Effect of compression ratio on combustion, performance, and emission characteristics of compression ignition engine fueled with palm (B20) biodiesel blend

Limited fossil fuel reserves led to focus on alternatives fuels for combustion engines. Several studies reported optimal (20%) biodiesel blend for utility in compression ignition engine at constant compression ratio. Literature lacks on the study of palm-based biodiesel in blended form at varying engine compression ratios. In this study, an initiative was undertaken to study the effect of variable compression ratio (16:1, 17:1 and 18:1) on various engine characteristics by fuelling 20% palm biodiesel blending compression ignition engine. The ignition delay period decreased, whereas the peak cylinder pressure and brake thermal efficiency increased with increase in the engine compression ratio from 16:1 to 18:1. At 3.5 bar bmep, brake thermal efficiency values were observed to be 28.9, 30.8 and 33.8% at 16:1, 17:1 and 18:1 CRs, respectively in B20 fuel. Moreover, increasing compression ratio from 16:1 to 18:1, the average reduction in emissions of hydrocarbon, carbon monoxide and smoke opacity were observed to be 47.8, 41.0 and 35.7%, respectively whereas, oxides of nitrogen emissions increased by 41.1%. Thus, it is inferred that B20 fuel performed well at high engine compression ratio. •B20 fuel utilized in CI engine by varying bmep and compression ratio.•Shorter ignition delay with B20 when compared to diesel.•PCP increases with increasing CR led to improve BTE.•Reduction in CO, HC and smoke emissions with increasing CR.•NOx emission increases with increasing compression ratio.