Study On The Modal Conversion Flow Characteristics Of TBCC Binary Adjustable Inlet

The combined cycle power system can realize the self-propelled take-off of the aircraft,and the flight Mach number range is wide and the reliability is high,so it has become a hot research topic.The turbo-based combined cycle engine is a combination of a ramjet engine and a turbine engine.The parallel layout can be divided into an external parallel type and an internal parallel type.The two different engines of the external parallel TBCC engine work in two different channels with less interference between each other.The more aerodynamic design of the control is relatively simpler.The mode transition of a TBCC engine is a process of switching between a ramjet engine and a turbine engine.The mode transition process is mainly realized by the shunt of the inlet.In this paper,the unsteady numerical simulation of the external parallel TBCC inlet mode transition process is carried out,and the unstarting characteristics,performance parameter changes,influencing factors and mode transition time of the inlet mode transition process are analyzed.Firstly,the external parallel TBCC inlet is subjected to forward and reverse mode transition in Ma2.1,and the inlet flow field changes and performance parameter changes are analyzed.Under different back pressures and the suction channel is provided with suction holes for forward and reverse mode transition,and the effects of back pressure and suction holes on the mode transition process of the inlet are studied.The results show that in the forward and reverse mode transition,the ramjet channel will have a mutual transition from start to unstarting and unstarting to start.The flow characteristics of the ramjet channel have hysteresis in the forward and reverse mode transitions.The flow coefficient and total pressure recovery form a hysteresis loop.Within a certain range,the back pressure has little effect on the forward and reverse mode transition,and the suction hole is more conducive to the starting of the ramjet channel.Then,the effects of different rotating shaft points,different Mach numbers and different Mach numbers under different back pressures on the mode transition process are studied.The external parallel TBCC inlets and three different rotating shaft points are analyzed.The flow field,performance parameters and starting characteristics of the inlet channel under different Mach numbers show that the position of the rotating shaft point of the splitter is close to the cowl,which is not conducive to the starting of the ramjet channel.The larger the Mach number,the ramjet channel The larger the Mach number at the exit,the better the start of the inlet.Finally,the influence of modal switching time on the modal switching process of two external parallel TBCC inlets is studied.The flow field,performance parameters and starting characteristics of the inlets under three different mode transition times are analyzed.In the forward mode transition process,the longer the modal transition time is,the smaller the range of the ramjet channel in the starting state,and the more easily the inlet is changed to the unstarting state,the reverse mode transition,the mode transition the longer the time,the ramjet channel is in a larger range of starting state,and the more easily the punching passage is turned into the starting state.