基于热色液晶技术的尾迹对涡轮动叶表面换热系数影响研究

Effects of Unsteady Wake on Heat Transfer Distributionof Turbine Blade Using Thermochromic Liquid Crystal Technique

关键词:  尾迹  涡轮动叶  换热系数  斯特劳哈尔数  热色液晶

Key words:  Wake  Turbine blade  Heat transfer coefficient  Strouhal number  Thermochromic liquid crystal

摘要:

为探究上游尾迹影响下的涡轮动叶表面换热特性，采用热色液晶技术测量了尾迹对光滑叶片表面换热分布的影响，获得了高低湍流度(2%，20%)来流时不同尾迹斯特劳哈尔数(0，0.12，0.36)条件下光滑动叶表面换热系数的实验数据。结果表明:当湍流度为2%时，随着尾迹斯特劳哈尔数增加，压力面换热系数增高幅度最大为142%，前缘区域增高幅度最大为7%，吸力面增高幅度最大为186%。当湍流度为20%时，尾迹对换热系数的影响相对减弱，随着尾迹斯特劳哈尔数增加，压力面换热系数增高幅度最大为10%，前缘区域增高幅度最大为10%，吸力面增高幅度最大为26%。尾迹导致吸力面转捩点提前，过渡区延长。整体看来，尾迹导致光滑叶片表面换热系数升高，对吸力面换热系数的影响大于压力面。

Abstract:

The effects of unsteady wake on the heat transfer coefficient of the turbine blade without film holes is studied using the Thermochromic Liquid Crystal (TLC) measurement technique. The turbulence intensity of the free-stream is 2% and 20% respectively， and the wake Strouhal number is varied from 0 to 0.36. Results show that as the wake Strouhal number increases， the heat transfer coefficient of the pressure surface increases by up to 142%， the heat transfer coefficient of the leading edge increases by up to 7% and that of the suction surface increases by up to 186% for the case of free-stream turbulence intensity Tu=2%. At the case of Tu=20%， the influence of the wake is weakened and the heat transfer coefficient of the pressure surface increases by up to 10%， the heat transfer coefficient of the leading edge increases by up to 10% and that of the suction surface increases by up to 26%. The unsteady wake causes an earlier laminar to turbulent boundary layer transition on the suction surface and the transition length increases. Overall， the wake causes an increase in the heat transfer coefficient of the turbine blade and the effect of wake on the suction surface is greater than that on the pressure surface.