带气膜冷却结构的高超声速平板不同前缘形状下表面传热特性研究

当带红外成像制导系统的飞行器在稠密大气层内做高超声速飞行时,必须采取主动冷却方式防止严重气动加热造成的窗口材料热畸变以及复杂流场造成的气动光学畸变。本文根据成像窗口周围流动具有受高超声速钝头体绕流和气膜冷却结构(即背面为空腔的超声速后台阶)共同作用的特点,在 KD-01高超声速炮风洞中开展了带气膜冷却结构的高超声速平板在不同前缘形状下表面传热特性的试验研究,测量了 Ma8来流条件下喷缝下游表面传热系数,试验获得了2种前缘形状的带气膜冷却结构的高超声速平板喷缝周围瞬态流场 NPLS 图像。通过分析试验数据,得出以下结论:对于带气膜冷却结构(气膜不工作状态)的高超声速平板,模型前缘的形状对喷缝下游区域的表面热流整体分布有明显影响,在钝前缘情形下,表面热流分布接近相同前缘形状的平板边界层为层流状态时的表面热流分布;在尖前缘情形下,表面热流分布则表现出从层流边界层状态向充分发展湍流边界层状态变化的特性;喷缝下游分离和再附区表面传热特性和超声速后台阶流动类似,取决于喷缝上缘处边界层相对厚度。

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.