Effect of seal clearance on the separation performance for a gearbox sealing system of a high-speed electric multiple unit

Abstract

Seal characteristic is based on the oil-gas separation performance of the gearbox sealing system of a high-speed electric multiple unit. A model of the gearbox sealing system is established to study the effect of seal clearance on separation performance, based on discrete phase method and droplet-wall collision models. The results show that the airflow drag force and oil droplet inertia force affect the locus of the droplet motion and the oil-gas separation efficiency of the sealing system. However, mass inertia force is the major influencing factor while acceleration inertia force and airflow drag force are secondary factors. The separation efficiency of small oil droplet (diameter 1 µm) decreases as the axial clearance width increases, while the separation efficiency of larger oil droplet (diameter 5 µm) remains unchanged. However, the separation efficiency of intermediate droplet (diameter 2–4 µm) decreases and then increases. Meanwhile, larger axial clearance height difference and radial tooth relative meshing ratio lead to higher separation efficiency. The separation efficiency decreases with increasing radial tooth angle, reaches a minimum at 80°, and then increases with further increase in tooth angle. Thus, the seal clearance has a slight effect on the oil-gas separation efficiency of oil droplet of 5 µm.