Investigation of flow field simulation and pulsation performance of non-circular gear hydraulic motor

The non-circular gear hydraulic motor is widely used in hydraulic transmission systems for mining and underground machinery, owing to its low velocity, high output torque, and compact structure. This paper focuses on the 4–6 type non-circular gear hydraulic motor as the research object. The influence of the coupling between the motor's internal flow field and the operation of the gear train on the motor's power pulsation performance is analysed using the mesh and particle-based methods. A three-dimensional fluid model of the motor is developed to systematically investigate the effects of pressure and flow velocity on the motor's stability. With regard to the pulsation rate of the motor, this study analyses the comparative relationship between the theoretical torque pulsation rate and the theoretical flow pulsation rate, while simultaneously considering the variation of the flow pulsation rate under the influence of oil entrapment in the gear teeth. The results show that the theoretical flow pulsation rate of the motor is basically consistent with the theoretical torque pulsation rate. However, when considering the oil entrapment in the motor gear teeth, the flow pulsation rate increases. In the flow field simulation, the flow velocity distribution in the flow field is found to be uneven. Specifically, high-velocity flow is formed in the air gap area, while in the area close to the sun gear and the inner gear ring, the flow is poor and stagnation phenomena occur, which aggravates the oil entrapment phenomenon. The findings of this study provide a theoretical basis for optimizing the performance of non-circular gear hydraulic motors and offer new insights into the simulation analysis of complex moving flow field, as well as the relationship between flow pulsation rate and oil entrapment characteristics.