The bluff-body stabilized flame is used in a numerical study of the non-premixed flames. This paper shows numerical investigations on the effects of hydrogen compositions and nonflammable diluent mixtures on the combustion and NO emission characteristics of syngas non-premixed flames for a bluff-body burner. The assessment of turbulent non-premixed combustion modeling techniques is presented and discussed. The simulations study the predictive capabilities of five turbulence models and are compared with the experiments of Correa and Gulati [1] for a non-premixed flame of 27.5%CO/32.3%H2/40.2%N2 and air. The Realizable k-ε and the Reynolds Stress (RSM) models were found to perform the best. Based on this, a numerical study to assess the effects of hydrogen component on syngas non-premixed combustion was performed. As a result, hydrogen addition caused the radial velocity and strain rate to decrease, which was important for mixing to decrease NO. Also, the effectiveness of nonflammable diluent mixtures, including N2, CO2 and H2O, were characterized in terms of the ability to reduce NO emission in syngas non-premixed flames. Results indicated that CO2 was the most effective diluent to reduce NO emission and H2O was more effective than N2. CO2 diluent produced low levels of OH radical, which makes CO2 the most effective diluent. Although H2O increased OH radicals, it was still effective to decrease the thermal NO because of its high specific heat.

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