Effects of exhaust gas recirculation on combustion and emissions of a homogeneous charge compression ignition engine fuelled with primary reference fuels

The effects of exhaust gas recirculation (EGR) of primary reference fuel on combustion and emissions of a homogeneous charge compression ignition (HCCI) engine are investigated. The results show that EGR delays the ignition timing, slows down the combustion reaction rate, reduces the pressure in cylinder, and extends the HCCI operation region. The maximum indicated thermal efficiency of fuels with different octane numbers appears in the region of high EGR rate and large fuel:air equivalence ratio. In the region of high EGR rate, hydrocarbon emissions rise up sharply as the EGR rate increases. Carbon monoxide emissions increase with the increase in EGR rate. Nitrogen oxides emissions increase abruptly as knocking combustion occurs.