重型燃气轮机透平叶片表面粗糙度对换热的影响

Effect of Surface Roughness on Heat Transfer Characteristics of Heavy Duty Gas Turbine Airfoils

以某重型燃气轮机透平第一级静叶的叶型为研究对象,采用商业软件CFX的等效砂粒粗糙度模型研究了表面粗糙度对叶片表面换热的影响。结果表明:表面粗糙度对叶片表面附近的时均流场影响不大;但在叶片典型表面粗糙度下,压力面和吸力面的换热水平分别比光滑表面时高36.6%和33.4%,换热发生恶化;较小的表面粗糙度对叶片前缘换热基本没有影响,但当等效砂粒粗糙度增大到51 μm时,无量纲线平均传热系数反而比光滑表面时减小了15%;根据叶片一维传热过程模型,在换热增强30%时,叶片金属表面平均温度上升17 K,极大地影响了叶片的寿命。

Taking the profile of the first-stage stator blade in a heavy duty gas turbine as an object of study, the effect of surface roughness on heat transfer characteristics of the blade airfoil was researched using the equivalent sand-grain roughness model of commercial software CFX. Results show that the variation of roughness affects little on the time-mean flow field near the airfoil, but under a typical surface roughness of turbine blade, the heat transfer coefficient would be increased by 36.6% and 33.4% respectively on the pressure side and suction side, compared with a smooth surface, indicating enhanced heat transfer effectiveness. Small-scale surface roughness has little effect on the heat transfer of a leading edge, but when the roughness hs gets up to 51 μm, the average heat transfer coefficient would drop by 15%, compared with a smooth surface. According to the one-dimensional model of heat conduction, when the heat transfer coefficient is increased by 30%, the average temperature of the blade metal would be increased by 17 K, resulting in significantly reduced life of the blade.