A Numerical Investigation For The Mixed Reacting Flowfield Of The Air Chemical Nonequilibrium Flow And Gaseous Jet Flow

With the continuous pursuit and exploration of high-speed flight,the real gas effect of the environment flowfield of hypersonic vehicles is becoming more and more obvious.With the wide application of ranjet and RCS control systems in propulsion and control systems,the high temperature air chemical nonequilibrium effect and the combustion effect have a great impact on the overall performance of the aircraft.In order to explore the influence of chemical reaction effects and restore the true flow characteristics as much as possible,it is of great significance to carry out numerical study of the mixed reacting flow in which air chemical nonequilibrium flow and combustion flow coexist.Based on the thermal-equilibrium gas hypothesis,numerical simulation techniques of the mixed reacting flow are developed starting from the multi-component N-S equations,including mathematical models of multi-component gas thermodynamic model,transport model and chemical kinetic model,and spatial discretisation scheme,temporal discretisation with the point implicit method.The hydrogen-air mixed reaction model and the ethylene-air mixed reaction model considering the high temperature air chemical reactions are established.Then,the typical jet interaction flow,the air chemical non-equilibrium flow and the combustion flow are simulated,respectively,for the verification of the numerical simulation method as well as the established mixed reaction model.The computational results are consistent with the experiment and literature data,which indicates that the numerical simulation method and mixed reaction model developed in this paper are reliable.In order to investigate the calculation ability of the developed numerical techniques for the3-dimensional complex reacting flow field,and to explore the influence mechanism of the air chemical non-equilibrium effect and combustion effect of the mixed reacting flowfield,the numerical simulation of the interaction flowfield is conducted on the ball head configuration with the gaseous hydrogen jet and the hypersonic mainstream at Mach number of 13.5.Three types of reacting flow are simulated respectively considering different reaction conditions and the influence of the two chemical reaction effects is discussed from the aspects of flowfield structure and flow parameters distribution.The results indicate that the shock wave detachment distance will be reduced by the air chemical nonequilibrium effect and increased by the combustion effect.In the region where the combustion effect dominates,the shape and spatial positions of the shock wave are little affected by the air chemical nonequilibrium effect.The jet penetration depth mainlyd epends on the combustion effect,but the occurrence of local regional air chemical reaction promotes the combustion efficiency,which broadens the jet penetration boundary.The air chemical nonequilibrium effect affects the flow structure by changing the shock position,and the temperature is more sensitive to the air chemical nonequilibrium effect than the combustion effect.The combustion effect causes the variation of concentration distribution of specific components near the jet exit.On the basis of research conducted above,numerical study is carried out on the blunt cone configuration for the interference flowfield of the gaseous ethylene jet and the hypersonic mainstream at Mach number of 11.6.The comparable numerical simulation of cold/hot jet flow is achieved by adjusting the reaction conditions.The jet interference characteristics are analyzed from the aspects of flowfield and aerodynamics with the changing jet Mach number and pressure.The results show that the hot jet flowfield has a larger range of jet expansion and penetration boundary under the same jet conditions,and the combustion effect causes the forward tilt of the jet bow shock.The momentum of the jet flow increases along with the increasing jet Mach number or pressure,and the difference between the hot jet and the cold jet expands.Under the conditions of this paper,the jet interference weakens the direct force of the jet but enhances the pitch control efficiency,and the direct force weakening and moment amplification decreases with the increasing momentum of the jet flow.The wave drag in the hot jet flow is larger than that of the cold jet flow due to the change of shock wave structures.As a result,the drag force is greater in the hot jet flow.In the meanwhile,it also produces a part of lift increment,which is beneficial to the reentry stage of the hypersonic vehicles.