不同流量工况下透平与排汽缸耦合流场变化特性数值研究

Numerical Investigation on the Coupled Flow Field of Turbine and Exhaust Hood Under Different Conditions

本文借助商用计算流体动力学软件CFX数值求解三维Reynolds-Averaged Navier-Stokes (RANS),研究了工况改变对末级透平与单侧径向排汽缸气动特性的影响,分析了120%到10%设计流量工况范围内,排汽缸与轴流透平内的耦合流场结构和气动性能参数。结果表明,流量降低将引起透平动叶负攻角增大,叶栅通道内流动分离增大,挤压气流从静叶根部和动叶顶部流向下游,透平输出功由正变负。流量减小,透平出口总压径向正梯度变化显著,气流旋转方向与透平旋转方向趋向一致,排汽缸内的流动形态发生变化,沿蜗壳后端壁直接流出的气流减少,总压损失及流场周向不均匀程度有所降低。

The influences of the mass flow rates on the coupled flow field of turbine and exhaust hood were numerical investigation by employing CFX. The coupling flow field and aerodynamic performance parameters of the turbine and exhaust hood were analyzed. The results show that the negative attack angle of turbine rotor increases with the inlet mass flow rate decreasing which leads to stronger flow separation in the blade passages and the fluid flows downstream from the regions of the stator hub and rotor tip. When the inlet mass flow rate less than 50% designed flow rate, the value of the turbine output power changes from positive to negative. Furthermore,at the turbine exit, the positive gradient of the total pressure radial distributions becomes significantly and directions of swirl angle trends to be consistent with the rotating direction of the blade with the reduction of the flow rate. In addition, the flow pattern in the exhaust hood varies which reduces the total pressure loss and circumferential no uniformity of the flow field in the hood.