涡动与偏心对气体力与泄露量的影响

机械设计制造及其自动化论文，论文编号:JX1086  论文字数:17806.页数:34

摘   要
    迷宫密封是一种非接触式密封，它具有无固相摩擦、不需润滑、能耗少等特点，在涡轮机械中广泛应用。但迷宫密封的使用往往会使高速旋转机械产生气流激振问题，出现振动噪声大、碰磨等问题，严重时甚至会使整个机组失效。因此通过迷宫密封腔内流场和压力场的数值计算，分析探讨迷宫密封失稳机理及其各种影响因素，是很有意义的，也有着良好的工程应用前景。
    流体在迷宫密封内的流动过程，遵循流体流动的所有控制方程。本文围绕迷宫密封激振机理以及动力特性系数的研究展开，应用FLUENT软件对迷宫密封内部流场进行了深入的研究，并提出了一种计算密封动力特性系数的方法。
 本文以CFD软件FLUENT为主要计算工具，建立了迷宫密封三维有限元模型，对边界条件的选取和网格的划分进行了分析。并将计算得到的腔内压力与经验公式计算结果进行了对比，模拟结果与经验公式计算结果相吻合。
    本文对迷宫密封内部三维流场进行完整地分析，讨论了偏心、转速对密封腔内转子表面周向压力分布的影响。 
 
关键词：迷宫密封；转子动力学；流场

Abstract
    Labyrinth seal is a kind of untouched dynamical seal which is commonly used in turbo-machinery to reduce the leakage loss. It is a well known problem that seals fluid forces on the rotor which can excite rotor vibrations and thereby destabilize the machine. So it is vital important to simulate the gas flow and pressure distribution inside labyrinth seal in order to deeply study the destabilization mechanism and the influence factors.
    The flow inside labyrinth seal obeys all the conservation equations of fluid flow for mass, momentum and energy. This paper first studied on the mechanism of gas exciting vibration and the internal flow field of labyrinth seals, using FLUENT software. And then put forward a method to compute the dynamic coefficients of labyrinth seals.
    A popular CFD software FLUENT is used in the numerical simulation of flow fields and calculation of labyrinth seal gas forces. Three-dimensional finite element models of the labyrinth seals were established, and the suitable models were changed. The influence of grid unit and its length to width ratio to the compute result and iterative convergence was discussed. The leakage and the pressure computed from the simulation and from experiential formulas were compared.
    The internal three-dimension flow field of labyrinth seals was completely analyzed in this paper. The influences of rotor eccentricity, rotating speed, pressure difference to the distribution of the circumferential pressure in the wall of the sealing cavity were discussed. And the mechanism of flow induced vibration was further realized.
Keyword: Labyrinth seal, Rotor dynamics, Flow field

目 录
摘   要 I
Abstract II
目 录 III
第一章  绪 论 1
1.1  本文研究的目的和意义 1
1.2  迷宫密封简介 2
1.2.1  迷宫密封流体激振机理 2
1.2.2  迷宫密封激振力模型 4
1.2.3  迷宫密封流场的研究现状 5
1.3  计算流体力学及FLUENT简介 6
第二章 迷宫密封流场计算模型 9
2.1  基本控制方程 9
2.2  迷宫密封三维几何模型的建立和网格划分 11
2.3 FLUENT的计算步骤 15
2.4  FLUENT的后处理方程 17
第三章 迷宫密封三维流场分析 19
3.1迷宫密封压力流场基本分析 19
3.2 气体力和泄露量随转子偏心的变化 22
3.3 涡动对转子气体力和泄露的影响 23
3.4同一偏心下涡动速度对气体力及泄露量的影响 26
第四章  总结与展望 28
5.1 总结 28
5.2 展望 28
致    谢 30
参考文献 31