Three-dimensional CFD study of a β-type Stirling Engine

A three-dimensional beta-type Stirling Engine is simulated with the use of Computational Fluid Dynamics. Numerical modelling enables the study of gas properties spatial distribution and gas flow patterns, as well as the understanding of the effects of engine's design. Results include the time variation of mean pressure and pressure drop, mass flow-rate and heat transfer, as well as the time variation and spatial distribution of temperature. The biggest portion of pressure drop is observed at the interfaces between adjacent engine spaces, where the flow patterns of working gas change rapidly. In addition to that, temperature is not uniform inside each engine space at a given time instance. Moreover, a time interval of about 60 degrees of crank angle is found, during which gas is flowing towards opposite directions in two different engine spaces. The results coming from the simulation are validated against a third order one-dimensional model. The work output of the simulated engine and the indicated work of the analytical model are in good agreement. Moreover, the efficiency resulting from the simulation is close to the efficiency of a real Stirling Engine. The magnitude of the thermal losses is within the range suggested by the bibliography for a beta-type rhombic-drive Stirling Engine similar to the simulated engine.