Dynamic simulation of thermal-lag Stirling engines

The present study is concerned with dynamic simulation of thermal-lag Stirling engines. A dynamic model is built and incorporated with a thermodynamic model to study the engine start process. A prototype engine is designed and simulated by using the dynamic model. In the simulation, different operating modes, including rotating mode, swinging mode, swinging-to-rotate mode, and swinging-to-decay mode, have been observed. The rotating mode is desired and can be achieved if the operating parameters are properly designed. In a poor design, the engine may switch to the swinging or even the swinging-to-decay mode. In addition, it is found that geometric parameters, such as bore size, stroke, and volume of working spaces, also determine the operating mode of the engine. Brake thermal efficiency of the engine is monotonically reduced by increasing engine speed. However, study of the dependence of the shaft power of the engine speed shows that there exists a maximum value of the shaft power at an optimal operating engine speed. The optimal engine speed leading to maximum shaft power is significantly influenced by the geometrical parameters.