基于动力学有限元模型的多跨转子轴系无试重整机动平衡研究

Whole-machine Dynamic Balancing Method without Trial Weights for Multi-span Rotor Shafting Based on Dynamic Finite Element Model

针对多跨转子轴系现场动平衡需频繁启停机的问题,结合影响系数平衡法和模态振型平衡法特点,提出一种新的基于动力学有限元模型的轴系无试重整机动平衡法。综合转子动力学相关理论和有限元技术,通过仿真构建与轴系结构尺寸和运行参数相符的转子动力学有限元模型。采用柔性转子共振分离原理,分析轴系振型和不平衡振动阶次以确定各跨转子加重平衡平面数和位置,分别在各跨转子平衡位置处施加不平衡激励,获取轴系平衡转速下各振动测点处不平衡响应,计算出相应的加重影响系数,从而取代轴系现场动平衡中需要多次启停机试重测取过程。然后采用最小二乘法通过解平衡矢量方程组得到轴系所需的平衡配重。最后以模拟百万兆瓦超超临界汽轮机的四跨五支承柔性转子轴系试验台为例,应用该方法开展了2700 r/min转速下轴系四个平面同时配重动平衡试验,单点降幅最高达53%,实现了无试重下柔性转子轴系整机动平衡,可有效减少因盲目试重次数,节省平衡费用和周期。

Arm to solve the problem of field dynamic balancing usually needs to be started many times for multi-span rotor shafting, a whole-machine dynamic balancing method without trial weights for shafting combined with the advantages of influence coefficient and modal shape is developed. According to the shafting structure and running parameters, the rotor dynamic finite element model is built by using rotor dynamics theory and finite element simulation. With the principle of flexible rotor resonance separation, balancing plane number and places of rotors can be determined by using the shafting modes and their orders of shafting unbalance. Unbalance excitation is applied in the balancing weighed place of multi-span rotors respectively. The shafting weighted influence coefficients for balancing speed can be obtained from the vibration response analysis of each measuring points on the shafting, which can replace field dynamic balancing with many times run-up by trial weights. The required shafting balancing weighted of each span rotor can be got by solving balancing vector equations with the least squares method. Finally, a four-rotor and five-bearing shafting experiment rig for simulating 1 000 MW ultra supercritical turbine rotors is taken as an example. The dynamic balancing of four planes at the speed of 2 700 r/min without trial weights is performed by the proposed method. The result shows that it can quality achieve the balancing of flexible shafting with corrective masses at a time with maximum amplitude drop up to percent of 53 for one point, which reduce the balancing times due to blind trial weight, and save balancing cost and period.