Comparison of macroscopic spray characteristics between biodiesel-pentanol blends and diesel

Spray characteristics of biodiesel-pentanol blends (with 0 v/v%, 10 v/v%, 20 v/v%, 30 v/v% and 40 v/v% pentanol) were investigated and compared with those of diesel in this work. Experiments under a variety of working conditions were carried out on a common-rail system and a constant volume chamber. High-speed Schlieren photography was used to capture the spray images. The analysis revealed that biodiesel and diesel showed the longest and the shortest spray tip penetration, the smallest and the largest spray cone angle, the smallest and the largest R (ratio between the liquid core area and the spray area), respectively. As the percentage of pentanol increased, the spray tip penetration of biodiesel-pentanol blends decreased, while the spray cone angle and R increased. BDP40 (60% biodiesel and 40% pentanol) showed similar spray characteristics as that of diesel. The comparison of tip velocities also showed that pentanol would reduce the initial axial momentum of injected fuels. Biodiesel showed the largest initial axial momentum while diesel owned the smallest one. Additionally, spray structures of blended fuels were more likely to fluctuate compared to biodiesel and diesel. The empirical equations of H-A model were used to verify the experimental results and showed great agreement between experimental results and predicts.