Numerical Simulation Research On Aerodynamic Characteristics Of A HTHL High-speed Demonstrator Aircraft

Horizontal take-off and landing,wide-speed flight is an important research direction of future aircraft,but the power system is the bottleneck problem restricting this type of aircraft.At present,the single power cannot meet the requirements of wide-speed flight.The turbo-based combined cycle(TBCC)engine is an ideal power system,but it also faces the thrust gap in the process of switching from the turbo engine to the ramjet engine.Xiamen University proposed a multi-duct combined cycle power scheme,used the ejector rocket as a bridge to solve this problem,and developed a small combined power system.In order to verify the power system,the research team specially developed a horizontal take-off and landing high-speed demonstrator aircraft.This paper conducts a comprehensive numerical simulation study on the aerodynamic characteristics of the aircraft,which lays a solid foundation for its aerodynamic design,flight control design and first flight,and thus provides a good guarantee for the verification of the combined power system.Therefore,the research work in this paper not only has certain theoretical research value,but also has great engineering significance.The governing equation used in the numerical simulation in this paper is the compressible Reynolds average Navier-Stokes equation,which is solved by the finite volume method.The spatial dispersion of the governing equation adopts the Jameson central format plus artificial dissipation,and the time dispersion adopts LU-SGS implicit method.The Sparlat-Allmaras model is used as the turbulence model,and the correctness of the numerical simulation method is verified by standard calculation examples such as the CRM model.In this paper,based on the flight envelope of the demonstrator aircraft,a largescale numerical simulation of the aerodynamic characteristics of the demonstrator aircraft at different speeds and altitudes is carried out,an aerodynamic database is established,and the effects of the angle of attack and Mach number on the aerodynamic characteristics of the aircraft are analyzed.The numerical simulation results show that the lift coefficient of the demonstrator aircraft basically increases linearly with increasing angle of attack.After exceeding the critical angle of attack,the lift coefficient begins to decrease.As the angle of attack increases,the drag coefficient shows a trend of decreasing first and then increasing.The lift-to-drag ratio increases first and then decreases as the angle of attack increases.In addition,at the same angle of attack,the lift coefficient of the aircraft increases first and then decreases as the Mach number increases,and reaches the maximum value near the speed of sound.The drag coefficient remains basically unchanged at subsonic speed,and the Mach number increases to about 1 and the drag coefficient increases significantly.This paper further carries out numerical simulations on the influence of the landing gear and ground effects on the aerodynamic characteristics of the whole aircraft.The research shows that the landing gear increases the drag coefficient of the whole aircraft significantly,but there is no significant difference between the lift coefficient and the pitching moment coefficient.The ground effect makes the lift coefficient of the whole aircraft increase,the maximum increment is up to 28%,the drag coefficient has little effect,the downward force moment of the whole aircraft increases significantly,and the aerodynamic parameters show nonlinear changes with the height of the ground.In addition,this paper also studies the impact of engine on the aerodynamic characteristics of the whole aircraft.The results show that the impact of engine(inlet and nozzle plugging/through-flow/set boundary condition)on the flow field of the whole aircraft is concentrated on the inlet and nozzle position,and the through-flow model can well simulate the flow field when the engine is working,and the calculation amount is small,and it can be used as the calculation model for the establishment of the aircraft aerodynamic database.In this paper,the calculation method of the dynamic derivative of pitch damping and rolling damping is deduced according to the motion equation of forced vibration of rigid body,and the standard model of dynamic derivative calculation is numerically simulated.The calculated dynamic damping derivative of pitch damping and rolling damping derivative are in good agreement with the experimental data,which verifies the correctness of the numerical simulation method of dynamic derivatives in this paper.On this basis,this paper further numerically simulates the dynamic aerodynamic characteristics of the demonstrator aircraft and calculates the pitch damping derivative and rolling damping derivative of the demonstrator aircraft at MO.7.The calculated results are similar to the engineering estimates.Based on the calculated aerodynamic data in this article,the research team carried out the aerodynamic design,flight control design,prototype manufacturing of the demonstrator aircraft,and finally successfully achieved the first flight.This paper obtained the flight simulation results based on the aerodynamic database by modeling the aircraft dynamics,and compared with the flight test data of the validator.The results show that the flight simulation data and the flight test data are similar,thus the aerodynamic characteristic data of the horizontal takeoff and landing high-speed demonstrator aircraft calculated in this paper are comprehensively evaluating to be accurate and reliable.