透平叶栅二次流瞬态特性试验及动力学分析

Transient Performance Test and Dynamics Analysis of Secondary Flow in Turbine Vane Cascade

基于作者提出的片光跟随主流偏移的新测试方法,成功对后加载环形叶栅的二次流瞬态流场进行了试验研究,通过实测瞬态矢量场定量展示了二次涡的强烈非定常性.试验结果表明,随着气流速度的增大,通道涡更靠近吸力面和端壁,而其流线结构也更加不稳定,在同一区域常常存在分叉与不分叉、多次分叉与一次分叉交互出现的非定常现象.基于对通道涡流线结构的涡动力学及其物理本质的分析,认为其流线结构取决于局部压力梯度和正、负耗散区的竞争,在各种抑制二次流措施的基础上,若能一直保持通道涡为不稳定焦点结构,将可以进一步减少二次流损失.

Based on the authors＇ new measurement method, the second laser light sheet is modulated to trace the motion of particles and main flow, the secondary flow instantaneous vector field is measured in aft-loaded annular cascade of turbine, and strong unsteady evolution of vortex is found and shown quantitatively. The results indicate that one Hopf bifurcation and unstable limit cycle appear in the vortex core of local channel diffusion area, and the streamline structure of channel vortex belongs to the unstable focus in other areas. The analysis results of vorticity aerodynamics and physical nature of the channel vortex indicate that the streamline structure is determined by the contest between pressure gradient and positive or negative dissipation. Moreover, even though different kinds of method to restrain secondary flow have been taken, the flow loss can be further reduced if the streamline structure of channel vortex is kept the unsteady focus.