The present paper addresses the development of a lumped parameters model used to analyze the dynamic behavior of a so-called tandem gear pump. The pump is composed of two coaxial stages, both with external gears: a high pressure stage with spur gears and a low pressure one with helical gears. In particular, the paper deals with the modelling and the analysis of the phenomena bound to the pressure distribution around the gears, since they have the most important effect in the dynamic behavior of the pump. The pressure variation in the inlet and outlet chambers, the variable pressure in the trapped volume as well as the pressure evolution from the low to the high pressure chamber is estimated based on the Euler’s approach. The model is developed in Matlab environment. Attention is particularly focused on the description of the methodology adopted for modelling the low-pressure stage, constituted by helical gears, and its influence on the calculation of the pump geometrical parameters. The results provided by the numerical model are compared with experimental measurements in terms of outlet pressure ripple and volumetric efficiency under different working conditions. The results of the validation can be considered satisfactory. Predicted pressure ripple is shown and the effects of interconnections between stages are analyzed studying the outlet pressure ripple in the frequency domain as well.

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