m mahmoodi arya - Department of Mechanical Engineering, Faculty of Engineering, Mashhad Branch, Islamic Azad University, Mashhad, Iran.
a fahimirad - Research and Development Center (R&D), Iran Heavy Diesel Mfg. Co. (Desa), Amol, Iran.
p baziar - FZA University of Applied Science and Technology, Amol, Iran.
h.m heravi - Department of Mechanical Engineering, Faculty of Engineering, Mashhad Branch, Islamic Azad University, Mashhad, Iran.

Dilution is considered as a method, which reduces the temperature of furnace and decreases the formation of thermal NO. All of the NOx controlling methods are based on the control of temperature or limiting the concentration of O2. In this study, the numerical and experimental effects of N2 and CO2 diluents on a premixed methane–air flame in a furnace are investigated. This experimental study is achieved by use of a cylindrical furnace for an equivalence ratio from 0.6 to 1.4 and different dilution ratios. The simulation is carried out by using a premix code of the CHEMKIN II software. The GRI-Mech 3.0 detailed reaction mechanism is employed for the combustion of methane. Numerical and experimental results show that the maximum temperature of a flame and the rate of NOx production are reduced by the increase of the dilution ratio. The results also demonstrate the fact that a CO2 diluent is more effective than an N2 due to its high thermal capacity that reduces the NOx production rate more than the N2 can.

Dilution, NOx, Experimental, Numerical, Premixed