Effects of Equivalence Ratio on Asymmetric Vortex Combustion in a Low NOx Burner

Abstract

This study presents a combustor with high combustion efficiency and low emissions. The flow field in a combustion chamber is significant in achieving good fuel–air mixing. The experimental and computational results of the temperature and emission of a vortex combustor are presented. Air enters into the combustor in a tangential direction relative to the combustor axis to produce vortex flow, which facilitates the recirculation of hot gas near the fuel nozzle for enhanced mixing. Propane is injected in the direction of the combustor axis at variable mass flow rates to produce variations in the equivalence ratio. The temperature measured along the center line of the combustor. The lowest temperature is measured under rich conditions first and then under lean and stoichiometric conditions. The trend of the combustor temperature at varying equivalence ratios is reproduced well in the simulation despite the increasing temperature near the inlet.  An expected trend of NOx is measured at the outlet where the lowest NOx is produced by the rich combustion first, followed by the lean and stoichiometric combustion. The relative NOx emission at different equivalence ratios is reproduced well in the simulation, although the magnitude of the NOx emission is reduced. As indicated by the calculated number of swirls, the combustion under rich conditions produces about 15% more swirls near the nozzle compared with that under stoichiometric conditions as a result of the low combustor temperature. Moreover, such rich conditions produce a more uniform temperature inside the combustor than lean and stoichiometric conditions.
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