Optimization method of extraction loss of axial flow compressor

Abstract

A method for optimizing the extraction loss of an axial flow compressor, which calculates the radial influence range of the extraction effect in the compressor mainstream according to the geometric parameters of the compressor blades, and calculates the potential vortex characteristic parameters caused by the extraction in the mainstream according to the extraction flow rate and the compressor mainstream flow rate and the inlet and outlet aerodynamic parameters; the total pressure loss coefficient at each blade height section within the radial influence range is calculated by the potential vortex characteristic parameters to further optimize the axial flow compressor structure. The present invention predicts the radial distribution of the compressor mainstream loss caused by interstage extraction, which is helpful for the flow design analysis of the axial flow compressor.

Description

Technical Field

[0001] The present invention relates to a technology in the field of aeroengines, in particular to a method for optimizing the air extraction loss of an axial compressor. Background Art

[0002] Interstage extraction has a significant impact on the aerodynamic performance of aircraft engine compressors. In the current multi-stage axial flow compressor design system, there is a lack of extraction effect prediction models, which makes it impossible to effectively evaluate the extraction effect during the compressor design stage. In addition, during the design process of the multi-stage axial flow compressor, the extraction effect continues to propagate between stages, causing a "snowball" effect, which makes the design results of the later stages of the multi-stage axial flow compressor far from the experimental results. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention proposes a method for optimizing the extraction loss of an axial flow compressor, which predicts the radial distribution of the compressor mainstream loss caused by inter-stage extraction, and is helpful for the flow design analysis of the axial flow compressor.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to a method for optimizing the extraction loss of an axial flow compressor. The method comprises the following steps: calculating the radial influence range of the extraction effect in the mainstream of the compressor according to the geometric parameters of the compressor blades, calculating the potential vortex characteristic parameters caused by the extraction in the mainstream according to the extraction flow rate and the mainstream flow rate of the compressor and the inlet and outlet aerodynamic parameters; and calculating the total pressure loss coefficient at each blade height section within the radial influence range by using the potential vortex characteristic parameters, so as to further optimize the structure of the axial flow compressor.

[0006] The radial influence range of the suction effect in the main flow of the compressor refers to: the distance from the compressor casing Where: AR is the aspect ratio of the compressor blade, σ is the density at the mid-diameter.

[0007] The radial influence range is preferably 0.2<Δh<0.5.

[0008] The potential vortex characteristic parameter, i.e., the potential vortex rotation angular velocity caused by the air extraction Relative air extraction volume Circulation r is the potential vortex radius, M bleed is the suction flow, M is the main flow of the compressor, and the radius of the potential vortex caused by the suction in the main flow K a is the vortex radius correction factor, which is 0.272, β1 is the inlet airflow angle, β2 is the outlet airflow angle, σ is the compressor consistency, and C is the compressor chord length.

[0009] The total pressure loss coefficient at each blade height section within the radial influence range is Where: x is the circumferential position in the blade channel, t is the grid pitch, and the local total pressure loss coefficient at each position in the potential vortex V1 is the inlet speed, V m is the average velocity in the channel, υ is the dynamic viscosity, R is the ratio of the distance from the vortex center to the vortex radius at each position in the potential vortex, and the function

[0010] The present invention relates to a system for realizing the above method, comprising: a range determination unit, a potential vortex radius and rotation speed unit, a pressure loss coefficient unit and a comprehensive unit, wherein: the range determination unit calculates the influence range of the air extraction in the mainstream according to the geometric parameters of the compressor, the potential vortex radius and rotation speed unit calculates the potential vortex radius and rotation speed caused by the air extraction in the mainstream according to the geometric and flow field data of the compressor, the pressure loss coefficient unit calculates the total pressure loss coefficient of each point of the outlet cross section according to the potential vortex radius, rotation speed and flow field data, and the comprehensive unit performs mass flow weighted averaging in the circumferential direction according to the air extraction influence range, the potential vortex radius and the total pressure loss coefficient of each outlet cross section, obtains the total pressure loss coefficient at different spanwise heights and updates the axial compressor structure to minimize the total pressure loss coefficient to achieve optimization.

[0011] Technical Effects

[0012] Compared with the prior art, the present invention can accurately predict the change of the mainstream total pressure loss coefficient caused by the extraction effect of the axial flow compressor, including the extraction influence range, radial distribution and total pressure loss coefficient, and can incorporate the influence of extraction on the compressor stage performance into the compressor flow design system, thereby realizing the evaluation of the extraction effect in the early stage of multi-stage axial flow compressor design. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the calculation process of the present invention;

[0014] Figure 2 Schematic diagram of the potential vortex model caused by air extraction;

[0015] Figure 3 Comparison between the calculation results of the present invention and the results of numerical technology. DETAILED DESCRIPTION

[0016] like Figure 1As shown, this embodiment involves a method for optimizing the extraction loss of an axial flow compressor to predict the extraction loss of a compressor plane blade grid with a relative extraction amount of 4%, that is, firstly, the influence range of the extraction in the compressor channel is calculated according to the geometric parameters of the compressor plane blade grid; then, the potential vortex characteristic parameters caused by the extraction in the mainstream are calculated according to the extraction flow rate and the mainstream flow rate of the compressor as well as the inlet aerodynamic parameters and the outlet aerodynamic parameters; finally, the total pressure loss coefficient at each blade height section within the extraction influence range is calculated according to the characteristic parameters of the potential vortex.

[0017] The geometric parameters of the compressor plane blade grid include: aspect ratio, density, chord length and grid pitch;

[0018] The inlet aerodynamic parameters include: exhaust flow, mainstream flow, inlet velocity, average velocity in the channel, and inlet airflow angle; the outlet aerodynamic parameters include: outlet airflow angle, inlet total pressure at mid-diameter, inlet static pressure, inlet density, outlet total pressure and outlet static pressure.

[0019] The potential vortex characteristic parameters include the radius and rotation angular velocity of the potential vortex.

[0020] The comb teeth geometric parameters include: comb teeth gap, comb teeth diameter, and teeth number.

[0021] The geometric parameters of the compressor plane cascade are shown in Table 1.

[0022] Table 1 Compressor plane cascade geometric parameters

[0023]

[0024] like Figure 1 As shown in Figure 2, the prediction of compressor grate leakage loss includes:

[0025] 1) Calculate the radial influence range of the exhaust in the mainstream according to the aspect ratio AR of the compressor plane blade and the density σ at the mid-diameter

[0026] 2) The potential vortex characteristic parameters caused by the exhaust in the mainstream are calculated by the exhaust flow rate, the compressor mainstream flow rate, and the inlet and outlet aerodynamic parameters. The potential vortex characteristic parameters are as follows: Figure 2 As shown;

[0027] 2.1) According to the exhaust flow M bleed Calculate the relative suction volume with the compressor mainstream flow M

[0028] 2.2) Calculate the potential vortex radius caused by the exhaust in the mainstream based on the relative exhaust volume μ and the aerodynamic and geometric parameters of the compressor blade inlet and outlet. Where: K ais the vortex radius correction factor, which is 0.272, and Γ is the annularity, which can be calculated from the inlet flow angle β1, the outlet flow angle β2 and the compressor consistency σ:

[0029] 2.3) According to the relative air extraction volume μ, the aerodynamic circulation volume Γ and the potential vortex radius R, the angular velocity of the potential vortex caused by air extraction can be calculated: Among them: π is the circumference of a circle.

[0030] 3) The total pressure loss coefficient at each blade height section within the suction influence range is calculated using the characteristic parameters of the potential vortex and the aerodynamic parameters of the compressor blade grid.

[0031] 3.1) According to the potential vortex radius r and the rotational angular velocity ω, the local total pressure loss coefficient at each position in the potential vortex can be calculated at the compressor passage outlet section: Where: V1 is the inlet speed, V m is the average velocity in the channel, υ is the dynamic viscosity, R is the ratio of the distance from the vortex center to the vortex radius at each position in the potential vortex, and the function

[0032] 3.2) According to the local total pressure loss coefficient at each position in the potential vortex , at any blade height section position, the local total pressure loss coefficient in the circumferential direction By integrating, the total pressure loss coefficient at any blade height within the suction influence range can be obtained: Where: x is the circumferential position in the blade channel, and t is the grating pitch.

[0033] The total pressure loss distribution of the compressor plane cascade outlet under 0.4% relative air extraction rate is obtained by subtracting the predicted total pressure loss of the plane cascade outlet under the condition of no air extraction from the total pressure loss of the plane cascade outlet under the condition of no air extraction, and compared with the results of numerical calculation, such as Figure 3 As shown, the predicted results are in good agreement with the numerical calculation results.

[0034] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A method for optimizing the extraction loss of an axial flow compressor, characterized in that: The radial influence range of the suction effect in the compressor mainstream is calculated according to the geometric parameters of the compressor blades, and the potential vortex characteristic parameters caused by the suction in the mainstream are calculated according to the suction flow rate and the compressor mainstream flow rate as well as the inlet and outlet aerodynamic parameters; the total pressure loss coefficient at each blade height section within the radial influence range is calculated by the potential vortex characteristic parameters to further optimize the axial flow compressor structure; The radial influence range of the suction effect in the main flow of the compressor refers to: the distance from the compressor casing Where: AR is the aspect ratio of the compressor blade, σ is the consistency at the mid-diameter; The radial influence range is 0.2<Δh<0.5; The potential vortex characteristic parameter, i.e., the potential vortex rotation angular velocity caused by the air extraction Relative air extraction volume Circulation r is the potential vortex radius, M bleed is the suction flow, M is the compressor mainstream flow, and the potential vortex radius caused by the suction in the mainstream K a is the vortex radius correction factor, which is 0.272, β1 is the inlet airflow angle, β2 is the outlet airflow angle, and σ is the compressor consistency; The total pressure loss coefficient at each blade height section within the radial influence range is Where: x is the circumferential position in the blade channel, t is the grid pitch, and the local total pressure loss coefficient at each position in the potential vortex V1 is the inlet speed, V m is the average velocity in the channel, υ is the dynamic viscosity, R is the ratio of the distance from the vortex center to the vortex radius at each position in the potential vortex, and the function 2. A system for calculating the extraction loss of an axial compressor for implementing the method of claim 1, characterized in that: include: The range determination unit calculates the influence range of the extraction in the mainstream according to the geometric parameters of the compressor. The potential vortex radius and speed unit calculates the potential vortex radius and speed caused by the extraction in the mainstream according to the geometric and flow field data of the compressor. The pressure loss coefficient unit calculates the total pressure loss coefficient of each point on the outlet section according to the potential vortex radius, speed and flow field data. The comprehensive unit performs mass flow weighted averaging in the circumferential direction according to the extraction influence range, potential vortex radius and total pressure loss coefficient of each outlet section to obtain the total pressure loss coefficient at different spanwise heights and update the axial flow compressor structure to minimize the total pressure loss coefficient to achieve optimization.

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