Performance Evaluation for a 100 W Stirling Engine

A small 100 W displacer-type Stirling engine, Ecoboy-SCM81 has being developed by a committee of the Japan Society of Mechanical Engineers. The engine contains unique features, including an expansion cylinder which is heated by either combustion gas or direct solar energy. Also, a simple cooling system rejects heat from the working gas. A displacer piston has both heating and cooling inner tubes for the working gas which flows to and from outer tubes. A regenerator is located in the displacer piston. To improve the engine performance efficiently, an analysis model for the prototype engine was developed. The analysis model is based an isothermal method considered a pressure loss in the regenerator, a buffer space loss caused by a leakage of the working gas, and a mechanical loss. In the case of a calculation for the pressure loss, the analysis model adopts a new suggestion that considers effects of entrance and exit area on the velocity distribution in the regenerator. The buffer loss is calculated with three kinds of methods, an isothermal, an adiabatic and a heat transfer model to consider a suitable method for the buffer space model. Some improvement methods for the prototype engine are discussed after the effectiveness of the analysis model is evaluated.