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

Combustion characteristics of a homogeneous charge compression ignition (HCCI) engine fuelled with n-butanol-gasoline blends were investigated on a single cylinder four stroke engine using the negative valve overlap. Results show that exhaust valve closing timing evidently affects the residual gases in the cylinder and indicated mean effective pressure (IMEP). Intake valve opening (IVO) timing affects the in-cylinder temperature and ignition timing through changing the effective compression ratio. The effect of IVO timing on ignition delay is dependent on engine speed. Furthermore, with the increase of n-butanol volume fraction in the blends, ignition is advanced, combustion duration is shortened and IMEP is decreased under the same operating condition. In addition, the n-butanol-gasoline HCCI engine is prone to knock compared to the gasoline counterpart.