Experimental investigation of animal tallow-based microemulsion hybrid biofuel on CI engine parameters

This study investigates the performance, combustion, and emission characteristics of a four-stroke single-cylinder CI engine fueled with microemulsion hybrid biofuel derived from animal tallow. The microemulsion was formulated by blending animal tallow (68%) with ethanol (20%) and butanol (12%) to achieve a stable, homogeneous fuel. The experimental analysis evaluates fuel blends: microemulsion hybrid biofuel (MHBF), MHBF 90 (MHBF 90% + Diesel 10%), and MHBF 80 (MHBF 80% + Diesel 20%) and compares with diesel. Performance including brake power (BP), brake thermal efficiency (BTE), brake-specific fuel consumption (BSFC), mechanical efficiency, and volumetric efficiency were analyzed. Combustion characteristics, such as cylinder pressure, heat release rate, rate of pressure rise, and mass fraction fuel burned, were assessed to understand the fuel's combustion behavior. Emission properties, including carbon monoxide (CO), unburned hydrocarbons (UHC), nitrogen oxides (NOx), and carbon dioxide (CO2), were measured to evaluate environmental impact. Results indicate that the tallow-based microemulsion biofuel exhibits better properties than conventional diesel. MHBF delivers higher brake power at 50% and 100% load, with a slight drop at 75%. MHBF80 shows lower brake power at most loads except full load, while MHBF90 increases at 25% but equals diesel at 75% and 100%. Brake thermal efficiency improves by 7.3%–20.6% at part load but matches diesel at full load. BSFC decreases at 25% and 50% yet rises at 75%. Brake mean effective pressure varies slightly, with MHBF90 aligning with diesel at full load. Mechanical efficiency improves for all blends, though volumetric efficiency remains lower. Combustion trends resemble diesel, with reduced CO, UHC, and CO2, but slightly higher NOx.