Effect of inherent oxygen mass fraction of alcohol blends with diesel on combustion and emission parameters

Abstract

Increasing air pollution and implementation of stricter emission regulations led to the research for the clean combustion concept of combustion engines. To resolve this concern, it is important to look for a clean and stable combustion concept that can adapt easily to an old existing engine as well as newer engines. The present study was performed to investigate the combustion stability and emission for blends of methanol (M), ethanol (E), and butanol (B) to evaluate the effect of their inherent oxygen content. Alcohol blends were prepared for two different oxygen mass fractions of 2.5% and 5% oxygen, m/m (defined as M2.5, E2.5, B2.5 and M5, E5, B5). For this, different volume fraction of respective alcohol was required (M2.5 and M5 contained 5.2% and 10.3% methanol respectively, E2.5 and E5 contained 7.4% and 14.8% ethanol respectively, B2.5 and B5 contained 11.7% and 23.3% butanol respectively).Detailed combustion analysis was performed for the alcohol blends (2.5% and 5% oxygen mass fraction) using the parameters like cycle-to-cycle analysis, coefficient of variation, combustion phasing etc. M5 showed the better stable combustion considering the lowest coefficient of variation for CA50 and indicated mean effective pressure. Moreover, the performance of E5 showed improved efficiency with brake thermal efficiency (BTE) of 27.94% and reduced brake specific fuel consumption. Significant reductions in hydrocarbon (HC), smoke and carbon dioxide (CO 2 ) emissions were recorded for 2.5% and 5% oxygenated condition. M5 showed lowest emission level among tested fuel with 20% lower oxide of nitrogen (NO) and 50% lower HC.