333 Numerical Modeling of $NOx$ Emission in Turbulant Spray Flames Using Thermal and Fuel Models

The present study is concerned with numerical simulating of $NOx$ emission in turbulent liquid fuel spray flames using thermal and fuel models. The influence of fuel spray angle and inlet air temperature on the emission of nitric oxide is investigated. Numerical simulation of two phase flow and combustion modeling for pollutants formation are done with Fluent 6.32 software. The conservation equations of mass, momentum and energy in the turbulent flow field were solved in conjunction with the k − ε turbulence model. The formation of thermal NO from molecular nitrogen was modeled according to the extended Zeldovich mechanism. Fuel-based NO was modeled assuming that all the nitrogen in the fuel is released as hydrogen cyanide (HCN), which then further reacts forming nitric oxide NO or molecular nitrogen N₂, depending on the local combustion conditions. The results show that by increasing in spray angle $NOx$ emission increases. When the spray angle increases, the contact between fuel and air will raise and also the air-fuel mixing increases. Therefore with increasing in the mentioned spray angle, a more perfect combustion happens and the maximum flame temperature increases. Also, the concentration of $NOx$ which is affected by maximum temperature increased. The results reveal that fine droplet sprays lead to higher $NOx$ emission.