Combustion and Pressure Rise Characteristics of Butanol–Diesel Blends in a Multi-Cylinder Engine at Varying Loads and Speeds

Abstract

This study investigates the combustion characteristics and in-cylinder pressure rise behaviour of a single-cylinder diesel engine fueled with various diesel–butanol–water blends. Five fuel types were tested: pure diesel (Diesel), diesel with 5% water (W5D), and W5D further blended with 5%, 10%, and 15% butanol, labelled W5DBu5, W5DBu10, and W5DBu15, respectively. Experiments were conducted at a constant engine speed of 3,000 rpm under varying load conditions of 20%, 35%, and 50%. Results show that W5DBu10 produced the highest pressure rise at 20% load, reaching 11.9 bar at 6° after the top dead centre (ATDC), approximately 21% higher than pure diesel (9.8 bar). At 35% load, W5DBu15 demonstrated the highest rate of pressure rise (RoPR) with a peak of 16.25 bar at 5° ATDC, compared to 13.48 bar for diesel. Under 50% load, W5DBu15 again showed the highest RoPR at 14.84 bar (2.5° ATDC). The mass fraction burned (MFB) analysis revealed that W5DBu15 completed combustion slightly later but demonstrated higher thermal efficiency, especially at medium and high loads. Moreover, ignition delay tended to increase with higher butanol content. These findings suggest incorporating butanol into diesel–water blends can enhance in-cylinder pressure characteristics and combustion performance. However, the optimal blend ratio must be carefully selected to balance ignition delay and pressure rise behaviour.