Combustion Study of Biofuel Derived from Waste Fish Oils in Internal Combustion Engines

Abstract

The rising global energy demand, the depletion of fossil fuel reserves, and the environmental challenges associated with waste cooking oil disposal highlight the need for cleaner and more sustainable fuel alternatives. This thesis investigates the production, characterization, and en gine application of biodiesel derived from waste cooking oil, aiming to establish an efficient and environmentally responsible pathway for its utilization in existing diesel engines. Waste cooking oil was collected, stored, and pretreated following proper handling practices to ensure feedstock quality. Biodiesel was produced through an optimized transesterification pro cess in which the effects of alcohol-to-oil ratio, catalyst concentration, reaction time, and reac tion temperature were evaluated. The produced biodiesel was purified and assessed according to ASTM D6751 and EN 14214 standards to verify its physicochemical suitability as a diesel substitute. Fuel blends of B5, B10, B20, and B30 were then formulated and evaluated to en hance fuel stability and better understand the influence of biodiesel concentration on engine behaviour. Engine tests were conducted on a Deutz Z-MWM D302-1 single-cylinder, naturally aspirated, direct-injection diesel engine. Performance characteristics, fuel consumption, and pollutant emissions were examined across the different biodiesel blends. The validated experimental data were further used to develop a combustion model in CONVERGE CFD, providing numerical access to key spray and combustion characteristics such as in-cylinder pressure, temperature, heat release rate, and ignition delay. The optimized production process yielded high-quality biodiesel fully compliant with ASTM D6751 and EN 14214 specifications. Engine results showed stable operation for all blends, with a modest increase in CO emissions and a clear reduction in NOx, attributed to the intrinsic oxygenated nature of biodiesel and its lower combustion temperature. The modelling results supported and deepened the experimental findings, overcoming limitations in available meas urement techniques. Overall, this work demonstrates the viability of waste cooking oil biodiesel as a sustainable fuel and provides both experimental and computational contributions to the understanding of its combustion behaviour in diesel engines, confirming that WCO biodiesel and its blends represent an efficient, low-cost, and environmentally responsible fuel pathway with strong potential for real-world implementation