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The current study presents a method to model the flameless oxy-fuel system, with a comparative approach, as well as validation of the predictions. The validation has been done by comparing the predicted results with previously published experimental results from a 200 kW pilot furnace. A suction pyrometer has been used to measure the local temperature and concentrations of CO, CO 2 , and O 2 at 24 different locations. A three-dimensional CFD model was developed and the validity of using different submodels describing turbulence and chemical reactions was evaluated. The standard -model was compared with the realizable -model for turbulence, while Probability Density Function (PDF) with either chemical equilibrium or the Steady Laminar Flamelet Model (SLFM) was evaluated for combustion. Radiation was described using a Discrete Ordinates Model (DOM) with weighted-sumof-grey-gases model (WSGGM). The smallest deviation between predictions and experiments for temperature (1.2%) was found using the realizable -model and the SLFM. This improvement affects the prediction of gaseous species as well since the deviation between predictions and experiments for CO 2 volume percentages decreased from 6% to 1.5%. This provides a recommendation for model selections in further studies on flameless oxy-fuel combustion.

The effect of the combustion chamber's configuration on the characteristics of flow and combustion parameters has been numerically investigated for a multi injecting, LPG, Flameless Oxy-fuel burner in a real-size soaking pit furnace, using CFD simulation. The simulation has been performed on two different furnace configurations, namely; small and large chambers of 15 m 3 and 27 m 3 , with a height to width ratios of 1.49 and 2.02 respectively and with corresponding burner capacities of 560 kW and 900 kW. A major experimental trial has been performed in order to validate the results and reasonable consistency has been observed. The predicted results, with particular focus on the temperature distribution and heat transfer rate of two cases have been studied in detail.Flameless-oxyfuel;soaking pit furnace; heat transfer IntroductionCondition of soaking process, including the uniformity of temperature profile and heat transfer rate plays an essential role in the total energy consumption, final quality of soaking process and pollution production in the chain [2]. Simulation of industrial combustion systems involving multiple burners using CFD modelling is still a challenging problem. Integrating burners with jet scales in order of a few inches within a large domain in order of 10 to 1000meter is still a complex problem [5]. Increment of demanding rate for high quality steel in higher volume together with recent energy and pollution crisis brings up the necessity of a constant effort for development of existing facilities and optimizations. Regarding this new technology of Flameless-oxyfuel combustion has been introduced in 90s. In this study, the effect of the combustion chamber's configuration on the characteristics of flow and combustion parameters has been investigated for a multi injecting, LPG in a real-size soaking pit furnace, using CFD simulation.

Abstract:The flameless oxyfuel combustion technology has been proven to be a promising new method to reduce the fuel consumption and pollutants in industrial applications. Although this technology is widely used in industrial furnaces, a lack of understanding exists about the effect of the controlling parameters on the final operational conditions is tangible. In this study, a validated computational fluid dynamics (CFD) model is used to simulate six cases of flameless oxyfuel combustion burners with different lambda values (ratio of oxygen/fuel mass flow rates). The CFD model uses the steady laminar flamelet model (SLFM) to solve the probability density function (PDF) for combustion, the discreet ordinates (DO) radiation model with the weighted sum of the gray gases model (WSGGM) to solve radiation, and the realizable k-ε to model the turbulence. It is seen that an increased oxygen injection velocity due to an increased lambda value increases the exhaust losses, but produces a larger volumetric flame. This leads to a more uniform temperature distribution. The total temperature difference in a case with a λ value of 1.02 is reported to be 272 (14.9%), while the amount for a case with a λ value of 1.2 is 67 (4.7%). This effect is further explained by introducing a new definition value for the furnace efficiency that includes both the thermal and production losses.