A strongly coupled simulation model for external gear machines considering fluid-structure induced cavitation and mixed lubrication

This paper presents a strongly coupled simulation model, Multics HYGESim, for the displacing action of external gear machines coupled with a detailed simulation of the main lubricating interfaces (i.e. the gaps at the gear tooth tips, at the gear lateral side, and at the journal bearings). In order to allow this strong coupling, the solution of the main displacing action realized by the tooth space volumes is tied with the solution of the lubricating gaps through asynchronous time stepping. This approach is made possible by the introduction of the numerical impedance of the floating films, and by considering the dynamic fluid-structure interaction and boundary friction of the bodies with both the film and displacement chamber pressures. The resulting floating body dynamics are solved to inform the solution of both the displacing action and the lubricating films of the machine. This model is then used to simulate a reference reversible pressure-compensated external gear machine. An experimental activity is performed for preliminary validation of the model. Notable results for this reference machine are then discussed to demonstrate model potentials.