Influence of the fuel compositions on the homogeneous charge compression ignition combustion

Homogeneous charge compression ignition (HCCI) engines are drawing attention as the next-generation internal combustion engine, but have not been put to practical use because of several issues. One of the issues is that increasing the fuel charge causes rapid combustion in the combustion chamber, which results in knocking that limits its operation region. In this study, the focus was put on a method to increase the operation region of HCCI engines by mixing two fuels with different reactivities. First, dimethyl ether (I)ME), n-butane, or hydrogen was mixed with methane to investigate how the changes in mixing ratios affected the oxidation reaction of the pre-mixture based on numerical calculations with elementary reactions. From the calculation results, applicable types of double componential fuels for HCCI engines were considered. Based on the results of the consideration, DME or n-butane was mixed with methane to conduct combustion experiments and to clarify mixing conditions of the double componential fuels that realize high output and high thermal efficiency simultaneously.