Electric arc wind tunnel test coaxial calorimeter heat measurement correction method and system

Abstract

The invention relates to a coaxial calorimeter heat measurement correction method and system for an arc wind tunnel test, belongs to the field of aerodynamic heat test research, and provides a coaxial heat measurement heat diffusion coefficient temperature correction function alpha (T), and heat flow correction calculation is carried out according to a temperature change curve T (t) along with time and the heat diffusion coefficient temperature correction function alpha (T). Therefore, accurate measurement of the ground test heat flow of the arc wind tunnel can be realized. The coaxial calorimeter heat measurement correction method for the arc wind tunnel test can be suitable for heat measurement of an arc wind tunnel flat plate model test and a stagnation point model test, the heat flow test is very wide in application range and covers 10 kW / m < 2 > to 30000 kW / m < 2 >, and the application range is wide.

Description

Technical Field

[0001] The invention relates to a method and system for correcting heat measurement of a coaxial calorimeter in an arc wind tunnel test, and belongs to the field of aerodynamic thermal test research. Background Art

[0002] Arc heating equipment is often used for the assessment and verification of aircraft thermal protection materials and systems. Accurate measurement of test parameters is a necessary condition for the effectiveness of the test. Since the 1950s, arc heating equipment has been used to simulate the re-entry environment of the Earth's atmosphere. Many measurement methods that are still in use today also originated from that time. The main parameters measured in arc wind tunnel ground tests include heat flux density, enthalpy, and pressure. Among them, heat flux density is the key parameter to characterize the aerodynamic heating environment of aircraft. At present, the main method of heat flux measurement in arc wind tunnel tests is based on the assumption of one-dimensional thermal conductivity of the plug calorimeter. Heat flux measurement is carried out based on the structure of copper block + thermal insulation sleeve. However, under high heat flux conditions, the thermal insulation sleeve will cause difficulty in heat measurement due to overheating and ablation. Therefore, this method is generally suitable for 100-5000kW / m 2 , the scope of application is limited. At the same time, the flight speed of aircraft is getting higher and higher, which puts forward further requirements for the refined measurement of thermal environment, and also has further requirements for the heat flow of some local structures, protrusions, and interference areas. It requires that the measurement accuracy of heat flow sensors be higher, the scale of sensors be smaller, the response be faster, the scope of application be wider, and it can adapt to the needs of heat flow measurement of local complex structures. The coaxial calorimeter currently under development has great application potential. The coaxial calorimeter is basically a structure of outer ring nickel-chromium-inner ring constantan, and is mainly used in transient pulse wind tunnel equipment such as shock wind tunnel. Because its effective time is very short, often in hundreds of microseconds to tens of milliseconds, the temperature rise of the coaxial calorimeter is several degrees to tens of degrees. The thermal physical parameters (thermal conductivity, specific heat, density) of nickel-chromium-constantan can be considered to remain unchanged. Taking a constant can carry out heat flow measurement and calculation. However, for arc wind tunnels, which are continuously running wind tunnels, the effective test time of heat flow sensors and gases is much longer, in the order of seconds to tens of seconds. The surface temperature of the coaxial calorimeter can reach 1000K. At this time, the thermal physical parameters (thermal conductivity, specific heat, density) of nickel-chromium-constantan are no longer a constant, but change significantly with the increase of temperature. If the same measurement method as the coaxial calorimetry of the shock wind tunnel is used, the measured value will be lower than the actual value, and the deviation can reach 10%-50%. Therefore, when applying coaxial calorimeters to arc wind tunnel tests, it is necessary to consider the correction of the thermophysical properties of NiCr-Constantan. However, there is currently a lack of quantitative data within a wide temperature range (273-1000K). It is necessary to study the thermal correction method of coaxial calorimeters in arc wind tunnel tests. Summary of the invention

[0003] The technical problem solved by the present invention is: to provide a method and system for correcting heat measurement of a coaxial calorimeter in an arc wind tunnel test, and to propose a temperature correction function α(T) of the thermal diffusion coefficient of a coaxial thermal measurement, so as to realize accurate measurement of heat flux density in an arc wind tunnel test.

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

[0005] A method for correcting heat measurement of a coaxial calorimeter in an arc wind tunnel test, comprising:

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

[0007] In the arc wind tunnel test flow field, a coaxial calorimeter is used to measure the thermal environment of a flat plate model test piece or a stagnation point model test piece, and a surface temperature variation curve T(t) of the coaxial calorimeter is obtained, where T is the surface temperature of the coaxial calorimeter and t is the measurement time.

[0008] Calculating the thermal diffusion coefficient temperature correction function α(T) according to the temperature-time variation curve T(t);

[0009] According to the temperature-time variation curve T(t) and the thermal diffusion coefficient temperature correction function α(T), a heat flux correction calculation is performed to obtain a corrected heat flux q n , n represents the nth discrete point in the curve T(t).

[0010] In the above arc wind tunnel test coaxial calorimeter heat measurement correction method, the calculation formula of the thermal diffusion coefficient temperature correction function α(T) is as follows:

[0011] α(T)=A+BT+CT 2

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

[0013] In the above arc wind tunnel test coaxial calorimeter heat measurement correction method, the correction coefficients A, B, and C are: A = 0.70627, B = 0.001, C = -6.799 × 10 -8 .

[0014] In the above arc wind tunnel test coaxial calorimeter heat measurement correction method, according to the temperature change curve T(t) and the thermal diffusion coefficient temperature correction function α(T), the heat flow correction calculation is performed 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 arc wind tunnel test coaxial calorimeter heat measurement correction method, the value of the heat diffusion σ0 satisfies: σ0 = 8000-8700 J / (s 0.5 m 2 K).

[0018] In the above-mentioned arc wind tunnel test coaxial calorimeter heat measurement correction method, the coaxial calorimeter is used to measure the thermal environment of the flat plate model test piece or the stationary point model test piece, and the effective test time t' of the surface temperature variation curve T(t) of the coaxial calorimeter satisfies:

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

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

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

[0022] A coaxial calorimeter heat measurement correction system for arc wind tunnel test, comprising:

[0023] The curve generation module uses a coaxial calorimeter to measure the thermal environment of a flat plate model test piece or a stagnation point model test piece in the established arc wind tunnel test flow field, and obtains a surface temperature variation curve T(t) of the coaxial calorimeter over time, where T is the surface temperature of the coaxial calorimeter and t is the measurement time;

[0024] A first calculation module calculates a thermal diffusion coefficient temperature correction function α(T) according to the temperature-time variation curve T(t);

[0025] The second calculation module performs heat flow correction calculation according to the temperature change curve T(t) and the thermal diffusion coefficient temperature correction function α(T) to obtain the corrected heat flow q n , n represents the nth discrete point in the curve T(t).

[0026] A computer device comprises a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the above method.

[0027] A computer program product comprises a computer program, which implements the steps of the above method when executed by a processor.

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

[0029] (1) The embodiment of the present invention discloses a method for correcting heat measurement by a coaxial calorimeter in an arc wind tunnel test, and proposes a temperature correction function α(T) for the thermal diffusion coefficient of the coaxial thermal measurement. According to the temperature-time variation curve T(t) and the temperature correction function α(T), a heat flux correction calculation is performed to obtain a corrected heat flux q n , which can realize accurate measurement of heat flux in arc wind tunnel ground test.

[0030] (2) The embodiment of the present invention discloses a correction method for heat measurement of a coaxial calorimeter in an arc wind tunnel test, which can be applied to heat measurement in 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 / m 2 -30000 kW / m 2 , with a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The curve of the surface temperature of the coaxial calorimeter in the arc wind tunnel test over time in the embodiment of the present invention;

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

[0033] Figure 3 is the heat flux correction ratio of considering the temperature correction of the thermal diffusion coefficient to not considering the temperature correction of the thermal diffusion coefficient under different stagnation heat flux conditions in the arc wind tunnel stagnation model test in the embodiment of the present invention;

[0034] Figure 4 It is the heat flux correction ratio of considering the temperature correction of thermal diffusion coefficient and not considering the temperature correction of thermal diffusion coefficient under different plate heat flux conditions in the arc wind tunnel flat plate model test in the embodiment of the present invention. DETAILED DESCRIPTION

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

[0036] The arc wind tunnel test coaxial calorimeter heat measurement correction method of the embodiment of the present invention comprises the following steps:

[0037] 1. Establish the arc wind tunnel test flow field;

[0038] 2. In the arc wind tunnel test flow field, a coaxial calorimeter is used to measure the thermal environment of a flat plate model test piece or a stagnation point model test piece, and a surface temperature variation curve T(t) of the coaxial calorimeter is obtained, where T is the surface temperature of the coaxial calorimeter and t is the measurement time. Figure 1 shown.

[0039] In an optional embodiment, a coaxial calorimeter is used to measure the thermal environment of a flat plate model test piece or a stationary point model test piece, and an effective test time t' of a surface temperature versus time curve T(t) of the coaxial calorimeter satisfies:

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

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

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

[0043] 3. According to the temperature-time curve T(t), calculate the thermal diffusion coefficient temperature correction function α(T), as follows: Figure 2 shown.

[0044] Among them, the calculation formula of the thermal diffusion coefficient temperature correction function α(T) is as follows:

[0045] α(T)=A+BT+CT 2

[0046] Among them, A, B, and C are correction coefficients.

[0047] In an optional embodiment,

[0048] The values ​​of correction coefficients A, B, and C are: A = 0.70627, B = 0.001, C = -6.799 × 10 -8 .

[0049] 4. According to the temperature-time curve T(t) and the thermal diffusion coefficient temperature correction function α(T), the heat flow correction calculation is performed to obtain the corrected heat flow q n , n represents the nth discrete point 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 an optional embodiment, the value of heat diffusion σ0 satisfies: σ0 = 8000-8700 J / (s 0.5 m 2 K).

[0054] The present invention provides a coaxial calorimeter heat measurement correction system for arc wind tunnel test, comprising:

[0055] The curve generation module uses a coaxial calorimeter to measure the thermal environment of a flat plate model test piece or a stagnation point model test piece in the established arc wind tunnel test flow field, and obtains a surface temperature variation curve T(t) of the coaxial calorimeter over time, where T is the surface temperature of the coaxial calorimeter and t is the measurement time;

[0056] A first calculation module calculates a thermal diffusion coefficient temperature correction function α(T) according to the temperature-time variation curve T(t);

[0057] The second calculation module performs heat flow correction calculation according to the temperature change curve T(t) and the thermal diffusion coefficient temperature correction function α(T) to obtain the corrected heat flow q n , n represents the nth discrete point in the curve T(t).

[0058] The present invention provides a computer device, comprising a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement steps (1) to (4) of the above method.

[0059] The present invention provides a computer program product, comprising a computer program, which implements steps (1) to (4) of the above method when executed by a processor.

[0060] Example

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

[0062] like Figure 1 The surface temperature of the coaxial calorimeter obtained in the arc wind tunnel stagnation test changes with time. The coaxial calorimeter is used to measure the thermal environment of the stagnation model test piece. The surface temperature of the coaxial calorimeter rises rapidly to nearly 250°C within 0.2s (t = 15.8-16.0).

[0063] like Figure 2 The change of the normalized thermal diffusion coefficient correction function of the coaxial calorimeter with temperature T. Figure 1 The surface temperature curve and Figure 2 The thermal diffusion coefficient correction function can be obtained by Figure 1 The thermal diffusion coefficient correction value of the coaxial calorimeter surface temperature at each moment. On this basis, the corrected heat flow is obtained according to the actually measured coaxial calorimeter surface temperature and the corresponding thermal diffusion coefficient temperature correction value at each moment.

[0064] like Figure 3 The heat flux correction ratio is the heat flux correction ratio under different heat flux conditions obtained from multiple tests of the arc wind tunnel stagnation test. The heat flux correction ratio is the heat flux value obtained after considering the correction of the coaxial calorimeter thermal diffusion coefficient and the heat flux value obtained without considering the correction of the coaxial calorimeter thermal diffusion coefficient. 2 Under heat flow conditions, the heat flow correction ratio is about 1.1 to 1.26.

[0065] like Figure 4 The heat flux correction ratio is the heat flux correction ratio obtained under different heat flux conditions under multiple tests of the arc wind tunnel flat plate test. The heat flux correction ratio is the heat flux value obtained after considering the correction of the coaxial calorimeter thermal diffusion coefficient and the heat flux value obtained without considering the correction of the coaxial calorimeter thermal diffusion coefficient. 2 Under heat flow conditions, the correction ratio of heat flow is around 1.04-1.12.

[0066] The above description is only the best specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

[0067] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. A method for correcting heat measurement of a coaxial calorimeter in an arc wind tunnel test, characterized in that: include: Establish the arc wind tunnel test flow field; In the arc wind tunnel test flow field, a coaxial calorimeter is used to measure the thermal environment of a flat plate model test piece or a stagnation point model test piece, and a surface temperature variation curve T(t) of the coaxial calorimeter is obtained, where T is the surface temperature of the coaxial calorimeter and t is the measurement time. Calculating the thermal diffusion coefficient temperature correction function α(T) according to the temperature-time variation curve T(t); According to the temperature-time variation curve T(t) and the thermal diffusion coefficient temperature correction function α(T), a heat flux correction calculation is performed to obtain a corrected heat flux q n , n represents the nth discrete point in the curve T(t).

2. The arc wind tunnel test coaxial calorimeter heat measurement correction method according to claim 1, characterized in that: The calculation formula of the thermal diffusion coefficient temperature correction function α(T) is as follows: α(T)=A+BT+CT 2 Among them, A, B, and C are correction coefficients.

3. The arc wind tunnel test coaxial calorimeter heat measurement correction method according to claim 2, characterized in that: The values ​​of correction coefficients A, B, and C are: A = 0.70627, B = 0.001, C = -6.799 × 10 -8 .

4. The arc wind tunnel test coaxial calorimeter heat measurement correction method according to claim 1, characterized in that: According to the temperature-time variation curve T(t) and the thermal diffusion coefficient temperature correction function α(T), a heat flux correction calculation is performed to obtain a 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 arc wind tunnel test coaxial calorimeter heat measurement correction method according to claim 4, characterized in that: The value of the heat diffusion σ0 satisfies: σ0=8000-8700J / (s 0.5 m 2 K).

6. The arc wind tunnel test coaxial calorimeter heat measurement correction method according to claim 4, characterized in that: The thermal environment of the flat plate model test piece or the stagnation model test piece is measured by a coaxial calorimeter, and the effective test time t' of the surface temperature variation curve T(t) of the coaxial calorimeter satisfies: For the flat plate model test piece: t' = 1 ~ 10s; For the stationary point model test piece: t' = 0.1 ~ 0.5s.

7. The arc wind tunnel test coaxial calorimeter heat measurement correction method according to claim 4, characterized in that: The surface temperature T of the coaxial calorimeter satisfies: T≤1000K.

8. A coaxial calorimeter heat measurement correction system for arc wind tunnel test, characterized in that: include: The curve generation module uses a coaxial calorimeter to measure the thermal environment of a flat plate model test piece or a stagnation point model test piece in the established arc wind tunnel test flow field, and obtains a surface temperature variation curve T(t) of the coaxial calorimeter over time, where T is the surface temperature of the coaxial calorimeter and t is the measurement time; A first calculation module calculates a thermal diffusion coefficient temperature correction function α(T) according to the temperature-time variation curve T(t); The second calculation module performs heat flow correction calculation according to the temperature change curve T(t) and the thermal diffusion coefficient temperature correction function α(T) to obtain the corrected heat flow q n , n represents the nth discrete point 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, the steps of the method according to claim 1 are implemented.

Images