用端壁造型减小涡轮叶栅二次流损失的数值研究

Numerical investigation for effect of non-axisymmetric endwall profiling on secondary flow in turbine cascade

分别对常规叶栅、下端壁上凸和下端壁下凹叶栅的流场进行了详尽的数值模拟,通过将下端壁上凸和下端壁下凹叶栅中的通道涡的发生、发展过程与常规叶栅进行对比分析,对非轴对称端壁造型减小涡轮叶栅二次流损失的机理进行了初步的探讨。结果表明:下端壁上凸叶栅出口处的总压损失比常规叶栅下降了4.2%,下端壁下凹叶栅出口处的总压损失比常规叶栅增加了11.9%;在下端壁上凸叶栅中,下通道涡的形成比常规叶栅和下端壁下凹叶栅滞后,失去了充分发展的"机会"。这是非轴对称端壁造型能够减小涡轮叶栅二次流损失的根本原因。

Numerical simulation has been carried out to obtain detailed flow structure in conventional turbine cascade and two kinds of turbine cascade with non-axisymmetric endwall. Comparison and analysis of development process of passage vortex in three kinds of turbine cascade have been performed to find out how non-axisymmetric endwall profiling affect secondary flow in turbine cascade. Investigation result shows ：When lower endwall of turbine cascade protrudes upward, total pressure loss at exit of cascade decreases 4.2% than conventional turbine cascade; When lower endwall of turbine cascade protrudes downward, total pressure loss at exit of cascade increases 11.9% than conventional turbine cascade. When lower endwall of turbine cascade protrudes upward, compared with conventional cascade and cascade with lower endwall protruded downward, formation of lower passage vortex is ＂later＂ , so less ＂opportunity＂ is acquired to grow fully. This is the key point which makes non-axisymmetric endwall profiling work effectively.