Nitrogen oxides and smoke are the substantial emissions for the diesel engines. Fuels comprising high-level oxygen content can have low smoke emission due to better oxidation of soot. The objective of the paper is to assess the potential to employ oxygenated fuel, i.e., n-butanol and its blends with the neat diesel from 0 to 30% by volume. The experimental and computational fluid dynamic (CFD) simulation is carried out to estimate the performance, combustion, and exhaust emission characteristics of n-butanol-diesel blends for various injection timings (9°, 12°, 15°, and 18°) using modern twin-cylinder, four-stroke, common rail direct injection (CRDI) engine. Experimental results reveal the increase in brake thermal efficiency (BTE) by ~ 4.5, 6, and 8% for butanol-diesel blends of 10% (Bu10), 20% (Bu20), and 30% (Bu30), respectively, compared to neat diesel (Bu0). Maximum BTE for Bu0 is 38.4%, which is obtained at 12° BTDC; however, for Bu10, Bu20 and Bu30 are 40.19, 40.9, and 41.7%, which are obtained at 15° BTDC, respectively. Higher flame speed of n-butanol-diesel blends burn a large amount of fuel in the premixed phase, which improves the combustion as well as emission characteristics. CFD and experimental results are compared and validated for all fuel blends for in-cylinder pressure and nitrogen oxides (NO), and found to be in good agreement. Both experimental and simulation results witnessed in reduction of smoke opacity, NO, and carbon monoxide emissions with the increasing n-butanol percentage in diesel fuel.
