An experimental study on the development of a β-type Stirling engine for low and moderate temperature heat sources

In this study, a [beta]-type Stirling engine was designed and manufactured which works at relatively lower temperatures. To increase the heat transfer area, the inner surface of the displacer cylinder was augmented by means of growing spanwise slots. To perform a better approach to the theoretical Stirling cycle, the motion of displacer was governed by a lever. The engine block was used as pressurized working fluid reservoir. The escape of working fluid, through the end-pin bearing of crankshaft, was prevented by means of adapting an oil pool around the end-pin. Experimental results presented in this paper were obtained by testing the engine with air as working fluid. The hot end of the displacer cylinder was heated with a LPG flame and kept about 200 °C constant temperature throughout the testing period. The other end of the displacer cylinder was cooled with a water circulation having 27 °C temperature. Starting from ambient pressure, the engine was tested at several charge pressures up to 4.6 bars. Maximum power output was obtained at 2.8 bars charge pressure as 51.93 W at 453 rpm engine speed. The maximum torque was obtained as 1.17 Nm at 2.8 bars charge pressure. By comparing experimental work with theoretical work calculated by nodal analysis, the convective heat transfer coefficient at working fluid side of the displacer cylinder was predicted as 447 W/m2 K for air. At maximum shaft power, the internal thermal efficiency of the engine was predicted as 15%.