All kinds of rotary fluid conveying machinery to large-scale, high parameterization, multi-phase media transportation, variable working conditions of the direction of rapid development, the working stability of mechanical seals requirements are getting higher and higher, China′s offshore equipment including offshore platforms and submarine oil and gas mixing pump as a key equipment in the process of submarine oil exploitation and transportation has been dependent on imports, supporting high-performance mechanical seals are also imported. The mechanical seal for mixing pump faces gas-liquid-solid multiphase media and high solid particles (oil, gas, water and sand, etc.), high temperature 200 °C, high pressure (15MPa) and high corrosiveness and other multi-phase media with high participation conditions, and its quality and performance directly determine the operating cycle and use efficiency of the mixing pump. Therefore, it is necessary to optimize the overall structure and end groove of the mechanical seal to increase the end face lubrication, reduce friction and ensure the leakage suppression effect.
In this paper, the laser face shallow groove micro-contact seal is taken as the research object, the Reynolds equation considering the characteristics of the miscible medium and the roughness effect of the sealing end face is solved, the microconvex contact force is solved by fractal contact theory, and the grid independence verification and model validity verification are carried out, the lubrication state of the seal is analyzed by performance parameters such as opening force, liquid film bearing coefficient, critical speed, etc., and the mixed lubrication state of the mixed-phase micro-contact mechanical seal is graded by using the liquid film bearing coefficient solved in different microconvex contact states. The mixed lubrication state is divided into three levels: elastic lubrication, elastoplastic lubrication and plastic lubrication, which is helpful to study the lubrication of micro-contact mechanical seals and its simple life prediction, and also explores the influence of pressure, speed and other working conditions and grooving forms on the lubrication state transformation of seals. The results show that the laser face shallow groove mechanical seal has a good sealing lubrication effect, which is very suitable for high-pressure sealing. The mixed lubrication state of mixed-phase micro-contact mechanical seal can be divided into three levels: elastic mixed lubrication state, elastoplastic mixed lubrication state and plastic mixed lubrication state, among which the liquid film bearing coefficient is the smallest in the elastic lubrication state, the mixed lubrication effect is the best, the elastoplastic lubrication state is the second, and the plastic lubrication state is the second; With the increase of speed, the bearing capacity of the liquid film continues to increase, the contact force of the microconvex body gradually tends to 0, and the sealing ring is separated to achieve non-contact, and the bearing coefficient of the liquid film is 1. The pressure difference, the larger the tank depth, the higher the gas-phase volume ratio of the miscible medium, the smaller the rectangular groove angle and the number of cycles, the weaker the dynamic and static pressure effect, the smaller the liquid film force generated, the smaller the liquid film bearing ratio, the larger the critical speed, the more stable the lubrication state, and the more difficult the separation of friction pairs, so this paper recommends selecting the groove depth of 6~8 μm, and the number of cycles is 10~12.
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