DISTINCTIVE BURNING RATE OF DIESEL LIGHT OIL AND LIGHT CYCLE OIL DROPLETS

摘要

This study is devoted to testing the single droplet combustion of a diesel light oil (LO) and a light cycle oil (LCO). The tests were carried out in an atmospheric hot chamber preset at a temperature of 1173 K. A quartz fiber was used to suspend the oil droplet. The results showed that the LCO droplet had higher soot yield, whereas both the LCO and LO droplets did not have obvious coke formation. Microexplosions were obvious during the combustion but the LO droplets were more apt to microexplode. The ignition delay was relatively shorter for the LCO droplet but the flame lifetime and droplet lifetime were nearly the same for the droplets of both the oils (flame lifetime being the time between ignition and extinction, and droplet lifetime being the sum of ignition delay and flame lifetime). The disruptive burning more or less complicated the time-series variations of droplet size (d). A linear region, however, can still be identified on the curve d~2 vs. t to show the overall changes of droplet size with burning time (t). This allowed an apparent burning rate constant to be defined according to the d~2-law. The burning rate constant varied with the initial droplet diameter (d_0), which caused the relative droplet size, (d/d_0)~2, to be normalized by the relative time t/d_0~n (n=1.10). Further analysis showed that this normalization resulted from the respective unification of the unsteady and quasi-steady burning phases of different droplets. These results were also corroborated by burning an oil blend of LO and LCO at volume fractions of 50% in the same conditions.