Study of surface heat transfer characteristics of hypersonic flat plate with film-cooling structure under different leading edge shape conditions

For an aircraft equipped with the infrared imaging homing seeker flying at hyper-sonic speed inside the dense atmosphere,some active cooling methods are needed to prevent the areothermal aberration caused by serious aerothermal heating and the aero-optical effect caused by the complex flow field.Based on the effect of both hypersonic blunt body flow and film cooling structure (i.e.supersonic backward step with slot at step base),the characteristics of surface heat transfer distribution over the hypersonic flat plate with a film cooling structure under differ-ent leading edge shape conditions are studied.The tests are implemented on the KD-01 hypersonic gun tunnel,and the heat flux in the downstream region of the slot under Mach 8 free stream condition is measured.The NPLS images of the instantaneous flow field around the slot of hyper-sonic flat plate with the film cooling structure (when the cooling film is laid idle)are obtained for different leading edge shape situations.Based on the analysis of the test data,it is concluded that:for the hypersonic flat plate with a film cooling structure (when the cooling film is laid idle),the leading edge shape has a distinctive influence on the distribution of surface heat flux;for the blunt leading edge,the surface heat flux is close to the analytical result of heat flux of the laminar boundary layer of a flat plate with the same leading edge shape;for the sharp leading edge,the heat transfer features develops from laminar to turbulent status;the heat transfer features in the separation and r eattached region downstream of the slot depend on the relative boundary layer thickness at the slot lip,which is similar to the situation of a common supersonic step flow.