SOOT FORMATION CHARACTERISTICS OF PALM METHYL ESTER SPRAY FLAMES IN COUNTERFLOW SUSTAINED BY METHANE/AIR PREMIXED FLAME

To evaluate the potential of palm methyl ester (PME) as an alternative fuel, the characteristics of soot formation in PME spray flames were experimentally investigated. The spatial distribution of the soot volume fraction in a PME spray flame, which was stabilized in a laminar counterflow field using a stable lean premixed flame, was measured using two-dimensional laser-induced incandescence (2D-LII). The structure of the PME spray flames and the characteristics of the soot formation were compared with those of diesel fuel and n-dodecane. The results showed that PME and n- dodecane exhibited similar structures of spray flame and indicated time-averaged and instantaneous characteristics of soot formation, despite only PME containing oxygen in its molecular structure. In contrast, the time-averaged soot volume fraction in the PME spray flame was much smaller than that of the diesel fuel because the diesel fuel contains some polycyclic aromatic hydrocarbon components. These results suggest that the straight chain structure in PME is the primary cause of the lower volume fraction of soot in the PME spray flames than that in the diesel fuel spray flames.