摘要
基于汽轮机低压末级流动的非稳态数值计算结果,研究了低质量流量下低压末级流道发生的旋转不稳定现象。为了更好地了解在低流量下汽轮机运行的旋转不稳定性,采用低压末级整圈动静叶流道耦合排汽缸进行非稳态数值计算。发现末级动叶已经处于压气机状态并且流动的周向均匀性被破坏,以及在叶顶间隙泄漏流与主流的挤压下形成的泄漏涡撞击到毗邻叶片吸力面并发生溢出、形成二次泄漏流等情况。泄漏涡进一步影响叶片间叶顶前缘的压差分布,以长波的性质形成旋转不稳定。频谱分析捕捉到了旋转不稳定在绝对与相对坐标系下的旋转频率以及周向扰动个数。
The overall objective of the study is to understand the rotating instability in steam turbines under off-design conditions. The rotating instability in the last stage of a low-pressure steam turbine operated under very low mass flow conditions was numerically studied. A numerical analysis using a validated unsteady nonlinear time-domain CFD solver was performed with a whole annulus domain on the 3D blade coupling the diffuser. The result shows that the last stage has been operating as a compressor locally and the flow is non- uniform circumferentially. A leakage vortex formed by the interaction of the leak at the tip clearance and the mainstream strikes the adjacent blade, forming the secondary leakage flow and overflow. The leakage vortex influences the pressure distribution of the blade tip leading edge and forms the rotating instability with a long wave mode. The spectrum analysis captures the frequency of rotating instability in absolute and relative coordinate system and the number of circumferential disturbance.
出处
《热力透平》
2016年第4期259-264,共6页
Thermal Turbine
基金
上海市科学技术委员会资助项目(14DZ1118200)
关键词
汽轮机低压末级
旋转不稳定
旋转频率
泄漏涡
steam turbine last stage
rotating instability
rotating frequency
leakage vortex
