Design of a High Speed Internal Gear Pump to Increase the Power Density of Electro Hydraulic Actuators (EHA) in Mobile Applications

Increasing the rotational speed of the internal gear pump entails addressing topics such as cavitation, overheating and filling problems of the tooth spaces. Besides the development of a tooth geometry and flow optimization, using CFD simulation is necessary. This paper discusses the design of the newly developed high speed internal gear pump. This includes a detailed description of the different parts as well as the dimensioning of the pump by using CFD simulations. The geometry of the pressure build-up groove has a significant effect of pressure build up inside the pump. Therefore, three different geometries are investigated. The calculation of the journal bearings for the internal gear as well as for the driving shaft is shown. To avoid cavitation problems, the suction pressure of the pump will be increased up to 25 bar. This paper will show the technical arrangements to reach this high suction pressure level whilst still using a radial shaft seal ring. In order to determine the efficiency of the newly developed high speed pump, a test rig was built up. The test rig allows the measurement of the volumetric efficiency as well as the hydraulic-mechanical efficiency at different operation points up to 10 000 rpm and 250 bar.