​Robert Barlow received his PhD in Mechanical Engineering from Stanford University in 1985.  He has worked at the Combustion Research Facility at Sandia National Laboratories for over thirty years.  His research has focused on fundamental aspects of turbulent combustion, emphasizing application of quantitative laser diagnostics for simultaneous multiscalar measurements in flames of gaseous fuels.  He is the lead organizer of the TNF Workshop series and a recipient of the Edgerton Gold Medal of the Combustion Institute.  

Abstract

Characterization of multi-regime reaction zones in a piloted inhomogeneous jet flame with local extinction

 R. S. Barlowa, S. Hartlb, C. Hasseb, H.C. Cutcherc, A.R. Masric

^a Combustion Research Facility, Sandia National Laboratories, Livermore, CA, USA (Retired)
^b FG Simulation of Reactive Thermo-Fluid Systems, TU Darmstadt, Darmstadt, Germany
^c School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 Australia

Gradient free regime identification (GFRI) is applied to 1D Raman/Rayleigh/LIF measurements of temperature and major species from the intermediate velocity case of the Sydney piloted inhomogeneous jet flame series in order to better understand the structure of reaction zones and the downstream evolution of multi-regime characteristics.  The GFRI approach allows local reaction zones to be detected and characterized as premixed, dominantly premixed, multi-regime, dominantly non-premixed, or non-premixed flame structures, based on flame markers (mixture fraction, chemical mode, and heat release rate) derived from the experimental data.  The statistics of chemical mode zero-crossings, which mark premixed reaction zones, and the relative populations of flame structures are shown to be sensitive to the state of mixing in the near field of the flame and to the level of local extinction farther downstream.  Multi-regime structures, where premixed and non-premixed reaction zones occur in close proximity and both contribute to overall heat release, account for nearly half the total population at streamwise locations within the first several jet diameters.  There is a rapid transition within the near field whereby the relative population of non-premixed and dominantly non-premixed structures grows from 0.06 to nearly 0.5, and the population of premixed and dominantly premixed structures decreases correspondingly, as fluid entering the reaction zone becomes progressively fuel-rich.  Local extinction and re-ignition brings a resurgence in premixed-type structures, many of which occur at fuel-lean conditions.  There are also modest populations of multi-regime structures, having chemical mode zero-crossings at near-stoichiometric or lean conditions, which would not exist in a fully burning jet flame.