Influence of high compression ratio on the performance of ethanol-gasoline fuelled lean burn spark ignition engine at part throttle condition

Abstract

As a viable solution to meet rising energy costs and reduce greenhouse gases, alcohol fuels are considered the most promising renewable fuel and ethanol is a potential fuel for spark ignition engines. In the present study, experiments were conducted on a spark ignition engine modified from a diesel engine that uses an ethanol-gasoline mixture as fuel under lean operating conditions. The engine was operated at 1500 rpm at a high compression ratio of 10.5:1. The different proportions of ethanol namely 5 %, 10 %, 20 %, and 30 % with gasoline, were studied and compared. The throttle was set to 25 % to operate the engine at various equivalence ratios to study the performance and emissions. Experimental outcomes reveal that 10 % ethanol with gasoline enhances the brake thermal efficiency and brake power by 7 % and 4.5 % respectively, due to an enhanced compression ratio. Further, the gasoline lean limit is also extended from 0.74 to 0.70 equivalence ratios. In addition, ethanol blending with gasoline enhances the combustion characteristics and heat release rates. The influence of ethanol greatly decreases cycle-by-cycle variations and hydrocarbon emissions. Adopting a high compression ratio and lean-burn operation can effectively improve performance and decrease emissions in an ethanol-gasoline-fuelled spark ignition engine.