Combustion and emission characteristics of a HCCI engine fuelled with n-butanol–gasoline blends

Biobutanol, i.e. n-butanol, is a promising alternative fuel or fuel blend to gasoline to reduce the consumption of fossil fuel and carbon dioxide emissions from spark ignition (SI) and homogeneous charge compression ignition (HCCI), also known as controlled autoignition (CAI), engines. In this work, investigation was conducted on a single cylinder port fuel injection four-stroke HCCI/CAI engine fuelled with gasoline (Bu0), the blend containing 30% n-butanol and 70% gasoline by volume (Bu30), and pure n-butanol (Bu100). The HCCI/CAI operation was achieved by the negative valve overlap strategy through variable exhaust and intake valve timing and lift devices. The results show that independent of engine speeds at a given exhaust valve closing (EVC) timing, the onset of the autoignition occurs earlier and combustion duration becomes shorter when an increasing amount of n-butanol is used in place of gasoline. The increase in the engine speed also advances the autoignition timing. However, indicated mean effective pressure (IMEP) decreases with increasing n-butanol in the blends and engine speeds. Furthermore, the effect of n-butanol on the emissions was studied, including oxides of nitrogen, formaldehyde, acetaldehyde, ethanol and aromatics in the engine exhaust.