Investigation on combustion and emission performance of a common rail diesel engine fueled with diesel-ethylene glycol dual fuel

Highlights: • Low energy ratio of ethylene glycol is applied on a dual fuel engine. • Ethylene glycol is easy to auto-ignition from 0.96 MPa to 1.29 MPa. • Combustion is improved by use of ethylene glycol. • The trade-off relationship between NOx and soot emissions disappears. • The use of ethylene glycol can reduce the emissions of NOx, CO₂ and UFPs. EG (ethylene glycol) is a good oxygenated fuel for diesel due to structure and thermal conductivity. Based on dual fuel experiment on a modified diesel engine, combustion and emission characteristics are investigated at 1400 r/min with four low EG energy ratio (EGER) (named EG0, EG5, EG10 and EG15 respectively). Combustion results show that the peak cylinder pressure, the peak heat release rates (HRRs) and pressure rise rate increase when EG is used in fumigation mode. However, the maximum in-cylinder temperature changed little. Owing to the auto-ignition character, EG is ignited before diesel injection at 1.29 MPa BMEP, ignition delay is shorten from 0.97 MPa to 1.29 MPa BMEP, and postpone slightly from 0.48 MPa to 0.64 MPa BMEP. Combustion duration decreases with the increase of EGER. The brake thermal efficiency (BTE) is lower and the diesel equivalent brake specific fuel consumption (BSFC) is higher followed by the rise of EGER. For emissions, the NO_X, THC, CO₂ and soot emissions decrease followed by the rise of EGER at the same time, while CO emissions increase. EG reduce ultrafine particles (UFPs) and decrease the average diameter of UFPs particularly. In conclusion, EG is found to be a good choice for dual fuel diesel engine from 0.81 MPa to 1.29 MPa BMEP in the aspect of performance and emissions.