涡轮叶栅前缘上游端壁气膜冷却的流场实验研究

Experimental Investigation of Flow Fields in a Turbine Cascade with Endwall Film-Cooling Upstream of Leading Edge

对前缘上游端壁有单排和双排孔冷却的大尺寸低速涡轮导向叶栅进行了气动测量、热示踪和端壁流场显示 ,在吹风比 1～ 3范围获得了叶栅内的详细流场、冷气的空间分布和端壁上的流动图案。结合先前测得的没有冷却时的流场数据 ,这些结果表明端壁气膜冷却对叶栅流场结构有重大影响 ,吹风比是主宰射流与二次流间相互作用的主要因素 ,双排孔喷射使冷气比单排孔喷射更贴近端壁。低吹风比喷射冷气不能到达压力面并被二次流逐渐卷离端壁 ;中吹风比喷射有效的抑制了二次流的形成 ,并使端壁流线偏向于无粘流流线 ,冷气很均匀的覆盖在端壁上 ;高吹风比喷射可将冷气抛射到压力面上 ,双排孔情况下甚至使二次流反向 。

Aerodynamic measurements,thermal tracing and surface flow visualization were carried out in a large scale low speed turbine cascade with single and double row injection on the endwall upstream of the leading edge.The detailed flow fields in the cascade,spacial distribution of cooling air and flow patterns on the endwall with coolant injection at blowing ratio 1～3 were obtained.In conjunction with the previously measured flow fields without cooling injection,the obtained results reveal that the flow fields in the cascade are obviously changed by endwall film cooling,and blowing ratio is a vital factor dominating the behavior of the injected coolant and secondary flow in the passage.It was also shown that the interaction between the two rows of injection makes the coolant air press closer to the endwall than with single row injection.The coolant injected at low blowing ratio could not reach the pressure side and was rolled up by the secondary flow.Medium blowing ratio injection can suppress the secondary flow effectively and tends to turn the endwall streamlines toward the inviscid streamlines and make perfect coverage of coolant on the endwall.The injection at high blowing ratio can throw the coolant onto the pressure surface,and even reverse the secondary flow and create a passage vortex with the rotation sense contrary to that of the traditional passage vortex in case of double row injection.