The application of an innovative integrated Swiss-roll-combustor/Stirling-hot-end component on an unpressurized Stirling engine

Highlights: • An innovative combined Swiss-roll-combustor/Stirling-bottom-plate unit is proposed and tested. • It reinforces the Stirling engine's bottom plate and promotes its heat transfer rate. • It can burn biofuels such as DME and syngas without preheating. • The combustion efficiency of DME is above 90%. • The system generates 18.7 W electric power under a moderate temperature difference of 254 °C. An innovative integrated Swiss-roll-combustor/Stirling-hot-end component is proposed in this paper. A power generation system in conjunction with a Stirling engine is also built around the component and tested. The Stirling engine is a compact-size, unpressurized, γ-type engine that uses air as working gas. The Swiss-roll combustor is laden with small catalytic beads to decrease the ignition temperature and improve combustion efficiency. Experiments respectively burning dimethyl ether and syngas were conducted to better understand the potential of the system on tapping into green biomass energy. The marriage between the Swiss-roll combustor and the Stirling engine's hot end offers many advantages as follows: The structural support from the spiral-channel wall in the Swiss-roll combustor enables the bottom wall of the Stirling engine to be made very thin, which improves the rate of heat transfer from the heat source to the engine significantly. Meanwhile, the system inherits those advantageous features in combustion from the Swiss-roll combustor, including a broader range of fuel/air ratio, higher combustion efficiency, and higher efficiency in harvesting the heat of flue gas. Compared to the predecessor of the present engine, the incorporation of the proposed component is proven to improve engine's performance remarkably. In the experiment of burning dimethyl ether, the system produced 18.7 W of electric power and achieved 2.4% thermal to electric efficiency under a temperature difference of 254 °C. Such performance is remarkable among atmospheric-pressure Stirling engines. The proposed component has accomplished its design goal and would hopefully inspire new ideas for the development of green-energy Stirling-engine power generation systems in the future.