Gerotor Pump

This example shows how to model, parameterize, and test a gerotor pump.

Model

The following figure shows a model of the gerotor pump with a lubrication system. The flow circuit consists of an inlet system upstream of the pump, the gerotor pump and a load system downstream of the pump.

Gerotor Pump Subsystem

This subsystem shows how the gerotor pump is modeled. The gerotor pump comprises of an outer gear (driven gear) and an inner gear (driving gear) mounted on a rotating shaft, modeled as an angular velocity source. For the pump modeled here, the inner gear teeth profile is based on a trochoid curve geometry, and the outer gear teeth profile is a conjugate of the inner gear teeth profile. Gerotor pump is a positive displacement type pump, as the volumetric flow is effectively produced by the continual suction and delivery actions performed by the cyclical variation of the volume between the teeth of the mating gear set. This liquid volume between the mating gears can be divided into a number of sub-volumes or chambers which are connected with the adjacent ones through a gap due to teeth (or tip) clearance leading to tip leakage between chambers. The inlet and outlet port volumes are connected through a leakage flow called face leakage resulting from the clearance between the gear faces and housing inner faces. The volumes of the chambers change as the pump rotates and they are connected to the inlet port volume and outlet port volume through port area profiles. The number of variable volume liquid chambers equal the number of outer gear teeth.

Inlet System Subsystem

This subsystem shows a representation of a inlet system or suction system upstream of a gerotor pump. The inlet system is modeled using a combination of pipes, bends, sudden area changes and an orifice representing a pressure drop across a filter. These components contribute to pressure drop upstream of the pump.

Load System Subsystem

This subsystem shows a representation of a lubrication and cooling system in an automotive where a motor is lubricated and cooled by the delivery flow of a gerotor pump. The load system is modeled using a combination of pipes, bends, sudden area changes, and orifices representing the pressure drop across a heat exchanger and orifices at entry to stator and rotor. All components contribute to load system pressure drop. The thermal effects are not considered in this model as it is purely isothermal.

Simulation Results from Simscape™ Logging

This model generates a plot of the mass flow rate and pressure at the outlet of the gerotor pump versus time.