An investigation into bioethanol homogeneous charge compression ignition (HCCI) engine operation with residual gas trapping

Given the increasing interest in renewable fuels, bioethanol has been successfully used in conventional internal combustion engines. However, its application in homogeneous charge compression ignition (HCCI) engines requires various approaches, such as high compression ratios and/or intake charge heating, to achieve auto ignition. The approach documented here utilizes the trapping of internal residual gas (as used previously in gasoline-fueled controlled auto ignition engines) to lower the thermal requirements for the auto ignition process. In the present work, the achievable engine load range is controlled by the degree of internal trapping of exhaust gas, supplemented by moderate intake charge heating. Moderate intake heating extends the narrow auto ignition load window while varying the inlet valve timing extends the upper load range. Nitrogen oxide (NOx) emissions are characteristically low, because of the nature of homogeneous combustion.