大型汽轮机转子—刷式密封系统动力学特性研究

发布时间：2019-05-21 21:27

【摘要】：现代火力发电技术对动力装置越来越高的技术经济性要求更加推动了高性能透平机械密封技术的发展,由于先进刷式密封技术可以显著提高大型火电机组的可靠性及其工作效率,使得刷密封在电厂中得到越来越多的应用,但在长时间运行后发现刷式密封与转轴间产生的摩擦热不仅对会刷丝产生影响,进而影响封严特性和流场特性,而且还会影响转子的固有振动特性。因此有必要研究刷式密封流场特性和转子-刷式密封系统流固耦合振动特性,而这也体现了重要的科学价值和实用意义。本文首先研究了单根刷丝与转子几何与力学关系,进而得到了整圈刷丝对转子作用力表达式；然后类比Thomas八参数模型,对转子-刷式密封作用力进行二次多项式拟合,按照Taylor公式展开,可得到支撑刚度系数表达式,并推导出易于应用的转子-刷式密封刚度模型,并进行了仿真模拟,为第三章和第五章转子-刷式密封-轴承系统模态分析提供了模型基础。介绍了有限元分析求解方法及有限元方程,同时对相应的建模单元进行简单介绍,然后根据某电厂实际10OOMW机组建立有限元模型。利用不含有热应力和离心力的模态分析求解出固有频率及振型。对有限元数值仿真结果与电厂所提供数据进行比较,发现仿真结果比较精确,从而验证了所建模型正确,为第五章流固耦合作用下的模态分析打下了基础。研究了转子-刷式密封系统流场特性。建立了多孔介质数值分析模型,通过采用经验公式计算出刷式密封粘性阻力系数和惯性阻力系数,然后采用ANSYS Workbench协同平台中的FLUENT模块数值求解了刷式密封出口泄漏率,并与文献中的试验数据进行比照,间接验证了采用此方法计算阻力系数的合理性和正确性；然后进行刷式密封流场和温度场分析,同时研究了比压、转速对温度场的影响及压差、转速、干涉量和摩擦热流量对最高温度的影响。研究了转子-刷式密封系统流体-热-结构耦合作用对转子应力及变形的影响。在第三章流场分析的基础上,采用FLUENT模块和Static Structural模块,进行了流体-热-结构单向流固耦合仿真计算,重点考虑了同时加载流场温度载荷和离心力载荷情况下,转速及干涉量对转子应力和变形的影响。应用Moda膜块和Mechanical APDI模块对含有热应力和离心力的转子进行了模态分析,并与第三章无流固耦合时的模态进行对比,分析了流固耦合作用对转子固有振动特性的影响。
[Abstract]:Modern thermal power generation technology has promoted the development of high performance turbine mechanical sealing technology because of the higher and higher technical and economic requirements of power plant. Because the advanced brush sealing technology can significantly improve the reliability and working efficiency of large thermal power units, brush sealing has been more and more used in power plants. However, after a long period of operation, it is found that the friction heat between the brush seal and the rotating shaft not only affects the wire brushing, and then affects the sealing characteristics and flow field characteristics, but also affects the natural vibration characteristics of the rotor. Therefore, it is necessary to study the flow field characteristics of brush seal and the fluid-solid coupling vibration characteristics of rotor-brush seal system, which also reflects important scientific value and practical significance. In this paper, the relationship between the geometry and mechanics of a single brush wire and the rotor is studied, and then the expression of the force acting on the rotor by the whole circle brush wire is obtained. Then, by analogy with Thomas eight-parameter model, the rotor-brush seal force is fitted by quadratic multinomial fitting, and the expression of support stiffness coefficient can be obtained according to Taylor formula, and the rotor-brush seal stiffness model is deduced, which is easy to be applied. The simulation is carried out, which provides the model basis for the modal analysis of rotor-brush seal-bearing system in chapter 3 and chapter 5. The finite element analysis method and finite element equation are introduced. at the same time, the corresponding modeling element is briefly introduced, and then the finite element model is established according to the actual 10OOMW unit of a power plant. The natural frequency and vibration mode are solved by modal analysis without thermal stress and centrifugal force. The finite element numerical simulation results are compared with the data provided by the power plant, and it is found that the simulation results are more accurate, which verifies the correctness of the model and lays a foundation for the modal analysis under the action of fluid-solid coupling in the fifth chapter. The flow field characteristics of rotor-brush seal system are studied. The numerical analysis model of porous media is established, and the viscous resistance coefficient and inertia resistance coefficient of brush seal are calculated by using empirical formula, and then the leakage rate of brush seal outlet is solved by using FLUENT module in ANSYS Workbench collaborative platform. Compared with the experimental data in the literature, the rationality and correctness of using this method to calculate the resistance coefficient are indirectly verified. Then the flow field and temperature field of brush seal are analyzed. at the same time, the effects of specific pressure and rotating speed on the temperature field and the effects of pressure difference, rotating speed, interference and friction heat flow on the maximum temperature are studied. The effect of fluid-thermal-structure coupling on the stress and deformation of rotor-brush seal system is studied. On the basis of the flow field analysis in the third chapter, the fluid-thermal-structure unidirectional fluid-solid coupling simulation is carried out by using FLUENT module and Static Structural module, with emphasis on the simultaneous loading of flow field temperature load and centrifugal force load. The influence of rotating speed and interference on the stress and deformation of rotor. The modal analysis of rotor with thermal stress and centrifugal force is carried out by using Moda film block and Mechanical APDI module, and compared with the mode without fluid-solid coupling in chapter 3, the influence of fluid-solid coupling on the natural vibration characteristics of rotor is analyzed.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM621

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