Experimental Investigation on Spray Evaporation and Dispersion Characteristics of Impinged Biodiesel-Butanol Blends

The objective of the investigation is to explore the spray evaporation and dispersion characteristics of impinged biodiesel-butanol blends at various n-butanol ratios (0, 10%, 30%, 50%) and ambient conditions. A total of 180 experimental cases were performed in a constant-volume combustion chamber. The liquid- and vapor-phase sprays were captured by backlight imaging technique and Schlieren imaging technique, respectively. Several macroscopic parameters were measured and discussed, including impinged spray structure, width, height, and area. Some novel parameters are derived to analyze spray evaporation and dispersion. Results show that biodiesel blended with 30% n-butanol transits better from liquid-phase to vapor-phase compared with other blends, displaying rapid liquid-phase evaporation an steady vapor-phase dispersion. After wall impingement, an increase in the ambient pressure or temperature hinders the liquid-phase dispersion in the vertical direction significantly, leading to a rapid decrease in the height of the impinged spray. The vapor-phase diffusion rate in the horizontal direction is about four times the rate in the vertical direction, and the rate ratio is slightly affected by ambient conditions and injection pressure. Compared with the free jet, the impinged spray is not beneficial for liquid-phase evaporation and vapor-phase dispersion, presenting larger liquid-phase area and smaller vapor-phase area. However, impinged biodiesel blended with 30% n-butanol displays better spray evaporation and dispersion.