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Show Paper #25 Aerodynamics of a Steady Spray Flame in the Near-Injector Region of a Research Furnace by Laser Doppler Velocimetryt ABSTRACT C. F. Edwards Combustion Research Facility Sandia National Laboratories Livermore, California Data have been obtained for the three components of velocity and accompanying fluctuations in the near-injector region of a laboratory-scale research furnace. Flame stabilization was accomplished aerodynamically, with a swirl number of 1. Kerosene was used as fuel, excess air was supplied at 50%. The data show that the flow contains six distinct regions: the main air and fuel jets, internal and external recirculation zones, a high intensity combustion zone, and an intermittent recirculation zone in the nozzle wake region. Fluctuations in the three velocity components were found to be of approximately the same value, except immediately adjacent to mean velocity gradients. Inlet boundary conditions of the main air stream show a high degree of sensitivity to the entrainment ability of the fuel jet. INTRODUCTION Recent tightening of pollutant emission constraints has made the task of spray combustion engineers more complex than ever before. Competition between the primary objective of providing optimum process efficiency and the mandated requirement that pollutant emission levels not be exceeded, has left the design engineer with a problem that traditional design methods are ill-suited to accept. Improved methodologies for the design of spray flames need to be developed-methodologies which lend themselves to answering the questions posed by modem emission constraints. Common to the advancement of all of the design methodologies is the need for a better description of the details or sub-processes of spray combustion. Examples of the sub-processes about which more information is required are droplet drag and breakup during rapid evaporation and the effects of the condensed phase on the turbulence structure of the continuum phase and vice versa. Details required to improve our physical understanding of spray combustion include a better description of droplet/vapor/flame interactions in the primary reaction zone. This paper reports results from an experimental program aimed at providing the information required to improve design methodologies. The flame chosen for study is a compromise between the simple laboratory flames classically used by combustion scientists and the threedimensional, irregular and ill-characterized flames generally required to suit the practical constraints of an operational combustor. As such, a conscientious effort has been made to retain the most important physical processes of the industrial spray flame, while simultaneously making the flame accessible to both optical diagnostics and numerical computation. tWork performed at the Combustion Research Facility. Sandia National Laboratories. supported by the U.S. Deparunent of Energy. Energy Conversion and Utilization Technologies Program. - 1 - |
