| Spiral groove dry gas seal is a new type of non-contacting mechanical seal.Comparing with the conventional shaft end seals, the spiral groove dry gas seal hasmany advantages,such as small leakage,little surface abrasion, low power loss, longservice life and high reliability. In this paper, the spiral groove model is establishedby UG, the model is meshed by Gambit, then calculate the performance of spiralgroove dry gas seal by Fluent. At the same time, the physical model of the gas lfowbetween the spiral groove dry gas seal faces is established. Utilizing the Finitevolume method, a Finite volume method program is developed and thehydrodynamic lubrication formula is solved numerically. The results of two kinds ofcalculation methods are contrasted, and the influence of spiral groove's geometricparameters on the seal performance is discussed with the benchmark of Fluentcalculation results. Through the orthogonal test, the influence degree of the spiralgroove's geometric parameters is also discussed. The mechanical seal testingmachine of laboratory is modified to adapt to the dry gas seal test requirements.The main research contents and results are summarized as follows.(1)The spiral groove model is established by UG. The model is meshed byGambit. The difficulty of meshing the model because of conjugated problembetween micro-scale and macroscopic-scale is solved. The problem of large errorcaused by the grid density is solved through increasing the grid density gradually, sothe error is controlled in the reasonable scope. The gas field of the spiral groove drygas seal is researched and simulated by the software Fluent. A high pressure area isobserved at the groove roots, and the high pressure area is caused by the compressedgas which is resisted at the groove roots. Eventually the high pressure area forms theopening force.(2)The physical model of the gas lfow between the spiral groove dry gas sealfaces is established,then According to Navier-Stokes formula, continuity formulaand gas state equation the hydrodynamic lubrication formula of isothermalcompressible lfuid is deduced. Utilizing the Finite volume method, a Finite volumemethod program is developed and the hydrodynamic lubrication formula is solvednumerically. Because of the finite volume method has higher precision with regular grid, between the discrete process the irregular grid is converted into square grid bycoordinates variation method. The pressure distribution of the gas film is obtainedby the Numerical calculation. The main seal performance parameters, such as openforce,friction force of the face, frictional power loss,axial stiffness and leakage arecalculated subsequently.(3)The comparison of two kinds of calculation results indicates that therecommended geometric parameters of the spiral groove are presented (18°<a<25°,10|am</z;<15|a,m<52.5(xm</^4|am0.5<5<0.7,0.4<y<0.6,10<A^<18). The analysis oforthogonal test indicates that the spiral angle,the groove depth and the groove-damlength ratio have a significant effect on the leakage. The groove-ridge width ratioand the film clearance have relatively little effect on the leakage. The spiral angleand the film clearance have a significant effect on the axial stiffness. Thegroove-dam length ratio has an important effect on the axial stiffness. Thegroove-ridge width ratio and the groove depth have relatively little effect on theaxial stiffness. Two kinds of results have some differences which are caused by thecalculation error and the mesh density.(4)From the known technology, the normal dry gas seal testing machine hassome shortcomings. In this paper, three shortcomings of dry gas seal testing machineare solved.1. The axial force of seal testing device with single cantilever shaft andone pair of seal rings is eliminated;2.The problem of the complicated structures ofmechanical seal testing device with double cantilever shaft solved;3. The problemof regulating disequilibrium of spring compression of seal testing device with singlecantilever shaft and two pairs of seal rings is solved. |
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