In this paper, two alternative numerical approaches for the simulation of Gerotor units are compared: a fast lumped parameter approach for the fluid dynamics through the unit that permits the co-simulation of the radial micro-motion of the rotors, and a computational fluid dynamics approach that puts emphasis on the description of the detailed features of the flow through the unit. Each approach provides unique insights on the unit operation, although with different assumptions and level of result details. For an objective comparison of these two state-of-art models, the authors compared their results with experiments. A commercial pump taken as reference, and tests focused on steady-state volumetric performance as well as the transient features of the outlet port pressure oscillations. The results presented in the paper permit to gain a high level of understanding of the operation of the unit and of the critical aspects that a designer should consider while analyzing such design of positive displacement machines. While comparing the two simulation approaches, the paper highlights the limits and the strengths of each one of the two approaches. In particular, it is shown how both models can match the experimental results considering proper assumptions, in terms of technological clearances and rotors’ micro-motions.

The paper constitutes a unique contribution in the field of numerical simulation of Gerotor units and represents a useful reference to the designers looking for suitable methods for simulating existing or novel design solutions.