高参数机械密封热流体动力特性研究

发布时间：2018-02-25 08:33

本文关键词： 机械密封 CFD 腔内介质物理场热流固耦合液膜特性固有振动特性　出处：《新疆大学》2012年硕士论文　论文类型：学位论文

【摘要】：机械密封装置是动力装备安全运行的重要屏障。高压、高温、高速、高腐蚀等极端工况易造成密封端面的温升过大，将引起密封副形成热锥面或波度、非正常的热磨损及热腐蚀、热裂或龟裂及端面间液膜失稳等失效现象。本文以石化行业热油泵用高参数波纹管机械密封为研究对象，首先建立了密封腔内工作流场的三维数值模型，，设置了边界条件初始条件后，基于计算流体动力学(C FD)数值计算法，选用基压式求解器及RNG k ε湍流模型，通过求解工作流场的三维N S方程、能力方程及连续性方程，得到了工作流场及密封副与接触面处的压力梯度云图、速度梯度云图、温度梯度云图、流场区域的涡量分布、质点运动迹线云图、湍动能及湍能耗散率等热流体动力物理场特性分布，与此同时，得到了上述参数的矢量图、等值线图。基于腔内流场的热流体动力学特性的研究，建立了以腔内介质、动环、静环及冲洗介质等部分为整体的数值计算模型，实现了热、流、固多场耦合数值计算。首先分别建立了各部分的数值模型，将高参数工况的物料属性及模型的边界条件写入了数值计算模型，其中在流固交界面设置了实际工况热对流系数，选用合理的压力松弛因子及差值格式后，计算得到了液膜的压力梯度及压力系数、摩擦力及摩擦扭矩、温度梯度分布以及液膜质点的运动迹线等流场特性参数分布规律；得到了动、静环的热荷载轴向及径向的梯度分布特性，基于有限元算法，通过求解物理方程、几何方程、虚功方程，得到了在热荷载作用下的动、静环轴向及径向的热应变、热应力及热变形。另外，基于有限元动力学分析原理，数值计算了预热荷载作用下的动环的模态分析，并将其与无热荷载因素下的结果进行了对比分析，得到了密封副在高参数工况下的振动机理。通过对不同工况条件下的数值计算结果的对比分析，得到了主轴转速、密封压力、介质粘度、介质温度及液膜膜厚等因素对于液膜热流场物理特性、对动、静环的热变形及热应力以及对于动环振动特性的影响规律，这为高参数极端工况下所用机械密封的优化设计提供了依据。
[Abstract]:Mechanical sealing device is an important barrier for the safe operation of power equipment. Extreme working conditions such as high pressure, high temperature, high speed and high corrosion will easily cause the temperature rise of the seal end surface to be too large, which will cause the sealing pair to form a hot cone surface or waviness. Abnormal thermal wear and corrosion, hot cracking or cracking, and end-to-face liquid film instability and other failure phenomena. In this paper, the high parameter corrugated pipe mechanical seal for hot oil pump in petrochemical industry is studied. Firstly, a three-dimensional numerical model of workflow field in seal chamber is established, and the initial boundary condition is set up. Based on the computational fluid dynamics (CFD) numerical method, the basic pressure solver and RNG k 蔚 turbulence model are used to solve the three dimensional N S equation, capability equation and continuity equation of workflow field. The pressure gradient cloud, velocity gradient cloud, temperature gradient cloud, vorticity distribution in the flow field, particle movement trace and cloud image of the workflow field and the sealing pair and contact surface are obtained. At the same time, the vector diagram and isoline diagram of the above parameters are obtained. Based on the study of the thermohydrodynamic characteristics of the flow field in the cavity, a numerical model is established, which takes the inner cavity medium, the moving ring, the static ring and the washing medium as the whole, and realizes the heat and flow. First, the numerical models of each part are established, and the material properties and the boundary conditions of the model are written into the numerical model, in which the actual thermal convection coefficient is set up at the fluid-solid interface. The pressure gradient and pressure coefficient, friction force and friction torque, temperature gradient distribution, and the distribution of flow field parameters such as the motion trace of liquid film particle are obtained by selecting reasonable pressure relaxation factor and difference scheme. In this paper, the axial and radial gradient distributions of the thermal loads in the dynamic and static rings are obtained. Based on the finite element method, the dynamic, static and radial thermal strains are obtained by solving the physical equations, geometric equations and virtual work equations. In addition, based on the finite element dynamic analysis principle, the modal analysis of the dynamic ring under preheating load is numerically calculated, and the results are compared with the results under no thermal load. The vibration mechanism of sealing pair under high parameter working condition is obtained. By comparing and analyzing the results of numerical calculation under different working conditions, the main shaft speed, sealing pressure, medium viscosity, medium temperature and film thickness are obtained to the physical characteristics of the liquid film heat flow field. The thermal deformation and thermal stress of the static ring and its influence on the vibration characteristics of the moving ring provide the basis for the optimum design of the mechanical seal under the extreme working conditions with high parameters.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH136

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