Abstract: Centrifugal pumps may fail for a short time during the startup and shutdown phase of the equipment due to drastic changes in the internal pressure of the pump body, poor contact of the mechanical seals and so forth. Aiming at the problem of seal failure of upstream pumping mechanical seals under offdesign condition, this paper analyzes the failure causes. The analysis shows that the original dynamic pressure groove is unidirectional spiral, which is prone to poor sealing effect under offdesign condition of the equipment. And this is the root cause of the seal failure. In order to solve this problem, a new bidirectional interconnecting groove is designed by combining with the structural characteristics of bidirectional groove. The speed, pressure, and leakage of the fluid film in the bidirectional interconnecting groove are investigated by numerical simulation. The results show that the pressure at the top of the moving ring is the largest; the outer diameter speed of the sealing ring is maximum; when the groove depth is less than 6, the number of slots is between 8 and 10, the platform width ratio is 0.3 to 0.4, and the dam length ratio is less than 0.5, the mechanical seal can achieve good sealing effect under offdesign condition. Based on the results of the above study, the structural parameters of the bidirectional interconnecting groove are optimized.

Key words: centrifugal pump, mechanical deal, offdesign condition, numerical simulation, geometric parameter