Reduction of NOx and Smoke Emissions in a Diesel Engine Fueled by Biodiesel Emulsion Combined with EGR

Transesterified fuels (biodiesel fuels; BDF) from vegetable oils are alternative fuels for diesel engines, they are renewable and offer potential reductions in carbon dioxide emissions. Many studies have reported that exhaust from BDF has equal or higher NOx concentrations while HC and PM emissions are significantly lower than with gas oil. The aim of the present investigation is to achieve drastic reductions in NOx emissions. Performance tests of a single cylinder DI diesel engine were conducted using water emulsified fuels from BDF and gas oil with varying water addition rates combined with cooled EGR. The result showed that at a rated output, the emulsified gas oil with water to base fuel volume ratio of 30% reduced NOx (from 1020ppm) to 190ppm with the 21% EGR condition maintaining the minimum BSEC value achieved with EGR free gas oil operation. However, the smoke density increased by 28%. The combined operation of 21% EGR and emulsified BDF with 30% water showed significant reductions in NOx (to 170ppm) without worsening smoke emissions, although the BSEC increased by 4%.