Numerical research on dynamic lateral vibration of a pump turbine’s shaft system

Abstract

The vibration state of pump turbine’s shaft system not only affects the units work efficiency, but also affects the life span of the units. In this research, a novel transient dynamic vibration model of pump turbine’s shaft system, including the coupled effects of unbalanced magnetic pull (UMP), guide bearing force, nonlinear seal fluid force, unbalanced mass force and hydraulic force, is proposed base on Finite Element Method (FEM) and Lagrange equation. Node automation division method (NADM) is also applied to ensure the nodes are divided quickly and accurately. The motion differential equations and the dynamic response of the units are solved by implicit Newmark method. The nonlinear dynamic relations of crown seal force and UMP with related parameters are researched. The dynamic lateral vibrations of three bearings are also analyzed by transient cycle response diagrams, axis orbits and waterfall diagrams. The calculating results demonstrate that the installing eccentricity, crown seal channel clearance and air-gap length have significant effect on the dynamic vibration of shaft system, and small installing eccentricity, proper crown seal channel clearance and air-gap length can enhance the stability of the system, which provide a theoretical foundation for the research of pump turbine’s shaft system vibration.