Cylinder Pressure and Heat Release Analysis of Diesel-Butanol Blends at High Engine Load

Abstract

This study investigates the impact of butanol-water blended fuels on the combustion characteristics of a diesel engine, focusing on cylinder pressure and heat release rate under high engine speed (3,000 rpm) and varying load conditions (20%, 35%, and 50%). With increasing butanol concentrations, the blends tested include W5DBu5, W5DBu10, and W5DBu15. Results show that higher butanol content increases peak in-cylinder pressure and enhances thermal performance. At 35% load, W5DBu15 recorded the highest peak pressure compared to other blends, indicating improved combustion due to better air-fuel mixing. At 50% load, the peak in-cylinder gas temperature reached nearly 2,000°C for all blends, slightly lower than pure diesel, suggesting effective NOx reduction from water cooling effects. The heat release rate analysis reveals a higher premixed combustion phase for all blends, with W5DBu15 showing the most significant increase. This increase is attributed to a longer ignition delay caused by the lower cetane number of butanol. Moreover, the heat release pattern of all blends closely resembles that of base diesel, ensuring compatibility without engine harm. The study confirms that diesel-butanol-water emulsions improve thermal efficiency and combustion behaviour without compromising engine safety, especially at medium to high loads and speeds.