Lean Combustion Enhancement and Decarbonization Technologies for Natural Gas Engines

This study explores key technological challenges and innovative strategies for improving the combustion performance and emission characteristics of low-carbon fuel engines, with a focus on natural gas applications. The core bottlenecks of natural gas combustion, including slow combustion speed and high methane slip under lean burn conditions due to wall quenching, crevice effects, and the long distance of flame propagation from the ignition zone to the whole cylinder, are analyzed. The decarbonization of engines further aggravates these issues. Technological solutions are summarized in four categories, including turbulence enhancement, high-energy ignition, fuel reactivity modification, and fuel synergy with zero-carbon fuels. Geometry modifications of the combustion chamber, dual-fuel operation, pre-chamber ignition, and fuel activation are systematically reviewed and evaluated. A fusion technology integrating diesel pilot ignition with jet flame propagation is analyzed as a new combustion concept, termed induced jet flame combustion. This approach demonstrates significant potential in enhancing both combustion efficiency and stability, especially for lean burn conditions. This work highlights the role of natural gas engines as a transitional technology and a support platform for ultralow-emission and high-efficiency power systems fueled with low/zero-carbon fuels in the context of global decarbonization goals.