HYBRID FUEL COMBUSTION OF DIESEL LIGHT OIL AND HEAVY OIL RESIDUAL

摘要

Combustion of heavy oil droplets emphasizes not only the burnout of volatile matters but also the burn-up of solid cokes that formed during fuel combustion. As a result, the total burning time of an oil droplet is supposed to be made up of four componential times, in succession, the ignition delay, flame lifetime, coke glowing delay and coke ember time. Using hybrid oils of a heavy oil residual (HOR) and a diesel light oil (LO) to analogize the diversified heavy oils, the droplets of HOR-LO blends, suspended by a quartz fiber, were combusted in an atmospheric hot chamber to investigate the various burning times with respect to oil compositions. The results showed that the increase in the LO fraction considerably reduced the ignition delay and coke ember time but little affected the flame lifetime and coke glowing delay. This led the total burning time to more or less decrease with increasing the LO fraction. The various burning times were also subject to the initial droplet diameter and chamber temperature. The larger the droplet diameter was, the greater the ignition delay, flame lifetime and coke ember time tended to be. The coke glowing delay, however, was almost independent of the droplet diameter (unless the droplet being too small). The higher chamber temperature caused lower ignition delay and coke glowing delay, little varied flame lifetime and higher coke ember time. These made the total burning time increase with increasing the droplet diameter and chamber temperature. Based on these test results, the work suggested that the burner designs for different heavy oils should focus on the differences in fuel ignition and coke burn-up rather than in the fuel burnout.