超超临界汽轮机密封非线性汽流激振力影响的转子运动特性

Rotor dynamic characteristics affected by seal nonlinear steam flow excitation force in ultra supercritical steam turbine

密封汽流激振作用常诱导转子非线性运动失稳。建立某1 000 MW汽轮机高压缸隔板密封模型,通过动网格技术和多频涡动模型得到非线性密封汽流激振力拟合模型。基于转子动力学建立包含非线性油膜力的转子-轴承-密封系统运动耦合模型,分析非线性密封汽流激振力对系统运动特性的影响。研究表明:非线性密封激振力的拟合模型具有较好的计算精度,且更贴近实际情况;汽轮机在冲转升速过程中,以转子的不平衡响应以及非线性油膜力诱发系统失稳为主。对于不同压比工况,额定转速运行后,当负荷一定时,压比越大,汽流激振现象越明显。随着负荷升高,汽流激振的影响显著增强,也加剧了压比对汽流激振的影响程度,使得密封汽流激振的影响增加,导致系统严重失稳。

Seal steam flow excitation often induces nonlinear motion instability of a rotor.Here,a seal model for high-pressure cylinder diaphragm of a certain 1 000 MW steam turbine was established,and a nonlinear seal steam flow excitation force fitting model was obtained using dynamic grid technology and multi-frequency whirling model.The dynamic coupling model of a rotor-bearing-seal system including nonlinear oil film forces was built based on rotor dynamics to analyze effects of nonlinear seal steam flow excitation force on system's dynamic characteristics.The study showed that the fitting model of nonlinear seal excitation force has better calculation accuracy and it is closer to the actual situation;in rotating speed increasing process of steam turbine,unbalance response of rotor and nonlinear oil film force are main factors to induce system instability;for different pressure ratio working conditions,after running at rated rotating speed and with a constant load,the larger the pressure ratio,the more obvious the phenomenon of steam flow excitation;with increase in load,effects of steam flow excitation significantly increases,and effects of pressure ratio on steam flow excitation also increase to cause increase in effects of seal steam flow excitation and serious instability of the system.