呼吸性裂纹转子的瞬态振动特性分析

Transient vibration characteristics of a rotor with breathing crack

旋转机械转子轴萌生裂纹后,瞬态加速过程中转涡差角时变使裂纹周期性开合,系统发生不同于稳态情况的振动。基于中性轴法确定裂纹开合,数值计算了呼吸裂纹引起刚度时变的转子过临界转速的瞬态振动,分析裂纹大小、方向角和重力对线性加速转子瞬态振动的影响,以及定功率加速瞬态过程中系统振动响应及稳定性。结果发现,瞬态条件下带呼吸裂纹转子系统亚谐波共振并不明显;裂纹越大,过临界转速时瞬态振幅越大;在临界转速附近裂纹瞬时张开会激起很大的振动;定功率加速过程下,若功率不足以提供转子顺利穿过临界转速,则会出现外界扭矩与瞬态振动的能量耦合,大裂纹还可能造成瞬态振动发展成混沌。

When a crack emerges on a rotor of rotating machineries,time-varying rotation-whirl phase difference makes crack open and close periodically,it causes the transient vibration of the rotor being different from its steady vibration. The neutral axis method was adopted to determine if the crack is opening or closing. The transient vibration response caused by crack breathing of a single disc rotor passing its critical speed was calculated numerically,and the influences of crack depth,orientation angle and gravity on the transient vibration of the rotor with a linear rotation acceleration,and the transient vibration characteristics and the stability of the system accelerated with a constant power were analyzed. The results showed that under the transient condition,the sub-harmonic resonance of the breathing crack rotor is not obvious; the deeper the crack,the larger the transient vibration amplitude passing its critical speed; when the crack opens near the critical speed,larger transient vibration is excited; when the crack rotor is accelerated with a constant power and the power is not enough to make the rotor smoothly pass its critical speed,the energy coupling between the outside torque and the transient vibration occurs,a big crack may cause the transient vibration of the rotor to be chaos.