The prominently unsteady effect of the control stage in a steam turbine will result in strong flow excitation force. On the basis of the software ANSYS CFX, a 3-D unsteady viscous model for the control stage of a steam turbine with a partial admission room and a reinforced rib was constructed with the RNG k-e turbulence model, the dual time step method, the sliding interface model and the structural hexahedron mesh. The simulation results show that the time-averaged unsteady wheel efficiency is lower than steady wheel efficiency. There are greater unsteady axial and circumferential forces in the inlet and outlet blocked areas of the rotor blades. Spectrum analysis indicates that the typical low frequency of the exciting force is 50 Hz. The circumferential distributions of pressure and static entropy are nonuniform and the nonuniformity decreases gradually towards the downstream sections. The mixing and windage losses are larger in the blocked channel, leading to the decrease in the blade work. In addition, the suction pressure of the rotor blade is affected significantly earlier than that of pressure side when the flow passes the blocked channel.%针对汽轮机调节级的非定常效应产生汽流激振力的问题,基于ANSYS CFX软件,采用RNG κ-ε湍流模型、双时间步法、滑移界面模型和结构化六面体网格对带有进汽室和加强筋的汽轮机调节级进行了全周三维非定常黏性流场的数值模拟.研究发现:调节级非定常时均轮周效率低于定常轮周效率；动叶在进出堵塞区域时存在较大的轴向汽流力和切向汽流力；低频汽流激振力的基频为50 Hz；汽流压力和静熵在不同截面的周向分布差异较大,在向下游运动过程中逐渐趋于平均；堵塞区域的动叶通道掺混损失及鼓风损失较大,其将影响动叶的做功能力,进入堵塞区域时动叶吸力面首先受到影响.
展开▼
