Influence of Swirl and Primary Zone Airflow Rate on the Emissions and Performance of a Liquid-Fueled Gas Turbine Combustor

This paper presents the results of an experimental study on the influence of swirl number (S) and primary zone airflow rate on the temperature, emission indices of the pollutants, and combustion efficiency in an atmospheric pressure liquid-fueled gas turbine (GT) combustor, equipped with a swirling jet air blast atomizer and operated with Jet A1 fuel. Experiments were conducted at three primary zone air flow rates and three swirl numbers (0.49, 0.86, and 1.32). For all the cases, it was found that the NOx emissions were very low (< 2 g/kg of fuel). At all the swirl numbers, an increase in primary zone airflow led to a nonmonotonous variation in CO while minimally affecting the NOx emissions. However, increase in the swirl number generated relatively higher NOx and lower CO owing to higher temperature resulting from efficient combustion caused by a superior fuel-air mixing. Also, the unburnt hydrocarbons (UHC) was quite high at S = 0.49 because of the unmixedness of fuel and air, and zero at S = 0.86 and 1.32. The combustion efficiency was very low (around 60%) at S = 0.49 while almost 100% at S = 0.86 and 1.32. The study conducted demonstrates a significant dependence of emissions and GT performance on the swirl number governed by the convective time scales and the residence time of the combustible mixture in the combustion zone.