Parametric Computational Studies to Decrease NOx Emissions in Combustion of an Ideal Fuel Air Mixture with Management of Several Stabilization Zones1

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The present article is the first of a series of articles concerned with computational studies on optimization of the process of combustion of a fuel air mixture with temperatures of the gases at the exit from the combustion chamber of around 1600°C where the emission requirements are satisfied. Results of calculations of the combustion of an ideally mixed fuel air mixture in a combustion chamber of typical design possessing several flame stabilization zones formed by swirling of the flows of two swirl nozzles and sudden expansion of the flow in the space of a flue tube are presented. The influence of the position and form of the flame, the concentration and the different variants in which the fuel air mixture is fed into the combustion chamber, the input temperature, preheating in the combustion chamber, swirling of the flow, occupation time, and the pressure and mass of the recirculated flow on the formation of nitric oxides and the completeness of combustion is investigated. Dependences of NO_x emission on different influencing factors are obtained. Using the results obtained we are able to estimate the minimally possible level of nitric oxide emissions attainable with a standard optimized design of single-zone combustion of an ideally mixed fuel air mixture. A further decrease in NO_x emissions is possible through the creation of two or more sequential zones of fuel afterburning in a depleted oxygen-based oxidant. The form and position of the front of the flame and the completeness and length of combustion of the fuel as a function of the above factors, enabled by varying the design of the combustion chamber while maintaining stable and complete combustion of the fuel, are investigated.