Effect of Injection Strategy on the Combustion and Exhaust Emission Characteristics of a Biodiesel-Ethanol Blend in a DI Diesel Engine

An experimental investigation was performed on the effect of injection strategy on the combustion, exhaust emission characteristics and the particle size distribution in a small direct-injection (DI) compression ignition engine fueled with a biodiesel-ethanol blended fuel. The results obtained from the experiment of the particle distributions for the blended fuel are compared with that of diesel fuel. In addition to the distribution of the particles, exhaust emissions, such as oxides of nitrogen $(NOx)$⁠, hydrocarbon (HC), and carbon monoxide (CO) emissions, and combustion characteristics under different injection parameters were investigated. The injection parameters in terms of first injection mass and second injection mass were varied to investigate the combustion and emission reduction in the biodiesel and ethanol blended fuel. The results show that the first combustion and heat release generated from the first injection, and then the second injected fuel rapidly combusted with an extremely short ignition delay. The maximum combustion pressures and heat releases of a biodiesel-ethanol blend are generally higher than those of the ultra-low sulfur diesel (ULSD) in all cases, regardless if an equal quantity of fuel is injected. The soot and $NOx$ emissions for a blend are relatively lower than the ULSD at all test ranges. In addition, HC and CO emissions for a blend also indicated relatively low levels compared with those of the ULSD. Double injection cases for biodiesel-ethanol blend, the number concentrations of larger size particles which are closely related to the weight of smoke emissions mass were significantly reduced.