Arc wind tunnel test coaxial calorimeter heat correction method and system

Abstract

The application relates to an arc wind tunnel test coaxial calorimeter heat measurement correction method and system, and belongs to the field of aerodynamic heat test research. n The application can realize accurate measurement of the ground test heat flow of the arc wind tunnel; the arc wind tunnel test coaxial calorimeter heat measurement correction method can be suitable for heat measurement of arc wind tunnel flat plate model test and stagnation point model test, and the heat flow test is suitable for very wide, covering 10kW / m 2 -30000kW / m 2 , and has a wide application range.

Description

Technical Field

[0001] This invention relates to a method and system for correcting the heat measurement of a coaxial calorimeter in an electric arc wind tunnel test, belonging to the field of aerodynamic thermal testing research. Background Technology

[0002] Arc heating equipment is commonly used for the evaluation and verification of thermal protection materials and systems for aircraft. Accurate measurement of test parameters is essential for the validity of the test. Since the 1950s, arc heating equipment has been used to simulate the Earth's atmospheric reentry environment, and many measurement methods still in use today originated from that period. The main parameters measured in arc wind tunnel ground tests include heat flux density, enthalpy, and pressure, with heat flux density being a key parameter characterizing the aerodynamic heating environment of an aircraft. Currently, the main method for heat flux measurement in arc wind tunnel tests is based on the assumption of one-dimensional thermal conduction using a plug calorimeter, employing a copper block + insulation jacket structure for heat flux measurement. However, under high heat flux conditions, the insulation jacket can overheat and erode, making heat measurement difficult. Therefore, this method is generally suitable for temperatures ranging from 100 to 5000 kW / m². 2 However, the applicability is limited. At the same time, as the flight speed of aircraft increases, there is a greater demand for more precise measurement of the thermal environment. There are also higher requirements for the heat flow of some local structures, protrusions, and interference areas. This requires heat flow sensors to have higher measurement accuracy, smaller sensor size, faster response, wider applicability, and the ability to adapt to the heat flow measurement needs of local complex structures. The coaxial calorimeter currently under development has enormous application potential. It is primarily based on an outer ring nickel-chromium and inner ring constantan structure, mainly used in transient pulse-type wind tunnel equipment such as shock tunnels. Due to its very short effective time, often ranging from hundreds of microseconds to tens of milliseconds, the temperature rise of the coaxial calorimeter is only a few to tens of degrees Celsius. The thermophysical properties of the nickel-chromium-constantan (thermal conductivity, specific heat, density) can be considered constant, allowing for heat flux measurement and calculation. However, for arc wind tunnels, which are continuously operating, the effective testing time between the heat flux sensor and the gas is much longer, on the order of seconds to tens of seconds. The surface temperature of the coaxial calorimeter can reach 1000K. At this point, the thermophysical properties of the nickel-chromium-constantan (thermal conductivity, specific heat, density) are no longer constant but change significantly with increasing temperature. If the same measurement method used for coaxial calorimetry in shock tunnels is applied, the measured value will be lower than the actual value, with a deviation of 10%-50%. Therefore, when applying coaxial calorimeters to electric arc wind tunnel tests, the correction of nickel-chromium-constantan thermophysical parameters must be considered. However, quantitative data in a wide temperature range (273-1000K) is currently lacking, making it necessary to conduct research on the correction method of coaxial calorimeter measurements in electric arc wind tunnel tests. Summary of the Invention

[0003] The technical problem solved by this invention is to provide a method and system for correcting the heat flux density of a coaxial calorimeter in an electric arc wind tunnel test, and to propose a temperature correction function α(T) for the thermal diffusivity of the coaxial calorimeter, thereby achieving accurate measurement of the heat flux density in an electric arc wind tunnel test.

[0004] The above-mentioned objectives of the present invention are mainly achieved through the following technical solutions:

[0005] A method for correcting the calorimeter readings in an electric arc wind tunnel test includes:

[0006] Establish the flow field for the electric arc wind tunnel test;

[0007] In the flow field of the electric arc wind tunnel test, the thermal environment of the flat plate model test piece or the stagnation point model test piece is measured using a coaxial calorimeter to obtain the surface temperature of the coaxial calorimeter as a function of time, T(t), where T is the surface temperature of the coaxial calorimeter and t is the measurement time.

[0008] Based on the temperature-time curve T(t), calculate the temperature correction function α(T) for the thermal diffusivity.

[0009] Based on the temperature-time curve T(t) and the temperature correction function α(T) for the thermal diffusivity, heat flux correction calculations are performed to obtain the corrected heat flux q. n , where n represents the nth point of the discrete points in the curve T(t).

[0010] In the above-mentioned coaxial calorimeter thermal correction method for electric arc wind tunnel tests, the calculation formula for the thermal diffusivity temperature correction function α(T) is as follows:

[0011] α(T)=A+BT+CT 2

[0012] Among them, A, B, and C are all correction coefficients.

[0013] In the above-mentioned correction method for coaxial calorimeter measurements in the electric arc wind tunnel test, the correction coefficients A, B, and C are: A = 0.70627, B = 0.001, C = -6.799 × 10⁻⁶. -8 .

[0014] In the above-mentioned coaxial calorimeter heat measurement correction method for electric arc wind tunnel tests, heat flow correction calculations are performed based on the temperature-time curve T(t) and the thermal diffusivity temperature correction function α(T) to obtain the corrected heat flow q. n ,include:

[0015]

[0016] Where i represents the i-th discrete point, and σ0 represents the thermal diffusion at a temperature of 300K.

[0017] In the above-mentioned coaxial calorimeter correction method for arc wind tunnel tests, the value of the heat diffusion σ0 satisfies: σ0=8000-8700J / (s) 0.5 m 2 K).

[0018] In the above-mentioned coaxial calorimeter thermal correction method for electric arc wind tunnel tests, the effective test time t' of the surface temperature change curve T(t) of the coaxial calorimeter obtained by measuring the thermal environment of the flat plate model test piece or the stagnation point model test piece using a coaxial calorimeter satisfies the following:

[0019] For the flat plate model test piece: t' = 1~10s;

[0020] For stationary model test specimens: t' = 0.1~0.5s.

[0021] In the above-mentioned coaxial calorimeter heat measurement correction method for electric arc wind tunnel test, the surface temperature T of the coaxial calorimeter satisfies: T≤1000K.

[0022] A coaxial calorimeter thermal correction system for electric arc wind tunnel testing includes:

[0023] The curve generation module measures the thermal environment of the flat plate model test piece or the stagnation point model test piece using a coaxial calorimeter in the established electric arc wind tunnel test flow field, and obtains the surface temperature of the coaxial calorimeter as a function of time curve T(t), where T is the surface temperature of the coaxial calorimeter and t is the measurement time.

[0024] The first calculation module calculates the temperature correction function α(T) of the thermal diffusivity based on the temperature change curve T(t) over time.

[0025] The second calculation module performs heat flow correction calculations based on the temperature-time curve T(t) and the thermal diffusivity temperature correction function α(T) to obtain the corrected heat flow q. n , where n represents the nth point of the discrete points in the curve T(t).

[0026] A computer device includes a memory, a processor, and a computer program stored in the memory, characterized in that the processor executes the computer program to implement the steps of the above-described method.

[0027] A computer program product includes a computer program that, when executed by a processor, implements the steps of the above-described method.

[0028] Compared with the prior art, the embodiments of the present invention have at least the following beneficial effects:

[0029] (1) This invention discloses a method for correcting the heat measurement of a coaxial calorimeter in an electric arc wind tunnel test. It proposes a temperature correction function α(T) for the thermal diffusivity coefficient of the coaxial calorimeter. Based on the temperature-time curve T(t) and the temperature correction function α(T), heat flow correction calculations are performed to obtain the corrected heat flow q. n It can achieve accurate measurement of heat flux in ground tests of electric arc wind tunnels.

[0030] (2) This invention discloses a method for correcting the heat measurement of a coaxial calorimeter in an electric arc wind tunnel test. It is applicable to heat measurement in electric arc wind tunnel flat plate model tests and stagnation point model tests. The heat flow test is applicable to a very wide range, covering 10kW / m². 2 -30000 kW / m 2 It has a wide range of applications. Attached Figure Description

[0031] Figure 1 This is a curve showing the surface temperature of the coaxial calorimeter in the electric arc wind tunnel test over time, as described in this embodiment of the invention.

[0032] Figure 2 This is a graph showing the relationship between the thermal diffusivity temperature correction function α(T) and temperature in an embodiment of the present invention.

[0033] Figure 3 In the electric arc wind tunnel stagnation point model test of this invention, the heat flow correction ratio considering the thermal diffusivity temperature correction is compared with that not considering the thermal diffusivity temperature correction under different stagnation point heat flow conditions.

[0034] Figure 4 In the electric arc wind tunnel flat plate model test of this invention, the heat flow correction ratio considering the thermal diffusivity temperature correction is compared with that not considering the thermal diffusivity temperature correction under different flat plate heat flow conditions. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments:

[0036] The method for correcting the thermal measurement of a coaxial calorimeter in an electric arc wind tunnel test according to an embodiment of the present invention includes the following steps:

[0037] I. Establishing the flow field for the electric arc wind tunnel test;

[0038] II. In the flow field of an electric arc wind tunnel test, the thermal environment of a flat plate model test specimen or a stagnation point model test specimen is measured using a coaxial calorimeter. The surface temperature of the coaxial calorimeter as a function of time, T(t), is obtained, where T is the surface temperature of the coaxial calorimeter and t is the measurement time. Figure 1 As shown.

[0039] In one optional embodiment, the thermal environment of the flat plate model test specimen or the stagnation point model test specimen is measured using a coaxial calorimeter, and the effective test time t' of the surface temperature change curve T(t) of the coaxial calorimeter over time satisfies:

[0040] For the flat plate model test piece: t' = 1~10s;

[0041] For stationary model test specimens: t' = 0.1~0.5s.

[0042] In one optional embodiment, the surface temperature T of the coaxial calorimeter satisfies: T≤1000K.

[0043] III. Based on the temperature-time curve T(t), calculate the temperature correction function α(T) for the thermal diffusivity, as follows: Figure 2 As shown.

[0044] The formula for calculating the temperature correction function α(T) of the thermal diffusivity is as follows:

[0045] α(T)=A+BT+CT 2

[0046] Where A, B, and C are all correction coefficients.

[0047] In one optional embodiment,

[0048] The correction factors A, B, and C are set as follows: A = 0.70627, B = 0.001, C = -6.799 × 10⁻⁶. -8 .

[0049] IV. Based on the temperature-time curve T(t) and the temperature correction function α(T) for the thermal diffusivity, perform heat flux correction calculations to obtain the corrected heat flux q. n , where n represents the nth point of the discrete points in the curve T(t).

[0050] The specific calculation formula is as follows:

[0051]

[0052] Where i represents the i-th discrete point, and σ0 represents the thermal diffusion at a temperature of 300K.

[0053] In one optional embodiment, the value of thermal diffusion σ0 satisfies: σ0 = 8000-8700 J / (s) 0.5 m 2 K).

[0054] This invention provides a coaxial calorimeter thermal correction system for electric arc wind tunnel testing, comprising:

[0055] The curve generation module measures the thermal environment of the flat plate model test piece or the stagnation point model test piece using a coaxial calorimeter in the established electric arc wind tunnel test flow field, and obtains the surface temperature of the coaxial calorimeter as a function of time curve T(t), where T is the surface temperature of the coaxial calorimeter and t is the measurement time.

[0056] The first calculation module calculates the temperature correction function α(T) of the thermal diffusivity based on the temperature change curve T(t) over time.

[0057] The second calculation module performs heat flow correction calculations based on the temperature-time curve T(t) and the thermal diffusivity temperature correction function α(T) to obtain the corrected heat flow q. n , where n represents the nth point of the discrete points in the curve T(t).

[0058] The present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement steps (i) to (iv) of the above method.

[0059] The present invention provides a computer program product, including a computer program that, when executed by a processor, implements steps (i) to (iv) of the above method.

[0060] Example

[0061] This embodiment takes an electric arc wind tunnel stagnation test as an example. In the flow field of the electric arc wind tunnel test, a coaxial calorimeter is used to measure the thermal environment of the flat plate model test piece or the stagnation model test piece, obtaining the surface temperature of the coaxial calorimeter as a function of time, T(t), where T is the surface temperature of the coaxial calorimeter and t is the measurement time. Based on the temperature-time curve T(t), a temperature correction function for the thermal diffusivity is calculated. Based on the temperature-time curve T(t) and the temperature correction function for the thermal diffusivity, a heat flux correction calculation is performed to obtain the corrected heat flux q. n , where n represents the nth point of the discrete points in the curve T(t).

[0062] like Figure 1 The image shows the surface temperature of the coaxial calorimeter as a function of time, obtained from the stagnation test in the electric arc wind tunnel. The thermal environment of the stagnation model test specimen was measured using the coaxial calorimeter. Within 0.2 s (t = 15.8 - 16.0), the surface temperature of the coaxial calorimeter rapidly increased to nearly 250℃.

[0063] like Figure 2 This is the normalized thermal diffusivity correction function for a coaxial calorimeter, varying with temperature T. Combined with... Figure 1 The surface temperature curve of the coaxial calorimeter obtained from a certain stagnation point test measurement and Figure 2 The thermal diffusivity correction function can be obtained. Figure 1 The thermal diffusivity correction value of the coaxial calorimeter surface temperature at each moment is calculated. Based on this, the corrected heat flow is obtained according to the actual measured coaxial calorimeter surface temperature and the corresponding thermal diffusivity temperature correction value at each moment.

[0064] like Figure 3 The heat flux correction ratio is calculated by dividing the heat flux value obtained from multiple tests at the stagnation point of the electric arc wind tunnel under different heat flux conditions. The correction ratio is the ratio of the heat flux value obtained considering the correction for the thermal diffusivity of the coaxial calorimeter to the value obtained without considering the correction for the thermal diffusivity of the coaxial calorimeter. The heat flux ranges from 3 to 14 MW / m. 2 Under heat flux conditions, the heat flux correction ratio is approximately 1.1 to 1.26.

[0065] like Figure 4 The heat flux correction ratio is calculated by dividing the heat flux values ​​obtained from multiple tests in the electric arc wind tunnel flat plate test under different heat flux conditions. The correction ratio is the ratio of the heat flux values ​​obtained considering the coaxial calorimeter thermal diffusivity correction to those obtained without considering it. The heat flux ranges from 3 to 14 MW / m². 2 Under heat flux conditions, the heat flux correction ratio is around 1.04-1.12.

[0066] The above description is only the best specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes 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 protection scope of the present invention.

[0067] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for correcting the calorimeter readings in an electric arc wind tunnel test, characterized in that, include: Establish the flow field for the electric arc wind tunnel test; In the flow field of the electric arc wind tunnel test, the thermal environment of the flat plate model test piece or the stagnation point model test piece is measured using a coaxial calorimeter to obtain the surface temperature of the coaxial calorimeter as a function of time, T(t), where T is the surface temperature of the coaxial calorimeter and t is the measurement time. Based on the temperature-time curve T(t), calculate the temperature correction function α(T) for the thermal diffusivity. Based on the temperature-time curve T(t) and the temperature correction function α(T) for the thermal diffusivity, heat flux correction calculations are performed to obtain the corrected heat flux q. n , where n represents the nth point of the discrete points in the curve T(t).

2. The method for correcting the calorimeter readings in an electric arc wind tunnel test according to claim 1, characterized in that, The formula for calculating the thermal diffusivity temperature correction function α(T) is as follows: α(T)=A+BT+CT 2 Among them, A, B, and C are all correction coefficients.

3. The method for correcting the calorimeter readings in an electric arc wind tunnel test according to claim 2, characterized in that, The correction factors A, B, and C are set as follows: A = 0.70627, B = 0.001, C = -6.799 × 10⁻⁶. -8 .

4. The method for correcting the calorimeter readings in an electric arc wind tunnel test according to claim 1, characterized in that, Based on the temperature-time curve T(t) and the temperature correction function α(T) for the thermal diffusivity, heat flux correction calculations are performed to obtain the corrected heat flux q. n ,include: Where i represents the i-th discrete point, and σ0 represents the thermal diffusion at a temperature of 300K.

5. The method for correcting the calorimeter readings in an electric arc wind tunnel test according to claim 4, characterized in that, The value of the thermal diffusion σ0 satisfies: σ0 = 8000-8700 J / (s) 0.5 m 2 K).

6. The method for correcting the calorimeter readings in an electric arc wind tunnel test according to claim 4, characterized in that, The thermal environment of a flat plate model test specimen or a stagnation point model test specimen is measured using a coaxial calorimeter. The effective test time t' of the surface temperature change curve T(t) of the coaxial calorimeter over time satisfies the following: For the flat plate model test piece: t' = 1~10s; For stationary model test specimens: t' = 0.1~0.5s.

7. The method for correcting the calorimeter readings in an electric arc wind tunnel test according to claim 4, characterized in that, The surface temperature T of the coaxial calorimeter satisfies: T≤1000K.

8. A coaxial calorimeter thermal correction system for electric arc wind tunnel testing, characterized in that, include: The curve generation module measures the thermal environment of the flat plate model test piece or the stagnation point model test piece using a coaxial calorimeter in the established electric arc wind tunnel test flow field, and obtains the surface temperature of the coaxial calorimeter as a function of time curve T(t), where T is the surface temperature of the coaxial calorimeter and t is the measurement time. The first calculation module calculates the temperature correction function α(T) of the thermal diffusivity based on the temperature change curve T(t) over time. The second calculation module performs heat flow correction calculations based on the temperature-time curve T(t) and the thermal diffusivity temperature correction function α(T) to obtain the corrected heat flow q. n , where n represents the nth point of the discrete points in the curve T(t).

9. A computer device comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the method of claim 1.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method of claim 1.

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