卧螺离心机振动分析与动力学特性研究

发布时间：2018-08-08 12:29

【摘要】：卧式螺旋卸料沉降离心机是一种应用广泛的离心沉降分离设备,结构上存在螺旋和转鼓两个转子,由于特殊的双转子结构,振动问题是制约其发展的主要因素。为此,本文针对某类型的高速卧螺离心机开展了振动测试和数值模拟计算研究,分析得到了该型离心机主要的振动故障,研究了卧螺离心机双转子结构的动力学特性,以期为卧螺离心机的结构设计提供依据。本文通过对空载下的某型号卧螺离心机进行振动测试,采用幅频图和幅值谱分析其振动特征,结果表明,由于螺旋转子径向刚度不对称,该型卧螺离心机在低转速共振时幅值谱表现出明显的二倍频特征。由于二倍频的影响,卧螺离心机在低转速下发生倍频共振,振动剧烈,对机组影响较大,因此设计过程中应尽量提高螺旋转子的对称性。分别测试了负载和同步转速下系统的振动,结果表明负载后系统振动加剧,共振区变宽;转速差的存在虽然没有提高整体振动烈度,但是由于拍振的作用,存在转速差时转子振动的危险性更高。本文基于ANSYS的非线性瞬态分析,以旋转位移约束模拟转动,建立了非对称转子的有限元模型,研究了重力作用下非对称转子的动力学特性,得到了低速倍频共振、转子各方向振动相同的结论。通过对非对称转子不平衡响应特性的研究,结果表明,相同轴向位置不同相位的加重,转子的振幅和相位响应差别较大,传统的动平衡方法不适用于非对称转子。为此,研究提出了改进的适用于非对称转子的动平衡方法。针对卧螺离心机复杂支撑的超静定结构,本文建立了轴承非线性刚度迭代计算模型,考虑齿轮啮合刚度、变形阻尼和油膜阻尼,采用实体单元建立螺旋-差速器-转鼓双转子耦合振动转子动力学模型。应用ANSYS模态分析分别计算双转子和单转子临界转速与主振型,得到了差速器、单转子固有模态对双转子固有模态的作用,并进一步研究了轴承刚度和转子壁厚对转子固有模态的影响规律。利用谐响应分析分别计算系统在转鼓、螺旋不平衡作用下的动态响应,结果表明,系统对于不同转子相同不平衡量下的振幅和相位响应不尽相同,单转子的“重径积相等,系统不平衡响应相同”的准则并不适用于双转子。应用瞬态分析计算微速差双转子的拍振特性,对比双转子和单转子不平衡时的振动特征,发现低转速下系统对于各转子不平衡的响应互不影响。本文的研究结果,对卧螺离心机结构的优化设计和高速动平衡具有重要的指导价值,对旋转机械的振动故障诊断和防振设计具有重要的意义。
[Abstract]:Horizontal screw discharge centrifuge is a widely used centrifuge for settling separation. There are two rotors of screw and drum in the structure. Because of the special double rotor structure, the vibration problem is the main factor that restricts the development of the centrifuge. For this reason, the vibration test and numerical simulation of a certain type of high-speed horizontal centrifuge are carried out in this paper. The main vibration faults of the centrifuge are analyzed, and the dynamic characteristics of the double rotor structure of the horizontal spiral centrifuge are studied. In order to provide the basis for the structure design of the horizontal spiral centrifuge. In this paper, the vibration characteristics of a certain type of horizontal spiral centrifuge under no load are analyzed by amplitude frequency diagram and amplitude spectrum. The results show that the radial stiffness of spiral rotor is not symmetrical. The amplitude spectrum of this type of horizontal spiral centrifuge shows obvious double frequency characteristics at low speed resonance. Because of the influence of double frequency, the double frequency resonance of horizontal spiral centrifuge occurs at low speed, and the vibration is violent, which has a great influence on the unit. Therefore, the symmetry of spiral rotor should be improved in the design process as far as possible. The vibration of the system under the load and the synchronous rotational speed is measured respectively. The results show that the vibration of the system intensifies after the load, and the resonance region becomes wider. The existence of the rotational speed difference does not improve the overall vibration intensity, but because of the action of the beat vibration, The rotor vibration is more dangerous when the speed difference exists. Based on the nonlinear transient analysis of ANSYS, the finite element model of asymmetric rotor is established by using rotating displacement constraint to simulate rotation. The dynamic characteristics of asymmetric rotor under gravity are studied, and the low speed frequency doubling resonance is obtained. The rotor vibration in all directions is the same conclusion. By studying the unbalance response characteristics of asymmetric rotor, the results show that the amplitude and phase response of the rotor vary greatly with the same axial position and different phases, and the traditional dynamic balancing method is not suitable for asymmetric rotor. Therefore, an improved dynamic balancing method for asymmetric rotor is proposed. Aiming at the statically indeterminate structure of complex support of horizontal spiral centrifuge, an iterative calculation model of bearing nonlinear stiffness is established in this paper, in which gear meshing stiffness, deformation damping and oil film damping are considered. The rotor dynamics model of screw-differential-drum-rotor coupling vibration is established by using solid element. The ANSYS modal analysis is used to calculate the critical speed and the main mode of the double rotor and the single rotor respectively, and the effect of the differential mode and the single rotor mode on the natural mode of the double rotor is obtained. The effects of bearing stiffness and rotor wall thickness on the inherent modes of the rotor are further studied. The harmonic response analysis is used to calculate the dynamic response of the system under the action of drum and screw unbalance respectively. The results show that the amplitude and phase response of the system are different for different rotor under the same unbalance, and the "weight diameter product" of the single rotor is equal. The same unbalance response criterion is not applicable to double rotors. Transient analysis is applied to calculate the beat vibration characteristics of two rotors with slight velocity difference, and the vibration characteristics of double rotors and single rotors are compared. It is found that the response of the system to the unbalance of each rotor is not affected at low speed. The results of this paper have important guiding value for the optimum design of horizontal screw centrifuge structure and high-speed dynamic balance, and are of great significance for vibration fault diagnosis and anti-vibration design of rotating machinery.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.84

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