Engineering Science and Technology, an International Journal, vol.52, 2024 (SCI-Expanded)
In this experimental study, the effects of the working gap between the displacer and its cylinder on the performance of a gamma configuration Stirling engine were investigated. The torque and power variations with engine speed were investigated for four different working gap values as 0.5, 0.7, 0.9, and 1.1 mm. Experiments were carried out with an LPG-fueled heater at a hot surface temperature of 375 °C and a cold surface temperature of 30 °C. Helium was used as the working mass and the tests were performed between 0.5 and 3.5 bar initial pressure with 0.5 bar ranges. According to the experimental results, the gap width has a significant effect on the gap losses and heat transfer and directly affects the performance of the gamma Stirling engine. Therefore, optimizing the gap width is necessary if the Stirling engine's efficiency is to be increased. In this study, the optimum displacer gap value was obtained as 0.9 mm for 90 mm cylinder diameter and 190 mm displacer length of a gamma Stirling engine. Maximum output power and torque were obtained at 3 bar initial pressure and 0.9 mm displacer gap as 45.06 W at 260 rpm and 2.18 Nm at 170 rpm, respectively. This study made an essential contribution to the literature by performing an experimental gap width optimization.