Highly turbulent combustion: A study of lifted and shredded flames.

The impact of turbulence on flame chemistry in highly turbulent flames has been studied in order to test existing theories and produce data that are useful to the computer modeling community. In these flames, the fuel is injected separately from the air, but a significant amount of premixing occurs prior to combustion. By employing Particle Image Velocimetry (PIV), Planar Laser Induced Fluorescence (PLIF) of chemical species, and exhaust gas sampling, the effect of turbulence on flame chemistry has been quantified for a highly lifted, supersonic flame and for a highly swirled, shredded flame. In the supersonic flame, OH PLIF measurements were combined with combustion efficiency measurements and PIV to help to understand the mixing and flame structure. Negative velocities of more than 200 m/s were identified in the recirculating zones. Mechanisms of fuel-air mixing that result in decreased combustion efficiencies were identified. In the shredded flame, an ultra-high turbulence region was generated to examine what occurs when reaction layers encounter high turbulence levels. The flame was probed with simultaneous CH and OH PLIF and then simultaneous PIV and OH PLIF. It was found that the normalized turbulence level, even though it was ten-times greater than any previous imaging study, still produced no measurable impact on flame reaction layer thickness. This flame was also quantified by measurements of Flame Surface Density (Sigma). The thin flamelet assumption of flamelet theory is found to be valid in these highly turbulent flames. Data are presented that can be used to assess computational models as well as to provide insight into the physical processes of turbulent combustion.PhDAerospace engineeringApplied SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/132870/2/9990969.pd