Effect of Mixing Ratio of Biodiesel on Breakup Mechanisms of Monodispersed Droplets

摘要

In this paper, the breakup characteristics of a monodispersed droplets were analyzed as a function of a mixing ratio of the biodiesel based on the images captured using a long-distance microscope and a spark lamp. To investigate the effects of physical properties of biodiesel such as high surface tension and viscosity on the breakup mechanism of a monodispersed droplet, the experiments were performed at various mixing ratios of biodiesel. In addition, the physical properties such as density, kinematic viscosity, and surface tension of the biodiesel blended fuels were measured to study the relations between Weber number and the transition of breakup regime. The experimental apparatus of this study consisted of a droplet generation system, an air flow nozzle, a light source, a long-distance microscope, and a CCD camera. In the first breakup stage, the droplet deformation rate was measured in order to reveal out the effect of high surface tension and viscosity on the deformation rate of a droplet of biodiesel blended fuels. The results of these experiments showed that breakup regime of droplet transited to deformation, bag breakup, stretching and thinning breakup, and catastrophic breakup regimes sequentially as the Weber number is increased. In addition, the higher surface tension and kinematic viscosity of biodiesel slowed the disintegration of a droplet and transition of breakup regime. The lower mixing ratio of biodiesel promotes the deformation of droplet in the first breakup stage, and the breakup mechanism transited to next regime at higher relative velocity between droplet and ambient gas as the mixing ratio is increased.