Method for predicting leakage losses in axial compressor grates

Abstract

A method for predicting leakage losses in axial compressor grates is disclosed. This method calculates the grate leakage flow rate based on the inlet and outlet aerodynamic parameters at the compressor's planar blade mid-diameter and the grate geometric parameters. Then, it calculates the compressor's mainstream loss caused by the grate leakage by comparing the grate leakage flow rate with the compressor's mainstream flow rate. Finally, it determines the influence range and radial distribution law of the grate leakage loss using the compressor's planar blade geometric parameters. This invention targets compressor stators with grate seals. During compressor design and analysis, it eliminates the need for experimental measurements. It predicts grate leakage flow losses using the aerodynamic parameters at the stator's mid-diameter and the geometric parameters of the grate cavity, considering the impact of the leakage flow on the compressor stator blade passages. This allows for the incorporation of the radial influence of grate leakage on compressor outlet performance into the compressor's flow path design and analysis, predicting the grate leakage flow rate, and the influence range and magnitude of the stator outlet loss caused by the grate leakage flow, thus achieving more refined flow path calculations for axial compressors.

Description

Technical Field

[0001] This invention relates to a technology in the field of impeller manufacturing, specifically a method for predicting leakage losses in the grates of an axial compressor. Background Technology

[0002] The ferrule structure of modern axial compressors is a typical aerodynamic sealing structure at the stator root. Due to the unavoidable gap between the rotating hub and the stator root, a certain amount of leakage flow occurs at the stator root. The mixing of this leakage flow with the mainstream flow affects the compressor's aerodynamic performance. To achieve refined flow calculations, a ferrule leakage loss model is needed to evaluate the impact of the ferrule gap on the compressor's aerodynamic performance. Existing methods predict the overall loss caused by ferrule leakage based on compressor geometry and aerodynamic parameters. However, this method struggles to calculate the distribution of ferrule leakage loss in the radial direction of the compressor, especially when the aspect ratio of the downstream stage is small in high-pressure compressors. This makes it difficult to accurately predict the radial distribution of the total pressure loss at the compressor outlet, resulting in low accuracy in compressor design based on flow calculations. Summary of the Invention

[0003] This invention addresses the shortcomings of existing technologies that cannot consider the impact of grate cavity leakage on the compressor stator blade passage. It proposes a method for predicting grate leakage losses in axial compressors. For compressor stators with grate seals, this method eliminates the need for experimental measurements during compressor design and analysis. It predicts grate leakage flow losses using aerodynamic parameters at the stator's mid-diameter and geometric parameters of the grate cavity, while also considering the impact of the leakage flow on the compressor stator blade passage. This allows for the incorporation of the radial influence of grate leakage on compressor outlet performance into the compressor's flow path design and analysis. It predicts the grate leakage flow rate, as well as the range and magnitude of the stator outlet loss caused by the grate leakage flow, achieving more refined flow path calculations for axial compressors.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to a method for predicting leakage loss of axial compressor grates. The method calculates the leakage flow rate of the grates based on the inlet and outlet aerodynamic parameters at the median diameter of the compressor planar blades and the geometric parameters of the grates. Then, the mainstream compressor loss caused by the grates leakage is calculated by comparing the leakage flow rate with the mainstream compressor flow rate. Finally, the influence range and radial distribution law of the leakage loss of the grates are determined by the geometric parameters of the compressor planar blades.

[0006] The aerodynamic parameters of the compressor planar blade cascade include: total inlet pressure at the mid-diameter, static inlet pressure, inlet density, total outlet pressure, and static outlet pressure.

[0007] The aforementioned comb tooth geometric parameters include: comb tooth gap, comb tooth diameter, and number of teeth.

[0008] The geometric parameters of the planar blade cascade include: chord length and blade height.

[0009] This invention relates to a system for implementing the above method, comprising: a leakage flow unit, a mainstream loss unit, and a radial distribution unit, wherein: the leakage flow unit calculates the grate leakage flow based on the total inlet and outlet pressure, static pressure, density, number of grate teeth, grate gap, and grate radius at the median diameter of the compressor stator; the mainstream loss unit calculates the compressor mainstream loss caused by the grate leakage based on the grate leakage flow calculated by the leakage flow unit and the mainstream flow; the radial distribution unit calculates the radial influence range and distribution law of the mainstream loss caused by the grate leakage based on the chord length and blade height of the compressor stator; and finally, the mainstream loss calculated by the mainstream loss unit is multiplied by the radial influence range and distribution law calculated by the radial distribution unit to obtain the radial distribution of the compressor stator mainstream loss caused by the grate leakage.

[0010] Technical effect

[0011] This invention predicts the influence range and radial distribution of the main pressure loss of the compressor stator caused by grate leakage based on the geometric parameters of the compressor stator. Compared with the prior art, this invention can consider the impact of grate cavity leakage flow on compressor performance during the flow path design and analysis stage of axial compressors, and predict the radial distribution of the total pressure loss at the compressor stator outlet caused by grate leakage flow. Attached Figure Description

[0012] Figure 1 This is a flowchart of the present invention;

[0013] Figure 2 This is a geometric schematic diagram of the compressor planar blade cascade with a grating cavity structure in the embodiment;

[0014] Figure 3 This is a diagram showing the radial distribution of leakage loss from the toothed grates.

[0015] Figure 4 This is a comparison chart of the calculated and numerical results of the leakage loss from the toothed grates. Detailed Implementation

[0016] This embodiment relates to a method for predicting the leakage loss of the grating teeth in an axial compressor. The method predicts the leakage loss of the grating teeth in a compressor planar blade cascade with a grating tooth cavity structure. Specifically, the method involves: calculating the grating tooth leakage flow rate based on the inlet and outlet aerodynamic parameters at the median diameter of the compressor planar blade cascade and the grating tooth geometric parameters; then calculating the compressor mainstream loss caused by the grating tooth leakage by comparing the grating tooth leakage flow rate with the compressor mainstream flow rate; and finally determining the influence range and radial distribution law of the grating tooth leakage loss by using the geometric parameters of the compressor planar blade cascade.

[0017] The design parameters of the compressor planar blade cascade in this embodiment are shown in Table 1.

[0018] Table 1 Design parameters of the compressor planar blade cascade

[0019]

[0020]

[0021] like Figure 1 As shown, the prediction method includes:

[0022] 1) According to such Figure 2 The calculation of the grate leakage flow rate is based on the inlet static pressure, outlet total pressure, and grate geometric parameters at the median diameter of the compressor planar blades, specifically including:

[0023] 1.1) Based on the inlet static pressure P1 at the median diameter of the compressor planar blades and the outlet total pressure... Leakage velocity is calculated based on the number of teeth on the comb. Where: ρ is the inlet density at the compressor's mid-diameter, and z is the number of teeth on the comb.

[0024] 1.2) Calculate the leakage flow rate M of the toothed comb. L =C c ρπD L δ L c L , where: c L δ represents the leakage velocity of the toothed comb. L D represents the gap between the teeth. L C is the diameter of the comb teeth. c The leakage shrinkage coefficient of the comb cavity is 0.8 in this embodiment.

[0025] 2) Calculate the compressor mainstream loss caused by the grate leakage by comparing the grate leakage flow rate with the compressor mainstream flow rate, specifically including:

[0026] 2.1) Calculate the relative leakage rate Where: M is the compressor's main flow rate;

[0027] 2.2) Calculate the total pressure loss of the main flow path caused by leakage from the toothed comb. in: This is the total inlet pressure at the median diameter of the compressor's planar blades.

[0028] 3) Determine the influence range and radial distribution law of the leakage loss of the compressor tooth based on the chord length and blade height of the compressor planar blade cascade, specifically including:

[0029] 3.1) Determine the radial influence range of the leakage loss of the toothed grates. Where: C is the chord length of the compressor planar blade cascade, H is the blade height, and in order to ensure the robustness of the prediction method, it is limited to 0.25 < Δh < 0.5;

[0030] 3.2) Calculate the distribution coefficient Where: h is the relative blade height position, and is based on the total pressure loss ω of the tooth leakage. sh With radial distribution coefficient f sh The tooth leakage loss ω at different radial positions at the compressor planar blade outlet was calculated. L =ω sh f sh The distribution coefficient distribution pattern is as follows: Figure 3 As shown.

[0031] 4) The predicted tooth leakage loss is superimposed with the total pressure loss at the outlet of the planar blade cascade under zero clearance condition to obtain the radial distribution of the total pressure loss at the outlet of the planar blade cascade with tooth leakage.

[0032] Based on specific practical experiments, CFD numerical simulations were conducted using a planar blade cascade with a grating cavity structure at an inlet Mach number of 0.66 and an inlet angle of attack of 0°. The results yielded the radial distribution of the total pressure loss at the outlet and the total pressure loss caused by grating leakage. The simulation results were compared with existing technologies, such as... Figure 4 As shown, the predicted results agree well with the numerical calculation results.

[0033] Compared to the existing technology, which predicts a leakage loss range of 0.23 for this implementation case, the leakage loss range predicted by this method is 0.34, which is consistent with the numerical simulation results. Regarding the prediction error of leakage loss, the existing technology has a relative error of 9% between the predicted and numerical results for the range of influence, while the relative error between the predicted and numerical results for leakage loss is 3%.

[0034] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A method for predicting leakage loss of axial compressor grates, characterized in that, The grate leakage flow rate is calculated based on the inlet and outlet aerodynamic parameters at the median diameter of the compressor planar blades and the grate geometric parameters. Then, the compressor mainstream loss caused by grate leakage is calculated by comparing the grate leakage flow rate with the compressor mainstream flow rate. Finally, the influence range and radial distribution law of the grate leakage loss are determined using the compressor planar blade geometric parameters, specifically including: 1) Calculate the grate leakage flow rate based on the inlet static pressure, outlet total pressure, and grate geometry parameters at the median diameter of the compressor planar blades. Specifically, this includes: 1.1) Based on the inlet static pressure at the median diameter of the compressor planar blades. Total export pressure Leakage velocity is calculated based on the number of teeth on the comb. ,in: denoted as ρ, where ρ is the inlet density at the compressor's mid-diameter, and z is the number of teeth on the grating. 1.2) Calculate the leakage flow rate of the toothed comb. ,in: For the leakage rate of the toothed teeth, For the gap between the comb teeth, The diameter of the comb teeth. The leakage shrinkage coefficient of the comb cavity; 2) Calculate the compressor mainstream loss caused by the grate leakage by comparing the grate leakage flow rate with the compressor mainstream flow rate, specifically including: 2.1) Calculate the relative leakage rate ,in: This is the mainstream flow rate of the compressor; 2.2) Calculate the total pressure loss of the main flow path caused by leakage from the toothed comb. ,in: This refers to the total inlet pressure at the median diameter of the compressor's planar blades. 3) Determine the influence range and radial distribution law of the leakage loss of the compressor tooth based on the chord length and blade height of the compressor planar blade cascade, specifically including: 3.1) Determine the radial influence range of the leakage loss of the toothed grates. ,in: Let be the chord length of the compressor planar blades. To ensure the robustness of the prediction method, it is limited to [specific parameters]. between; 3.2) Calculate the distribution coefficient ,in: The relative blade height position, and based on the total pressure loss due to tooth leakage. With radial distribution coefficient The leakage loss of the grates at different radial positions at the compressor planar blade outlet was calculated. ; 4) The predicted tooth leakage loss is superimposed with the total pressure loss at the outlet of the planar blade cascade under zero clearance condition to obtain the radial distribution of the total pressure loss at the outlet of the planar blade cascade with tooth leakage.

2. The method for predicting leakage loss of axial compressor grates according to claim 1, characterized in that, The aerodynamic parameters of the compressor planar blade cascade include: total inlet pressure at the mid-diameter, static inlet pressure, inlet density, total outlet pressure, and static outlet pressure. The aforementioned comb tooth geometric parameters include: comb tooth gap, comb tooth diameter, and number of teeth; The geometric parameters of the planar blade cascade include: chord length and blade height.

3. A system for implementing the method for predicting leakage losses of axial compressor grates as described in claim 1 or 2, characterized in that, include: The compressor consists of a leakage flow unit, a mainstream loss unit, and a radial distribution unit. The leakage flow unit calculates the grate leakage flow based on the total inlet and outlet pressure, static pressure, density, number of grate teeth, grate gap, and grate radius at the compressor stator mid-diameter. The mainstream loss unit calculates the compressor mainstream loss caused by grate leakage based on the grate leakage flow calculated by the leakage flow unit and the mainstream flow. The radial distribution unit calculates the radial influence range and distribution law of the mainstream loss caused by grate leakage based on the chord length and blade height of the compressor stator. Finally, the mainstream loss calculated by the mainstream loss unit is multiplied by the radial influence range and distribution law calculated by the radial distribution unit to obtain the radial distribution of the compressor stator mainstream loss caused by grate leakage.

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