轮毂封严冷气对涡轮性能和热负荷的影响

Effect of rim seal purge flow on performance and thermal loading of turbine

采用气动传热耦合方法计算分析了轮毂封严冷气对多级涡轮流动结构、性能和热负荷的影响.结果表明:在多级涡轮中冷气与主流燃气的相互作用会显著影响盘腔流动结构以及冷气在封严腔出口间的分配,并导致冷却效果和性能随冷气流量非线性变化,在这种情况下采用气动传热耦合计算可以兼顾捕捉和考察温度调控能力和气动损失的急剧改变.在涡轮级间冷气带来的堵塞效应会使相邻涡轮级工况点沿特性线移动,下游涡轮级2.5%的封严冷气就可以导致上游涡轮主流流量变化约0.6%,膨胀比变化约1.2%.在涡轮级内部未经预旋的封严冷气会减小转子叶根气动载荷,并形成黏性剪切层造成掺混损失,同时通过改变端区二次涡强度来影响流动结构,最终导致涡轮性能下降.

The effect of rim seal purge flow on flow field,performance and thermal loading for a two-stage turbine was studied by utilizing conjugate heat transfer.It was found that under the effect of purge flow and main flow interaction,a nonlinear relationship between cooling effect and coolant flow rate was observed.In this case,utilizing the conjugate heat transfer could observe the dramatical change in the temperature field and aerodynamic losses simultaneously.Moreover,the operation point shifted along performance map due to the blockage effect of coolant flow in the adjacent stage,a 2.5%coolant flow rate could result in a 0.6%variation of main flow rate and a 1.2%reduction of expansion ratio for upstream turbine stage.In the main passage,the coolant flow could reduce the aerodynamic loading at the root forming the viscous shear layer,and significantly modify the secondary vortex,eventually resulting in performance penalty.