【作者】 朱旻；

【导师】 杨建刚； 沈德明；

【作者基本信息】 东南大学 ， 动力工程（专业学位）， 2020， 硕士

【摘要】 近年来出现了多起大型汽轮发电机组因转子发生渐进式弯曲导致振动发散的案例,严重影响机组安全运行。研究旋转机械转子渐进式弯曲及振动响应,对现场故障诊断与治理有现实意义。首先,建立外力作用下转子渐进式弯曲计算模型,以某燃机负荷短轴和汽轮机高中压转子为研究对象,分析了蠕变弯曲影响因素。在外力长时间作用下,转子在弹性变形上会叠加一个蠕变变形。随着时间的发展,蠕变变形量增大并趋向于以恒定速率变化。蠕变变形与外力大小呈非线性。作用时间越长,外力越大,蠕变现象越明显。建立了转子弯曲与质量不平衡耦合作用下有限元动力学模型。分析了某高中压转子在纯弯曲、纯质量不平衡及弯曲与质量不平衡耦合作用下振动响应特性。耦合作用下,当转子弯曲与质量不平衡夹角为0°,两者完全正向叠加;当夹角为180°,弯曲与质量不平衡作用相互抵消,出现“倒临界”现象,相位出现波动。其次,搭建了转子试验台以研究转子蠕变弯曲及渐进式振动现象。当轴系中部存在不平衡时,两侧配重在短时间内可以取得较好效果。运行一段时间后,停机过程振动明显大于启机。经测量,停机后转子弯曲量明显变大。分析认为,在中部不平衡量及两端配重的共同作用下,转子发生不可恢复的蠕变变形,引发转子渐进式振动现象。最后,针对某大型汽轮发电机组高中压转子渐进式振动现象,从转子蠕变弯曲的角度给出解释。转子两端配重后,在中部不平衡量及配重三力所产生的弯矩作用下,转子会发生渐进式弯曲,该弯曲变形不可恢复,导致停机过程过临界振动不断爬升,出现渐进式振动的现象。蠕变引起的渐进式弯曲呈一阶振型,对振动的影响主要表现在临界转速附近区域。现场试验表明,在失衡面上进行配重,可以减小振动并抑制弯曲发展,动平衡试验应尽可能在转子的失衡面上进行。更多还原

【Abstract】 In recent years,there have been many cases of vibration divergence caused by gradual bending of the rotor of large turbo generator unit,these cases affects the operation of the set seriously.The study of progressive bending and vibration response of rotating machinery rotor is of practical significance to the field fault diagnosis and treatment.First of all,the calculation model of progressive bending of rotor under the action of external force is established,and the influence factors of creep bending are analyzed based on the load short shaft of a gas turbine and the high and medium pressure rotor of a steam turbine.Under the action of external force for a long time,the rotor will superimpose a creep deformation on the elastic deformation.With the development of time,the creep deformation increases and tends to change at a constant rate.The creep deformation is nonlinear to the external force.The longer the action time is,the larger the external force is and the more obvious the creep phenomenon is.The finite element dynamic model is established under the coupling effect of rotor bending and mass unbalance.The vibration response characteristics of a high and medium pressure rotor under pure bending,pure mass unbalance and coupling of bending and mass unbalance are analyzed.Under the coupling action,when the angle between the bending and the mass unbalance is 0°,the two are superposed in a positive direction;when the angle is180°,the bending and the mass unbalance counteract each other,resulting in the "inverted critical" phenomenon and phase fluctuation.Secondly,a rotor test-bed is built to study the creep bending and progressive vibration of the rotor.When there is imbalance in the middle of the shaft,the balance weight on both sides can achieve better results in a short time.After running for a period of time,the vibration during shutdown is obviously greater than that during startup.After measurement,the bending of the rotor is obviously increased after shutdown.The analysis shows that under the joint action of the unbalance in the middle and the counterweight at both ends,the rotor will have irreversible creep deformation,which will lead to the gradual vibration of the rotor.Finally,in view of the progressive vibration phenomenon of the high and medium pressure rotors of a large turbogenerator set,an explanation is given from the point of view of the creep bending of the rotors.After balancing weights at both ends of the rotor,under the action of the bending moment generated by the unbalance amount in the middle and the three forces of the balance weight,the rotor will undergo progressive bending,which can not be recovered,resulting in the continuous climbing of the over critical vibration during the shutdown process,resulting in the phenomenon of progressive vibration.The progressive bending caused by creep takes on a first-order mode shape,and its effect on the vibration is mainly in the region near the critical speed.The field test shows that the counterweight on the unbalance surface can reduce the vibration and restrain the bending development.The dynamic balance test should be carried out on the unbalance surface of the rotor as far as possible.更多还原