Research On Aerodynamic Characteristics Of Counterflow Thrust Vectoring Nozzle

Fluidic thrust vectoring nozzle has the function of engine's thrust vectoring. When compared to traditional mechanical thrust vectoring nozzle, it has the advantage of reducing weight and mechanical support, reducing the observability, the high control rate of vectoring, and so on. Counterflow thrust vectoring nozzle utilizes the suction second flow to control main jet, and achieves vectoring thrust. This scheme is promising, especially, for the aerocraft of high performance, reliability, low cost and observability.The steady and unsteady aerodynamic characteristics of this counterflow scheme are conducted by using numerical simulation in this paper. After analyzing the basic principle, the validity of simulation method and the feasibility of counterflow scheme are verified by comparing the results of simulation and experiment. Moreover, flow structure, counterflow shear layer and jet attachment are researched, and some conclusions are obtained: Mass balance exists between converse secondary mass flux, suction secondary mass flux and main mass flux; velocity ratio of counterflow shear layer greatly affects its turbulent characteristics and eddy structure; when jet attaches, suction secondary mass flux descends and thrust vectoring angle is almost constant.Secondly, the effect of some geometry and aerodynamic parameters on the nozzle performance parameters is conducted by simulation research. The max thrust vectoring angle wins 30 degrees. In order to show the difference of the flowflied between 2D and 3D model, this paper investigates 3D model simulation, and finds the velocity of converse second flow is asymmetry in the spanwise and secondary flow exists. But the total performance parameters are almost identical.Besides, one unsteady problem as the variety of suction pressure is researched, and it finds the hysteretic nature of fluidic control and the stability of jet attachment exist in this unsteady process. Another unsteady problem as self-flow is researched, and it finds the velocity ratio of counterflow shear layer is a critical factor and the instability of eddy is the efficient cause.Lastly, this paper first brings forward two vacuum schemes, and conducts their total performance by simulation research. What's more, this paper discusses the merit and demerit of them, too.Above, this paper achieves some directive conclusions about aerodynamic characteristics of counterflow thrust vectoring nozzle. And these conclusions will be in favor of the future engineering experiment researches.