Numerical Study On Starting Processes Of Hypersonic Inlets

The restarting process caused by removing plug at the exit and the self-starting process of two dimensional hypersonic inlets were studied using unsteady numerical simulation to explore the differences between the restarting ability and the self-starting ability.and a novel self-starting test method based on continuous varying attack angle of a shielding plate fixed on the upstream of hypersonic inlets was developed.The method was verified with the 2D and 3D numerical simulations,and results show that the novel method can be used to test the self-starting ability of hypersonic inlets in a supersonic blow-down wind tunnel.Firstly,to explore the influence of different internal contraction section configurations on self-starting ability of hypersonic inlets,the self-starting process of two dimensional hypersonic inlets with angulated and curved internal contraction section were investigated using quasi-steady numerical simulations.The self-starting ability and the variation of separation zone in the self-starting process of two inlet configurations with different cowl compression angles were compared.And effects of compression strength distributions along internal contraction section on self-starting ability were also analyzed.Results show:(1)for the same internal contraction ratio,different internal contraction sections and cowl compression angles influence the self-starting ability of hypersonic inlets greatly.(2)both the total compression strength of the internal contraction section and the compression strength distributions along internal contraction section have major effects on the self-starting ability of hypersonic inlets.Secondly,the restarting processes caused by slow and rapid removing plug at the exit and the self-starting process of two-dimensional hypersonic inlets were studied using unsteady numerical simulation to explore the differences between the restarting ability and the self-starting ability.Results show that: the unsteady flow effect caused by the inlet buzz can improve the inlet restarting ability.For two inlet configurations investigated in this paper,even though the freestream Mach number is smaller than self-starting Mach number,removing plug slowly at the exit can finally help the inlet rebuild started flowfields.But the processes of the swallowing of the primary separation zone are different.At the freestream Mach number that is smaller than self-starting Mach number,the right moment of the beginning of rapid removing plug at the exit is important for hypersonic inlets to enter into the started mode.At last,to explore the feasibility of testing the self-starting ability of hypersonic inlets in a blow-down wind tunnel,a novel self-starting test method based on continuous varying attack angle of a shielding plate fixed on the upstream of hypersonic inlets was developed.In the test,the hypersonic inlet,together with the plate,rotates from the limiting positive attack angle to the limiting negative attack angle.The plate decelerates the freestream by shock wave,or accelerates the freestream by expansion waves.Hence,the continuous accelerating freestream can be obtained for the inlet.The method was verified with the 2D and 3D numerical simulations.Results show that: the novel method can be used to test the self-starting ability of hypersonic inlets in a blow-down wind tunnel.