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Integrated electrohydraulic pump (IEHP) is conceived as an innovative design concept to achieve the higher power density, lower noise level, and leakage-free with respect to the traditional hydraulic power units. Nevertheless, the complex cooling circuit may increase the flow resistance, reducing the effective delivery flow rate of IEHP, which will be more serious at high rotational speed. In this context, a novel centrifugal charging pump (CCP) integrated on the hollow drive shaft is arranged on the suction path of positive-displacement vane pump (main pump) to boost its inlet pressure, thus efficiently improving the suction capability of IEHP. The contribution of this study is to develop a full flow field CFD model of IEHP, in which the fluid domain of main pump and CCP are connected in series. Based on the CFD model validated subsequently by prototype experiment in terms of volumetric efficiency, the charging effect of CCP modeled with different geometric parameters, at 1,500 r/min, has been investigated. Finally, combined with experiment and simulation, the delivery flow rate of IEHP, in the speed range 600–6,000 r/min, are also analyzed by means of comparing with a standard vane pump. The results show that the CCP makes an outstanding contribution to the filling of main pump, especially when the rotational speed exceeds 3,000 r/min; Since then, the flow rate saturation of standard vane pump tends to occur due to serious incomplete filling, while the IEHP still maintains valid output. It can be concluded that, with the help of charging effect of CCP, the IEHP can keep the same volume efficiency as the vane pump under rated speed, and there is a certain potential for the application of IEHP in a wide speed range.

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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.

Based on Solidworks software, the three-dimensional model of two wheels scooter is set up. The finite element model of two wheels scooter is generated. Finite element analysis of telescopic mechanism of bar on two wheels scooter is investigated. The stress and strain of telescopic mechanism of bar is investigated. The stress diagram and the strain diagram are obtained. The method and the result can be used as a reference of innovative design of two wheels scooter.