【作者】 谭丽丽；

【导师】 彭旭东； 白少先；

【作者基本信息】 浙江工业大学 ， 化工过程机械， 2009， 硕士

【摘要】 在石油和石化行业中,干式气体端面密封(DGS)在高速旋转机械(如离心压缩机)上应用日趋广泛,并正逐渐扩展到泵及反应釜等中低速回转设备上。但是由于DGS在启动时不易开启,低速低压下难以建立稳定的气膜,同时也缺少完善的中低速设计理论和方法,因此制约了DGS的推广应用。所以,研究并完善中低速条件下DGS的设计理论,改善DGS在低速低压条件下和启动时的工作性能,具有重要意义。首先,针对光滑面螺旋槽干式气体端面密封(S-DGS)建立了端面气膜压力控制方程组,采用有限单元法进行求解,计算了密封性能参数,并与相关文献进行了比较,验证了有限元程序的可靠性。在此基础上,研究比较了收敛型槽深S-DGS与普通等槽深S-DGS的密封性能,结果表明,在低速低压条件下,收敛型槽深S-DGS的密封性能没有明显优势。其次,建立了带内环槽S-DGS端面气膜压力控制方程,并采用有限单元法求解,研究了低速低压条件下密封性能随端面微槽几何参数变化的规律,以获得较大气膜刚度或开启力以及较小泄漏量为几何结构优化原则,对微槽几何参数进行了优化。最后,基于流体润滑理论,考虑端面气膜滑移流,建立并采用有限单元法求解了带内环槽S-DGS的端面膜压控制方程,系统研究了低速低压条件下滑移流对该种密封性能的影响。结果表明,当0.05≤Kn＜1时,滑移流对密封性能产生明显影响。在此基础上,以获得较大气膜刚度和较小泄漏量为端面几何参数优化准则,对考虑滑移流条件下带内环槽S-DGS密封端面几何结构参数进行了优化。研究结果为改善S-DGS的开启特性,提高S-DGS的低速低压工作能力,以及带内环槽S-DGS的实际设计与应用提供了较全面的理论依据。更多还原

【Abstract】 Dry gas face seals (DGSs) have been successfully applied to rotating equipments with high speed such as compressors and gradually under slow speed conditions. But it’s difficult to form a stable gas film between the two faces when starting up and at slow speeds and low pressures, which restricts the application widely. Therefore it’s very important to perfect the basic theories of design and to improve start-up performances of DGSs at low and moderate speeds.Firstly, the finit element method (FEM) was used to solve the governing equations for compressible gases for a spiral-groove dry gas seal (S-DGS) with smooth surfaces. Comparisons of the sealing performances with a typical S-DGS proved the validity of the calculation. It is also found that a S-DGS with some converged groove depth has no advantages over the typical S-DGS under slow speed and low pressure conditions. Secondly, a mathematic model was built to analyze the sealing performances for a S-DGS with an inner annular groove connected to the spiral groove on the face and the micro-groove structure parameters were optimized based on the rule of getting larger film stiffness or opening force while maintaining lower leakage. Lastly, based on theory of lubrication, a model for gas film pressure considering slip flow was developed and the effects of slip flow on sealing performances were systematically studied at slow speeds and low pressures. It is suggested that when Knudsen number is larger than or equals 0.05 and less than 1.0, the effects of the slip flow on sealing performances are significant. Based on the same optimization rule, the principle for optimized face geometry parameters of such a DGS was presented, which provides theory guidance for improving start-up performances at slow speeds and low pressures and practical application and design.更多还原