| A mechanical seal with laser-textured faces (LST-MS) is an innovative type of mechanical seals developed in last decade, which can run non-contact due to the hydrodynamic effect produced by micro-pores onto the hard face. Compared with a conventional mechanical seal, such seals perform more perfectly because of its outstanding sealing ability and lubrication behavior, but their opening characteristics is unknown and under developed. So the critical opening characteristics of such a seal have been studied in this thesis.Firstly, Reynolds equation controlling gas film pressure between the two faces with square dimples is set up based on reasonable simplifications and some assumptions and resolved by finite element method. The definitions of face opening force, film stiffness, ratio of hydrostatic stiffness or hydrodynamic stiffness to opening force are presented. Then, the models of both mathematical and physical of the critical opening characteristics of such a LST-MS are established for the hydrostatic case or the hydrodynamic case. The sealing performance, the critical hydrostatic and hydrodynamic opening characteristics are theoretically analyzed. The effects of dimple geometrical parameters such as area density of dimples, the radial texturing proportion, the circumferential texturing proportion, the ratio of dimple depth to dimple diameter on the critical opening behavior are studied. Lastly, the principle for optimizing the texturing parameters is presented to ensure that a gas lubricated LST-MS can be opened at low speeds or low pressures while the stability of the seal is kept high. According to the principle, the mimimum openning force and the maximum ratio of stiffness to opening force are selected as the objective functions for the optimization of the texturing geometric parameters.The study makes contributions to the design theory of a gas lubricated LST-MS, which maybe helpful to designers, the related manufactures and users when they delt with such seals.
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