A sustainable and eco-friendly fueling approach for direct-injection diesel engines using restaurant yellow grease and n-pentanol in blends with diesel fuel

•Waste yellow grease from restaurants is recycled for use in diesel engines.•Ternary blends of yellow grease, n-pentanol and diesel has less viscosity.•50% of diesel is replaced by up to 45% recycled component and 20% bio component.•Ternary blends showed less NOx and smoke opacity but high HC and CO emissions.•Ternary blends delivered improved BSFC with n-pentanol addition. Yellow grease from restaurants is typically waste cooking oil (WCO) that is free from suspended food particles and with free fatty acid (FFA) content less than 15%. This study proposes an approach to formulate a renewable, eco-friendly fuel by recycling WCO with diesel (D) and n-pentanol (P) to improve fuel-spray characteristics. Three ternary blends (D50-WCO45-P5, D50-WCO40-P10 and D50-WCO30-P20) were selected based on the stability tests and prepared with an objective to substitute diesel by 50% with up to 45% recycled component (WCO) and up to 20% bio-component (n-pentanol) by volume. The fuel properties of these ternary blends were measured and compared. The effect of these blends on combustion, performance and emissions of a stationary DI diesel engine was analyzed in comparison with diesel and D50-WCO50 (50% of diesel+50% of WCO) with and without exhaust gas recirculation (EGR). Results indicated that addition of n-pentanol showed improved fuel properties when compared to D50-WCO50. While viscosity reduced up to 45%, cetane number and density were comparable to that of diesel. Addition of n-pentanol to D50-WCO50 presented improved brake specific fuel consumption (BSFC) for all ternary blends. BSFC of the blend D50-WCO30-P20 was 8.8% higher than diesel at high engine load without EGR. Brake thermal efficiency (BTE) for D50-WCO30-P20 blend is comparable to diesel due to improved atomization. However it deteriorated by up to 15.7% at 30% EGR. Smoke opacity reduced by up to 13.6% for D50-WCO30-P20 blend without EGR at high engine load. But it aggravated up to 73% at 30% EGR for D50-WCO30-P20 blend. NOx emission increased with increase in n-pentanol content in D50-WCO50 but remained lower than diesel. However increasing n-pentanol content beyond 20% may increase NOx emissions higher than diesel. NOx can be decreased three-fold using EGR. HC emissions increased and CO emissions remained unchanged with increasing n-pentanol in the blends. By adopting this approach, WCO can be effectively reused as a clean energy source by negating environmental hazards before and after its use in diesel