Use of some advanced biofuels for overcoming smoke/NOx trade-off in a light-duty DI diesel engine

Diesel engines do not have the luxury of a thoroughly premixed charge like gasoline engines. Fossil-diesel auto-ignites quickly after its injection, resulting in high smoke and NOx emissions due to heterogeneous fuel/air distribution and high combustion temperatures. Injection timing modification and exhaust gas re-circulation can provide ample duration for air and fuel to pre-mix 'inside' the cylinder and burn under low temperatures which reduces harmful NOx/smoke in a diesel engine simultaneously. This study proposes the use of three advanced biofuels with a low cetane number, viz. dimethyl carbonate (DMC), iso-butanol and n-pentanol with blend-ratios of 15, 38 and 45 vol% in diesel, respectively (that corresponds to a uniform oxygen-content of 8%) in a single-cylinder DI diesel engine. The engine characteristics were investigated under high loads@1500 rpm by controlling the charge dilution and combustion phasing using moderate EGR rates and start of injection (SOI) modification. The blends presented large amounts of premixed combustion that resulted in high in-cylinder pressures and heat release rates. Results indicated that NOx and smoke could be simultaneously reduced using the combination of the proposed advanced biofuel/diesel blends, late injection and moderate EGR rates. However, there is an increase in HC and CO emissions at all test conditions. (C) 2016 Elsevier Ltd. All rights reserved.