Dynamics of Radiative Low-Stretch Diffusion Flames

Case Western Reserve University, Cleveland OH

Investigators

Abstract

This is an experimental and theoretical investigation of the structure and extinction behavior of gaseous diffusion flames at low stretch rates. The low-stretch condition is created by bottom-burning of a fuel mixture discharged from a porous axisymmetric burner of very large radius. Fuels studied include methane, hydrogen, carbon monoxide/hydrogen, and carbon monoxide/methane. Spatially resolved species, temperature, and velocity profiles are measured with laser diagnostics. Flame radiation and burner-surface radiation are also examined. Corresponding theoretical models are developed incorporating a narrowband radiation model. The study consists of five elements: (1) experimental determination of the flammability limit boundaries as functions of stretch rate and the amount of fuel dilution with emphasis on the radiation- induced extinction; (2) experimental exploration for the existence of "flamelets"; (3) experimental mapping of flame structure including hydrodynamic, thermal, and species profiles and radiation intensities from the flame and burner surface; (4) detailed modeling of low-stretch diffusion with detailed chemistry, transport properties, and flame/surface radiation; and (5) development of detailed radiation models including flame-surface interaction in a spectral manner and reevaluation of mean band parameters.