UV Radiation Characteristics Of Hypersonic Aircraft Plume Using Spherical Harmonics Discrete Ordinate Method

Based on the requirements of application of hypersonic aircraft plume UV detection,the physical properties of hypersonic aircraft plume were studied and the radiation mechanisms for different UV radiation source functions in plume were analyzed in this thesis.The Spherical Harmonics Discrete Ordinate Method(SHDOM)for calculating atmospheric radiation characteristics was introduced when solving the plume's UV radiation transfer equation.The effects of different UV radiation source functions on the plume's UV radiation characteristics were discussed.The main research aspects involved in this paper includes:1.The monomer radious following a normal distribution were introduced to DLA algorithm and the alumina particle cluster model in plume was established.Based on the multi-sphere T-matrix algorithm,the phase state and fractal dimension of alumina particle cluster,as well as the effect of monomer number on scattering phase function,linear polarization characteristics,and non-sphericity of the single alumina particle cluster,were studied.In terms of scattering characteristics,the alumina particle cluster was also compared with equal volume spheres,equal surface spheres and particle clusters with equal monopole radius.The scattering characteristics calculated using multiple-sphere T-matrix algorithm and CST software respectively were compared,and the results of these two methods match well.2.An algorithm for calculating the statistical average optical properties of alumina particle cluster in plume was given.The effects of the monomer number and detection wavelength on the alumina particle cluster's statistical average scattering phase function,asymmetry factor,single albedo,extinction efficiency factor,absorption efficiency factor and scattering efficiency factor were studied.The statistical average optical properties of the alumina particle clusters whose radii follow different distributions were analyzed.The effects of different alumina monomer models on their statistical average optical properties were compared.3.According to the theory of black body radiation,the heat radiances of different alumina particles models in plume at the UV band were calculated.The collision-radiation model was used to study the algorithm for finding energy level densities of OH and NO gas molecules in plume.According to the spectral line intensity,linear function,energy level density and Plank function of each gas molecule in UV band,the spectral emission coefficients for the gas molecules in chemiluminescence emission were calculated.The spectral emission coefficient for the simulated chemical emission of OH gas molecules was compared with the Atlas aircraft plume data in literature,with good consistency between the results.4.The radiation source function under SHDOM has been extended.The heat radiation source function of the alumina particle cluster,the chemiluminescence radiation source function of the OH and NO gas molecules,and the internal scattering source function of the alumina particle cluster have been introduced.The SHDOM,which is used for calculating the atmospheric radiation characteristics,was introduced in solving the plume's UV radiative transfer equation.The plume's UV radiance was calculated using SHDOM as same as the experimental result.The effect of various the radiation source functions on its UV radiation characteristics was discussed.5.The UV radiation model of the plumes of hypersonic aircraft solid/liquid rocket propellants was established.A SHDOM-based study of UV radiation characteristics of plume under different conditions was conducted.In the solid rocket propulsion section,the plume's UV radiation sources are mainly dominated by alumina particle cluster heat radiation,chemiluminescence radiation of OH and NO gas molecules,and radiation due to the scattering of the alumina particle cluster.The UV radiation characteristics of the hypersonic aircraft plume,at different flight altitudes,engine thrusts,and detection wavebands,with re-ignition and without re-ignition,were analyzed.In the liquid fuel propulsion section,the plume's UV radiation source is mainly the chemiluminescence radiation of OH gas molecules.In general,the effects of flight speed,attack angle,and flight altitude on UV radiation characteristics of the hypersonic aircraft plume were studied.