Abstract
The growing global energy demand and the urgent need to reduce greenhouse gas emissions have driven significant interest in sustainable and alternative fuels with biogas emerging as a promising renewable energy source derived from the anaerobic digestion of organic waste. Despite its carbon-neutral combustion and waste-to-energy potential, biogas faces challenges, such as low energy density and slow flame propagation, limiting its direct use in conventional diesel engines. This study explores the feasibility of using biogas in a four-stroke, single-cylinder, water-cooled, direct-injection diesel engine operating in dual-fuel mode with diethyl ether (DEE) employed as a combustion enhancer blended with diesel in varying proportions. A custom-designed Venturi-style biogas-air mixer was optimized using ANSYS Fluent CFD simulations to ensure efficient fuel mixing, and engine performance and emissions were evaluated at a constant speed of 1500 rpm under varying loads, biogas flow rates (2, 4, and 6 L/min), and DEE blending ratios (5, 10, and 15%). Results showed that dual-fuel operation with biogas significantly reduced NO (x) emissions due to its lower flame temperature, but increased HC and CO emissions due to its high CO(2) content and low combustibility, while the addition of DEE improved ignition, combustion efficiency, and engine performance. The optimal configuration of a 2 L/min biogas flow rate and 5% DEE blend achieved the best balance of increased brake thermal efficiency (BTE), reduced brake-specific fuel consumption (BSFC), and minimized emissions, demonstrating the potential of DEE-enhanced biogas-diesel blends in dual-fuel engines as a practical pathway for integrating renewable energy into existing systems and advancing sustainable energy solutions in transportation and power generation.