CFD analysis of gerotor pumps (2014-2016)

Using Simerics MP+ (formerly PumpLinx), 3D dynamic models of gerotor pumps were developed. All models were experimentally validated on our test rig.

In particular, an in-depth analysis of the behavior under conditions of incomplete chamber filling was carried out. Figure 1 shows the complete pump model developed in Simerics MP+. To verify the software’s ability to account for variations in pipe geometry, two restrictors (R1 and R2) were inserted. The three configurations analyzed are: (1) without restrictors, (2) with restrictor R1 only, and (3) with both restrictors.

Figure 1

Figure 2 shows the model validation as a function of speed. Tests were performed on the lubricating pumps test rig. Two typical regions can be observed: at low speed, a linear behavior indicating complete filling; at high speed, the flow rate tends to saturate, indicating incomplete filling.

Figure 2

The pump was also tested in a closed circuit, with the possibility of increasing and decreasing the inlet pressure. Figure 3 shows the flow rate at three different speeds as a function of the suction pressure measured inside the inlet volume. It is interesting to note that at 2500 rpm the pressure can be reduced to about 0.25 bar absolute without any reduction in flow rate.

Figure 3

The influence of some geometric parameters on pump filling has been analyzed. For instance, by changing the eccentricity e of the reference gears, it is possible to modify their axial height H while maintaining the same pump displacement. The new profiles are shown in Figure 4.

Figure 4

Under defective filling conditions (high speed), reducing the axial thickness significantly increases the volumetric efficiency (Figure 5).

Figure 5

More analyses and details are available in:

ALTARE G, RUNDO M, 2016: Computational Fluid Dynamics Analysis of gerotor lubricating pumps at high speed ...

ALTARE G, RUNDO M, 2017: Advances in simulation of gerotor pumps: An integrated approach

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• MASSIMO RUNDO