【作者】 刘焰明；

【导师】 朱汉华； 钟骏杰；

【作者基本信息】 武汉理工大学 ， 载运工具运用工程， 2008， 硕士

【摘要】 机械密封在船舶尾轴密封的应用越来越广泛,同时,由于主机的大型化、尾轴长度与重量的增加,尾轴运动特性更加复杂。为了确保船舶运行的可靠性,有必要准确分析影响尾轴动力学特性的因素,目前已经逐渐认识到轴承与密封装置影响尾轴的振动特性,在诸个非线性因素中,油膜力与密封力是关键的两个。本文利用Jeffcott转子模型,分析密封力的单独作用、轴承油膜力与密封力耦合作用两种情况下转子的动力特性,主要研究内容如下。(1)艉轴推进系统是非线性动力学系统,因此,首先介绍了非线性转子动力学相关的基本理论以及本文采用的非线性油膜力与密封力模型。(2)研究单圆盘转子—密封系统的Jeffcott模型,求解密封力作用下系统的响应,讨论了振幅随转速的变化趋势,利用时程历程曲线图、轴心轨迹图及Poincare映射图、功率谱密度图反映系统的动力学特性,并分析密封压差、密封间隙、转子偏心量、密封长度四种因素对转子动力学特性的影响。(3)运用转子—轴承—机械密封系统的模型,求解了油膜力与密封力的耦合作用下系统的响应,分析了振幅随转速的变化趋势,利用时程历程曲线图、轴心轨迹图、功率谱密度图、Poincare映射图来反映系统的动力学特性,分析密封压差、密封间隙、转子偏心量、密封长度、轴承间隙、轴承长度六种因素对转子运动的影响。通过比较分析得出保持系统稳定的参数范围,为推进系统设计与选型提供了理论依据。(4)介绍了转子稳定性判断的常用的三种方法,即相平面法、最大Lyapunov指数法、Floquet乘子法,列出了求取对应系统最大Lyapunov指数和Floquet乘子的一般范式。最后对全文的研究工作进行了总结,提出了今后需要进一步研究的方向与任务。更多还原

【Abstract】 The mechanical seal is widely used in the stern seal of shaft. Meanwhile, the size of marines and the weight & length of stern shaft are becoming large, and dynamic properties of stern shaft are more complicate. So as to insure the reliability of operating, reasonable analysis of factors, which influences the dynamic properties of stern shaft, should be taken. It is gradually known that bearings and seals influence the vibration characteristics of stern shaft, and oil-film force and seal fluid force are two key factors among the given nonlinear ones.The model of Jeffcott rotor is applied, and the dynamic response of rotor under the ict of seal fluid force is analyzed. Conclusions are summarized as follows:(1) Because the shaft system in the dissertation is nonlinear dynamic system, it is introduced basic nonlinear theory used frequently in the study on dynamics of rotor, model of nonlinear oil-film force and seal-fluid force in the paper.(2) Nonlinear response of single Jeffcott rotor excited by seal force is studied. It comes out that the amplitude varies with the rotor speed. The time histories, tracks of the rotor center, power density and Poincare maps are used to illustrate the dynamic characteristics and the influences of varying pressure, eccentricity, seal length and clearance.(3) The response of the rotor-bearing-mechanical seal system is solved under the seal fluid force coupled with oil-film force. The discussion shows the amplitude is varied with the rotor speed. Time histories, tracks of the rotor center, power density and Poincare maps are used to demonstrate the dynamic features. The influences of varying pressure, eccentricity, seal length and clearance, rotor clearance and length are analyzed, and the range of parameters used to keep the system stable is gotten, which provides theoretical basis for design and choice of devices.(4) Three methods to judge the stability of rotors are introduced, which are Phase plane method, Maximum Lyapunov exponent and Floquet multipliers. In final the methods of getting Maximum Lyapunov exponent and Floquet multipliers of corresponding systems are introduced.At the end of the dissertation, research works to bring forth new ideas for the dissertation are summarized, and the research problems to go to a step further are pointed out.更多还原