A Porous Media Numerical Approach for the Simulation of Stirling Engine Regenerators

The Stirling engine design process is mostly focused on the study of the engine regenerator, whose thermal efficiency is strictly related to the global efficiency of the engine. The present work aims to setup a numerical model by means of OpenFOAM libraries to simulate the engine regenerator as a porous media, in order to reduce the overall computational cost of the simulations and to obtain a suitable model that can be eventually used for topological optimization. The solid part of the numerical domain, i.e. the stoked wires, is represented as a zone with the highest porosity, whereas intermediate areas are defined in order to simulate the boundary layers in proximity of the walls. The presence of porous media is modelled by introducing a Darcy-type pressure drop in the momentum equation, whereas in the energy equation the thermal properties of the solid, intermediate and fluid materials are modelled by means of a linear function of the porosity value in the domain. After a process of tuning, the results obtained with this model are reported for different flow conditions in terms of both aerodynamic and thermal performances, thus showing a good agreement with the numerical results obtained with a more classical CFD methodology.