轮缘封严气流与转子干涉损失机理的数值研究

Numerical Investigation for Interaction and Loss Mechanisms Between Rim Seal Flow and Rotor

为了研究涡轮转静盘腔中轮缘封严气流与下游转子的干涉机理和损失机制,在不同封严流量下,针对轮缘封严气流对下游转子气动性能和流场分布的影响进行了数值模拟。结果表明,随着封严流量增加,涡轮级效率不断降低。在轮毂到10%叶高和30%～60%叶高,流量系数增加。封严气流主要通过在转子进口封严出流不同的分布和在通道输运过程中与转子通道二次流的交互作用对转子的气动性能产生影响。同时,封严气流引起下游转子气动性能的降低,存在三个损失机制:一是封严腔体摩擦泵效应减弱,增加了封严出流与主流之间周向速度差所引起的粘性剪切损失;二是不同分布的封严出流造成进气负攻角和堵塞效应,降低了转子的做功能力;三是不同分布的封严出流在输运过程中与转子通道二次流的交互作用,导致了二次流损失加剧。

In order to investigate the interaction and loss mechanisms between turbine stator-rotor cavity rim seal flow and downstream rotor, numerical investigations were conducted for effects of rim seal flow on the aerodynamic performance and flow field of rotor at different rim seal flow rate. The results show that with the in- crease of rim seal flow rate, the stage efficiency keeps on decreasing. In addition, the mass flow coefficient in- creases in the region from hub to 10% span and from 30% to 60% span. The rim seal flow mainly influences the rotor performance by the different distributions of egress flow at rotor inlet and interaction with secondary flow in rotor passage. Besides, there are three loss factors related to the decreasing of rotor performance caused by rim seal flow. One is the viscous shear loss caused by increasing circumferential velocity difference between the rim seal flow and mainstream. The increasing circumferential velocity difference results from the reducing pump effect of the rotational disc with the increment of rim seal flow rate. Second is the blockage effects and negative incidence angle caused by egress flow lead to decreasing work. The last one is the interaction in transportation process between different egress flow and secondary flow in rotor passage results in increasing secondary loss.