With the development of automotive fuel cells towards high power and high efficiency, higher requirements are put forward for the speed and boost ratio of hydrogen circulation pump, while high speed and boost ratio increase the pulsation characteristics and accelerate the aging of hydrogen fuel cells. Cam type hydrogen cycle pump has the advantages of compact structure, high efficiency under low boost ratio, and good adaptability to low temperature, so it has become an important research direction. The efficient and reasonable rotor profile design can improve the volumetric efficiency of the cam rotor pump. It can reduce the pressure pulsation and flow pulsation in the pump. The equation of multi-stage circular arc rotor profile is established according to the meshing principle of the rotor. Motion Simulation module in UG NX is employed to conduct dynamic interference detection of rotor mechanism and simulation analysis of rotor mechanism meshing motion on the rotating parts of the hydrogen circulating pump. So the angular velocity curve and meshing force change curve of the driven gear is obtained. In order to verify the rationality of rotor profile design, the meshing force is compared with the standard spur gear.

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A three-dimensional transient numerical model was developed to obtain the two-phase flow characteristics in a twin-screw multiphase pump based on dynamic mesh technology and the multiphase flow model. The pump performance under different inlet gas volume fractions (IGVF) was predicted by the numerical model and was tested. Then, the numerical model was validated after comparing the simulation and experimental results. After that, the flow field in the pump under 10% IGVF was analyzed. When the IGVF is 10%, the pressure increases step by step and is symmetrical from both ends to the middle of the screw rotors. The pressure distribution through a single working chamber is uniform. It falls rapidly at the inlet of the tooth tip gap and then drops linearly in the gap channel. At the outlet of the tip gap, the pressure temporarily falls due to the high-speed jet. The GVF distribution in the working chamber is uneven. The leakage flow is laminar in the tip gap, and the liquid concentrates on the top of the gap. When the last working chamber connects with the discharge chamber, the discharge jet flow causes the vortices in the discharge pipe. The gas gradually moves to the center of the vortices, forming four gas-phase aggregation regions. The velocity of the interlobe leakage is the largest. The maximum velocity appears at the second cross-section and reaches 35m/s. This research can be used to improve the performance of the twin-screw multiphase pump under two-phase working conditions.

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For water-jet propellers, the geometry size of the guide vane change can effectively improve the performance of the pump. If other parameters remain unchanged, CFD numerical simulation of the guide vane number and wrap angle of the change can be used to effectively adjust the operation conditions of the pump. The relationship between the changes in pump head, pump efficiency, and water-jet propeller propulsive efficiency can be used, to find the best guide vane parameters to achieve the highest thrust efficiency. The calculation results show that an increase in the guide vane number coefficient and wrap angle coefficient will reduce size of the pump head. Meanwhile, an increase in the wrap angle coefficient and the guide vane number coefficient will reduce the propulsive efficiency of the whole water-jet propeller. In this experiment, it was found that the propulsion effect is best when the guide vane number coefficient remains unchanged and the wrap angle coefficient is 1.

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In deep surges in compressors, the behaviors tend to show either a near-resonant one or a convective one, the latter performing emptying and filling actions. However, detailed information on the differences between them have not been obtained so far. In order to understand the situations, surge simulations by a one-dimensional simulation code were conducted with respect to a single-stage centrifugal compressor, paying attention to the effects of changes in the compressor tip speed and in the geometry of the flowpaths. As the results, it has been found that near-resonant surges appear at very low tip speeds and for relatively narrow sectional areas of the delivery flowpath, and they transform to convective surges of emptying and filling actions toward higher speeds and wider sectional areas. The features of the behaviors are generalized in terms of several non-dimensional surge frequency parameters. The results are visualized by several global framework maps showing the relations among the parameters. The obtained results will give deeper understandings on the surge phenomena.

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As a key component of a multistage pump, the diffuser affects the efficiency of the multistage centrifugal pump. However, the loss mechanism inside the diffuser and links between the loss mechanism and vane numbers of diffuser were still not fully understood. In order to investigate the influence of the number of diffuser vane on the energy loss characteristics of multistage centrifugal pump, this paper analyzes the energy loss characteristics of pump with different number of diffuser vane by utilizing entropy production theory. The results show that under the design condition, when the number of diffuser vane increases to 11, the head is increased by 1.2m and the efficiency is increased by 3%. At the same time, with the increase of the number of diffuser vane, the backflow and eddy phenomena are gradually weakened, flow stream is more stable, the entropy production rate is significantly reduced, but the intensity of pressure pulsation in the diffuser is increased slightly.

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Simulation models of permanent magnet brushless DC motor with cam rotors and two kinds of uniform air gap motor determined by two limit arcs of the cam rotor were established on the basis of JMAG software. These simulation models were used to determine the influence of regularly varying air gap, which is formed during the rotation of the two cam rotors of the hydraulic motor pumps integrated with a cam rotor vane pump and a permanent magnet brushless DC motor, on the electromagnetic performance of the motor. The electromagnetic performance of the three kinds of motors were simulated and compared under rated and variable loads, respectively. Finally, the cam rotor motor prototype was developed for experimental research. Results show that the starting time of cam rotor motor under rated load is 20% shorter, and its output torque ripple is 23% smaller than those of the uniform air gap motor determined by the minimum limit arc of the cam rotor. However, the air gap flux density curve of the cam rotor motor weakens obviously amongst the three motors. Under different loads, the efficiency of the cam rotor motor is the highest amongst the three motors, and its mechanical property is hard. The research results can lay a theoretical foundation for the development of cam rotor motor pumps.

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