Analysis Of Ultraviolet Radiation Spectrum Characteristics Of Mixed Components

There are many kinds of molecules,atoms and ions such as NO,OH,O,N,N₂⁺in the shock layer and plume of hypersonic vehicle.The interaction between molecules leads to the excitation and de-excitation process,and the coincidence of characteristic peaks of ultraviolet radiation of different molecules.Both of them put forward higher requirements for the correct modeling of spectral radiation of mixed components in the ultraviolet band.Therefore,it is extremely necessary to establish a physical model that correctly describes the multi-component ultraviolet radiation spectrum.It is considered that the ultraviolet radiation characteristics of shock layer and plume of hypersonic vehicle are closely related to vehicle type,flight state,propellant fuel and other parameters.It is very important for target recognition and feature inversion to determine the corresponding relationship between ultraviolet radiation characteristics and flight parameters.In this paper,the shock layer and plume of hypersonic vehicle are taken as the research objects,and the calculation model of particle number density in thermochemical non-equilibrium state is established.Based on the line-of-sight integration method,the mixed components spectrum of the inhomogeneous flow field along the line of sight is obtained.Combined with the spectral parameters,obtains the specific method of OH,NO,N₂⁺spectrum inversion of vibration/rotation temperature.The main contents of the paper are as follows:1)Numerical simulation of non-equilibrium radiation modelBased on the UV spectrum parameters of common particles in the flow field,the excitation/de-excitation effects of N₂ molecules,N and O atoms on the OH in the chemical non-equilibrium state are considered.The reverse reaction rate of the displacement reaction is remodeled,and an improved collision radiation model is proposed to calculate the particle number density of OH（A）.The Boltzmann distribution was used to calculate the rotational energy level of OH（A）,and the collision-radiation model of OH（A）was simplified.The correctness of the model was verified by comparison with the Atlas experiment.Based on the collision-radiation model of NO（A）,the relationship between the number density of NO（A）and N₂（A）with temperature changes is calculated.The sensitivity analysis of the chemical reactions involved in the model is carried out,and three groups of reactions with strong sensitivity are summarized.Based on the thermodynamic non-equilibrium state,the corresponding relationship between the characterization temperature and the ultraviolet radiation spectrum is calculated by changing the electron,vibration and rotation temperature.Comprehensive consideration of the thermochemical non-equilibrium state,compared to only considering the chemical non-equilibrium effect,the BSUV test shock layer spectral radiance results calculated by substituting the multi-temperature model into the OH collision-radiation model are better fitted to the test.2)Analysis of spectral radiation transmission characteristics of inhomogeneous mediaBased on the differential form of the line-of-sight integration method,the calculation formula of the total spectral radiance in the inhomogeneous medium along the line of sight is derived and verified.Based on the HTV-2 shock layer flow field data,the influence of the number of layers on the calculation results of the shock layer spectral radiance is discussed.It can be seen that as the number of layers increases,the error in the calculation results of the spectral radiance decreases first and then remains same.According to the line-of-sight integration method,the HTV-2 shock layer multi-component mixed ultraviolet spectrum is calculated.The main radiation sources are O atom and NO（A-X）,NO（B-X）states of NO.Considering the inhomogeneous Atlas plume flow field in a chemically non-equilibrium state,combined with the collision-radiation model of OH,the ultraviolet radiation spectrum of OH is calculated.3)Temperature inversion method of characteristic molecular spectrumThrough the refined spectral structure analysis of OH（A-X）,NO（A-X）and N₂⁺（B-X）molecules,various methods of inverting rotation and vibration temperature in the ultraviolet band are discussed.Based on the existing OH（A-X）（0-0）peak inversion theory,a method of inverting the rotational temperature using the ratio of the relative intensity of the characteristic peak of OH（A-X）（1-1）to the reference peak is proposed.The relationship between the ratio of relative strength and rotation temperature is established.Based on the NO（A-X）spectral band structure,the corresponding relationship between the half-width of the maximum peak（0-1）peak of NO（A-X）and the rotation temperature is established.Based on the N₂⁺（B-X）spectrum,the relationship between the relative intensity of（0-0）and（2-1）vibration peaks and the rotation temperature is established.According to the structure of two groups of vibration peaks,the method of inversion of vibration temperature using（0-0）and（2-1）peaks is proposed.