A real-time measurement method for the enthalpy value of the ablation process of heat-resistant materials in arc wind tunnel tests

Abstract

The present invention relates to a real-time measurement method for the enthalpy of the ablation process of a heat-resistant material in an arc wind tunnel test. The method is used for ground tests of arc wind tunnel thermal protection systems and belongs to the research field of ground aerodynamic thermal tests on aircraft. Based on a developed emission spectrum system and enthalpy measurement method, the present invention obtains the non-equilibrium temperature (rotation, rotation, electron) and the concentrations of atomic nitrogen and atomic oxygen in the stagnation area of ​​a stagnation model of the heat-resistant material, realizes online measurement of the local central stagnation point enthalpy of the heat-resistant material, and realizes real-time monitoring of the entire material ablation process. The method can cover the enthalpy simulation range of various types of arc wind tunnels, such as tubular, segmented, and laminated, and has very wide applicability. It can also realize rapid and long-term measurement of the entire ablation process of the heat-resistant material, with a response frequency of up to 100 Hz and a measurement period of ≥1 hour.

Description

Technical Field

[0001] The present invention relates to the measurement of parameters of the ablation process of an aircraft thermal protection system, which is used for ground tests of the thermal protection system in an arc wind tunnel, and in particular to a real-time measurement method for the enthalpy value of the ablation process of a heat-protection material in an arc wind tunnel test, belonging to the field of research on ground aerodynamic thermal tests of aircraft. Background Art

[0002] Aircraft gliding, cruising, and reentering at extremely high speeds subject their surfaces to severe aerodynamic heating. Airflow temperatures near the walls can reach 10,000K. Conventional materials cannot withstand such high temperatures, necessitating the development of specialized thermal protection materials for heat protection. A primary method for thermal protection materials to prevent heat transfer into the aircraft is through ablation, which absorbs and removes heat, thereby preventing it from transferring into the aircraft. This process requires specialized wind tunnel ground testing to evaluate the material ablation process. Arc wind tunnel equipment is the primary equipment used for evaluating and assessing thermal protection materials both domestically and internationally.

[0003] The arc wind tunnel test is used to evaluate the ablation of heat-resistant materials, which is generally divided into test debugging and test evaluation. First, after debugging the incoming flow state of the wind tunnel itself, the enthalpy and heat flow required for the thermal protection material are determined. After the solidification state, the material ablation test is performed. During the material ablation test, the flow field state on the material surface is no longer monitored or measured in real time. Under the wind tunnel ground ablation test, due to ablation, the surface of the model is constantly changing. There are local ablation retreat, bulges, oxidation and other phenomena, which in turn cause the local airflow state, especially the airflow enthalpy value to change over time. Specifically, for the measurement of the airflow enthalpy value of the arc wind tunnel stagnation test, the enthalpy value is generally obtained by measuring the stagnation pressure and stagnation heat flow to obtain the stagnation enthalpy. The airflow enthalpy value is measured in the test debugging link, and the solidification state, the test piece for pressure and heat flow measurement is in a completely non-ablative state with no change in appearance. The enthalpy measurement methods I developed (ZL202111015133.2, ZL202111012554.X, ZL201910440190.1, and ZL201811494282.X) measure airflow enthalpy during test and commissioning, and do not involve real-time measurement of the thermal shielding material itself during long-term ablation testing. Patent (ZL201711003142.3) develops a method for measuring the local enthalpy of arc heaters based on a calibrated quantitative relationship between the emission spectrum intensity ratio of the target component and the enthalpy of the high-temperature airflow. This method is applicable to the 5MJ / kg-25MJ / kg range and enables real-time, long-term monitoring of arc heaters. Currently, there is a lack of effective methods for real-time enthalpy measurement during the ablation process of thermal shielding materials. Developing corresponding methods to achieve long-term, real-time monitoring of the ablation process of thermal shielding materials is crucial. Summary of the Invention

[0004] The technology of the present invention solves the problem: a real-time measurement method for the enthalpy value of the ablation process of heat-resistant materials in arc wind tunnel tests is proposed. Based on the developed emission spectrum system and enthalpy value measurement method, the non-equilibrium temperature (rotation, rotation, electron) and the concentration of atomic nitrogen and atomic oxygen in the stagnation point area of ​​the stagnation point model of the heat-resistant material are obtained, thereby realizing online measurement of the local central stagnation point enthalpy of the heat-resistant material and realizing real-time monitoring of the entire process of the material ablation process.

[0005] The technical solutions of the present invention are as follows:

[0006] A method for real-time measurement of enthalpy value during ablation of heat-resistant materials in arc wind tunnel tests comprises the following steps:

[0007] (1) Establish a high-enthalpy airflow environment for the arc wind tunnel test, place the heat shield material downstream of the high-enthalpy airflow, and align the center axis of the heat shield material with the center axis of the arc wind tunnel;

[0008] (2) using an emission spectrum system to measure the original radiation spectrum at the center of the stationary point on the surface of the heat-resistant material, and dividing the original radiation spectrum by the spectral response of the emission spectrum system to obtain a relative radiation spectrum;

[0009] (3) Based on the relative radiation spectrum, each intercepts CN or N2 + The continuous spectrum of the target band range is normalized and based on the normalized CN continuous spectrum or N2 + Continuum spectrum to obtain rotation temperature T rot and vibration temperature T vib ;

[0010] (4) Based on the relative radiation spectrum, the spectral intensity I of the two selected argon characteristic spectral lines is obtained. i , i takes 1 or 2, based on the spectral intensity I i Get the electron excitation temperature T exc ;

[0011] (5) Based on the rotation temperature T rot , vibration temperature T vib and the electron excitation temperature T exc , get the coupling temperature T s , and according to the coupling temperature T s Obtain constant pressure specific heat C p and internal energy enthalpy h s , where: T s =(T rot ·T vib ·T exc ) 1 / 3 ;

[0012] (6) Based on the relative radiation spectrum, the spectral intensity I of the characteristic spectral line of atomic nitrogen is obtained.N and the spectral intensity of the atomic oxygen characteristic line I O ;

[0013] (7) Based on the argon mass fraction ω Ar , the spectral intensity of the first argon characteristic line I1, the spectral intensity of the atomic nitrogen characteristic line I N and the spectral intensity of the atomic oxygen characteristic line I O , to obtain the mass fraction of atomic nitrogen ω N and the mass fraction of atomic oxygen ω O ;

[0014] (8) Based on the atomic nitrogen mass fraction ω N and the mass fraction of atomic oxygen ω O , obtain the chemical enthalpy h c ;

[0015] (9) Based on the internal energy enthalpy h s and chemical enthalpy h c , and obtain the ultra-high enthalpy non-equilibrium airflow stagnation point enthalpy H0.

[0016] In the above-mentioned arc wind tunnel test heat protection material ablation process enthalpy real-time measurement method, the step (3) is based on the normalized CN continuous spectrum or N2 + Continuum spectrum to obtain rotation temperature T rot and vibration temperature T vib , including: calculating CN or N2 + The theoretical spectrum is compared with the normalized CN continuous spectrum or N2 + The continuous spectrum is compared and approximated continuously, that is, when the deviation between the theoretical spectrum and the normalized continuous spectrum is ≤10%, CN or N2 + The theoretical spectrum corresponds to the rotation temperature T rot and vibration temperature T vib is the final value.

[0017] In the above-mentioned arc wind tunnel test heat protection material ablation process enthalpy real-time measurement method, the CN or N2 in step (3) + The target wavelength is 375-392nm.

[0018] In the above-mentioned method for real-time measurement of enthalpy value during ablation of heat-resistant materials in arc wind tunnel tests, the spectral resolution δ and spectral response range σ of the emission spectrum system in step (2) satisfy: δ is between 0.05-0.2nm, and σ covers 350-900nm.

[0019] In the above-mentioned arc wind tunnel test heat protection material ablation process enthalpy real-time measurement method, the step (4) is based on the spectral intensity I i Get the electron excitation temperature Texc ,include:

[0020] T exc =5.02+0.6log(I2 / I1).

[0021] In the above-mentioned method for real-time measurement of enthalpy value during ablation of heat-resistant materials in arc wind tunnel tests, the central wavelengths of the characteristic spectral lines of argon in step (4) are 763.51 nm and 703.03 nm, respectively; the central wavelengths of atomic nitrogen and atomic oxygen in step (6) are 868.03 nm and 777.19 nm, respectively.

[0022] In the above-mentioned arc wind tunnel test heat protection material ablation process enthalpy real-time measurement method, the step (5) is based on the coupling temperature T s Obtain constant pressure specific heat C p and internal energy enthalpy h s ,include:

[0023] h s =C p ×T s

[0024] C p =0.9938-7.787×10 -4 P s +1.98×10 -4 T s +7.067×10 -7 P s ·T s -4.587×10 -8 T s 2 -1.25×10 -10 P s ·T s 2 +4.19×10 -12 T s 3

[0025] Among them, P s It is the stagnation pressure of heat-proof material.

[0026] In the above-mentioned arc wind tunnel test heat protection material ablation process enthalpy real-time measurement method, the step (7) is based on the argon mass fraction ω Ar , the spectral intensity of the first argon characteristic line I1, the spectral intensity of the atomic nitrogen characteristic line I N and the spectral intensity of the atomic oxygen characteristic line I O , to obtain the mass fraction of atomic nitrogen ω N and the mass fraction of atomic oxygen ω O ,include:

[0027]

[0028] In the above-mentioned arc wind tunnel test heat protection material ablation process enthalpy real-time measurement method, the step (8) is based on the atomic nitrogen mass fraction ω N and the mass fraction of atomic oxygen ω O Get chemical enthalpy h c ,include:

[0029] h c =33.7ω N +15.6ω O .

[0030] In the above-mentioned arc wind tunnel test heat protection material ablation process enthalpy real-time measurement method, the step (9) is based on the internal energy enthalpy h s and chemical enthalpy h c , obtain the ultra-high enthalpy non-equilibrium airflow stagnation point enthalpy H0, including:

[0031] H0=h s +h c .

[0032] Compared with the prior art, the present invention has at least the following beneficial effects:

[0033] (1) The embodiment of the present invention provides a method for real-time measurement of enthalpy during ablation of heat-resistant materials in arc wind tunnel tests. This method is based on a developed emission spectroscopy system and enthalpy measurement method, and obtains the non-equilibrium temperature (rotation, rotation, electron) and the concentration of atomic nitrogen and atomic oxygen in the stagnation point area of ​​the stagnation point model of the heat-resistant material. This method realizes online measurement of the local central stagnation point enthalpy of the heat-resistant material and enables real-time monitoring of the entire material ablation process.

[0034] (2) The method for real-time measurement of the enthalpy value of the ablation process of heat-resistant materials in arc wind tunnel tests provided by the embodiment of the present invention relates to the measurement of parameters of the ablation process of aircraft thermal protection systems and is used for ground tests of arc wind tunnel thermal protection systems. It can realize real-time monitoring of the stagnation point enthalpy of the ablation process of heat-resistant materials, filling the gaps in existing methods.

[0035] (3) In the method for real-time measurement of enthalpy during the ablation process of heat-resistant materials in arc wind tunnel tests provided by the embodiment of the present invention, the enthalpy value applicable range of the method is 10-50 MJ / kg, which can cover the enthalpy value simulation range of various types of arc wind tunnels such as tubular, segmented, and laminated, and has very wide applicability;

[0036] (4) The real-time measurement method of the enthalpy value of the ablation process of the heat-resistant material in the arc wind tunnel test provided by the embodiment of the present invention can realize rapid and long-term measurement of the entire ablation process of the heat-resistant material, with a response frequency of up to 100 Hz and a measurement period of ≥1h. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of the layout of a method for real-time measurement of enthalpy during ablation of heat-resistant materials in arc wind tunnel tests provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0039] like Figure 1 FIG. 1 is a schematic diagram of a layout of a method for real-time measurement of enthalpy during ablation of heat-resistant materials in an arc wind tunnel test according to an embodiment of the present invention. The method for real-time measurement of enthalpy during ablation of heat-resistant materials in an arc wind tunnel test according to an embodiment of the present invention comprises the following steps:

[0040] (1) Establish a high-enthalpy airflow environment for arc wind tunnel testing, place the heat shield material downstream of the high-enthalpy airflow, and align the center axis of the heat shield material with the center axis of the arc wind tunnel.

[0041] (2) Using an emission spectrum system to measure the original radiation spectrum at the center of the stagnation point on the surface of the heat-resistant material, the original radiation spectrum is divided by the spectral response of the emission spectrum system to obtain a relative radiation spectrum.

[0042] In an optional embodiment, the spectral resolution δ and spectral response range σ of the emission spectroscopy system satisfy: δ is between 0.05-0.2 nm, and σ covers 350-900 nm.

[0043] (3) Based on the relative radiation spectrum, each intercepts CN or N2 + The continuous spectrum of the target band range is normalized and based on the normalized CN continuous spectrum or N2 + Continuum spectrum to obtain rotation temperature T rot and vibration temperature T vib .

[0044] In an optional embodiment, based on the normalized CN continuous spectrum or N2 + Continuum spectrum to obtain rotation temperature T rot and vibration temperature T vib , including: calculating CN or N2 + The theoretical spectrum is compared with the normalized CN continuous spectrum or N2 + The continuous spectrum is compared and approximated continuously, that is, when the deviation between the theoretical spectrum and the normalized continuous spectrum is ≤10%, CN or N2 + The theoretical spectrum corresponds to the rotation temperature T rot and vibration temperature T vib is the final value.

[0045] In an optional embodiment, CN or N2+ The target wavelength is 375-392nm.

[0046] (IV) Based on the relative radiation spectrum, the spectral intensity I of the two selected argon characteristic spectral lines is obtained. i , i takes 1 or 2, based on the spectral intensity I i Get the electron excitation temperature T exc , the specific formula is as follows:

[0047] T exc =5.02+0.6log(I2 / I1)

[0048] In an optional embodiment, the central wavelengths of the characteristic spectral lines of argon are 763.51 nm and 703.03 nm respectively.

[0049] (V) Based on the rotation temperature T rot , vibration temperature T vib and the electron excitation temperature T exc , get the coupling temperature T s , and according to the coupling temperature T s Obtain constant pressure specific heat C p and internal energy enthalpy h s .

[0050] The coupling temperature T s , is calculated as follows:

[0051] T s =(T rot ·T vib ·T exc ) 1 / 3

[0052] In an optional embodiment, according to the coupling temperature T s Obtain constant pressure specific heat C p and internal energy enthalpy h s ,include:

[0053] h s =C p ×T s

[0054] C p =0.9938-7.787×10 -4 P s +1.98×10 -4 T s +7.067×10 -7 P s ·T s -4.587×10 -8 T s 2-1.25×10 -10 P s ·T s 2 +4.19×10 -12 T s 3

[0055] Among them, P s It is the stagnation pressure of heat-proof material.

[0056] (6) Based on the relative radiation spectrum, the spectral intensity I of the characteristic spectral line of atomic nitrogen is obtained. N and the spectral intensity of the atomic oxygen characteristic line I O .

[0057] In an alternative embodiment, the central wavelengths of atomic nitrogen and atomic oxygen are 868.03 nm and 777.19 nm, respectively.

[0058] (VII) Based on the argon mass fraction ω Ar , the spectral intensity of the first argon characteristic line I1, the spectral intensity of the atomic nitrogen characteristic line I N and the spectral intensity of the atomic oxygen characteristic line I O , to obtain the mass fraction of atomic nitrogen ω N and the mass fraction of atomic oxygen ω O , the specific calculation formula is as follows:

[0059]

[0060] (VIII) Based on the atomic nitrogen mass fraction ω N and the mass fraction of atomic oxygen ω O , obtain the chemical enthalpy h c , the specific calculation formula is as follows:

[0061] h c =33.7ω N +15.6ω O

[0062] (IX) Based on internal energy enthalpy h s and chemical enthalpy h c , the ultra-high enthalpy non-equilibrium airflow stagnation point enthalpy H0 is obtained. The specific calculation formula is as follows:

[0063] H0=h s +h c .

[0064] The embodiment of the present invention provides a real-time measurement method for the enthalpy value of the ablation process of heat-resistant materials in arc wind tunnel tests. The method is based on a developed emission spectroscopy system and enthalpy value measurement method to obtain the non-equilibrium temperature (rotation, rotation, electron) and the concentration of atomic nitrogen and atomic oxygen in the stagnation point area of ​​the stagnation point model of the heat-resistant material, thereby realizing online measurement of the local central stagnation point enthalpy of the heat-resistant material and real-time monitoring of the entire material ablation process.

[0065] The above description is only the best specific implementation method of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

[0066] The contents not described in detail in the specification of the present invention belong to the common knowledge of professionals in this field.

Claims

1. A method for real-time measurement of enthalpy value of ablation process of heat-resistant material in arc wind tunnel test, characterized in that: The steps include: (1) Establish a high-enthalpy airflow environment for the arc wind tunnel test, place the heat shield material downstream of the high-enthalpy airflow, and align the center axis of the heat shield material with the center axis of the arc wind tunnel; (2) using an emission spectrum system to measure the original radiation spectrum at the center of the stationary point on the surface of the heat-resistant material, and dividing the original radiation spectrum by the spectral response of the emission spectrum system to obtain a relative radiation spectrum; (3) Based on the relative radiation spectrum, each intercepts CN or N2 + The continuous spectrum of the target band range is normalized and based on the normalized CN continuous spectrum or N2 + Continuum spectrum to obtain rotation temperature T rot and vibration temperature T vib ; (4) Based on the relative radiation spectrum, the spectral intensity I of the two selected argon characteristic spectral lines is obtained. i , i takes 1 or 2, based on the spectral intensity I i Get the electron excitation temperature T exc ; (5) Based on the rotation temperature T rot , vibration temperature T vib and the electron excitation temperature T exc , get the coupling temperature T s , and according to the coupling temperature T s Obtain constant pressure specific heat C p and internal energy enthalpy h s , where: T s =(T rot ·T vib ·T exc ) 1 / 3 ; (6) Based on the relative radiation spectrum, the spectral intensity I of the characteristic spectral line of atomic nitrogen is obtained. N and the spectral intensity of the atomic oxygen characteristic line I O ; (7) Based on the argon mass fraction ω Ar , the spectral intensity of the first argon characteristic line I1, the spectral intensity of the atomic nitrogen characteristic line I N and the spectral intensity of the atomic oxygen characteristic line I O , obtain the mass fraction of atomic nitrogen ω N and the mass fraction of atomic oxygen ω O ; (8) Based on the atomic nitrogen mass fraction ω N and the mass fraction of atomic oxygen ω O , obtain the chemical enthalpy h c ; (9) Based on the internal energy enthalpy h s and chemical enthalpy h c , and obtain the ultra-high enthalpy non-equilibrium airflow stagnation point enthalpy H0.

2. The method for real-time measurement of enthalpy of ablation process of heat-resistant materials in arc wind tunnel tests according to claim 1, characterized in that: In the step (3), the normalized CN continuous spectrum or N2 + Continuum spectrum to obtain rotation temperature T rot and vibration temperature T vib , including: calculating CN or N2 + The theoretical spectrum is compared with the normalized CN continuous spectrum or N2 + The continuous spectrum is compared and approximated continuously, that is, when the deviation between the theoretical spectrum and the normalized continuous spectrum is ≤10%, CN or N2 + The theoretical spectrum corresponds to the rotation temperature T rot and vibration temperature T vib is the final value.

3. The method for real-time measurement of enthalpy of ablation process of heat-resistant materials in arc wind tunnel tests according to claim 1, characterized in that: In the step (3), CN or N2 + The target wavelength is 375-392nm.

4. The method for real-time measurement of enthalpy of ablation process of heat-resistant materials in arc wind tunnel tests according to claim 1, characterized in that: In the step (2), the spectral resolution δ and spectral response range σ of the emission spectrum system satisfy: δ is between 0.05-0.2nm, and σ covers 350-900nm.

5. The method for real-time measurement of enthalpy of ablation process of heat-resistant materials in arc wind tunnel tests according to claim 1, characterized in that: In step (4), based on the spectral intensity I i Get the electron excitation temperature T exc ,include: T exc =5.02+0.6log(I2 / I1)。 6. The method for real-time measurement of enthalpy of ablation process of heat-resistant materials in arc wind tunnel tests according to claim 1, characterized in that: The central wavelengths of the characteristic spectral lines of argon in step (4) are 763.51 nm and 703.03 nm respectively; the central wavelengths of atomic nitrogen and atomic oxygen in step (6) are 868.03 nm and 777.19 nm respectively.

7. The method for real-time measurement of enthalpy of ablation process of heat-resistant materials in arc wind tunnel tests according to claim 1, characterized in that: In step (5), the coupling temperature T s Obtain constant pressure specific heat C p and internal energy enthalpy h s ,include: h s =C p ×T s C p =0.9938-7.787×10 -4 P s +1.98×10 -4 T s +7.067×10 -7 P s ·T s -4.587×10 -8 T s 2 -1.25×10 -10 P s ·T 2 +4.19×10 -12 T 3 Among them, P s It is the stagnation pressure of heat-proof material.

8. The method for real-time measurement of enthalpy of ablation process of heat-resistant materials in arc wind tunnel tests according to claim 1, characterized in that: In the step (7), based on the argon mass fraction ω Ar , the spectral intensity of the first argon characteristic line I1, the spectral intensity of the atomic nitrogen characteristic line I N and the spectral intensity of the atomic oxygen characteristic line I O , to obtain the mass fraction of atomic nitrogen ω N and the mass fraction of atomic oxygen ω O , include:

9. The method for real-time measurement of enthalpy of ablation process of heat-resistant materials in arc wind tunnel tests according to claim 1, characterized in that: In the step (8), based on the atomic nitrogen mass fraction ω N and the mass fraction of atomic oxygen ω O Get chemical enthalpy h c ,include: h c =33.7h N +15.6h O 。 10. The method for real-time measurement of enthalpy of ablation process of heat-resistant materials in arc wind tunnel tests according to claim 1, characterized in that: In step (9), based on the internal energy enthalpy h s and chemical enthalpy h c , obtain the ultra-high enthalpy non-equilibrium airflow stagnation point enthalpy H0, include: H0=h s + h c 。

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