Analysis of enhanced flame speed in the transition droplet sizes for n-alkane aerosols generated by electrospray

Abstract

Fire and explosion incidents related to aerosol occur occasionally throughout the industries. However, its hazards are relatively overlooked due to the misconception of that liquids are safe below their flash point. As well as scarcity of data stems from the difficulty of aerosol generation by a well-controlled manner. In this research, n-alkane aerosols were produced from an improved electrospray device, and their flame speeds were measured to verify the transition range. When droplet sizes fell into this range, the flame speed would be enhanced and pose greater threats to people and surroundings. Theoretic simulation and empirical equation were performed to predict the trend of flame propagation. Application of convective droplet evaporation improved the theoretic simulation but still failed to recognize the transition range. On the other hand, the empirical equation provided a good fitting and explained possible reason for the trend. It should notice that the transition droplet size range is not a fixed range for aerosols. Therefore, process design and operation should consider the potential generation of aerosol size and location of transition range to reduce the hazards. By understanding the flammability of aerosol, the associated risk can be managed to an acceptable level.