Evaluation of Water-Diesel-Butanol Fuel Blends Under Varying Engine Conditions

Abstract

Rising fuel demand, dwindling petroleum reserves and stricter emission limits have renewed interest in oxygenated and emulsified fuels for compression-ignition engines. Water-in-diesel emulsions moderate combustion temperature and drive secondary atomisation through micro-explosion, while butanol supplies fuel-bound oxygen and improves fuel-air mixing. The coupled behaviour of water and butanol in a single ternary blend, and its response to engine load, is still not fully resolved. This study aims to evaluate the combustion behaviour of water-diesel-butanol blends under varying engine loads in a four-cylinder, 3.0-litre turbocharged Isuzu 4JJ1 direct-injection diesel engine. Neat diesel, a water-diesel emulsion (W5D) and three ternary blends with a fixed 5% water fraction and 5%, 10% and 15% butanol (W5DBu5, W5DBu10 and W5DBu15) were tested at 3000 rpm under loads of 20%, 35% and 50%. In-cylinder pressure, apparent heat release rate and mass fraction burned were derived from the measured pressure trace. Butanol raised the peak pressure and sharpened the heat release through stronger premixed combustion, whereas the water fraction smoothed the pressure rise and lengthened the burn. At low load, the ternary blends ignited later but burned more completely, while at higher load the combustion phasing of all fuels converged. W5DBu10 gave the most balanced response, combining a strong pressure rise with stable, complete combustion at medium-to-high loads. These combustion outcomes indicate potential for improved efficiency and cleaner oxidation, but direct emission and brake-efficiency measurements are required before environmental benefits can be quantified. The findings confirm that carefully proportioned water-diesel-butanol blends can run in an unmodified diesel engine; future work should integrate performance and exhaust-emission measurements with injection-timing optimisation to exploit their efficiency potential.