Single droplet ignition models via evaporation and ignition competition

Abstract

There is individual droplet burning phenomenon in spray flames but the ignition prediction and criteria are lack of both experimental and theoretical study. In this paper, firstly based on the energy balance analysis method, two new droplet ignition models are proposed by analyzing the single droplet evaporation and ignition process in relatively static high temperature air environment. These new models can be used to predict the droplet ignition phenomenon in spray flames. Then, single droplets of RP3 aviation kerosene, common kerosene and diesel were suspended in static air environment with ambient temperature from 845 ​K to 1085 ​K to test the ignition limits of the fuel droplet. The experimental ignition boundary was obtained by measuring and recording the minimum ignitable initial diameters of the experimental droplet in every temperature condition. The experimental results show that the ignitable minimum initial diameter of the fuel droplet decreases along with the increase of ambient temperature. And at the same ambient temperature, the minimum ignitable initial diameter of common kerosene droplet is the biggest, then is diesel and RP3 aviation kerosene is the smallest. Finally, the predicted ignition boundaries of the two new models are compared with the experimental data. And the comparison results show that the models’ predictions are in good agreement with the experimental data, whose error is within 10%.

Keywords

• Single droplet ignition model
• Aviation kerosene
• Droplet ignition experiment
• High temperature air environment
• Time scale competition