation. . When the fans/compressors have much more stability margin available, they are of course more stable. Conversely, the high stability and robustness of the compressor can reduce the reserved available stability margin, so that the compressor can work in a high-efficiency and high-pressure ratio operating region closer to the stability boundary without generating aerodynamic instability . Therefore, the stability of the fan/compressor is greatly improved, that is, the restrictive condition of the fan/compressor to further increase the pressure ratio is lifted, and it is possible to develop a fan/compressor with higher efficiency and higher load.

The stability problems of fans/compressors (surge and rotating stall) occur almost simultaneously with axial compressors. As the limit of reliable and stable operation of compressors, they have plagued industry and academia for nearly half a century. After decades of research, the dynamic characteristics of the internal flow instability of the axial flow compressor have been described clearly, the basic conditions for the occurrence of compressor instability have been revealed, and a theory to describe the compressor instability has been proposed. The model and the corresponding stability criterion have achieved remarkable results in predicting the occurrence of compressor instability and further suppressing its harm. Scientific researchers are actively exploring and developing various compressor stabilization methods. Flow control technologies such as casing treatment, blade tip jetting, blowing/adsorption surface layer, and plasma aerodynamic excitation have become the current research hotspots, effectively improving fan compressors. The anti-interference and anti-distortion capability delays the airflow stagnation and widens the stable working range of the compressor.

The internal flow of the turbomachinery is inherently unsteady, and the blades experience unsteady fluctuations at all times. During the rotation of the blades, they feel the non-uniform flow at the outlet of the upper guide vane and the downstream stator. Due to the unequal potential flow in the circumferential direction, even in the design condition of the compressor, the angle of attack of the incoming flow of the blade changes all the time. There are many factors that affect the fluctuation of the incoming flow angle of attack, such as the channel vortex, tip leakage vortex, end wall boundary layer, separation and other flow structures of the upstream blade, which all affect the incoming flow attack angle of the downstream blade to varying degrees, especially by the blisks and blades. The wake flow formed by the backside layer flowing through the trailing edge of the blade, the flow velocity and total pressure are far from the main flow area, and it is the most significant disturbance source for the attack angle of the downstream blade flow.

According to the assumption of critical angle of attack for compressor instability, when the incoming angle of attack of some of the blades in the blade row exceeds its critical angle of attack, a large separation flow occurs, resulting in a compressor rotational stall or surge phenomenon. When the upstream wake sweeps, the transient angle of attack experienced by the blade may exceed the critical angle of attack and induce compressor stall. The present invention proposes to use serrated trailing edge blades as a flow control strategy to improve fan/compressor stability by changing the flow characteristics of the upstream blade wake.

The sawtooth trailing edge can strengthen the mixing between the low-speed flow and the main flow in the wake area, shorten the length of the shear layer, and has a remarkable effect in noise reduction, which has been paid attention to in many fields. Some scholars have long proposed the trailing edge of a sawtooth wing that "reduces drag and increases lift and noise reduction" in the field of aircraft outflow, and has also successfully applied the sawtooth trailing edge to the nozzle of the exhaust system of civil aircraft engines to strengthen the gap between the engine jet and the outflow. Mixing, reduce the noise of civil aircraft.

The Brunel University London University conducted a serrated trailing edge flat plate blowing experiment to study the effect of the serrated trailing edge on the turbulent flow of the flat plate. It was found that the serrated trailing edge changed the turbulent flow structure of the flat plate, thereby reducing the noise frequency. RWTH Aachen University in Germany conducted research on the phenomenon of serrated trailing edge airfoil waves, and found that serrated trailing edge would interfere with the formation of wake vortices, enhance the three-dimensional structure of the flow, and greatly reduce the wave amplitude in the flow field.

Chinese scholars have also carried out a lot of related research on the noise reduction of the sawtooth trailing edge in recent years. Among them, Beihang used a low-speed opening wind tunnel with a fully anechoic environment to carry out a research on the trailing edge of the sawtooth airfoil to control the airfoil noise. It was found that the noise reduction effect is related to the tooth shape, and the noise reduction effect of the large tooth is better, especially in the low frequency part. When the large-scale vortex system hits the sawtooth, it will lead to the rupture of the vortex system, so that the large-scale vortex system develops to a small scale, which transfers energy from low frequency to high frequency and reduces low-frequency noise. The numerical simulation study of the aerodynamic characteristics of the sawtooth trailing edge blade conducted by the Institute of Engineering Thermophysics found that the trailing edge sawtooth causes the flow to form a row of counter-rotating vortex pairs at the trailing edge, which changes the wake vortex structure and weakens the span of the downstream wake region. Correlation, reducing the far-field radiation of noise. When studying the basic characteristics of the turbulent flow field at the trailing edge of the sawtooth trailing airfoil, NPU found that the sawtooth widened the wake area and accelerated the breaking of large eddies. .

Although the above studies are all for the purpose of noise reduction, and the work is carried out on a single airfoil or single row fan. However, in-depth analysis of the wake flow field structure shows that the sawtooth can effectively change the wake vortex structure, distribution and decay speed. This provides the possibility and basis for us to utilize the dynamic-static interference flow field dominated by the wake in the multi-stage compressor with the sawtooth trailing edge.

SUMMARY OF THE INVENTION

Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention is supported by the serrated trailing edge in noise reduction and noise reduction, and proposes the idea of using the serrated trailing edge blade as a flow control strategy for compressor stabilization. Using the sawtooth configuration and the pressure difference on both sides of the blade, the flow direction vortex is generated, and the flow direction vortex sucks the main flow in and interacts with the wake shear layer, breaking the large-scale vortex structure in the wake, improving the shape of the blade wake and connecting with the downstream blade. Coherent flow field characteristics, thereby delaying the compressor stall and widening the compressor stability margin. Compared with the existing stabilization technologies such as casing treatment, blade tip jetting, blowing/adsorption surface layer, etc., the sawtooth trailing edge blade has the advantages of no additional equipment and light structure.

Technical scheme: In order to realize the above-mentioned purpose, the technical scheme adopted in the present invention is:

The invention proposes a multi-stage axial flow compressor stabilization structure based on sawtooth trailing edge blades. The sawtooth structure can be triangular, trapezoidal, etc. The tooth height H of the sawtooth trailing edge blade is generally controlled at 8 to 16% of the blade chord length, the tooth tip angle θ is roughly 20 to 60°, and the number of saw teeth is 1-20; The blade can be arranged with a sawtooth structure on the trailing edge of 5 to 50% of the leaf height near the tip of the blade, or with a sawtooth structure on the trailing edge of 5 to 50% of the leaf height near the blade root, or the trailing edge of the full leaf height with a sawtooth structure; Arrange 1 to 5 sawtooth trailing edge blades on symmetrical 3 to 5 phases, or the entire blade row (full ring) is a sawtooth trailing edge blade; this sawtooth trailing edge blade is arranged as far as possible in the stall starter stage (stall starter blade row) upstream, it can be arranged on a stator blade row or a rotor blade row; sawtooth trailing edge blades can be arranged on one blade row of a multi-stage axial compressor, or can be arranged on multiple blade rows.

Beneficial effects: The multi-stage axial flow compressor stabilization technology of the sawtooth trailing edge blade provided by the present invention has the following advantages:

1. The serrated trailing edge blades increase the stable working range of the multi-stage axial compressor;

2. The sawtooth trailing edge blade has the advantages of no additional equipment and light structure;

3. The high serrated trailing edge blades of the upper part of the circumferential local phase have little effect on the performance of the multi-stage axial flow compressor, and the compressor characteristics (flow rate, pressure and efficiency) are almost unchanged.

Description of drawings

Fig. 1 Blades with sawtooth structure arranged at the trailing edge of 5-50% of the blade height near the blade tip.

Fig. 2 A blade row of 3 sawtooth trailing edge blades arranged on 3 phases of circumferential symmetry.

Figure 3. Multistage axial compressor with sawtooth trailing edge blades arranged in rows of stator blades.

Figure 4. Multistage axial compressor with sawtooth trailing edge blades arranged in rows of rotor blades.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

Example

Since a small piece is missing in the chord length direction of the serrated trailing edge structure, the processing pressurization capability of this section is inevitably weakened. In order to reduce the performance of the multi-stage axial flow compressor as little as possible and widen the stable working range of the compressor, it is necessary to conduct experiments, numerical calculations, The stall characteristics of the axial flow compressor are obtained by technical means such as theoretical analysis. The aerodynamic stabilization strategy of sawtooth trailing edge blades is determined based on the stall characteristics of a multistage axial compressor.

After obtaining the stall starter stage or stall starter blade row of a multistage axial compressor with insufficient stability margin, determine that the stall starter stage or the blade row upstream of the stall starter blade row adopts serrated trailing edge blades; (the stability margin of each compressor is There are specific numerical requirements for the degree of stability, and the stability margin of different types of engines is different, and the aero-engine is roughly 15% to 25%, which is negotiated by the end user of the engine and the engine developer).

According to the radial range of the stall mass of the stall starter stage/starter blade row of the multistage axial flow compressor, determine whether the serrated trailing edge blade is a partial leaf height sawtooth or a full leaf height sawtooth: if the partial leaf height stalls, the partial leaf height sawtooth is arranged. The full blade high stall is arranged with full blade high serrations.

The position of the blade tip or the root position of some blade height teeth depends on the radial position of the stall group: the position of the blade trailing edge sawtooth corresponds to the radial position of the stall group, and the blade tip stall is arranged near the blade tip. For stall, the trailing edge serrations are arranged near the root of the blade, and the radial extent of the blade trailing edge serrations is less than or equal to the radial extent of the stall mass, as shown in Figure 1.

According to the circumferential range and propagation frequency of the stall clusters of the stall starter stage/starter blade row of the multistage axial flow compressor, determine whether the serrated trailing edge blades are full rings, or the serrated trailing edge blade groups are arranged in a circumferential local phase, and the corresponding How many groups of blade trailing edges adopt 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°. Among them, the number of groups arranged symmetrically in the circumferential direction is determined according to the propagation frequency of the stall group. The lower the propagation frequency, the more groups, as shown in Figure 2-4.

The above is only the preferred embodiment of the present invention, it should be pointed out that: for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made, and these improvements and modifications are also It should be regarded as the protection scope of the present invention.

Claims (10)

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 symmetrical, or the entire blade row is set as a serrated trailing edge blade. 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 triangular and trapezoidal shapes. 6 . 6 . The multi-stage axial flow compressor stabilization structure based on serrated trailing edge blades according to claim 1 , wherein 1 to 5 serrated trailing edge blades are arranged on 3 to 5 phases symmetrically in the circumferential direction of the blade row. 7 . Sawtooth trailing edge leaves. 7. The multi-stage axial-flow compressor stabilization structure based on sawtooth trailing edge blades according to claim 1, characterized in that: according to the radial extent of the stall mass of the multi-stage axial-flow compressor stall starter stage/starter blade row , to determine whether the serrated trailing edge blade is partial leaf height sawtooth or full leaf height sawtooth: partial leaf height sawtooth is arranged at partial leaf height stall, and full leaf height sawtooth is arranged at full leaf height stall. 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: according to the circumferential extent of the stall mass of the multi-stage axial-flow compressor stalling starter stage/starter blade row and the propagation frequency, determine whether the serrated trailing edge blades are full rings, or whether the serrated trailing edge blade group is arranged in a partial phase in the circumferential direction, and the corresponding number of blade trailing edges in each group adopts the serration 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°. 10 . The multi-stage axial compressor stabilization structure based on sawtooth trailing edge blades according to claim 9 , wherein: 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. 11 . Depends on the propagation frequency, the lower the propagation frequency, the greater the number of groups.

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