The effects of different channel geometries in the displacer cylinder, working fluids, and engine speed on the energy and exergy performance characteristics of a β-type Stirling engine with a slider-crank drive mechanism

Abstract

Stirling engines are power generation systems working with the external heating principle and converting heat energy into mechanical energy. In this study, thermodynamic analyses were performed using the data of performance tests in which helium, nitrogen, and air were utilized as working fluids in a β-type Stirling engine with a swept volume of 365 cm3 and a slider-crank drive mechanism. Moreover, the impact of different channel geometries in the displacer cylinder on engine power was revealed. In the study, three displacer cylinders, smooth, 66-slot channel, and 120-slot channel displacer cylinders, were used. Performance tests were conducted at five charge pressures varying between 1 and 5 bar, with the hot end temperature of 1000 ± 10 K and the cold end temperature of 300 ± 5 K. The heat transferred to the hot zone, thermal losses and efficiency were calculated in the energy analysis. The highest thermal efficiency was 45.50% when a 120-slot channel displacer cylinder was used with helium as the working fluid. Thermal efficiency values were 32.87% and 32.60% for nitrogen and air, respectively, under the same conditions. Entropy generation, exergy destruction, and exergy efficiency were calculated in the exergy analysis. The lowest exergy destruction was obtained using a 120-slot channel displacer cylinder with helium as the working fluid. Furthermore, the impact of engine speed on exergy efficiency was determined.