粗糙度对涡轮叶片流动转捩及传热特性的影响

为研究表面粗糙度对涡轮叶片流动转捩以及传热特性的影响，在自行开发的CFD程序平台上提出了对γ-Re_θ转捩模型的粗糙度修正方法，并参考平板绕流和涡轮叶栅的实验数据对该方法进行验证。考虑粗糙度效应的影响，对Mark Ⅱ涡轮导叶5411工况进行数值模拟，得到如下结论：表面粗糙度对层流边界层换热系数影响不大，而对湍流边界层则有较大影响，进而显著改变壁面温度分布；与光滑壁面相比，5μm的等效沙粒粗糙度使吸力面湍流区域壁面温度升高约5.7K，100μm粗糙度使壁面温度升高28.4 K，增幅达5%左右；当壁面粗糙度较低时，激波干涉对吸力面边界层的转捩起主导作用，而当粗糙度大于某临界值时，其作用会使转捩位置突然变化，本算例中该临界值近似为150μm。

Effect of surface roughness on flow transition and heat transfer of turbine blade

For the purpose of researching the effect of surface roughness on flow transition and heat transfer of turbine blade, a roughness modification method for γ-Re_θ transition model was proposed through self-developed CFD code. Verification was conducted referring to the experimental data of flat plate and turbine vane cases, and satisfactory results were obtained. Taking surface roughness effect into consideration, No. 5411 working condition of Mark Ⅱ turbine vane was simulated and the result was analyzed in detail. Main conclusions are as follows: surface roughness has little effect on heat transfer of laminar boundary layer, while it has considerable effect on turbulent boundary layer. Compared with smooth surface, 5 μm equivalent sand roughness increases the suction side wall temperature by about 5.7 K in turbulent boundary layer, while 100 μm roughness increases the temperature by about 28.4 K, reaching an increase of 5%. Under low roughness degree, effect of shock wave on boundary layer transition process of suction side plays a dominant role, while after reaching a critical degree, effect of surface roughness abruptly changes the transition position, and the critical degree is around 150 μm in the current case.