涡轮盘腔轴向封严流动的数值研究

Numerical investigation of axial seal flow in turbine cavity

利用数值方法研究了轴向封严结构内的燃气入侵与封严流动.研究表明:由于封严间隙处流场参数梯度较大,封严面非匹配网格影响了数值传递从而造成封严效率数值结果偏高.定常数值模拟结果低估了导叶下游静压的周向不均匀性,同时没有考虑转静干涉,所得到的封严效率较非定常结果要高.非定常计算得到的导叶下游静压周向分布与试验结果符合较好,在盘腔子午面内形成3个涡核结构,引导静盘壁面流体流向动盘以补充动盘泵效应所需流量.封严间隙内存在旋转的燃气入侵与出流结构,燃气入侵伴随较大的切向速度,封严间隙内的封严间隙涡对封严效率有积极影响,封严面上径向速度的瞬时值为时均值的3倍以上.燃气入侵受到导叶尾缘周向静压分布和转子旋转的共同影响.

Hot gas ingestion and seal flow in axial seal configuration was investigated numerically.The results show that the unmatched mesh strategy on sealing surface affects the numerical transfer because of bigger gradient of parameters which lead to higher sealing effectiveness.The steady simulation underestimates the circumference pressure unevenness downstream the vane and ignores the interaction of stator and rotor;as a result the sealing effectiveness is much bigger than unsteady simulation.The unsteady results agree with the experimental date very well.Three vortexes appear in the cavity meridian plane,and guide the flow near static disc to rotor disc for supplement the flow required by disc entrainment. Rotating hot gas ingestion and egress structures appear in seal clearance,and the ingestion flow has bigger tangential velocity.The seal clearance vortexes in seal clearance have positive effects on sealing efficiency.The transient radial velocity is 3times bigger than time-averaged value on sealing surface.The hot gas ingestion is affected by the circumferential distribution of static pressure downstream of vane and rotor rotation.