The Study Of Separation Mixing In Unstarted Hypersonic Inlet

Hypersonic inlet is an important part of the ramjet engine,its main role is to pressurize the flowing air,provide the certain pressure,temperature and velocity of air into the combustion chamber,and produce enough thrust for the engine.When the inlet is unstart,the flow field quality deteriorates rapidly,and the whole propulsion system can not produce thrust.Therefore,it is very important to study the unstart of the hypersonic inlet.In this paper,experiments and simulations are carried out to investigate the influence of the movement of the separation zone in the inlet.There is a strong shock boundary layer interference in hypersonic inlet.When the inlet is unstart,it will produce a large scale separation flow at the lip.The separation flow produced rapidly and changed violently,which put higher requirements for the research methods.The wind tunnel experiments were carried out to study the flow mechanism,the Nano-tracer Planar Laser Scattering(NPLS)technology and schlieren pictures technique is used to observe the field.using the high frequency pressure sensor records the changing of pressure.On the basis of experimental research,the numerical simulation method is used.First of all,it extracts the fusion phenomenon of the separation zone in the inlet,through numerical simulation gets the separation zone fusion process and the process of separation causing by the double shock incidence flat plate boundary layer,,and separate flow integration will produce large scale integration.Integration,s separation zone and produce the same flow deflection angle of single incident shock flat plate boundary layer induced by flow separation are approximately equal in length.It is also found that there is hysteresis in the process of fusion / separation.According to the compression angle and boundary layer thickness on the separation / separation effect of fusion were compared and found that the thickness of boundary layer is thicker,the separation zone more prone to fusion,fusion and separation area is prone to separate.Secondly,using the simplified two-dimensional variable geometry inlet model,the phenomenon of large scale separation flow caused by the unstart of the inlet is studied.Using dynamic grid technology gets the unstart process find that the large separation flow at the lip of the inlet is an important factor in the unstart in the inlet.The experiment gets the unstart/restart process by the schlieren image,observes the unstart / restart hysteresis phenomenon in the process,and obtains the inlet starting when starting flow and fine structure.Through the experiment analysis and verification,we find that the fusion inlet in the separation zone is an important reason resulting in large scale separation flow generated,and the unstart/restart hysteresis phenomenon is caused by the separation zone fusion / separation process.Finally,according to the Mach number changing gets the unstart flow field,and the reason of the inlet from the perspective of flow were analyzed,we also find the fusion phenomenon of separation zone before the inlet entering unstart.