Numerical Study of Flame Properties and Nitrogen Oxide Formation in High Temperature Air Combustion

Abstract

The influences of different air preheating temperature, oxygen concentration, and fuel inlet temperature on flame properties and NO x formation/emission in furnace were studied with numerical simulation. In this work, the turbulence behavior was modeled by using the standard k-e model with wall function and radiation was handled using discrete ordinate radiation model. The PDF/mixture fraction combustion model was applied to simulate the propane combustion. Additionally, computations of NO formation rates and NO concentration were carried out using a post-processor based on previous calculated velocities, turbulence, temperature, and chemistry fields. The results showed that, HiTAC is spread over much larger volume than traditional combustion, flame volume increases with a reduction of oxygen concentration, and this trend is clearer if oxygen concentration in the preheated air is below 10%. The temperature profile becomes more uniform when oxygen concentration in preheated air decreases, especially in low oxygen levels. Increase of fuel inlet temperature lessens the mixing of the fuel and air in primary combustion zone, create more uniform distribution of reactants inside the flame, decrease the maximum temperature in furnace, and reduce NO x emission greatly.