非线性汽流激振力对超超临界汽轮机转子运动特性的影响

Effects of nonlinear steam flow exciting force on motion characteristics of ultra-supercritical steam turbine rotor

汽流激振力严重影响超超临界汽轮机的安全稳定运行,为此建立某1000 MW汽轮机高压缸1.5级的三维全周模型,通过数值模拟得到不同负荷下的非线性汽流激振力,将汽流激振力耦合到转子-轴承-密封系统中,利用Runge-Kutta法求解微分方程组,对转子非线性运动特性进行分析。结果表明:随着转速升高,转子运动幅度变小,额定转速下转子处于一周期运动。随着负荷增加,系统由带混沌倾向的周期性运动向周期性的混沌运动过渡,此后进入复杂紊乱的混沌运动。非线性汽流激振力以分频的形式影响转子运动。低负荷时,振动频率以1/2工频为主,随着负荷升高,振动以工频为主,期间还出现1/3、2/3工频振动。受非线性汽流激振力的影响,转子系统处于混沌运动,最大Lyapunov指数大于零,系统可能失稳。

Steam flow exciting force seriously affects safe and stable operation of an ultra-supercritical steam turbine.Here,a 3-D full cycle model for 1.5 stage high pressure cylinder of a 1000 MW steam turbine was established.Nonlinear steam flow exciting forces under different loads were obtained using numerical simulation.The steam flow exciting force was coupled into a rotor-bearing-seal system to establish the system’s dynamic model,Runge-Kutta method was used to solve dynamic differential equations,and nonlinear motion characteristics of the rotor system were analyzed.The results showed that with increase in rotor rotating speed,the rotor vibration amplitude becomes smaller,and it is in a periodic motion under the rated rotating speed;with increase in load,the rotor system transits from periodic motion with chaotic tendency to periodic chaotic motion,and then enters complex chaotic motion;nonlinear steam flow exciting force affects the rotor motion in the form of frequency division;when load is low,the system vibration frequency is mainly 1/2 power frequency;with increase in load,the system vibration frequency is mainly power frequency,during this period,there are vibrations with 1/3 and 2/3 power frequencies too;due to effects of nonlinear steam flow exciting force,the rotor system is in chaotic motion,if the maximum Lyapunov exponent is larger than zero,the system may lose stability.