汽流激振力诱导汽轮机转子的非线性运动特征

Nonlinear Motion Characteristics of Steam Turbine Rotor Induced by Steam Exciting Force

非线性汽流激振力严重影响转子运动,通过实验与数值模拟方法对带有叶片的超超临界机组高压转子的三维流场进行计算,根据流场压力积分得到非线性汽流激振力,并拟合成方程以弥补传统公式的不足。将汽流激振力的拟合方程带入转子-轴承运动系统,得到非线性汽流激振力作用下汽轮机转子的非线性运动特征,分析了转子运动的分岔和混沌特性。结果表明:基于流场计算所得到的非线性汽流激振力方程具有较高的准确性。非线性汽流激振力可导致转子涡动中心偏移,由周期运动变为混沌运动。转子运动的混沌区域随负荷的增加呈现"增加-减小-增加"的变化趋势。振动频率出现1/2转速频率、一阶临界转速频率(约为2/3分频)以及1/2转速以下的连续低频。随着机组负荷的增加,转子运动的混沌区域变宽,转子运动的稳定性降低。

Nonlinear steam flow exciting force seriously affects the rotor motion. The three-dimensional flow field of the rotor with blades in high-pressure cylinder of ultra-supercritical steam turbine was solved by combining numerical simulation with experiment. The nonlinear steam flow exciting force integrated from the pressure of flow field was fitted by nonlinear equation to make up the shortcomings of the traditional equation. On this basis, the nonlinear dynamic rotor-bearing system including nonlinear steam flow exciting force was established. The nonlinear characteristics of the rotor under the effect of nonlinear steam flow exciting force were researched, and the bifurcation and chaos characteristics of the rotor were presented. The results show that the equation of nonlinear steam flow exciting force fitted by the flow field calculation has a good accuracy. The nonlinear steam flow exciting force makes the center of rotor deflecting and the motion of rotor change from periodic motion to chaotic motion. With the increase of load, the chaotic region of rotor motion shows a variation of first increasing then decreasing and increasing again. The vibration frequency includes 1/2 fundamental frequency, first critical frequency(about 2/3 fundamental frequency) and continuous low frequency below 1/2 fundamental frequency. With the increase of unit load, the chaotic region of rotor motion becomes wider and the stability of rotor motion decreases.