An innovative method for enhancing the combustion and emission performance of a zero-carbon fuel Wankel rotary engine with high ammonia to hydrogen ratio and stoichiometric ratio conditions

Driven by the goal of carbon neutrality, ammonia-hydrogen blended fuel has emerged as a promising alternative for achieving zero carbon emissions, owing to the high reactivity of hydrogen and the high energy density and excellent storage and transportation characteristics of ammonia. In this study, a three-dimensional computational fluid dynamic model based on the Mazda 13B Wankel rotary engine was established, and the converge software was employed to conduct numerical simulations of the combustion process under high-speed, high-load, and stoichiometric conditions. The effects of different excess air ratio and ammonia volume fraction on engine flow characteristics, combustion performance, emissions, and work output capability were systematically analyzed. The results show that moderately reducing excess air ratio to 1.4 significantly improves the thermal efficiency, reaching 37.68 %. Under stoichiometric conditions, increasing the ammonia content to 30 % yields the maximum work output capability representing increases of 12.14 % and 12.57 % in indicated mean effective pressure and Indicated thermal efficiency, respectively, compared to the 20 % ammonia condition. In addition, nitrogen oxide emissions exhibit a monotonic decreasing trend with increasing ammonia content. The results indicate that properly matching the ammonia-hydrogen ratio and the air-fuel ratio not only enhances the thermal efficiency and power performance of the Wankel rotary engine, but also effectively suppresses nitrogen oxide emissions. This provides both theoretical support and a viable technical pathway for the development of high-performance zero-carbon fuel engines.