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Show injection holes and a bluff centerbody. Air is introduced through an annular inlet and moveable swirl blocks are used to impart swirl. A detailed description of the geometry is available in [1]. Two configurations were considered during experiments, one with water cooled furnace walls, and the other with the furnace wall lined with refractory. The current study presents results only for the case with the refractory lining, i.e., the so-called "hot-wall" configuration. The problem was modeled as axi-symmetric, and appropriate area adjustments were made to account for the 2D representation of an inherently 3D problem . A close-up view of the furnace quarl area is shown in Figure 2. Care was taken to ensure that the cross-sectional areas of the modeled furnace and real furnace remained the same. It is worthwhile studying the axisymmetric model before embarking on the more complicated and time consuming 3D modeling effort. The wall thermal conditions for the hot-wall configuration are given in Table 1. [1] Boundary Temperature (K) Emissivity Walls near the inlet ducts 312 0.6 Bluff body front wall 1173 0.6 Inlet duct insert (oblique) 1173 0.6 Quarl wall (oblique) 1273 0.6 Furnace bottom wall 1100 0.5 Furnace cylinder wall (hot) profile 0.5 Furnace top wall (hood) 1305 0.5 Chimney wall 1370 0.5 Table 1: Wall Thermal Conditions The profile along the furnace cylinder wall was given by the following equation[l]: T(x) = ao + al(x + 0.195) + ... + a6(x + 0.195)6 (1) where 0 ~ x ~ 1.65 m is the position along the wall and the coefficients ai are given in Table 2. ao 1.257 x 10J al -2.1777 x10J a2 9.93349 x 10J a3 -1.74799 x104 a4 1.46151 x 104 a5 -5.83885 x 103 a6 8.98612 X 102 Table 2: Coefficient.s of the Temperature Profile along the Furnace Cylinder Wall in the "Hot-Wall" Configuration Formulation The st.eady-state. Reynolds averaged N avier-Stokes equations for mass, momentum, energy and scalar transport are used to describe the flow physics. The density is obtained using the ideal gas law. The standard k - f turbulence closure model was considered appropriate because of the relatively low inlet swirl (swirl number=0.56). Also, for combusting flows. the swirling inlet flow is accelerated due to combustion and the importance of the centrifugal forces due to swirl decreases vis a vis the inertial forces [2]. The two different models used for turbulent combustion are now described briefly. 2 |