Aerodynamic And Fluid Dynamics Investigation Of Inlet Mode Transition For Turbine Based Combined Cycle Propulsion System

Turbine based combined cycle(TBCC)is one of the most prominent propulsion systems for hypersonic vehicles.The TBCC inlet component and smooth inlet mode transition are the keys of the TBCC propulsion systems.Firstly,the size and mode transition Mach number of TBCC inlet were decided by thermaldynamic cycle analysis of the TBCC propulsion systems along a specific trajectory.Then the wind tunnel experiment tests and numerical simulation were conducted to investigate the steady and unstready characteristics of TBCC inlet mode transition and the inlet performance across the whole Mach number range.Firstly,according to the performance of TBCC propulsion system along a constant 50 k Pa dynamic pressure trajectory,the TBCC inlet mode transition Mach number was between 2.2 and 2.5and the geometry constrain which satisfy the requirement of the propulsion system was determined.Then the geometry of the TBCC inlet including translation and rotation schemes of inlet mode transition was designed.The idea of controlling two geometry variables including the ramp angle and the position of lower wall of the throat by a single variable was proposed.The translation scheme of the inlet mode transition which is helpful to reduce the flow separation during this process was proposed and the device to fulfill this scheme was designed.Meanwhile,rotation scheme inlet mode transition was investigated based on the same geometry constrains.The geometry of turbine and ramjet diffusers was determined through parametric investigation of several variables.Secondly,the experiment model was designed and manufactured according to the TBCC inlet geometry and variable geometry scheme mention above.After that the wind tunnel tests of translation and rotation schemes inlet mode transition were investigated to explore the steady inlet performance at different modes during the transition.The backpressure performance of turbine/ramjet flowpaths and the coupling of massflow between two flowpaths were acquired at different modes of the translation and rotation mode transition process.Besides,the common and different points of these two mode transition devices were compared.Then the different mode transition schemes as the terminal shock locating upstream and downstream the mode transition plate were investigated.Followed by the mode transition control schemes from the aspect of the inlet and propulsion system were determined.The unsteady inlet mode transition of rotation scheme was investigated through wind tunnel tests.The characteristics of terminal shock and turbine/ramjet flowpaths performance were acquired.Thirdly,three dimensional steady numerical simulations of TBCC inlet were done.The numerical simulation results agreed well with the experiment tests which indicate the numerical method used in the present paper was valid.The numerical simulation results indicated that when the terminal shock moved from downstream to the throat,the mass flow coupling between turbine and ramjet flowpath was 3%.The dynamic mesh and unsteady numerical simulation results indicated that during the translation scheme inlet mode transition the separation occurred at the lower wall of the turbine flowpath caused the terminal shock oscillation at frequency of 40 Hz,the oscillation disappeared during the mode transition.During the rotation scheme inlet mode transition,the terminal shock was oscillation at different frequency during the whole process.The variable inflow Mach number inlet mode transition numerical simulation results indicated the influence of inflow Mach number increasing from 2.2 to 2.5 was insignificant to the shock oscillation characteristics and performance of two flowpaths during the beginning of mode transition,but at the end of mode transition the shock oscillation reappeared.Finally,the velocity performance of TBCC inlet across the whole Mach number range was investigated through wind tunnel tests and numerical simulations.The backpressure characteristics of the TBCC inlet from Ma 1.5 to 4.0 were acquired.The design scheme of the TBCC inlet based on the controlling multiple geometry variables with one motor was verified to be credible and validated according to the results from experiment tests and numerical simulation.In addition,the acceleration process of the TBCC inlet was investigated through numerical simulation method.The terminal shock characteristics and the performance of turbine/ramjet flowpaths were acquired at turbine mode(Ma1.5-2.5)and ramjet mode(Ma 2.5-4.0).