Impact of enhanced oxygen levels on cyclic variability and performance parameters in a diesel engine fuelled by food waste-derived biogas

The global push to reduce fossil fuel dependence and minimize environmental impact has heightened interest in renewable alternatives like biogas. Despite its promise, dual-fuel diesel engines operating with biogas often face challenges such as reduced efficiency, unstable combustion, and elevated emissions. This study evaluates the impact of oxygen enrichment ranging from 21% to 27% by volume on the performance, combustion stability, and emission behavior of a 5.2 kW single-cylinder diesel engine running in dual-fuel mode with 50% food waste-derived biogas (BG50). Oxygen was introduced through the intake manifold in 2% increments across various engine loads. The findings reveal that oxygen enrichment significantly improved combustion by shortening ignition delay, reducing cyclic variations, and boosting power and thermal efficiency. At 27% oxygen, brake thermal efficiency increased by 18.37%, brake power by 22.22%, and peak cylinder pressure by 27.16% compared to unenriched BG50. Emissions of carbon monoxide and unburnt hydrocarbons were reduced by 20% and 27.27%, respectively, while nitrogen oxide emissions rose by 46.61% at full load. Cyclic variability, measured through the coefficient of variation of indicated mean effective pressure and peak pressure, decreased to below 2%, indicating improved combustion consistency. This study provides a novel and comprehensive quantitative analysis of oxygen-enriched biogas combustion and offers critical insights for optimizing engine performance in sustainable energy applications, while highlighting the need to manage NO x emissions.