Method for measuring enthalpy value of thermal protection material in ablation process in arc wind tunnel test in real time

Abstract

The invention relates to a real-time measurement method for an enthalpy value in an ablation process of a thermal protection material in an electric arc wind tunnel test, is used for a ground test of an electric arc wind tunnel thermal protection system, and belongs to the research field of ground aerodynamic thermal tests of aircrafts. The non-equilibrium temperature (rotation, rotation and electron) and the concentration of atomic nitrogen and atomic oxygen of a stagnation point area of a stagnation point model of the heat-proof material are obtained, online measurement of the local center stagnation point enthalpy value of the heat-proof material is achieved, the whole-process real-time monitoring of the material ablation process is achieved, the enthalpy value simulation range of various types of arc wind tunnels such as tubular, segmented and laminated arc wind tunnels can be covered, and the performance of the heat-proof material is improved. The method has very wide applicability; and rapid and long-time measurement of the whole ablation process of the heat-proof material can be realized, the response frequency can be up to 100Hz, and the measurement period is greater than or equal to 1h.

Description

Technical Field

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

[0002] When an aircraft glides, cruises, or reenters at extremely high speeds, the surface of the aircraft will be severely aerodynamically heated, and the airflow temperature near the wall can reach 10,000K. Conventional materials cannot withstand such high temperatures, and special thermal protection materials need to be developed for heat protection design. One of the main ways for thermal protection materials to protect against heat is through ablation, which absorbs and takes away heat, thereby preventing heat from being transferred to the interior of the aircraft. This process requires special wind tunnel ground tests to evaluate the material ablation process, and arc wind tunnel equipment is the main equipment for evaluating and assessing thermal protection materials at home and abroad.

[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 and measured in real time. Under the wind tunnel ground ablation test, due to ablation, the surface of the model is constantly changing, and 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 a completely non-ablated state with no change in appearance. The enthalpy measurement methods developed by me (ZL202111015133.2, ZL202111012554.X, ZL201910440190.1, ZL201811494282.X) measure the enthalpy of the airflow in the test and debugging stage, and do not involve the real-time measurement of the heat-resistant material itself during the long-term ablation test process; the patent (ZL201711003142.3) is based on the calibration quantitative relationship between the emission spectrum intensity ratio of the target component and the enthalpy of the high-temperature airflow, and develops a method for measuring the local enthalpy of the arc heater, which is suitable for the range of 5MJ / kg-25MJ / kg, and realizes real-time and long-term monitoring of the arc heater. There is currently a lack of effective methods for real-time measurement of enthalpy in the ablation process of heat-resistant materials. It is very necessary to develop corresponding methods to realize long-term real-time monitoring of the ablation process of heat-resistant materials. Summary of the invention

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

[0005] The technical solution of the present invention is as follows:

[0006] A real-time measurement method for the enthalpy value of the ablation process of a heat-resistant material in an arc wind tunnel test comprises the following steps:

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

[0008] (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 protection 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, CN or N2 is intercepted respectively. + The continuous spectrum of the target band range is normalized and based on the normalized CN continuous spectrum or N2 + The continuous spectrum obtains the 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 is 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 Get the 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 characteristic spectral line of atomic oxygen 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 characteristic spectral line of atomic oxygen I O , and 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 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 + The continuous spectrum obtains the rotation temperature T rot and vibration temperature T vib , including: calculation of 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 + The target band is 375-392nm.

[0018] In the above-mentioned arc wind tunnel test heat protection material ablation process enthalpy real-time measurement method, 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 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 of ablation process of heat-resistant materials in arc wind tunnel test, 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 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 Get the 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 point pressure of heat protection material.

[0026] In the above 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 characteristic spectral line of atomic oxygen I O , and obtain the mass fraction of atomic nitrogen ω N and the mass fraction of atomic oxygen ω O ,include:

[0027]

[0028] In the above 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 the 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 real-time measurement method of enthalpy during ablation of heat-resistant materials in arc wind tunnel tests provided in the embodiments of the present invention is based on the developed emission spectroscopy system and enthalpy measurement method to obtain the non-equilibrium temperature (rotation, rotation, electron) of the stagnation point area of ​​the stagnation point model of the heat-resistant material and the concentration of atomic nitrogen and atomic oxygen, 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;

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

[0035] (3) In the method for real-time measurement of enthalpy of ablation process of heat-resistant materials in arc wind tunnel test provided by the embodiment of the present invention, the enthalpy value applicable range of the method is 10-50MJ / 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 an arc wind tunnel test provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention is 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 value of ablation process of heat-resistant materials in an arc wind tunnel test provided by an embodiment of the present invention. The method for real-time measurement of enthalpy value of ablation process of heat-resistant materials in an arc wind tunnel test provided by an embodiment of the present invention comprises the following steps:

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

[0041] (ii) using an emission spectrum system to measure the original radiation spectrum at the center of the stagnation point on the surface of the heat protection material, and dividing the original radiation spectrum 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 0.05-0.2nm, and σ covers 350-900nm.

[0043] (III) Based on the relative radiation spectrum, CN or N2 is intercepted respectively + The continuous spectrum of the target band range is normalized and based on the normalized CN continuous spectrum or N2 + The continuous spectrum obtains the rotation temperature T rot and vibration temperature T vib .

[0044] In an optional embodiment, based on the normalized CN continuous spectrum or N2 + The continuous spectrum obtains the rotation temperature T rot and vibration temperature T vib , including: calculation of 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 band 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 gas 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 Get the constant pressure specific heat C p and internal energy enthalpy h s .

[0050] The coupling temperature T s , the calculation formula is 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 Get the 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 point pressure of heat protection material.

[0056] (VI) 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 characteristic spectral line of atomic oxygen 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 characteristic spectral line of atomic oxygen I O , and 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, and the specific calculation formula is as follows:

[0063] H0=h s +h c .

[0064] The real-time measurement method of enthalpy value in the ablation process of heat-resistant materials in arc wind tunnel tests provided in an embodiment of the present invention is based on the developed emission spectroscopy system and enthalpy value measurement method, which 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, realizes the online measurement of the local central stagnation point enthalpy of the heat-resistant material, and realizes real-time monitoring of the entire process of material ablation.

[0065] 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.

[0066] 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 real-time measurement method for the enthalpy value of the ablation process of heat-resistant materials in arc wind tunnel tests, characterized in that: The steps include: (1) Establish a high-enthalpy airflow field environment for the arc wind tunnel test, arrange the heat protection material downstream of the high-enthalpy airflow, and align the central axis of the heat protection material with the central axis of the arc wind tunnel; (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 protection 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, CN or N2 is intercepted respectively. + The continuous spectrum of the target band range is normalized and based on the normalized CN continuous spectrum or N2 + The continuous spectrum obtains the 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 is 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 Get the 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 characteristic spectral line of atomic oxygen 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 characteristic spectral line of atomic oxygen I O , and 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 value of ablation process of heat-resistant materials in arc wind tunnel test according to claim 1 is characterized in that: In the step (3), based on the normalized CN continuous spectrum or N2 + The continuous spectrum obtains the rotation temperature T rot and vibration temperature T vib , including: calculation of 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 value of ablation process of heat-resistant materials in arc wind tunnel test according to claim 1, characterized in that: In step (3), CN or N2 + The target band is 375-392nm.

4. The method for real-time measurement of enthalpy value of ablation process of heat-resistant materials in arc wind tunnel test 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 value of ablation process of heat-resistant materials in arc wind tunnel test 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 value of ablation process of heat-resistant materials in arc wind tunnel test 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 value of ablation process of heat-resistant materials in arc wind tunnel test according to claim 1, characterized in that: In step (5), according to the coupling temperature T s Get the 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 point pressure of heat protection material.

8. The method for real-time measurement of enthalpy value of ablation process of heat-resistant materials in arc wind tunnel test according to claim 1, characterized in that: In 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 characteristic spectral line of atomic oxygen I O , and 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 value of ablation process of heat-resistant materials in arc wind tunnel test according to claim 1, characterized in that: In step (8), based on the atomic nitrogen mass fraction ω N and the mass fraction of atomic oxygen ω O Get the chemical enthalpy h c ,include: h c =33.7h N +15.6h O 。 10. The method for real-time measurement of enthalpy value of ablation process of heat-resistant materials in arc wind tunnel test 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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