Numerical Investigation of Influence of Dilution in Air and Fuel Sides on MILD Combustion Burner

Understanding of how and where NOx formation occurs is very important for efficient and clean operation of utility burners. FGR is a new method adopted to control NOx formation in combustion chamber. In this method flue gas decreases flame temperature and reaction rate, resulting in the diminish in thermal NOx emission. Recently, it has been accomplished that the entered flue gas in fuel stream, that named, FIR method, could increase a much improved reduction in NOx production per unit mass of recirculated gas, as compared to the conventional FGR in air. In the present study, the MILD combustion regime have been simulated, and result validated with experimental data. In order to modification, variations including, temperature and flow of air inlet are performed. Also the effect of FGR/FIR methods on NOx reduction by using CO 2 , H 2 O, and N 2 as diluents gases are investigated. Results show that FIR is more effective to reduce NOx emission than FGR in the same recirculation ratio of dilution gas, and H2O dilutor because of large specific heat, is more effective compared to CO2 and N2 gases, Also with increasing of velocity and flow of air inlet, the thermal NOX concentration decreases.