Parametric study for reducing emission characteristics using different computational schemes

The present study numerically predicts emissions (NO_x & CO) characteristics issued from swirl burner using different computational schemes adopted in ANSYS 17.2. Various turbulence models were tested and compared in a structured grid having an average skewness of 0.04. RSM model shows the best results in predicting the central toroidal recirculation zone for such severe swirling flow (S>0.6). Three different schemes of combustion modeling were also tested and compared. Flamelet PDF model was preferred among other combustion models for its potential to consider non-equilibrium chemistry, where its choice was recommended form many studies in the literature. A radiation heat transfer analysis was carried out using P1 radiation model to account radiation effects in estimating NOx and CO concentrations. The effect of varying swirl ratio, excess air, diluting fuel with N₂ and CO₂, oxidizer preheating, and oxidizer composition on emissions (NOx and CO) reduction strategy concluded that increasing the swirl number, excess air factor, and (N₂ and CO₂) mixing ratios have a considerable influence on NOx and CO emissions reduction. While increasing the preheating temperature, and the oxidizer Oxygen concentration leads to an increase the NO_x and CO emissions. Hence, a considerable reduction in NO_x and CO formation was apparently observed by lowering the peak flame temperature less than 1800 K. These predicted outcomes are in agreement with measurements data published in the literature. (paper)