涡轮叶片型面换热系数计算

PREDICTION OF HEAT TRANSFER COEFFICIENT ON TURBINE BLADE PROFILES

本文用数值方法计算了无气膜冷却涡轮叶片上包括前驻点的整个型面上的换热系数。驻点区采用相似方程计算 ,并用圆柱绕流近似表示驻点附近流场。较成功地模拟了边界层转捩和过渡区的换热情况。计算中考虑了来流湍流度的影响。

Several problems involved in the prediction of heat transfer coefficient on the turbine blade profiles without film cooling are studied in this paper for the purpose of improving the accuracy.These problems are:heat transfer in the vicinity of stagnation point,the location of boundary layer transition,heat transfer of transitional boundary layer and the influence of free stream turbulence intensity.Cebeci Smith method is used to solve the boundary layer equations obtaining the similar solution in the vicinity of stagnation point.It is assumed that the free stream velocities near the leading edge of a blade can approximately be expressed as that for a cylinder,the radius of which equals to that of leading edge circle or to the radius of a“equivalent cylinder”,the solution obtained by this method in the vicinity of stagnation point is used as a initial profiles of velocity and enthalpy for the computation of boundary layer along the blade surface.STANS [9] with some modifications is used to calculate heat transfer coefficient on the rest part of the blade surface.Transition origin and transition length are predicted by using the models suggested by Seyb [5] and Dhawn at el. [12] respectively.In order to take the free stream turbulence intensities into account,a turbulence viscosity is introdued as a part of effective viscosity of the fluid.Several numerical examples obtained by the proposed method in this paper indicate better agreement with the experimental data than by original STAN 5.