A 3D-CFD study of a γ-type Stirling engine

Abstract

The goal of this work is to perform detailed 3D CFD analysis of heat transfer and flow dynamics inside a commercial gamma-type Stirling engine, including its structural details and variability of the working spaces. The study focuses on an impact of different initial engine parameters, i.e., filling pressures, rotational speeds and heater temperatures, on the engine's characteristics. One of the biggest advantages of using CFD in such kind of problems, is that it allows to reduce models uncertainty resulting from inaccurate assumptions inherent in the low-order models (analytical formulas for heat transfer coefficient or pressure losses etc.). Such empirical formulas are based on the literature data, therefore they are valid only for some range of engines' operational conditions. The results were validated against available experimental data, showing good agreement in terms of overall trends. Comparison of different turbulence and regenerator models demonstrated their little impact on the engine indicated work. The applied CFD model allowed us to accurately and deeply analyse 3D unsteady flow features including the velocity field, vorticity, temperature, friction coefficient and production/dissipation of the turbulent kinetic energy. We focused on identification of recirculation/stagnation regions as well as the regions of increased turbulence intensity.