Effects of waste cooking oil biodiesel addition on combustion, regulated and unregulated emission characteristics of common-rail diesel engine

The use of waste cooking oil biodiesel as diesel fuel is one of the essential measures to achieve global energy transition and sustainable development. This work aims to explore the influence mechanism of waste cooking oil biodiesel/diesel blended fuel on the combustion and emission characteristics of a common-rail diesel engine. The effects of four fuel blending ratios (0%, 10%, 20%, and 30%) on engine combustion and emission characteristics under different operating conditions were investigated experimentally. The study results showed that adding biodiesel from waste cooking oil prolongs the combustion duration and is also beneficial for combustion at medium and high load conditions (50% and 75%). For the low load condition (25%), the emission concentration showed a decreasing trend with the increase of the blending ratio. In particular, the NOx and CH3CHO emissions increased, and the Soot emission was insensitive to the blending ratio. For medium and high load conditions, as the blending ratio increases, the emission concentration decreases. Moreover, the NOx emission increased slightly. Within the scope of the current work, the addition of waste cooking oil biodiesel improves the combustion and emissions characteristics of a common-rail diesel engine for both 50% and 70% load conditions.