Study On Aerodynamic Performance And Infrared Radiation Characteristics Of Single Expansion Ramp Nozzle With Secondary Flow

In order to gain an advantage in modern air combat,how to improve the vector control and survivability of aircraft has been widely concerned by scholars all over the world.Because infrared detection has the advantages of high detection accuracy,more concealment,and strong anti-interference ability,it has been widely used in various kinds of aircraft detection technology.Therefore,improving the infrared stealth capability of the aircraft is the key to improving the survivability of the aircraft.Compared with traditional axisymmetric nozzles,single expansion ramp nozzles not only provide flexible vector thrust,but also have better integrated design and infrared suppression capability.The introduction of secondary cold flow into the single expansion ramp nozzle not only changes the aerodynamic performance of the nozzle,but also cools the inner wall surface of the nozzle and the tail flame to reduce its infrared radiation.Therefore,this paper mainly introduces secondary flow into the single expansion ramp nozzle to study the aerodynamic performance of the nozzle and the infrared radiation characteristics of the tail flame under different geometric parameters and aerodynamic parameters.The main research contents include two parts.First of all,simulation of exhaust plume flow field and analysis of aerodynamic performance of single expansion ramp nozzle with secondary flow: The tail flame field is simulated by the Fluent software platform,and the influence of the re-ignition phenomenon in the tail flame on the flow field parameter distribution is considered.For the selected calculation model,the typical flow characteristics of the inside and the tail flame field of the nozzle are verified to prove the rationality of the selected model for this problem.For the single expansion ramp nozzle,the single expansion ramp inclination angle and the slit ratio are changed to simulate the flow field,and the axial thrust and thrust vector angle are calculated.For the thrust vectoring nozzle with pneumatic throat,the secondary to primary total pressure ratio,the secondary flow injection angle and the secondary flow relative area ratio are simulated to simulate the flow field.Besides,the axial thrust and thrust vector angle are calculated,and the aerodynamic performance is analyzed.And then the second part analysis of infrared radiation characteristics of single expansion ramp nozzle with secondary flow: Since the tail flame studied in this paper is a pure absorption medium,it is only necessary to calculate the absorption coefficient of the gas.The K-distribution absorption coefficient library is calculated and established by the wide-band K-distribution model,and the absorption coefficient of each grid is calculated by database interpolation.The radiation transfer equation is solved by the line-of-sight method,and the total radiant intensity of the tail flame field at different detection angles is obtained.To change the single expansion ramp inclination angle and the slit ratio of the single expansion ramp nozzle,the secondary to primary total pressure ratio,the secondary flow injection angle and the secondary flow relative area ratio of the vectoring nozzle with pneumatic throat,the influence of these geometric parameters and aerodynamic parameters on the infrared radiation characteristics of the tail flame field is analyzed.