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

Abstract

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 engines, instead of being dumped into sewers and landfills.