【作者】 李辉；

【导师】 马辉；

【作者基本信息】 东北大学 ， 机械设计及理论， 2013， 硕士

【摘要】 油膜失稳是转子-滑动轴承系统故障中较为常见的一种故障,其具有突发性和破坏性较大的特点。油膜失稳的发生将使得转子系统在同频周期运动的基础上产生较大的低频振动,从而使系统产生非协调进动,使转轴产生较大的交变应力,此外油膜失稳还将会造成转子振动的加剧,从而可能诱发诸如转定子碰摩等其它故障,直接关系到机组的灾变防治和安全可靠运行。对于汽轮机这样的旋转机械,其蒸汽参数、密封间隙的改变很有可能增大其在转子密封间产生的密封力,从而使转子和密封间发生碰摩的概率增大。因而研究转子-轴承-密封系统滑动轴承和密封导致的失稳规律及复杂的非线性动力学特性,对于改进及提高旋转机械的运动稳定性具有非常重要的意义。考虑非线性油膜力、密封力以及转定子碰摩及支座松动的影响,本文主要研究了一个单跨双盘转子-轴承-密封系统的运动稳定性。首先,运用转子动力学的理论,建立了考虑陀螺效应的双盘光轴转子-轴承系统的集中质量模型,研究了两圆盘在偏心同相位和反相位两种工况下的油膜失稳规律；采用有限元模型和试验验证了集中质量模型的正确性。在此基础上,基于一个单跨双盘阶梯轴转子-轴承系统,证实了之前得到的油膜失稳规律对于单跨双盘转子-轴承系统来说,在一定程度上是具有普遍性的。进而基于单跨双盘光轴转子-轴承系统的集中质量模型,深入研究了两圆盘偏心相位差、偏心量、滑动轴承间隙、润滑油黏度以及滑动轴承长径比对转子系统第1、2阶油膜失稳规律的影响。其次,在单跨双盘光轴转子-轴承系统集中质量模型的基础上,考虑两圆盘处密封的影响,建立了光轴转子-轴承-密封系统的集中质量模型,分析了两圆盘在不同偏心相位差情况下,非线性密封力对转子系统油膜失稳规律的影响,以及各种密封参数(密封压差、密封间隙和密封长度)对系统油膜失稳的影响。然后,针对油膜轴承处可能出现的轴颈和轴承的碰摩问题。在之前建立的单跨双盘光轴转子-轴承-密封系统的集中质量模型的基础上,讨论了两圆盘在同向、反向偏心的两种工况下碰摩力对油膜失稳的影响,以及定子刚度和轴承不对中量的变化对系统油膜失稳规律的影响。最后,针对油膜轴承的支座在系统剧烈振动时可能发生松动的问题。在两圆盘同向、反向偏心的两种工况下,对单跨双盘光轴转子-轴承-密封系统在不同转速下的振动响应进行了仿真分析。分析了在两种工况下不平衡量、松动间隙和支座质量对系统松动的影响。更多还原

【Abstract】 Oil-film instability, one of the frequently confronted faults in rotor-bearing systems, has the characteristics of abruptness and destructiveness. The instability would contribute to excessive vibration at lower frequency on the basis of synchronous vibration. This would accelerate the nonsynchronous response of the system, and cause significant alternating stresses in the rotor. Due to the large vibration caused by the oil-film instability, many other faults such as the rub-impact of rotor-to-stator could appear, which would influence directly the catastrophes control and reliability of the system. For some rotating machines such as turbine machine, the seal force would significantly increase by the change of steam parameters and seal clearances, which would increase the probability of the rub-impact between the rotor and sealing device. So, the research on the dynamic characteristics of bearings and seals in the rotor-bearing-seal system is of great importance for the more stable and efficient rotating machines.This paper mainly studies motion stability of a rotor-bearing-seal considering the effect of oil-film, seal force, rub-impact between the rotor and the stator, and pedestal looseness. Firstly, a lumped mass model of a rotor-bearing system with two discs considering the gyroscopic effect is established. And the effect of two loading conditions determined by API Standard 617 (Axial and Centrifugal Compressors and Expander-compressors for Petroleum, Chemical and Gas Industry Services, Seventh Edition) on the onset of oil-film instability and nonlinear responses of the rotor-bearing system is studied. Moreover, the model validity is also examined by a finite element model and experiments. At the same time, the universality of the laws is verified by a rotor-bearing system with a stepped shaft and two different discs to some extent. Then, based on the lumped mass model established previously, the effects of the eccentric phase difference, eccentricity, bearing clearance, lubricant viscosity, and slenderness ratio of the right bearing(LID) on the first/second mode instability are further studied.Secondly, based on the two discs lumped mass model established previously, a new lumped mass model of a rotor-bearing-seal system is established, in which the seal is considered. Effects of the seal force on the first and second mode instabilities are investigated under two different eccentric phase differences of two discs, and several seal parameters (seal pressure, seal length and seal clearance), respectively.Then, in view of the rub-impact between the journal and bearing may be caused by the oil-film instability, based on the lumped mass model of rotor-bearing-seal system established previously, effects of the rub-impact on the first and second mode instabilities are investigated under two different eccentric phase differences of two discs, the stiffness of stator, and misalignment between the journal and bearing, respectively.Finally, in view of the pedestal looseness fault may be caused by the excessive vibration, the researches on vibration characteristics of the system is carried out based on the lumped mass model established previously under two different eccentric phase differences of two discs. Then, effects of eccentricities of two discs, loose clearance and pedestal mass on looseness are analysed under two loading conditions.更多还原