n-decane droplet autoignition experiments in microgravity

• Published in: Combustion and flame Vol. 268; p. 113624
• Main Authors: Johnson, M.J., Krause, T.S., Xu, Y., Nayagam, V., Dietrich, D.L.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.10.2024
• Subjects: Autoignition; Droplet combustion; Microgravity; Autoignition; Droplet combustion; Microgravity
• ISSN: 0010-2180
• DOI: 10.1016/j.combustflame.2024.113624

This communication examines the autoignition of 1.1 mm fiber-supported n-decane droplets in a high-temperature oven (700 K) at elevated pressure (3 atm) in microgravity extending previous work to very low ambient oxygen mole fractions (XO2). A high-speed, backlit (shadowgraph) view of the droplet yields the first (τ1) and total (τt) induction times as well as burning rate constants for the period where quasi-steady burning occurs. The experiments show the expected two-stage ignition behavior at ambient oxygen mole fractions greater than or equal to 0.10 with τ1 being independent of XO2 and τt increasing with decreasing XO2. At XO2 between 0.04 and 0.10 there is evidence of a single stage ignition to a cool flame and quasi-steady cool-flame burning, but no hot-flame ignition. At XO2<0.04 the τ1 could not be identified from the shadowgraph images, but the burning rate data as well as thermocouple data strongly suggest cool-flame burning. The burning rate constant increases continuously with XO2. The results of these experiments are useful in the validation of theoretical and computational models of droplet ignition.