| When high-speed aircraft with infrared detection / guidance capability flights among atmosphere at high speed,the gas in front of its hood will be compressed strongly and a very thin shock wave will form.In addition,the temperature of shock wave layer between shock wave and aircraft wall will rise sharply,the pressure will become stronger,and the molecular density will become larger.Thus its infrared radiation will reduce the signal-to-noise ratio of the detector,which will influence the infrared detection and guidance capability of aircrafts.In this paper,the spectral characteristics of the shock wave layer are studied,including the simulation of the aerodynamic flow field around the high-speed aircraft,the establishment of the calculation model of the medium and high temperature gas radiation,and the calculation of the radiation characteristics of the CO2 and H2 O rovibrational bands.The main research contents include:(1)Research on aerodynamic flow field around high-speed aircraft.The boundary conditions of the aerodynamic flow field around high-speed aircraft under 3Ma and 5Ma conditions are calculated.Based on the aerodynamics and finite element theory,the finite element method is used to build finite element calculation model of high-speed aircraft.Based on the finite element calculation model,the air density field,temperature field,pressure field and velocity field distribution of aerodynamic flow field around high-speed aircraft is calculated.That is,the distribution law of the aerodynamic flow field around high-speed aircraft is determined.(2)Study on thermal radiation calculation model of shock w ave layer in aerodynamic flow field around high-speed aircraft.The calculation model of the medium and high temperature gas radiation is studied,including line calculation method,wide band model and narrow band model.The applicable objects and conditions of each model are analyzed and compared.Based on the calculated environmental characteristics of the aerodynamic flow field,the Malkmus model in narrow band model is used to calculate the radiation characteristics of the aerodynamic flow field,and the calculation method of each parameter in the model is given.(3)Calculation of thermal radiation characteristics in shock wave layer around high-speed aircraft.The radiation characteristics of CO2 and H2 O,which are the main components of infrared radiation in the shock wave layer,are analyzed.The rovibrational partition function of CO2 and H2 O in the shock wave layer are calculated.The band intensity of 21 bands among 3300-3800cm-1 spectral region under given temperature and pressure is calculated,and the calculation results of spectral average absorption coefficient,spectral line spacing and spectral line half-width are given.The spectral transmittance of CO2 and H2 O among the 3300-3800cm-1 spectral region is calculated under 3Ma and 5Ma conditions.The accuracy of the calculation model is verified,and the validation results of the model are given. |
