Burning Droplets Composed of Light Cycle Oil and Diesel Light Oil

Abstract

Burning of single droplets composed of a light cycle oil (LCO) and a diesel light oil (LO) was investigated in normal and micro gravity conditions, with the intention of developing technologies burning these oils in gas turbines. While the normal gravity test used a hot-air chamber to simulate the burning condition that occurs in actual burners, the microgravity test employed an igniter, set beneath the droplet, to make the burning free of extra radiation. The result showed that the burning of the LCO droplet had higher soot yield, while that of the LO droplet was more disruptive. In the conditions tested, coke formation was negligible for both the oils. The LCO droplets exhibited lower ignition delay times, but the burning times between ignition and extinction of equi-sized droplets were slightly larger for LO. A burning rate constant, which was an explicit value when microexplosions were present, could be defined according to the d2-law. The constant, however, was closely related to the initial droplet diameter (d0), causing the relative size d/d0 to be unified (normalized) into a single curve by a relative burning time t/d0n (1.0 < n < 2.0). The droplet temperature histories in microgravity demonstrated that the burning of the LCO and LO droplets proceeded by vaporizing fuel constituents according to their volatility, suggesting a distillation-like mechanism dominating the burning. The test in gravity showed also that the soot particles from the LCO droplets were easier to glow (fire) after flame extinction, while the droplets required as well longer times to burn up the soot particles.