Nonane droplet combustion with and without buoyant convection: Flame structure, burning rate and extinction in air and helium

Automated Data Analysis for Consecutive Images From Droplet Combustion Experiments

“…As a base case for comparison we used the package Image-Pro Plus v.6.3 as our prior droplet burning studies (Bae and Avedisian, 2004;2009;Liu and Avedisian, 2012) employed this package for image analysis. A typical procedure for manually obtaining droplet diameter measurements includes the following steps: (1) the droplet image is loaded into the software; (2) a threshold value of grayscale intensity is selected to convert the original grayscale image (with intensity values ranging from 0 to 255) into a black and white (black = 0, white = 255) binary image; (3) an elliptical "area of interest" (AOI) tool is activated and the AOI is manually placed on what is perceived to be the droplet boundary based on the assigned threshold value; (4) the pixel readings for the width W and height H of the elliptical AOI are recorded; (5) the effective droplet diameter, in units of pixels, is calculated by taking a geometric average of the width and height of the ellipse (i.e., D = (W×H) 0.5 ); and (6) the process is repeated for each frame in the sequence.…”

Combustion behaviors of isolated n-decane and ethanol droplets in carbon dioxide-rich ambience under microgravity

“…The inert components provide a wide range of the molecular weight, thermal properties and transport effects. The soot production in helium [20,21] and carbon dioxide [22][23][24] inert is suppressed and even extinction occurs [21]. Unsteady combustion of fuel droplets has also been observed [20][21][22][23][24], and thus detailed understanding of the effects of inert gas is rather important.…”

“…The soot production in helium [20,21] and carbon dioxide [22][23][24] inert is suppressed and even extinction occurs [21]. Unsteady combustion of fuel droplets has also been observed [20][21][22][23][24], and thus detailed understanding of the effects of inert gas is rather important. We have conducted experimental researches on effects of the ambient component such as a prevaporized fuel and carbon dioxide on the droplet combustion and investigated especially on the ignition process, chemical reaction processes and the burning rate constant [25,26].…”

Effects of Carbon Dioxide on Unsteady Combustion of Isolated Fuel Droplet in Microgravity

“…Soot in the droplet flame is one of reasons for nonlinear burning of droplets. Most of droplet combustion models have not included soot and its effects and some experimental studies have been conducted using non sooting fuel [10][11][12] , controlled O 2 concentration 13) and inert substitution to mitigate the sooting effect [14][15][16] . The burning rate of the n-heptane droplet is affected by the accumulation of the soot shell 8) and the soot production increases with initial droplet diameter.…”

“…Fundamentally, the droplet combustion process is thought to be unsteady behavior, and however, studies which treat the instantaneous burning rate have been rather limited. As an example of the measurement of the instantaneous burning rate, fourth-order polynomial fits to the profiles of the droplet diameter squared and the burning rate is determined from the derivative 16) . The influence of the ambient pressure on the instantaneous burning rate of n-heptane droplet has also been investigated 17) .…”