Single Droplet Ignition: Theoretical Analyses and Experimental Findings
Suresh K. Aggarwal
10027/20133
https://indigo.uic.edu/articles/journal_contribution/Single_Droplet_Ignition_Theoretical_Analyses_and_Experimental_Findings/10957613
Spray ignition represents a critical process in numerous propulsion and energy
conversion devices. Compared to a gaseous mixture, ignition in a spray is significantly more
complex, as the state of ignition in the latter case can be defined by three distinct ignition modes
namely, droplet ignition, droplet cluster ignition, and spray ignition. Ignition for an individual
droplet represents the appearance of a flame surrounding the droplet or in the wake region, with
a dimension on the order of droplet diameter. The cluster or group ignition refers to the ignition
around or inside a droplet cloud, while the spray ignition implies the appearance of a global
flame with a characteristic dimension few orders of magnitude larger than a droplet. In all three
modes, ignition is preceded by the evaporation of fuel droplets, formation of a combustible
gaseous fuel-air mixture, and initiation of chemical reactions producing sufficient radical
species. The identification of the dominant ignition mode for given two-phase properties
represents a problem of significant fundamental and practical importance. Research dealing with
laminar and turbulent spray ignition has been reviewed by Aggarwal [1] and Mastorakos [2],
respectively, while Annamalai and Ryan [3] have provided a review of droplet group
combustion/ignition. In the present review, we discuss experimental, theoretical, and
computational research dealing with individual droplet ignition. Topics include the quasi-steady
and unsteady models for the ignition of a fuel droplet in a stagnant environment, the droplet
ignition in a high-pressure environment, the convective effects on droplet ignition, and
multicomponent fuel droplet ignition. Studies dealing with the two-stage and NTC ignition
behavior for a droplet are also discussed. Finally, relationship between the droplet ignition mode
to droplet cluster and spray ignition modes is briefly described. Potential topics for further
research are outlined.
2018-02-13 00:00:00
Droplet ignition,
quasi-steady
transient model,
two-stage ignition