A reynolds number correction method for heat exchange error of total temperature thermocouple

Abstract

The application provides a Reynolds number correction method for total temperature thermocouple heat exchange error, comprising the following steps: S1: obtaining total temperature thermocouple heat exchange error data corresponding to at least two different Reynolds number working points under the same Mach number condition; S2: using the at least two heat exchange error data to fit a fitting coefficient through a reference point normalization single-parameter power law model; S3: setting a known heat exchange error Reynolds number working point as a reference working point, and recording the Mach number, Reynolds number and heat exchange error of the reference working point; and S4: inputting a target working point Reynolds number, and calculating the heat exchange error of the target working point according to the fitting coefficient obtained in step S2 and the reference working point data obtained in step S3. The application is based on a reference point normalization single-parameter power law model, can quickly construct a functional relationship between the heat exchange error and the Reynolds number with very few experimental data, and solves the problem that the realization of a low Reynolds number environment requires high experimental equipment and is costly.

Description

Technical Field

[0001] This invention relates to the field of aero-engine technology, and specifically to a method for correcting the Reynolds number of total temperature thermocouple heat transfer error. Background Technology

[0002] Accurate temperature measurement is a prerequisite for accurately evaluating aero-engine performance, and accurate performance evaluation is crucial for the development of next-generation engines. With the increasing demand for aero-engines to "fly higher and faster," the air density at high altitudes decreases, highlighting the challenges of low Reynolds numbers. In low Reynolds number environments, due to decreased heat transfer density and reduced heat content per unit volume of fluid, the steady-state error of the total temperature thermocouple (composed of velocity error, thermal conduction error, and radiation error) increases significantly. However, the Reynolds number primarily affects the magnitude of heat transfer errors (including thermal conduction and radiation errors), while its impact on velocity error is minimal. Therefore, research on correcting the total temperature thermocouple heat transfer error in low Reynolds number environments is urgently needed.

[0003] However, achieving a low Reynolds number environment requires sophisticated equipment and is expensive, and conducting low Reynolds number tests solely for probe calibration is often not worth the effort. Summary of the Invention

[0004] In view of this, the present invention provides a method for correcting the Reynolds number of the total temperature thermocouple heat transfer error.

[0005] This invention provides the following technical solution: a method for correcting the Reynolds number of total temperature thermocouple heat transfer error, comprising:

[0006] S1: Under the same Mach number condition, obtain total temperature thermocouple heat transfer error data corresponding to at least two different Reynolds number operating points; S2: Using the at least two heat transfer error data, fit coefficients are obtained by fitting a reference point normalized single-parameter power-law model. S3: Set the Reynolds number operating point with known heat transfer error as the reference operating point, and record the Mach number, Reynolds number and heat transfer error of the reference operating point; S4: Input the Reynolds number of the target operating point, and calculate the heat transfer error of the target operating point based on the fitting coefficients obtained in step S2 and the reference operating point data obtained in step S3.

[0007] Compared with the prior art, the beneficial effects that the above-mentioned at least one technical solution adopted by the present invention can achieve include at least the following: The present invention is based on a single-parameter power-law model with reference point normalization, which can quickly construct the functional relationship between heat transfer error and Reynolds number with very little experimental data, and solve the problem that the realization of low Reynolds number environment requires high experimental equipment and is expensive. Attached Figure Description

[0008] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 This is a flowchart illustrating an embodiment of the present invention; Figure 2 This is a graph comparing the results of numerical simulation with the calculated values ​​from the fitting formula under the condition that Ma is 0.1; Figure 3 This is a graph comparing the results of numerical simulation with the calculated values ​​from the fitting formula under the condition that Ma is 0.2; Figure 4 This is a graph comparing the results of numerical simulation with the calculated values ​​from the fitting formula under the condition that Ma is 0.3; Figure 5 This is a graph comparing the results of numerical simulation with the calculated values ​​from the fitting formula under the condition that Ma is 0.4; Figure 6 This is a graph comparing the results of numerical simulation with the calculated values ​​from the fitting formula under the condition that Ma is 0.5; Figure 7 This is a graph comparing the results of numerical simulation with the calculated values ​​from the fitting formula under the condition that Ma is 0.6. Detailed Implementation

[0010] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0011] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0012] Under steady-state conditions, convective heat transfer occurs simultaneously between the sensing end of the total temperature thermocouple and the airflow, as well as heat conduction through the support rod and radiative heat dissipation to the surrounding walls. The energy conservation equation can be expressed as: (1) in The convective heat transfer coefficient is... Heat exchange area, The static temperature of the fluid inside the shield (i.e., the total temperature of the incoming flow minus the velocity error). This is the actual temperature of the thermocouple measuring end. The temperature of the rib root of the even wire. The thermal resistance of the even wire, For surface emissivity, Let be the blackbody radiation constant. The ambient temperature around the even wire node.

[0013] Among them, heat transfer error ,but Then the expression can be transformed into: (2) For total temperature thermocouples, the heat transfer error... Therefore, the radiation term can be linearized. ,Right now ,but After substituting, the formula can be simplified to: (3) It can be solved The expression is: (4) For a typical total temperature thermocouple, due to And in the molecule Regardless of the Reynolds number, we can simplify it to: (5) in .because Therefore, we can conclude that (6) Based on this, the following heat transfer error fitting formula is proposed: (7) in It is a constant, affected by parameters such as the structure, materials, and airflow temperature of the total temperature thermocouple. To facilitate engineering applications and reduce undetermined parameters, a reference point normalization method is further adopted to obtain the fitting formula for the heat transfer error, as shown in equation (8). Based on the known magnitude of the heat transfer error under a certain Reynolds number condition, the magnitude of the heat transfer error under different Reynolds number conditions can be predicted. Where the subscripts are... Data representing the reference point, subscript Data representing the target operating condition. The fitting coefficients are included. The expression is shown in equation (9). The fitting coefficients require fitting the heat transfer errors of two different Reynolds number conditions under the same Ma number condition. This represents the magnitude of the total temperature thermocouple heat transfer error, which is the sum of the thermal conduction error and the radiation error.

[0014] (8) (9) Based on this, Figure 1As shown, the Reynolds number correction method for total temperature thermocouple heat transfer error according to the present invention includes the following steps: S1: Under the same Mach number condition, obtain total temperature thermocouple heat transfer error data corresponding to at least two different Reynolds number operating points; S2: Using the at least two heat transfer error data, fit coefficients are obtained by fitting a reference point normalized single-parameter power-law model. S3: Set the Reynolds number operating point with known heat transfer error as the reference operating point, and record the Mach number, Reynolds number and heat transfer error of the reference operating point; S4: Input the Reynolds number of the target operating point, and calculate the heat transfer error of the target operating point based on the fitting coefficients obtained in step S2 and the reference operating point data obtained in step S3.

[0015] The following is a specific implementation of this patent, which is shown in Table 1, by inputting the heat transfer error of a shielded thermocouple with a certain configuration under a certain Reynolds number environment.

[0016] Table 1 Numerical simulation data used for fitting the formula

[0017] Parameter fitting was performed at two different Reynolds number conditions under different Mach numbers. Different fitting coefficients were obtained for each Mach number. The results of the numerical simulation were compared with the fitting formulas. The comparison results are shown in Figures 2 to 3. Figure 7 As shown in the figure, the solid line represents the fitted formula, and the data points represent the total temperature thermocouple heat transfer error under different Reynolds number environments obtained from numerical simulation. In summary, this fitted formula has high accuracy under different Reynolds number environments and requires minimal data.

[0018] The following description uses a specific embodiment as an example: S1: Input the magnitude of the heat transfer error at two different Reynolds number operating points under the same Ma number, as shown below: Operating point 1: =0.3, =13300, heat transfer error =25.61K; Operating point 2: =0.3, =253000, heat transfer error =4.67K.

[0019] S2: Fitting coefficients using two operating condition parameters The calculation formula is as follows: The fitting coefficient can be calculated to be . .

[0020] S2: Select a certain input working condition point as the reference point. Taking working condition point 2 as an example, the fitting formula can be transformed into: In this formula , The parameters at the reference point are known quantities; the only variable is the Reynolds number at the target operating point. .

[0021] S3: Input the Reynolds number for the target operating condition. For example, input the target Reynolds number respectively: =33464, =55694, =55694, substituting this into the fitting formula, we get =14.91K, =11.02K, =6.89K. Comparing this with the results obtained from numerical simulations, the heat transfer errors obtained from the numerical simulations at these three target Reynolds numbers are as follows: =16.66K, =12.45K, =7.59K. It can be found that the developed fitting formula can accurately predict the total temperature thermocouple heat transfer error at different Reynolds numbers.

[0022] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical solutions, and technical solutions in this invention can be freely combined and used.

Claims

1. A method for correcting the Reynolds number of total temperature thermocouple heat transfer error, characterized in that, include: S1: Under the same Mach number condition, obtain total temperature thermocouple heat transfer error data corresponding to at least two different Reynolds number operating points; S2: Using the at least two heat transfer error data, fit coefficients are obtained by fitting a reference point normalized single-parameter power-law model. S3: Set the Reynolds number operating point with known heat transfer error as the reference operating point, and record the Mach number, Reynolds number and heat transfer error of the reference operating point; S4: Input the Reynolds number of the target operating point, and calculate the heat transfer error of the target operating point based on the fitting coefficient obtained in step S2 and the reference operating point data obtained in step S3. In step S2: the fitting formula for the fitting coefficients is... E h1 The total temperature thermocouple heat transfer error data for the first operating point, R e1 E is the Reynolds number at the first operating point; h2 The total temperature thermocouple heat transfer error data for the second operating point, R e2 The Reynolds number at the second operating point; The reference point normalized single-parameter power-law model is as follows: under the condition that the total temperature thermocouple heat transfer error is less than the static temperature of the fluid inside the shield, the radiation term is linearized so that the heat transfer error and the Reynolds number have a power-law relationship.

2. The Reynolds number correction method for total temperature thermocouple heat transfer error according to claim 1, characterized in that, The heat transfer error is the sum of the thermal conductivity error and the radiation error.

3. The Reynolds number correction method for total temperature thermocouple heat transfer error according to claim 2, characterized in that, Step S2 is performed for different incoming Mach numbers to obtain the fitting coefficients corresponding to each Mach number.

4. The Reynolds number correction method for total temperature thermocouple heat transfer error according to claim 3, characterized in that, The total temperature thermocouple heat transfer error data at the two different Reynolds number operating points were obtained through fluid dynamics numerical simulation. The numerical simulation was based on the coupling effect of convective heat transfer, thermocouple wire heat conduction, and radiative heat dissipation of the fluid inside the shield.

5. The Reynolds number correction method for total temperature thermocouple heat transfer error according to claim 4, characterized in that, A shielded total temperature thermocouple is used as the total temperature thermocouple.

6. The Reynolds number correction method for total temperature thermocouple heat transfer error according to claim 5, characterized in that, The Reynolds number correction method for the total temperature thermocouple heat transfer error is applicable to airflow Mach numbers in the range of 0.1 ≤ Ma ≤ 0.6.

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