Performance and operating modes of a thermal-lag Stirling engine with a flywheel

The thermal-lag Stirling engine is a type of external combustion engine that differs from traditional Stirling engines in that it has only one cylinder and one piston. In the cylinder, a porous medium with a temperature gradient is installed to separate high-and low-temperature regions. Although its construction is simpler than that of the traditional Stirling engine, the thermal-lag Stirling engine has numerous operating modes at different heating temperatures and initial speeds. In this study, a theoretical model for analyzing the performance and operating modes of a thermal-lag Stirling engine is proposed. The model was solved by the method of multiple scales. The results indicate that the engine is operated by the thermal-lag effect caused by imperfect heat transfer in working spaces. Three operating modes were predicted: the decay, swinging, and rotating modes. Seven operating regions for the different modes were illustrated in the temperature-ratio and frequency-ratio domain. The transitions between modes were also predicted using the proposed theory. The performance of the proposed engine under different loadings in a stable operating state was evaluated. The dependence of the indicated power on engine speed was also determined. The results reveal that an optimal loading exists for achieving maximum power. A minimum value of the operating engine speed was also predicted by the proposed model.

Automated summary

This study proposes a theoretical model for analyzing the performance and operating modes of a thermal-lag Stirling engine. The model is solved by the method of multiple scales, and it predicts the performance, operating regions, and transitions between different modes. The performance of the engine under stable operating state and the dependence of the indicated power on engine speed are evaluated. An optimal loading and a minimum operating speed are also predicted.