| OCR Text |
Show Predictions from the combustion model, COMO, are compared to predictions from a combustion model developed by Sykes and Truelove . The modeled geometry is shown in Figure 1. A list of test conditions is shown in Table 3. Fuel is injected through a central nozzle at a rate of 1.185 x 10 " kg/sec corresponding to a mean axial velocity of 15.0 m/sec. Oxidant streams through an annulus at a rate of 2.94 x 10 " kg/sec corresponding to a mean axial velocity of 13.7 m/s and Reynolds number of 13,000. Flow was assumed swirling with a swirl number of 0.85. For combustion calculations, a nonuniform 30 x 30 grid was used. This grid is the same as used by Sykes and Truelove. Inlet velocity, turbulence energy, and dissipation profiles were taken from Sykes and Truelove. The emissivity of the furnace walls was estimated to be 0.8. The radiative properties of the gas were modeled using a single gray gas with an absorption coefficient of 0.55 m . This value approximately reproduces the emissivity for the products of complete combustion at a mean beam length for the furnace and the mean radiating temperature for the furnace gas. In Figure 2, the streamline pattern for the flow is shown. The swirling velocity causes the central fuel jet to deflect outward and enhances the mixing of fuel and oxidant. The trends exhibited, including the recirculation patterns, are qualitatively in agreement with experimental data. Figure 3 exhibits predictions for the axial velocity and the temperature along the centerline of the furnace. COMO predictions are compared with predictions made by Sykes and Truelove. The central jet does not penetrate the internal recirculation zone created by the swirling flow, resulting in a negative centerline velocity over a significant region downstream of the burner. Figure 3 also shows the distribution of the centerline temperature. Both predictions indicate a rapid rise in temperature downstream of the burner, followed by a gradual decrease in temperature toward the furnace exit. -15- |
