Nitrogen dioxide
When fossil fuels are burned, Nitric oxide and Nitrogen dioxide are produced. These pollutants initiate reactions which result in production of ozone and acid rain. NOx formation takes place due to (1) High temperature combustion i.e. thermal NOx and (2)Nitrogen bound to fuel i.e. fuel NOx and which is insignificant. In the majority of cases the level of thermal NOx can be reduced by lowering flame temperature. This can be done by modifying the burner to create a larger (hence lower temperature) flame, in turn reducing the NOx formation. The role of CFD analysis is vital for design and analysis of such low NOx burners. Many available CFD tools, such as CFX, Fluent, Star CCM++ with different models as RNG k-ε turbulence models with hybrid and CONDIF upwind differencing schemes has been used for analysis purpose and the data obtained with these analysis helped in modifying the burner design in turn lowering the adverse effect on the environment due to NOx formation during combustion.