Mechanism Investigation For Drag And Heat Reduction Of Opposing Jet On Hypersonic Vehicle

This paper concentrates on the analysis of the flow field characteristic around a hypersonic vehicle in near-space.Using a combination of theoretical analyses and numerical simulation,the aerodynamic and thermodynamic performance is investigated systematically.Waverider is the first candidate for the configurations of hypersonic vehicle owing to its better aerodynamic performance than conventional configurations at high speed condition.During the practical application,the sharp leading edge can't be obtained because of the limitation of manufacturing technology.At the same time,the vehicle will withdraw the serious aero-heating environment and it will bring the huge challenge for the thermal protection.Blunting the leading edge is a very effective method to relieve the aero-heating.However,the blunt leading edge will result in the obvious decrease for the aerodynamic performance.Thus,for the hypersonic vehicles which designed based on waverider configuration,it is a key problem to solve the conflict between its good aerodynamic performance and serious aero-heating environment which are induced by the sharp leading edge for the near-space vehicle.What's more,it is also very important to improve the aerodynamic and aero-heating characteristic for the waverider with the blunt leading edge.The aerodynamic performance decreases sharply with the increase of blunt radius for the blunt waverider,however,the aero-heating environment ameliorate obviously.The waverider with variable blunt radii not only owns the good aero-heating environment,but also can improve the aerodynamic performance.That will offset the shortage of aerodynamic performance decrease due to the increase of blunt radius.However,the head zone of blunt waverider will still withdraw the serious aero-heating environment and huge drag.It is the research key in the paper that how to improve the whole performance of blunt waverider by achieving the drag reduction and thermal protection.The opposing jet can achieve the drag reduction and thermal protection effectively by changing the flow field structure at high speed condition.The opposing jet is introduced into the blunt waverider to improve the aerodynamic and aero-heating characteristic by affecting the flow field structure around the blunt waverider.The paper proposes a novel design project which adapts to the blunt waverider.At the same time,the paper does research deeply on several key technology problems,for instance the mechanism of drag and aero-heating reduction for opposing jet,the performance of blunt waverider,the design theory for novel wide-speed vehicle and the application of opposing jet in the blunt waverider et.al.This paper contains mainly three parts: the first part is the related research on opposing jet,the second part is the related research on the blunt waverider and the third part is the related investigation on the combination application between the opposing jet and blunt waverider.Firstly,the numerical method in the paper is validated against the available experiment data in the open literature.And the grid independency analysis is also finished in the paper.Based on the theory analysis of opposing jet,the novel opposing jet projects are proposed and the pentacle shape has the better performance for the drag and aero-heating reduction by comparing the numerical simulation results of different projects.According to the research result,the schemes of equal polygon for opposing jet are proposed in the Chapter 3 and the design process is introduced in detail.At the same time,the properties of different polygons are also investigated numerically,and the drag and aero-heating reduction performance is the best when N is 7.Then,the effect of free flow parameters on the performance of N=7 are investigated systematically.Furthermore,the cone-derived waverider theory and the blunt method for leading edge are studied comprehensively.Taking the aerodynamic and aero-heating performance into account,the characteristic of waverider with blunt radii are investigated numerically and the flow characteristic around the stagnation point is analyzed theoretically.Based on the design method of waverider,several novel design concepts for wide-speed vehicle are created,for example “Tandem combined vehicle”,“Parallel combined vehicle” and “Variable Mach number wide-speed vehicle”.These concepts could be the reference for the design of hypersonic vehicle in near-space.What's more,the object of drag and aero-heating reduction for blunt waverider is achieved by combining the opposing jet and variable blunt radii method into waverider.According to the configuration characteristic of blunt waverider,the aperture as a novel way of opposing jet is proposed to improve the aerodynamic and aero-heating characteristics in the hypersonic flow.The characteristics of blunt waverider with opposing jet and variable blunt radii are investigated numerically and the effect of total pressure ratio on drag and aero-heating reduction performance is also discussed in detail.And the lowest total pressure ratio is obtained theoretically for different flow conditions.Based on the aperture configuration of opposing jet,the different jet types are designed and their effects on drag and aero-heating reduction are also discussed in Chapter 6.At the same time,the influence of long-to-width ratio for aperture on waverider's performance is analyzed.The results show that the configuration of opposing jet will play the key role in the 3-dimension flow field structure.Finally,the advantage that opposing jet is used in the blunt waverider is validated and the way is doable for hypersonic vehicle to reduce the drag and aero-heating.The influences of free flow conditions,the configuration and way of opposing jet are investigated systematically.The research in the paper could be reference for the configuration and thermal protection design of hypersonic vehicle in near-space.The studies are useful to promote the hypersonic vehicle from concept design to the practical application further.