Research On The Intereference Radiation Characteristics Of Highspeed Aircraft In Aero-thermal Environment

To the aircraft flying in high-speed within atmosphere,the surface of aircraft and atmosphere near the surface will reach a high temperature because of aerodynamic heating effect.In this condition,the optical window in the front of aircraft and atmosphere with high temperature around the aircraft will produce intense infrared radiation,which will further reach the imaging equipment inside the aircraft and become non-uniform thermal radiation noise,also called radiation interference,and eventually influence the quality of target image.With the aim of providing support for the modification of image with background noise,the characters of radiation interference in different working condition of aircraft are investigated in this paper.A kind of aircraft equipped with conformal dome is introduced in this paper.The character of radiation interference produced by atmosphere around the aircraft and optical window is investigated and the influence of Mach number and angle of attack are taken into consideration.Firstly,the character of flow field outside the aircraft is obtained through CFD method.Secondly,in order to calculate the radiation interference produced by atmosphere outside the aircraft,its radiation character is obtained through on Fortran program based on line-by-line method and narrow band model.Finally,based on the data obtained above and taking the thermal deformation of optical window into consideration,the distribution of the radiation interference on the receiving plane of imaging equipment is obtained.The main contents of this paper include three parts as fellow.Based on CFD method and FVM theory,the simulation model of aircraft’s flow field is established.And based on this model,the flow field of 20 different kind of working condition,including four Mach number and five angles of attack,is simulated.The distribution of temperature,pressure,density,velocity in external flow field of the aircraft equipped with conformal dome are obtained and their distribution character is analyzed.Furtherly,the simulation results of flow field provide data for the simulation of deformation of optical window and the calculation of interference radiation produced by atmosphere in external flow field.Based on HITEMP database,Fortran programs for the calculation of gas radiation properties are written by introducing LBL method and narrow band model.And the band model parameters of narrow band model of CO₂ and H₂O are obtained.The accuracy of the result is proved by compared with previous research.Based on the simulation results of external flow field,the deformation of optical window of the aircraft is simulated.Taking the deformation of optical window into account,the radiation interference received by imaging system in its working wavelength is calculated.The distribution of radiation interference in each working condition of aircraft are obtained and the influence of working parameters on radiation interference is analyzed.