Micro-explosion and combustion characteristics of multi-component fuel droplet clusters under elevated turbulence intensity

Abstract

In this study, the micro-explosion and combustion characteristics of a multi-component fuel droplet cluster are studied using a magnified high-speed backlit illumination technique. The multi-component fuel blends consist of n-butanol and n-pentanol as the low-boiling-point component, while biodiesel is used as the high-boiling-point constituent. The range of turbulence intensity is 0–0.72 m/s, and dimensionless droplet spacings (s/d0) are 3 and 5. The results indicate that the flames of droplet clusters exhibit significant fluctuations under turbulent conditions, especially at a spacing of 3. Furthermore, turbulence significantly accelerates the flame spread of droplet clusters at larger spacings. The flame spread time at 0.72 m/s is reduced by 51.5% compared to the stationary state at a droplet spacing of 5. The micro-explosion frequency of droplets significantly increases with the increase in turbulence intensity when the droplet spacing is 3, while the change is relatively small when the droplet spacing is 5. The interaction coefficient between droplets is usually less than 1 at small droplet spacing, indicating that turbulence weakens the combustion rate of droplet clusters. However, the interaction coefficient is significantly higher at larger droplet spacings than at smaller spacings. Therefore, droplet clusters in turbulent environments are more conducive to combustion at relatively large droplet spacings.