Numerical Simulation And Optimum Groove Geometric Parameters For Spiral Groove Dry Gas Seal

The reliability of compressor shaft end seals play a very important role inassuring the security, stability and long life of equipment, and achieving the maximumeconomic benefit of enterprises. The conventional shaft end seals include labyrinthseal, floating-ring seal, mechanical seal and so on. In recent years, with the rapiddevelopment of sealing technology, a new seal apparatus, named spiral groove dry gasseal, has been developed. The principle of spiral groove dry gas seal is that, utilizingthe relative motion of the seal faces, the hydrodynamic pressure is generated due tothe pumping effect and Rayleigh step effect of the groove. Therefore, a gas filmbehaves like a spring and like a spring has a spring rate that is called "gas stiffness" isset up. This film makes the two seal faces non-contact. Meanwhile, the mediumleakage of the seal apparatus is controlled under an acceptable level.Comparing with the conventional shaft end seals, the spiral groove dry gas sealhas many advantages, such as small leakage, little surface abrasion, low power loss,long service life and high reliability. At present, this seal is widely applied tocentrifugal compressor, centrifugal pump, expansion machine, gas turbine and otherhigh-pressure or high-speed machines.The technology of dry gas seal is come from the developed industrial countries.In China, research on the dry gas seal technology and development of the dry gas sealproduct are just at the beginning stage. The products have relied on import for a longtime. The whole system of design, development and manufacture of dry gas sealproduct has not yet been set up. In this thesis, the flow of the gas between the spiralgroove dry gas seal faces is investigated by numerical simulation, the influence ofspiral groove's geometric parameters on the seal performance is discussed and thegeometric parameters are optimized. The research is helpful for the design, reliableand long life operation of the spiral groove dry gas seal used in centrifugalcompressors.The main research contents and results are summarized as follows.(1) The physical model of the gas flow between the spiral groove dry gas sealfaces is established, then the hydrodynamic lubrication formula of isothermalcompressible fluid is deduced.(2) Utilizing the Galerkin method, a finite element program is developed and thehydrodynamic lubrication formula is solved numerically. The pressure distribution of III螺旋槽干气密封数值模拟及其槽形参数优化the gas film is obtained. The main seal performance parameters, such as open force,friction force of the face, frictional power loss, axial stiffness and leakage arecalculated subsequently.(3) The influence of the operation conditions and the spiral groove's geometricparameters on the seal performance is analyzed. The influence degree of the spiralgroove's geometric parameters is also discussed. The groove depth-film clearanceratio has an important effect on the seal performance. The spiral angle and thegroove-dam length ratio have a significant effect on the seal performance. However,the groove-ridge width ratio and the groove number have relatively little effect on theseal performance. In addition, the recommended geometric parameters of the spiralgroove are presented (66°<β<75°, 4.75