基于动网格技术的转子动力特性研究

Research on Rotor Dynamic Characteristics Based on Mesh Deformation

针对汽轮机转子偏心导致的汽流激振问题,本文采用动网格技术模拟转子真实的三维涡动,对转子的动力特性及汽流激振机理进行研究。结果表明:采用动网格实现转子真实涡动时,汽流激振力随转子中心位置发生改变,动力系数呈非线性变化。随着涡动频率的增加,动力系数呈增加趋势,有效阻尼增加。自转速度变化时,直接刚度、直接阻尼、交叉刚度和交叉阻尼的最大波动幅度可达16.6%、41.8%、97.1%和71.4%。当公转速度与自转速度为1500 r/min时,有效阻尼波动较大。随着压比的增加,直接刚度和直接阻尼呈上升趋势,且高压比下转子有效阻尼增大,有利于转子稳定。涡动转子表面压力波动剧烈,是诱发汽流激振的主要原因。

In allusion to the problem of steam flow excited vibration caused by rotor eccentricity in steam turbine,the mesh deformation was adopted to simulate the authentic rotor three-dimensional whirl motion in order to study rotor dynamic characteristics and mechanism of steam flow excited vibration.The results show that the exciting forces change with central position of rotor and rotor dynamic coefficients have non-linear changes when the rotor whirls by mesh deformation.The rotor dynamic coefficients increase with the whirling frequency increasing,as well as effective damping.As the rotational speed increasing,the fluctuations of direct stiffness,direct damping,cross stiffness and cross damping account corresponding maximum absolute value for 16.64%,41.76%,97.1%and 71.4%respectively.When the whirling speed and the rotational speed are 1500 r/min,the effective damping has a greater fluctuation.The direct stiffness,direct damping and effective damping increase with the pressure ratio increasing.The fluctuation of rotor surface pressure is the severe,which is main reason of steam flow excitation.