Numerical Investigation on Pairing Solutions of Non-Positive Displacement Pumps and Internal Gear Pump for High-Speed Design

Raising the working speed of hydraulic pumps to maximize the efficient matching range of electric motors is one of the possible ways to achieve energy efficiency in electric machinery. By means of a simulation method verified with subsequent experiments in terms of filling efficiency, this paper first analyzed the suction capacity of crescent-type internal gear pumps with different geometric parameters at high speed, and the gear pair that is more suitable for high-speed operation was obtained. Subsequently, as the more significant contributions, two pairing solutions of a non-positive displacement pump and an internal gear pump were proposed to pressurize the inlet of the gear pump to keep it from cavitating. In the compact design solution, the inclined-holes type and axial-flow blade pumps share the same speed as the hydraulic pump, while the decentralized layout solution allows for flexible adjustment of the centrifugal impeller-type pump speed to maximize the filling capability. The final simulation results show that, with the help of inclined-holes type and centrifugal impeller type pumps, the filling efficiency of the internal gear pump at 6000 rpm can be improved by 3.59% and 5.84%, respectively, while the axial-flow blades pump fails to eliminate cavitation regardless of speed. Moreover, when the hydraulic pump works at 6000 rpm, the centrifugal impeller speed needs to be set above 2500 rpm to make sense.