Characteristics and experimental verification of “critical following speed” on rotor system
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摘要:
为了深入探究转子系统“临界跟随”现象的机理,建立悬臂转子模型,分析“临界跟随”状态下的转子动力学特性,设计搭建了悬臂转子试验器,并在高速超转试验台上进行试验验证。研究结果表明:当直径转动惯量与极转动惯量相等时,从一定的转速开始,盘的振动摆角响应会随转速持续增大;具有“临界跟随”特征的模态振型表现为,直径转动惯量与极转动惯量相等的盘位于振型节点,在不平衡力矩作用下,盘心振动位移为零,但盘的摆角不为零且随转速增加而增大,其相位角维持不变;若转子结构并非简单的单盘,则需计算组件的直径转动惯量与极转动惯量,以此检验是否会出现“临界跟随”;考虑转轴质量时,盘的惯量符合直径转动惯量与极转动惯量相等时,不会出现“临界跟随”现象,但会出现自振频率在较宽的范围与转子转速靠近,使“共振”区域变宽;“临界跟随”使得转子对不平衡激励非常敏感,应在转子动力学设计时予以避免。
Abstract:In order to deeply investigate the mechanism of “critical following speed”, a cantilever rotor dynamic model was established. The dynamic characteristics of the rotor system under “critical following speed” were analyzed. The cantilever rotor experimental system was designed and established, and experimental verification was finished on the overspeed test bench. The analysis results showed that from a certain rotational speed, when the diameter rotational inertia was equal to polar rotational inertia, the vibration pendulum angle response of the disk increased with the increasing rotational speed. The characteristics of the mode shape under “critical following speed” lied in that the disk (diameter rotational inertia was equal to polar rotational inertia) was located at the node of mode shape. The vibration displacement of the disk center was 0, but the pendulum angle of the disk was not 0 and increased with the increasing rotational speed, and the phase angle was kept constant. If the rotor was not a single-disk structure, the diameter rotational inertia and polar rotational inertia of the component should be calculated to determine whether the “critical following speed” phenomenon occurred. Considering the mass of the rotating shaft, when the disk satisfied the condition which diameter rotational inertia was equal to polar rotational inertia, the phenomenon of “critical following speed” did not occur, and the natural frequency line could be close to the speed line within a wide range, which would widen the “resonance vibration” region. “critical following speed” made vibration extremely sensitive to unbalanced load, which should be avoided in rotor dynamics design.
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表 1 转子模型参数
Table 1. Parameters of rotor system
参数 数值 参数 数值 L/m 1.0 a/m 0.6 b/m 0.4 D/m 0.03 E/1011 Pa 2.09 H/m 0.2 Δm/kg 0.001 R/m 0.1 m/kg 40.0 Ip/(kg·m2) 0.4 sb1/106 (N/m) 4.0 sb2/106 (N/m) 5.0 c b1/(N·s/m) 200 c b2/(N·s/m) 200 ρ/(kg/m3) 7870 表 2 两件试验件的惯量参数
Table 2. Inertia parameters of two rotor test rigs
试验件 质量/
kg极转动惯量
Ip/(kg·m2)直径转动惯量
Id/(kg·m2)Ip/Id 1 9.18 0.0173 0.0168 1.02976 2 8.17 0.017 0.206 0.0825 -
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