An optical study on liquid-phase penetration, flame lift-off location and soot volume fraction distribution of gasoline-diesel blends in a constant volume vessel

Liquid-phase penetration, flame lift-off location and soot volume fraction distribution of gasoline-diesel blended fuel jets (gasoline volume fraction 0%, 20%, 40% and 60%) were measured in a constant volume vessel to investigate the combustion and soot formation processes of the wide-distillation fuel. The test was conducted under a constant ambient condition (Ta = 830 K, Pa = 4 MPa) with fixed injection parameters (d = 168 μm, Pinj = 80 MPa). Mie-scatter imaging, OH chemiluminescence imaging along with coupled Laser Induced Incandescence (LII) and Laser Extinction Method (LEM) were used to investigate the liquid spray length, lift-off length and quantitative soot concentration, respectively. It was found that the increase of gasoline proportion in gasoline-diesel blends results in the following effects: the liquid spray length decreases with a nearly linear tendency while the flame lift-off length increases non-linearly; the general soot concentration decreases significantly and the initial soot-formation location moves downstream; the peak soot volume fraction decreases and the soot inception time increases; the initial soot point and the peak concentration region of soot shift from the periphery to the center of the jet. It was also found that the lift-off length, first-soot distance, peak soot concentration and soot inception time vary more significantly at higher gasoline proportions.