Design And Optimization Of The Aerospike And Opposing Jet Combinational Thermal Protection System For Hypersonic Re-entry Vehicles

The huge economic and performance advantages make reentry vehicles with hypersonic velocity as one of the most promising technologies in the future aerospace industry.But reentry vehicles which are cruising long hours in hypersonic conditions may suffer from severe aerodynamic drag and heat problems.As a result,the operational performances of hypersonic vehicles will drop dramatically,and the aircrafts will face serious challenge in practical applications.Therefore,the study of the thermal protection system on hypersonic vehicles is extremely urgent.In this paper,a high-precision CFD numerical simulation method is combined with a surrogate model based optimization algorithm to design and optimize the configuration of a combinatorial spike and opposing jet thermal protection system in hypersonic flows.Firstly,research progress of both experimental and numerical research on drag and thermal protection method from home and abroad are overviewed by different types of mechanism,namely the aerospike,the opposing jet,the aerospike and opposing jet combinational system.In addition,the common application of surrogate model based optimization methods on aerodynamic design of aircrafts are summarized.Secondly,the effectiveness of the numerical methods are studied on the basis of single aerospike or opposing jet experimental models in open literatures.After comparing the simulation results with the experimental data,it is concluded that using single equation Spalart-Allmaras model to compute grid model which has a grid Reynolds number around 5 is the most promising scheme for the present study.Then,a detailed parametric investigation on the combinational aerospike and opposing jet configuration is conducted.The effects of some vital factors(the length of the spike,the diameter of the aerodisk and the nozzle,the pressure ratio of the jet flow)on the drag and heat reduction efficiency of the combined system and on the flow filed structure around the aircraft are analyzed.The results show that the effect of the aerospike and counterflowing combined system is not improved linearly with the extension of the spike length and the disk diameter.Besides,the total jet pressure ratio and the nozzle diameter should be limited in a certain extent to ensure the stability and flexibility of the aircraft.Finally,the design and optimization for a drag and heat flux reduction mechanism induced by a combinational aerospike and opposing jet concept is carried out.It could be noticed that the optimization algorithm coupled with a surrogate model and accompanied by a CFD verification method shows effectiveness.A higher efficiency combined configuration is obtained after the whole process of optimization,namely,the selection of objective functions and design variables,experimental design,surrogate model foundation,and design optimization.The results show that compared with conventional singal thermal protection systems or the pure blunt body,not only the shock wave ahead the aircraft with the optimized configuration has been pushed farther away but also a wider recirculation zone has appeared around the blunt body.This promise a better drag and heat reduction of the aircraft.