The formation of nitric oxide in combustion systems is a significant pollutant source in the environment, and the control of NO emissions is a world-wide concern. This paper presents a numerical prediction of nitric oxide formation in a liquid-fuelled furnace incorporating turbulent swirling flow. The aim of this paper is to analyze the effects of the fuel droplet size as well as air preheat and swirl on the formation of NO. In addition, the relative contributions of different mechanisms of nitric oxide formation are investigated. Numerical predictions are compared with experimental measurements and reasonably good agreement is achieved. It is found that, the formation of thermal NO increases by air preheat as well as swirl. The results indicate that, distribution pattern of prompt NO is quite different from the thermal one. However, the contribution of prompt NO is not significant in the total nitric oxide production. Although finer droplets provide higher mixing rates and lead to lower soot emission, it is shown that they suffers from a detrimental environmental effect due to the increased emission of NO.

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