Performance and Emission Characteristics of Biodiesel-Butanol Blends in Variable Engine Speeds and Loads

Abstract

This study investigates the impact of biodiesel–butanol fuel blends on the performance and emissions of a single-cylinder diesel engine under various loads and speeds. Biodiesel was blended with butanol in volumetric ratios of B100 (pure biodiesel), B90Bu10, B80Bu20, and B70Bu30 to evaluate their effects on specific fuel consumption (SFC) and carbon dioxide (CO₂) emissions. Experimental results indicate that at 25% engine load, the B80Bu20 blend achieved the lowest SFC at 1200 RPM, reducing fuel consumption by 8.5% compared to B100. At 50% load and 1800 RPM, B90Bu10 showed an 11.2% improvement in fuel efficiency over B100. Conversely, higher butanol content (B70Bu30) led to increased SFC at high engine speeds (2400 RPM), likely due to the lower cetane number and heating value of butanol. Regarding emissions, the B80Bu20 blend produced the lowest CO₂ emissions across all engine speeds, achieving a 12.6% reduction at 1800 RPM compared to the B100. This suggests that the moderate addition of butanol enhances combustion efficiency while reducing carbon output. Compared to previous studies that often focused on constant engine load or a single operating speed, this research comprehensively assesses multiple load-speed conditions, highlighting the optimal balance point for fuel blend composition. The findings suggest that B80Bu20 can be a viable alternative fuel for small-scale diesel engines, particularly in applications such as small fishing vessels and rural generators where fuel economy and emission control are critical.