A method for determining the leading edge of a low-speed simulated blade profile

Abstract

The present invention provides a method for determining the leading edge of a low-speed simulated blade profile, comprising the following steps: establishing a corresponding relationship between the blade profile curvature radius of a high-speed blade profile and a low-speed blade profile; selecting any number of positions of the high-speed blade profile as control points, and determining the curvature radius of the corresponding control point of the low-speed blade profile according to the corresponding relationship between the blade profile curvature radius of the high-speed blade profile and the low-speed blade profile; determining a preliminary curvature radius of the leading edge of the low-speed blade profile according to the curvature radius of the control point of the low-speed blade profile; determining a low-speed simulated blade profile according to the preliminary curvature radius of the leading edge of the low-speed blade profile and the parameters of the low-speed blade profile; and determining the leading edge D of the low-speed blade profile according to the low-speed simulated blade profile. Spike Peak, judge the low-speed blade leading edge D Spike Peak and high speed blade leading edge D Spike The peak satisfies the similarity condition. If the similarity condition is satisfied, the curvature radius of the leading edge of the low-speed blade is obtained. The present invention can quickly determine the shape, curvature radius and other parameters of the leading edge of the low-speed blade.

Description

Technical Field

[0001] The invention relates to the technical field of impeller machinery, and in particular to a method for determining a leading edge of a low-speed simulated blade profile. Background Art

[0002] Low-speed simulation test technology is a test technology that uses low-speed flow to simulate high-speed flow. Compared with high-speed compressors, low-speed model compressors have reduced speed and enlarged size. They have the advantages of low cost, low risk, and easy flow field measurement, and have become a key platform for the development and verification of key compressor technologies. The key issue in low-speed simulation test technology is the determination of low-speed model compressor parameters. According to the modeling idea of ​​low-speed simulation, Wisler of GE first constructed a low-speed modeling method and proposed a similarity criterion for the conversion of high-speed and low-speed compressors. Then, the high-speed compressor blades were decomposed into several primitives and low-speed simulation was performed on the primitive blade profile. In the current low-speed simulation, most of the design parameters including the mid-camber line, maximum thickness, and leading edge shape are adjusted based on the experience of designers through numerical simulation software. The leading edge has an important influence on the blade loss. The difference in the leading edge flow will bring about the difference in loss between high-speed and low-speed blade profiles, especially in the state of large angle of attack. Whether the leading edge flow is the same determines whether the loss changes with the angle of attack.

[0003] The leading edge obtained by the current determination method ignores the local difference of the flow around the leading edge of the blade at high speed and low speed, which makes the high and low speed blade loss change differently with the angle of attack. spike To measure the suction peak strength of the leading edge flow, Figure 1 Given D spike In the prior art design approach, the leading edge shape is kept consistent with the high-speed prototype. Figure 2 and Figure 3 The loss characteristics of low-speed simulated blades and high-speed blades in the existing design methods and the comparison of dimensionless velocity of blade surface are given respectively. It can be seen that the loss of low-speed simulated blades changes more slowly with the angle of attack, and there is a large difference at large angles of attack. The D of the design state spike Also weaker than high-speed blade type. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for determining the leading edge of a low-speed simulated blade profile. The method utilizes the relationship between the flow around the leading edges of a high-speed blade profile and a low-speed blade profile to derive key parameters such as the size, shape or curvature of the leading edge of the low-speed blade profile, thereby replacing the current manual iteration and achieving the effect of quickly determining the leading edge.

[0005] The present invention achieves the above technical objectives through the following technical means.

[0006] A method for determining a leading edge of a low-speed simulated blade profile comprises the following steps:

[0007] S01: Determine the chord length c at any position of the high-speed blade profile based on the high-speed blade profile h , density ρ at any position of high-speed blade h , the curvature radius r at any position of the high-speed blade h and the density ρ at the high-speed blade inlet h1 ;

[0008] S02: Establish the corresponding relationship between the blade curvature radius of the high-speed blade and the low-speed blade:

[0009]

[0010] in:

[0011] c h is the chord length at any position of the high-speed blade;

[0012] ρ h is the density at any position of the high-speed blade;

[0013] r h is the radius of curvature at any position of the high-speed blade;

[0014] ρ h1 is the density at the high-speed blade inlet;

[0015] c l is the chord length at any position of the low-speed blade;

[0016] ρ1 is the density at any position of the low-speed blade;

[0017] r i is the radius of curvature at any position of the low-speed blade;

[0018] ρ l1 is the density at the low-speed blade inlet;

[0019] S03: Selecting any number of positions of the high-speed blade profile as control points, and determining the curvature radius of the low-speed blade profile corresponding to the control point according to the corresponding relationship between the blade profile curvature radius of the high-speed blade profile and the low-speed blade profile;

[0020] S04: determining a preliminary curvature radius of a leading edge of a low-speed blade profile according to the curvature radius fitting of a low-speed blade profile control point; determining a blade profile for low-speed simulation according to the preliminary curvature radius of the leading edge of the low-speed blade profile and parameters of the low-speed blade profile;

[0021] S05: Determine the low-speed blade leading edge D based on the blade profile simulated at low speed Spike Peak, judge the low-speed blade leading edge D Spike Peak and high speed blade leading edge D SpikeWhether the peak meets the similarity condition, if not, the number of control points is increased in S03, and S03-S05 are repeated until the similarity condition is met; if the similarity condition is met, the curvature radius of the leading edge of the low-speed blade is obtained, thereby obtaining the leading edge of the low-speed blade.

[0022] Furthermore, the similarity condition is that the low-speed blade leading edge D Spike Peak and high speed blade leading edge D Spike The relative error of the peak is within ±0.02.

[0023] Furthermore, in the step S03, the stagnation point of the leading edge of the high-speed blade, the Spike position of the suction surface, the Spike position of the pressure surface, and the junction point between the leading trailing edge and the blade body are selected as control points.

[0024] Furthermore, the preliminary curvature radius of the leading edge of the low-speed blade profile is determined by fitting in the form of an ellipse according to the curvature radius of the low-speed blade profile control point.

[0025] A low-speed simulated blade profile is designed using a low-speed simulated blade profile leading edge determination method.

[0026] The beneficial effects of the present invention are:

[0027] 1. The method for determining the leading edge of a low-speed simulated blade profile described in the present invention provides a formula for determining the curvature radius at any position of the leading edge of the low-speed blade profile through the curvature radius constraint relationship between the high-speed blade profile and the low-speed blade profile. The shape, curvature radius and other parameters of the leading edge of the low-speed blade profile can be quickly determined, thereby replacing the current manual repeated iterations and achieving the effect of quickly determining the leading edge.

[0028] 2. The method for determining the leading edge of a low-speed simulated blade profile according to the present invention is to determine the leading edge of the low-speed blade profile D Spike Peak and high speed blade leading edge D Spike Peak is used as the judgment condition, and the leading edge of the low-speed blade is fine-tuned to make the loss development law of the high-speed and low-speed blades basically consistent, and the total pressure loss value at large angle of attack is basically the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For ordinary technicians in this field, it is obvious that other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 D spike Define the schematic diagram.

[0031] Figure 2The figure is a comparison chart of blade angle of attack-loss characteristics of high-speed and low-speed blades using existing design methods.

[0032] Figure 3 The leading edge D of the high and low speed blades in the existing design method spike Comparison chart.

[0033] Figure 4 This is a flow chart of the method for determining the leading edge of a low-speed simulated blade profile according to the present invention.

[0034] Figure 5 1 is a comparison diagram of the leading edge shapes of high-speed and low-speed blade profiles according to an embodiment of the present invention.

[0035] Figure 6 It is a comparison diagram of blade attack angle-loss characteristics of high-speed and low-speed blades according to an embodiment of the present invention.

[0036] Figure 7 Dimensionless velocity comparison of blade surface of high-speed and low-speed blade profiles according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0038] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0039] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0040] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] like Figure 4 As shown, the method for determining the leading edge of a low-speed simulated blade profile according to the present invention comprises the following steps:

[0042] S01: Determine the chord length c at any position of the high-speed blade profile based on the high-speed blade profile h , density ρ at any position of high-speed blade h , the curvature radius r at any position of the high-speed blade h and the density ρ at the high-speed blade inlet h1 ;

[0043] S02: Establish the corresponding relationship between the blade curvature radius of the high-speed blade and the low-speed blade. The calculation process is as follows:

[0044] Assuming that any position in the first stage can be regarded as a circular motion around the leading edge, the control equation can be expressed as:

[0045]

[0046] Where: u represents velocity, r represents the radius of curvature, ρ represents density, and p represents the leaf surface pressure.

[0047] The chord length and blade tip tangential velocity are introduced to make the radius and dynamic pressure head dimensionless:

[0048]

[0049] Where c1 represents the inlet chord length, u1 represents the inlet velocity, and ρ1 is the density at the inlet.

[0050] In the current low-speed simulation, the design results require that the dimensionless velocity of the blade surface based on the inlet velocity is equal, so:

[0051]

[0052] The subscript h in the formula indicates a high-speed blade, l indicates a low-speed blade, subscript 1 indicates the blade inlet, and u h Indicates the speed at any position of the high-speed blade, u l Indicates the speed at any position of the low-speed blade, u h1 represents the velocity at the high-speed blade inlet, ul1 Indicates the speed at the low-speed blade inlet position;

[0053] At the same time, the pressure distribution on the blade surface based on the inlet of the high-speed and low-speed blade leading edges should be consistent, so the pressure gradient based on the dimensionless arc length should be consistent, so:

[0054]

[0055] Combining formulas (2), (3), and (4), we can obtain:

[0056]

[0057] in:

[0058] c h is the chord length at any position of the high-speed blade;

[0059] ρ h is the density at any position of the high-speed blade;

[0060] r h is the radius of curvature at any position of the high-speed blade;

[0061] ρ h1 is the density at the high-speed blade inlet;

[0062] c l is the chord length at any position of the low-speed blade;

[0063] ρ l is the density at any position of the low-speed blade;

[0064] r l is the radius of curvature at any position of the low-speed blade;

[0065] ρ l1 is the density at the low-speed blade inlet;

[0066] S03: Select any number of positions of the high-speed blade profile as control points, and determine the curvature radius of the corresponding control point of the low-speed blade profile according to the corresponding relationship between the blade curvature radius of the high-speed blade profile and the low-speed blade profile; in order to simplify the process, in actual operation, the leading edge stagnation point of the high-speed blade profile, the suction surface Spike position, the pressure surface Spike position and the junction point between the leading trailing edge and the blade body are preferentially selected as control points.

[0067] S04: determining a preliminary curvature radius of a leading edge of the low-speed blade profile by fitting in the form of an ellipse according to the curvature radius of the low-speed blade profile control point; determining a blade profile for low-speed simulation according to the preliminary curvature radius of the leading edge of the low-speed blade profile and the parameters of the low-speed blade profile;

[0068] S05: Determine the low-speed blade leading edge D based on the blade profile simulated at low speed SpikePeak, judge the low-speed blade leading edge D Spike Peak and high speed blade leading edge D Spike Is the peak relative error within ±0.02? If it exceeds the range of ±0.02, add a point other than the stagnation point of the high-speed blade leading edge, the suction surface Spike position, the pressure surface Spike position, and the junction point between the leading trailing edge and the blade body in S03 as a control point, and repeat S03-S05 until the relative error is within ±0.02; if the relative error is within ±0.02, the curvature radius of the low-speed blade leading edge is obtained.

[0069] Example

[0070] A high-speed blade profile of a high-pressure compressor is selected, and the parameters are shown in Table 1. The leading edge of the high-speed blade profile is a circular leading edge, and the ratio of the leading edge radius to the chord length is 1.0%.

[0071] Table 1 Comparison of high-speed blade profile and low-speed simulated blade profile parameters

[0072]

[0073]

[0074] Figure 3 The low-speed blade profile and high-speed blade profile obtained by the existing design method are compared. spike The D of the low-speed blade is 0.388. spike is 0.2, and the difference between the two is quite large. spike will have a significant impact on the blade loss, so Figure 2 The loss characteristics of the high speed profile and the low speed simulated reference profile shown are significantly different.

[0075] The method for determining the leading edge of a low-speed simulated blade profile of the present invention comprises the following steps:

[0076] S01: The characteristic line of the high-speed blade and the dimensionless velocity distribution of the blade surface at the reference angle of attack are calculated using numerical simulation software to determine the chord length c at any position of the high-speed blade. h , density ρ at any position of high-speed blade h , the curvature radius r at any position of the high-speed blade h and the density ρ at the high-speed blade inlet h1 ;

[0077] S02: Establishing a corresponding relationship between the blade curvature radius of the high-speed blade and the low-speed blade;

[0078] S03: Select the leading edge stagnation point of the high-speed blade profile, the suction surface Spike position, the pressure surface Spike position and the junction point between the leading and trailing edge and the blade body as control points, and determine the curvature radius of the corresponding control point of the low-speed blade profile according to the corresponding relationship between the blade curvature radius of the high-speed blade profile and the low-speed blade profile;

[0079] S04: Use an ellipse to fit the curve to determine the initial curvature radius of the leading edge of the low-speed blade profile. The final low-speed blade profile is approximately an elliptical leading edge with a major axis radius of 1.95% of the chord length and a major-minor axis ratio of 2.17. The comparison of the leading edge is Figure 5 As shown. The blade profile for low-speed simulation is determined based on the preliminary curvature radius of the leading edge of the low-speed blade profile and the parameters of the low-speed blade profile;

[0080] S05: Use numerical simulation software to calculate the angle of attack-loss characteristics of the low-speed blade and the dimensionless velocity distribution of the blade surface at the reference angle of attack, and compare them with the high-speed blade. Figure 6 and Figure 7 As shown in the figure, it can be seen that the development law of high and low speed blade loss is basically the same, and the total pressure loss value at large angle of attack is basically the same; according to the blade shape simulated at low speed, the leading edge D of the low speed blade shape is determined Spike The peak is 0.379, while the D spike The peak is 0.388, and the difference between the two is 0.009, which satisfies the leading edge D spike The blade surface velocity distribution of high-speed and low-speed blades is also relatively consistent. Therefore, the method proposed in the present invention has a significant improvement over the original method.

[0081] A low-speed simulated blade profile is designed using the low-speed simulated blade profile leading edge determination method described in the present invention.

[0082] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0083] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for determining the leading edge of a low-speed simulated blade profile, characterized in that: The steps include: S01: Determine the chord length c at any position of the high-speed blade profile based on the high-speed blade profile h , density ρ at any position of high-speed blade h , the radius of curvature r at any position of the high-speed blade h and the density ρ at the high-speed blade inlet h1 ; S02: Establish the corresponding relationship between the blade curvature radius of the high-speed blade and the low-speed blade: in: c h is the chord length at any position of the high-speed blade; ρ h is the density at any position of the high-speed blade; r h is the radius of curvature at any position of the high-speed blade; ρ h1 is the density at the high-speed blade inlet; c l is the chord length at any position of the low-speed blade; ρ l is the density at any position of the low-speed blade; r l is the radius of curvature at any position of the low-speed blade; ρ l1 is the density at the low-speed blade inlet; S03: Selecting any number of positions of the high-speed blade profile as control points, and determining the curvature radius of the low-speed blade profile corresponding to the control point according to the corresponding relationship between the blade profile curvature radius of the high-speed blade profile and the low-speed blade profile; S04: determining a preliminary curvature radius of a leading edge of a low-speed blade profile according to the curvature radius fitting of a low-speed blade profile control point; determining a blade profile for low-speed simulation according to the preliminary curvature radius of the leading edge of the low-speed blade profile and parameters of the low-speed blade profile; S05: Determine the low-speed blade leading edge D based on the blade profile simulated at low speed Spike Peak, judge the low-speed blade leading edge D Spike Peak and high speed blade leading edge D Spike Whether the peak meets the similarity condition, if not, the number of control points is increased in S03, and S03-S05 are repeated until the similarity condition is met; if the similarity condition is met, the curvature radius of the leading edge of the low-speed blade is obtained, thereby obtaining the leading edge of the low-speed blade.

2. The method for determining the leading edge of a low-speed simulated blade profile according to claim 1, characterized in that: The similarity condition is the low speed blade leading edge D Spike Peak and high speed blade leading edge D Spike The relative error of the peak is within ±0.

02.

3. The method for determining the leading edge of a low-speed simulated blade profile according to claim 1, characterized in that: In the step S03, the high-speed blade leading edge stagnation point, the suction surface Spike position, the pressure surface Spike position and the junction point between the leading trailing edge and the blade body are selected as control points.

4. The method for determining the leading edge of a low-speed simulated blade profile according to claim 3, characterized in that: The initial curvature radius of the low-speed blade leading edge is determined by fitting in the form of an ellipse according to the curvature radius of the low-speed blade control point.

5. A low-speed simulated blade profile, characterized in that: A low-speed simulated blade profile designed using the low-speed simulated blade profile leading edge determination method described in any one of claims 1-4.

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