Combining lumped parameter modelling and CFD analysis for the pressure ripple estimation of tandem gear pumps

The development of a zero-dimensional model for analyzing pressure phenomena in multiple stage external gear pumps is addressed in the present work. The so-called tandem pump is composed of two coaxial stages: the high delivery pressure one, made by spur gears, and the low delivery pressure one, made by helical gears. The two stages have common shafts and are enclosed in a common case. On the basis of the Euler’s approach, the oil pressure course around the gearpair, as well as the suction/delivery pressure ripple, is estimated for both stages. Particular attention is focused on the description of the modeling approach: an original methodology has been developed in order to model the helical gears and their effects on the determination of the geometrical parameters. The lumped parameter (LP) model takes advantage of a Computational Fluid Dynamic (CFD) model applied to different pump regions. The CFD model is able to estimate several internal flow features, providing useful results for accuracy improving purposes. Measured delivery pressure ripple and volumetric efficiency are used to evaluate the model reliability under different working conditions.