Combustion analysis of higher order alcohols blended gasoline in a spark ignition engine using endoscopic visualization technique

Abstract

The experimental study was carried out on the port fuel injection system installed spark-ignition engine fuelled by 1.5%, 3%, and 5% higher order alcohol such as 1-hexanol and 2-heptanol blended gasoline. In this study, the endoscopic combustion visualization technique was employed to compare and analyze the changes observed in the spatial flame characteristics between the alcohol blends and sole gasoline. The Correlated Colour Temperature (CCT) method was used to predict the flame temperature distribution from the captured flame images. Also, the effect of blending alcohols on engine combustion, performance, and emission characteristics was studied. The endoscopic results revealed that the flame spread region with respect to different CA positions increases with the alcohol blending ratio in the sole gasoline at the early and middle stages of the combustion. Further, the engine characteristics study revealed that 5% hexanol and heptanol blends gave a brake thermal efficiency of 25.8% and 25.7%, respectively, which were higher than sole gasoline, having 24.8% at full load. In addition, it was observed that the early start of combustion (SoC) and a faster burn rate associated with alcohol blends raise the cylinder pressure and heat release rates (HRRs) and thereby result in higher peak pressure and HRR with slight advancement in the CA position. At 8 kW, the CO and HC emission of 5% 1-hexanol and 2-heptanol blends was decreased by about 10.3% and 13.7%, and 9.5% and 8%, respectively, and NO emission decreased slightly with a rise in alcohol concentration in the mix when compared to gasoline.