Spontaneous Ignition Behavior Of N-Decane Fuel Droplet Array Near Ignition Limit

A microgravity experiment utilizing sounding rocket is going to be held in 2021 to clarify cool flame occurrence from n-decane droplet array near spontaneous ignition limit. As a preliminary study for the experiment, the 2D numerical simulation is carried out. The almost identical numerical geometry to the actual furnace for the rocket experiment is used to predict the cool flame occurrence in the rocket experiment. The interference of the droplets is validated by calculation with different inter-droplet distance. The employed fuel is n-decane of 1.0 mm in diameter. The initial temperature and pressure are 550 K and 1 atm respectively. The results shows that the cool flame occurs from the outside of the fuel droplet array. A fuel concentration at inter-droplet is higher than the outer side, whereas the temperature at inter-droplet is lower than the outer side. It is thought that the lower temperature yields increase in the spontaneous ignition delay time surpassing the shorten effect of the ignition delay time due to higher fuel concentration.