Optimal Research On Supersonic Split Line Nozzle

In the future battlefield,all kinds of aircraft need to improve their mobility to deal with the more advanced air defense system and increase the success rate of penetration.The traditional aerodynamic control method could no longer meet the requirements of vector flight in the future,such demand promotes the rapid development of thrust vector technology.Among many forms of thrust vectoring device,Supersonic Split Line(SSSL)Nozzle is a kind of swing nozzle with great development potential.It has simple structure and low sealing difficulty.More importantly,compared with other thrust vector nozzle,an oblique shock wave can be generated inside SSSL nozzle’s expansion section through its swing structure.This shock wave could further deflect the airflow in the nozzle,it gives the SSSL nozzle higher deflection efficiency.Focusing on the geometric parameters of the inner profile and the thrust performance of the SSSL nozzle,this paper studies the method to carry out the optimal design of this type of nozzle.In addition,the relationship between geometric parameters and thrust performance of the nozzle is explored.The main contents are as follows:1.An SSSL nozzle design method is proposed based on the Method of Characteristics(MOC)and multi-objective evolutionary algorithm(MOEA).In this SSSL nozzle design method,the geometric parameters of nozzle inner profile are grouped into the basic geometric parameters and the spilt line geometric parameters.The MOC is used to calculate the basic geometric parameters and MOEA is applied to optimize the spilt line parameters.Finally,this SSSL nozzle design method is used to optimize the inner profile of SSSL nozzle with the objectives of maximum thrust when the nozzle works at 0 degree swing angle,axial and lateral thrusts when the nozzle works at 10° degree swing angle.2.The optimal results of the SSSL nozzle’s inner profile are analyzed by means of statistics and surrogate model.It is found that,for the SSSL nozzles working at their 0 degrees swing angle,there is little difference among the different results on the Pareto front.This proves that there is a weak correlation between the thrust performance of SSSL nozzle at 0 degrees and that at other degrees.The relationship between the split line geometric parameters and the thrust performance is also studied.According to the results on the Pareto front,suggestions for the design of SSSL nozzle inner profile are given:(1)Reducing the gap thickness and the front chamfer radius of the spilt line is helpful in improving the overall thrust performance of the SSSL nozzle.(2)Increasing the rear chamfer radius of the spilt line as much as possible improves the thrust vector performance of the SSSL nozzle.(3)The expansion ratio of the spiltline and the swing center ratio should always be increased or decreased simultaneously to achieve larger axial or lateral thrust under large swing angles.