Effect of air inlet angle variation on the efficiency of hydrogen-powered Stirling engines

Abstract

Stirling engines are significant for their high efficiency, low emissions, and capability to use various heat sources for renewable energy systems, waste heat recovery, and applications where low maintenance is crucial. Hydrogen-powered Stirling engines combine the high efficiency of Stirling engines with the clean-burning nature of hydrogen fuel. This study introduces a new approach by optimizing the air inlet angle in a hydrogen-fueled Stirling engine using CFD simulations. The effects of air inlet angle variation (60°, 90°, and 120°) on the performance of a hydrogen-fueled Stirling engine are studied. Unlike prior studies focusing on fuel type or scale, this work highlights the effects of inlet geometry on inducing combustion dynamics, thermal behavior, and engine performance. The parameters such as power output, thermal efficiency, hydrogen mass fraction, velocity, peak temperature, and flow organization are examined. Results show that the 90° air inlet angle offers the best performance, improving thermal efficiency and power output by 15% and 17.6%, respectively, compared to the 60° angle case, and by 12% and 11% compared to the 120° angle configuration. Enhanced performance is attributed to improved mixing, more complete hydrogen combustion, and a 28% increase in peak temperature. In contrast, the 60° case causes less efficient flow patterns and delayed combustion. These insights present a valuable framework for optimizing inlet angle design in hydrogen-fueled Stirling engines, advancing their potential for sustainable energy applications.