Modelling and parametric study of an efficient Alpha type Stirling engine performance based on 3D CFD analysis

As an externally heated engine the Stirling engine has the advantage of being able to efficiently exploit various waste heat sources. Computational fluid dynamic simulation (CFD) for the thermodynamic performance of such engines can provide a powerful tool to predict and improve the design and performance. Despite the advantages of alpha type Stirling engines, there has been very limited published work regarding the use of CFD modelling to improve its performance. This paper, proposed a new methodology combining the thermodynamic model with 3D CFD analysis to investigate the performance of a V-Alpha Type Stirling engine under various operating conditions and design parameters. The thermodynamic model of an alpha type Stirling engine has been developed using non-ideal adiabatic analysis and validated against experimental measurements of the engine prototype. A 3D CFD model was then developed and the results, compared to the those of the thermodynamic model, showed good agreement in predicting the indicated power. The CFD model was used to carry out a parametric study to investigate the effects of various design parameters and operating conditions such as, regenerator porosity, charge pressure, matrix wire diameter, dead volume and hot/cold ends temperatures on the engine performance in terms of power output through predicting the PV diagram of the engine. Results showed that maximum power can be achieved by increasing the porosity up to 80% and the wire matrix diameter to 0.02 mm at a temperature of the hot and cold sides at 600 °C and 20 °C respectively. Further decreasing of the cold end temperature to −20 °C can produce 162 W. For the heater and the cooler volumes, it was found that a height of 140 mm produced the highest engine power output of 170 W. This work highlights the potential of using CFD modelling to improve the design parameters and operating conditions to enhance the performance of alpha type Stirling engines.