Collaborative optimization design of intake and combustion chamber structures for heavy-duty natural gas engines under knock limitation

With the increasing attention to environmental issues, the selection of suitable alternative fuels for internal combustion engine has become a hot topic in research. Natural gas engines have many advantages and are considered a promising solution. However, there is still a lack of systematic research on heavy-duty natural gas engines in practical applications. The optimization of thermal efficiency is urgently needed due to knock limitations. This paper proposed two different intake schemes, and collaborative optimization research were conducted by combining two bowl shaped combustion chambers. The combustion phase was optimized under knock limitations. The influence of air flow and combustion characteristics on thermal efficiency of inlet and combustion chamber was analyzed. The distribution of tumble flow, swirl flow and turbulent kinetic energy in cylinder and their influence on thermal efficiency were emphasized. All optimized schemes improved the combustion rate, shortened the ignition delay period by 30 %, and improved the indicated thermal efficiency to over 43.5 %. The scheme using double tangential intake ports and B1 bowl shaped combustion chamber achieved the highest indicated thermal efficiency of 43.67 %.