Reynolds number correction method for turbofan engine based on equal load coefficient

Abstract

The turbofan engine Reynolds number correction method based on the equal load coefficient of the application, including S1: determining the test point of the non-self-model area and the self-model area; S2: taking the test point of the non-self-model area as a correction point, and taking the test point of the self-model area as a reference point; S3: obtaining the component Reynolds number correction factor under different Reynolds number index conditions according to the equal load coefficient correction, and establishing a Reynolds number correction relationship curve; S4: applying the component Reynolds number correction relationship curve to the corresponding component performance of the baseline overall performance calculation model to obtain an engine overall performance calculation model with Reynolds number correction. Avoid the situation that the calculation deviation of the whole machine model is large due to the influence of Reynolds number at high altitude and low Mach number.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine design and testing technology, and particularly relates to a method for correcting the Reynolds number of a turbofan engine based on an equal load coefficient. Background Technology

[0002] The Reynolds number is one of the important criteria for measuring the impact of fluid viscosity on the performance of various components of an aero-engine. Nowadays, with the continuous expansion of the operating range of aero-engines, especially under high-altitude and low-speed operating conditions, atmospheric pressure and density drop significantly. The Reynolds number at the engine inlet is far below the critical value and is in the non-self-mode region. This causes the airflow to separate at the suction surfaces of the compressor and turbine blades, increasing frictional drag and flow losses. The flow field characteristics deviate from the design state, and the performance of compressor and turbine components declines, thus affecting engine performance.

[0003] Domestic and international scholars have conducted extensive research on the impact of Reynolds number on aero-engine performance. Currently, the Wassell Reynolds number correction method is relatively widely used in Reynolds number correction. This method is a semi-empirical Reynolds number effect correction method established based on experimental data from a series of compressor test components with different stages. However, it is only applicable to Reynolds number correction of compression components. With the advancement of compressor technology, the accuracy of traditional semi-empirical Reynolds number effect correction methods has decreased. For turbine components, the main correction method is the Russian Litesnov unified empirical relation curve, which is a fitting result of statistically analyzing a large amount of turbine test data. However, the above correction methods reference component test data from the 1960s and 70s and are not applicable to current technological levels, therefore, they will have significant errors. Summary of the Invention

[0004] In view of this, the Reynolds number correction method for turbofan engines based on equal load coefficients provided by this invention solves the technical problem that existing methods have large errors.

[0005] A method for correcting the Reynolds number of a turbofan engine based on an equal load factor is provided, the method comprising:

[0006] S1: Determine the test points in the non-self-model region and the self-model region, wherein there are multiple test points in the non-self-model region, and the engine inlet Reynolds number of the test points in the non-self-model region meets the preset span; S2: The test points in the non-self-model region are used as correction points, and the test points in the self-model region are used as reference points. The engine inlet Reynolds number between the correction points must meet the preset span, and the reference point is selected from the region where the engine inlet Reynolds number is greater than the critical value. S3: Based on the equal load factor correction, the component Reynolds number correction factor under different Reynolds number exponents can be obtained, and the relationship curve between the Reynolds number exponent and the correction factor can be established.

[0007] S4: Apply the Reynolds number correction curves of each component to the component performance corresponding to the baseline overall performance calculation model to obtain the overall engine performance calculation model with Reynolds number correction.

[0008] The beneficial effects of this invention are: The method of this invention utilizes the results from a small number of test points to obtain the Reynolds number correction curves for each component, thereby revealing the impact of the Reynolds number on the performance of each component. This improves the calculation accuracy of the overall engine performance model in the non-self-modeling region, demonstrating significant engineering application value. In particular, it avoids the situation where the Reynolds number influences large calculation deviations in the overall engine model at high altitudes and low Mach numbers. Attached Figure Description

[0009] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 The calculation process for the Reynolds number correction curves for each component; Figure 2 For the characteristics of compression components; Figure 3 Characteristics of turbine components. Detailed Implementation

[0011] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0012] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0013] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this invention, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using other structures and / or functionalities besides one or more of the aspects set forth herein.

[0014] like Figure 1 The method for correcting the Reynolds number of a turbofan engine based on an equal load coefficient, as shown, is characterized in that the method includes: S1: Determine the test points in the non-self-modeling region and the self-modeling region. There are multiple test points in the non-self-modeling region. The engine inlet Reynolds number at the test points in the non-self-modeling region must meet a preset range. Specifically: The more correction points the better, with at least three recommended. The engine inlet Reynolds number between correction points should have a certain range (depending on the specifications). The reference point should be selected near the area where the engine inlet Reynolds number is greater than the critical value.

[0015] S2: The test points in the non-self-model region are used as correction points, and the test points in the self-model region are used as reference points. The engine inlet Reynolds number between the correction points must meet a preset span. The reference points are selected from regions where the engine inlet Reynolds number is greater than a critical value. Specifically: The Reynolds number exponent RNI is used to characterize the change or magnitude of the Reynolds number, satisfying the following: RNI is defined as the ratio of the corrected point Reynolds number to the reference point Reynolds number under the condition that the inlet Mach number of the components is the same, as shown in equation (2), where the RNI of the reference point is 1. Under the condition of the whole machine, the converted speed of the rotor component can approximately characterize its inlet Mach number. Therefore, under the same converted speed condition, the inlet Mach number of the components is basically the same.

[0016] Since the characteristic dimensions of the component remain constant, based on the ideal gas equation, the aerodynamic functions of total static pressure and total static temperature in one-dimensional isentropic flow, and the condition that the Mach number at the component inlet is the same, the Reynolds number exponent can be derived, satisfying:

[0017] in, Indicates the total inlet pressure of the component. Indicates the total temperature at the component inlet. This represents the dynamic viscosity coefficient, and the subscript ref indicates the reference point.

[0018] S3: Determine the Reynolds number correction factor for each component based on the load factor, and obtain the relationship curve between the Reynolds number exponent and the correction factor. Specifically, statistically fit the Reynolds number correction factor of each component to loge (Reynolds number exponent) into a quadratic relationship curve to obtain the Reynolds number correction relationship curve for each component. The Reynolds number correction factor used in this invention is the correction amount for the converted flow rate and efficiency of each component under the influence of the Reynolds number. Specifically: 1) Select test results under the same converted speed conditions at each correction point, and use the equal load coefficient to obtain the Reynolds number correction factor for the performance of each component at each correction point. Statistically analyze the relationship between the Reynolds number index and the performance correction factor of each component to obtain the Reynolds number correction relationship curve for each component. The form of the relationship curve is shown in equation (4). This curve can reflect the influence of the Reynolds number on the performance of each component, such as... (4), where abc is the fitting coefficient of the relationship curve; 2) Operating point A is the result of the test data evaluation, and the converted load factor of operating point A is calculated. On the component characteristic diagram, a point with the same converted speed line as point A is identified as operating point B. That is, the converted load factor of point A is determined on the component characteristic diagram through the converted speed line (the converted speed of the component is the same, so the speed of point B is the same as that of A), and the point with the same converted load factor as point A is identified as point B. 3) Calculate the Reynolds number correction factor for the compression component performance based on the characteristic parameters of operating points A and B. That is, calculate the Reynolds number correction factor, such as... Figure 2 The overall performance calculation model uses the characteristic diagram of the compression component (determined based on known component test results or simulation results, without considering the influence of Reynolds number). Operating point B on the compression component characteristic diagram and actual component test operating point A are selected. The Reynolds number correction factor for the compression component performance is calculated based on the characteristic parameters of points A and B. The calculation method for the Reynolds number correction factor of the turbine component is the same as that for the compression component characteristics, specifically: The load factor of the compression component satisfies: ,in, These are constants related to the conversion parameters of the compression components. For the compression component pressure ratio, To improve the efficiency of compressed components, To calculate the relative rotational speed of the compression components, Specific heat ratio; The equivalent load factor for the turbine components satisfies: In the formula, These are constants related to the turbine conversion parameters. The turbine expansion ratio, For turbine efficiency, To convert the speed relative to the speed, Specific heat ratio.

[0019] 4) Determine the correction factor for component efficiency. Correction factor for component flow ,satisfy: ,in, For the efficiency of work point A, The efficiency of work point B; See Figure 3 , , The converted flow rate for work point A. The converted flow rate for work point B; Obtain fitting curves for the correction factors of component efficiency and component flow rate, for example, plot the correction factors of component efficiency respectively. Correction factor for component flow The fitted curve to loge (Reynolds number exponent), where logx represents the natural logarithm function.

[0020] S4: Apply the Reynolds number correction curves of each component to the component performance corresponding to the baseline overall performance calculation model to obtain the overall engine performance calculation model with Reynolds number correction. Specifically: Substitute the obtained Reynolds number correction curves of each component into the overall performance calculation model to correct the performance of each component, and the overall engine performance calculation model with Reynolds number correction can be obtained.

[0021] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for correcting the Reynolds number of a turbofan engine based on an equal load coefficient, characterized in that, The method includes: S1: Determine the test points in the non-self-model region and the self-model region, wherein there are multiple test points in the non-self-model region, and the engine inlet Reynolds number of the test points in the non-self-model region meets the preset span; S2: The test points in the non-self-model region are used as correction points, and the test points in the self-model region are used as reference points. The engine inlet Reynolds number between correction points must meet a preset span. The reference points are selected from regions where the engine inlet Reynolds number is greater than a critical value. The Reynolds number index (RNI) is used to characterize the change or magnitude of the Reynolds number, satisfying the following: in, Indicates the total inlet pressure of the component. Indicates the total temperature at the component inlet. This represents the dynamic viscosity coefficient, and the subscript ref indicates the reference point; S3: Based on the equal load factor correction, obtain the component Reynolds number correction factor under different Reynolds number exponents, and establish the relationship curve between the Reynolds number exponent and the correction factor, including, After obtaining the operating point A of the compression component based on the test results, find the operating point B on the characteristic diagram of the compression component. Here, the operating point A is the result of the test data evaluation, and the converted load coefficient of the operating point A is calculated. On the iso-converted speed line on the component characteristics, determine the point with the same load coefficient as point A, and take it as the operating point B. The performance Reynolds number correction factor of the compression component is calculated based on the characteristic parameters of the operating points A and B. The load factor of the compression component satisfies: ,in, These are constants related to the conversion parameters of the compression components. For the compression component pressure ratio, To improve the efficiency of compressed components, To calculate the relative rotational speed of the compression components, Specific heat ratio; The equivalent load factor for the turbine components satisfies: In the formula, These are constants related to the turbine conversion parameters. The turbine expansion ratio, For turbine efficiency, To convert the speed relative to the speed, Specific heat ratio; Determine the correction factor for component efficiency Correction factor for component flow ,satisfy: ,in, For the efficiency of work point A, The efficiency of work point B; , The converted flow rate for work point A. The converted flow rate for work point B; Statistical analysis was performed to examine the relationship between the Reynolds number exponent and the performance correction factors of each component, and the correction factors for component efficiency were plotted separately. Correction factor for component flow and The fitted curve is expressed as follows: , where abc are the fitting coefficients of the relationship curve; By fitting multiple sets of data to obtain a curve, the fitting coefficients are determined. S4: Apply the Reynolds number correction curves of each component to the component performance corresponding to the baseline overall performance calculation model to obtain the overall engine performance calculation model with Reynolds number correction.

2. The correction method according to claim 1, characterized in that, The test point in the non-self-model region has an engine inlet Reynolds number that meets the preset range.

3. The correction method according to claim 1, characterized in that, In S4, the Reynolds number correction curves for each component are applied to the component performance corresponding to the baseline overall performance calculation model, resulting in an engine overall performance calculation model with Reynolds number correction, including: The Reynolds number correction curve is applied to the correction of component characteristics.

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