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Show Two-Stage Lagrangian Model for Turbulent Jet Flames As a step toward modeling practical burners, one approach is to develop a simplified turbulence model that incorporates a comprehensive chemical kinetic reaction mechanism. Lutz et al.S have developed a model using two perfectly stirred reactors that are connected in a way that represents the global turbulent mixing processes. Following the ideas introduced by Broadwell, Breidenthal, and Mungal,10-13 the model is based on experimental observations of the large scale structure of a turbulent jet. Experimental images of jet flames, such as those reported by Seitzmann et al,.14 suggest the large scale structure shown schematically in Fig. 3. Air enters the flame through diffusion layers at the outer edge, where the local strain rates are low enough to allow combustion. The products are subsequently distributed throughout the jet core by large scale motions. In the region near the nozzle, the central core is too rich to burn; farther downstream however, it approaches the stoichiometric condition and ignites. The basic idea of the mixing model is that entrained air first reacts with the jet fluid in strained diffusion layers, which then merge to form a homogeneous mixture. Of course, the actual mixing process is much more complex, but such a model may be expected to describe the mean Lagrangian concentration Figure 3. \ \ \ \ I Diffusion flame-sheets n Sketch depicting of the structure of a turbulent jet showing diffusion flame-sheets and homogeneously mixed regions. -6- |