Research On Performance Of Dry Gas Seal With Single-row Bidirectional Spiral Grooves

Compared with the conventional shaft end seals, dry gas seal has many advantages including small leakage, little surface abrasion, low power loss, long service life and high reliability. At present, dry gas seal is widely applied in centrifugal compressor, centrifugal pump, expansion machine, gas turbine and other high-pressure or high-speed machines. In recent years, with the rapid development of dry gas seal technology, a new seal pattern named single-row bidirectional spiral grooves dry gas seal is produced. This kind of grooved dry gas seal can not only produce suitable fluid dynamic pressure but also revolute two-directionally, which avoids the seal damage led by the contra-rotation and open-and-close working, causes the application scope of the single-row bidirectional spiral groove dry gas seal to be more widespread, and enhances its research and the use value greatly.Due to the correlation of the flow and heat transfer, the three-dimensional numerical studies employing CFD software for face single-row bidirectional spiral groove dry gas seal are presented. Firstly, through the study of the selected periodic gas film, the three-dimensional model is structured of which the transition from micro to macro size is made by adopting mesh element. By solving three-dimensional N-S equations, the flow process from entrance to interface clearance is analyzed including the pressure distribution, the speed distribution, the particle track and the swirling distribution. And the influence of geometric structural parameters of the rotor to the performance of seal is theoretically studied with the assumption of fixed closure force. Secondly, by solving energy equation the distribution of temperature field of the gas film, rotor and stator rings are obtained as well as the factures which influence the heat transfer, and the influence of temperature to viscosity is discussed especially, and the temperature field with the variable viscosity is presented. The effects of operating conditions on sealing performance are determined and compared with unilateral spiral groove dry gas seal.Through the simulation analysis,it is proved that the single-row bidirectional spiral groove dry gas seal having suitable fluid dynamic pressure and seal effect in different operating condition. According to the condition of fluid flowing, the process of heat transfer is explained, which demonstrates that the increase of temperature within the fluid film is resulted from the viscous shear and gradient of pressure, and then the heat is transferred outwards across the buffer fluid and the seal rings. And they can be available to experimental study, parameter and performance optional designs of the seals, and also lay the foundation for studying the thermal distortion of seal rings.