Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Quantitative Measurements of Enhanced Soot Production in a Flickering Methane/Air Diffusion Flame



C. R. Shaddix, J E. Harrington, K C. Smyth


Integrated models of soot production and oxidation are based upon experimental results obtained in steady, laminar flames. For successful application of these descriptions to turbulent combustion, it is instructive to test predictions of soot concentrations against experimental measurements obtained in time-varying flowfields. This paper reports quantitative measurements of the local soot volume fraction in a co-flowing, flickering CH4/air diffusion flame burning at atmospheric pressure. Acoustic forcing of the fuel flow rate is used to phase lock the periodic flame flicker close to the natural flicker frequency. Our measurements show that soot production is four times greater for a forcing condition in which flame tip clipping occurs, compared with a steady flame burning with the same mean fuel flow velocity. The soot field in the flickering flame has been characterized using tomographic reconstruction of extinction data obtained at 632.8 nm, laser-induced incandescence (LII) images calibrated against steady CH4/air extinction results, and vertically polarized scattering data. The LII method is found to track the soot volume fraction closely and to give better signal-to-noise than the extinction measurements in both the steady and time-varying flowfields. A Mie analysis of these results suggests that the flickering flame exhibits similar number densities but large particle sizes than the corresponding steady flame.
Combustion and Flame


diffusion flames, extinction, lasers, incandescence, methane, soot, flame flicker


Shaddix, C. , Harrington, J. and Smyth, K. (1994), Quantitative Measurements of Enhanced Soot Production in a Flickering Methane/Air Diffusion Flame, Combustion and Flame, [online], (Accessed July 23, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created January 1, 1994, Updated February 19, 2017