Clearance flow characteristics and thermodynamic properties of micro-gear pump with canned motor

High-speed micro-gear pumps are widely used in aerospace industry because of the small size and high efficiency with low flowrate. In these pumps, there exist lots of clearance channel structures, and the heat generated by high-speed motors must be discharged in time through these clearance channels. Therefore, the clearance channel structures have significant impacts on the hydraulic and thermodynamic performance of these pumps. In this paper, unsteady flow and thermodynamic simulations of a micro-gear pump with canned motor are carried out. The effects of clearance channel structures on the flow characteristics and thermodynamic properties are investigated. And the characteristics comparisons with different connecting flow channel diameters are conducted. The results show that with the diameters of the connecting flow channel increase, both the outlet flowrate of the pump and the heat transfer coefficient of the annular channel will decrease. And the threaded grooves on the inner surface of the axial channel will mitigate these effects. Additionally, through the investigations on the heat transfer factors in annular flow channels, it can be concluded that the heat exchange between the annular clearance of the motor and the medium is dominated by heat conduction through the wall boundary layer.