Effects of fuel properties on combustion and pollutant emissions of a low temperature combustion mode diesel engine

Abstract

Combustion and pollutant emission characteristics of diesel/gasoline/iso-butanol mixtures have been investigated in a low temperature combustion diesel engine at an engine speed of 1800 rpm and load of 3 bar brake mean effective pressure. The test fuels were denoted as D100 (diesel), DG (70% diesel + 30% gasoline, on a mass basis), DGB (70% diesel + 15% gasoline + 15% iso-butanol) and DB (70% diesel + 30% iso-butanol). The result reveals that blend fuels have longer ignition timing periods, delayed CA50 and higher brake thermal efficiencies than D100. Meanwhile, blend fuels have higher maximum pressure rise rates if the exhaust gas recirculation (EGR) rate is less than 14.2%, but an opposite trend is found as the EGR rate was increased sequentially. At a fixed EGR rate, blend fuels have lower CO emissions, large sized particle numbers and particle diameters, but higher HC and NOx emissions. An interesting result is that blend fuels have more nucleation mode and accumulation mode particle numbers at small EGR rate (≤14.2%), but it shows opposite change trends when the EGR rate higher than 14.2%. Furthermore, iso-butanol has a better effect than gasoline in reducing NOx and particulate matter emissions along with high levels of EGR. However, it is worth to noticed that diesel/iso-butanol has the highest number concentration of sub-10 nm particles.