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Abstract
Compression ignition (CI) engines are facing strong restrictive emission norms globally, which demand extremely low oxides of nitrogen (NOx) and particulate matter (PM) emissions. Homogeneous charge compression ignition (HCCI) engine is a very attractive solution to meet these stringent emission challenges due to its capability to simultaneously reduce NOx and PM. In this study, HCCI combustion was investigated using different test fuels such as diesoline (15% v/v gasoline with diesel), diesohol (15% v/v ethanol with diesel), and diesosene (15% v/v kerosene with diesel) vis-a-vis baseline mineral diesel. A dedicated fuel vaporizer was used for homogeneous fuel–air mixture preparation. The experiments were performed at constant intake charge temperature (180 °C), fixed exhaust gas recirculation (EGR) (15%) at different engine loads. Stable combustion characteristics were determined for diesosene at lower engine loads, however, diesoline and diesohol yielded improved emissions compared to baseline diesel HCCI combustion. At higher loads, diesoline and diesosene showed higher knocking tendency compared to baseline diesel and diesohol. Diesohol showed lower NOx and smoke opacity, however, diesoline and diesosene showed slightly lower hydrocarbon (HC) and carbon monoxide (CO) emissions compared to baseline diesel HCCI combustion. Performance results of diesohol and diesosene were slightly inferior compared to diesel and diesoline HCCI combustion. Physical characterization of exhaust particulates was done for these test fuels using engine exhaust particle sizer (EEPS). Particle number-size distribution showed that most particles emitted from diesoline and diesohol were in ultrafine size range and baseline diesel and diesosene emitted relatively larger particles. Reduction in total particle number concentration with addition of volatile fuel components in mineral diesel was another important observation of this study.
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