高速冲击波下的高温空气辐射光谱研究

Study of High-Temperature Air Radiation Spectrum Under High-Speed Shock Wave

飞行器再入地球大气层过程中,高速飞行器头部的温度可达到10000 K以上导致飞行器气动性能的变化。空气的辐射加热是飞行器表面传热的主要来源之一,对高速冲击波下的空气辐射光谱进行测量研究,是研究超高速飞行器飞行过程中辐射效应和动力学行为的重要基础。目前高温空气辐射光谱的测量数据依旧较少,还需要大量的实验数据对计算模型进行改进优化。利用氢氧爆轰激波管结合瞬态光谱测量系统获得了速度在3259~8218m·s-1下高温空气在紫外-可见区的辐射光谱,并对典型高温空气辐射光谱进行了特征光谱的光谱识别和模拟,模拟结果和实验结果吻合较好,验证了光谱识别的准确性和可靠性;同时探究了激波速度对于高温空气辐射特性的影响,并对特征光谱进行了动力学行为分析。结果表明,在波长225~675 nm范围内,特征光谱主要存在于波长小于500 nm的区域;不同速度下的辐射光谱中存在不同的特征光谱,通过光谱识别后发现随着激波速度的增加,先后出现OH(A-X)、NO(γ,ε,δ)、NH(A-X)、N_(2)(C-B)、N_(2)^(+)(B-X)和Hα等特征光谱,获得了辐射特性随激波速度的变化情况。还根据辐射光强度随时间变化曲线获得了波后空气激发的弛豫时间,随着速度的增加,弛豫时间在逐渐缩短,与速度近似呈现指数关系。研究了激波速度对高温空气辐射特性的影响,研究结果为飞行器热防护设计和超高声速再入大气层过程的计算模型的验证优化提供实验数据和参考。

During spacecraft reentry into Earth's atmosphere,the temperature of the high-speed air at the front of the spacecraft can reach over 10000 K,leading to changes in the aerodynamic performance of the spacecraft.Radiative heating is one of the main sources of surface heat transfer for spacecraft,and measuring the radiation spectra of air under high-speed shock waves is crucial for studying radiation effects and dynamic behavior during the flight of hypersonic vehicles.There is still a lack of measurement data for high-temperature air radiation spectra,and a large amount of experimental data is required to improve and optimize computational models.This paper uses a hydrogen-oxygen detonation shock tubecombined with a transient spectroscopic measurement system to obtain the radiation spectra of high-temperature air in the ultraviolet-visible region at velocities ranging from 3259~8218 m·s-1.The identification and simulation of typical high-temperature air radiation spectra characteristic spectra were carried out.The simulation results were in good agreement with the experimental results,validating the accuracy and reliability of the spectral identification.The impact of shock wave velocity on the radiation characteristics of high-temperature air was also analyzed,and the dynamic behavior of characteristic spectra was analyzed.The results showed that characteristic spectra mainly exist in the 225~675 nm wavelength range and the region with wavelengths below 500 nm.Different characteristic spectra were observed in the radiation spectra at different velocities.With increasing shock wave velocity,OH(A-X),NO(γ,ε,δ),NH(A-X),N_(2)(C-B),N_(2)^(+)(B-X),and Hαspectral lines appeared successively.The relative intensities of the characteristic spectra vary with shock wave velocity.Finally,the relaxation time of post-shock air excitation was determined based on the time-varying curve of radiation intensity.The relaxation time gradually shortened with increasing velocity and exhibited an exponential relationship with velocity.This study provides experimental data and references for spacecraft thermal protection design and the validation and optimization of computational models for hypersonic reentry into the atmosphere.