26 th ICDERS July 30 th – August 4 th , 2017 Boston, MA, USA Correspondence to: kunkuma@flame.ifs.tohoku.ac.jp 1 Combustion and Emission Characteristics of Premixed and Non-premixed Ammonia/air Turbulent Swirl Flames at the High Pressure and Temperature K.D.Kunkuma A. Somarathne, Akihiro Hayakawa and Hideaki Kobayashi Tohoku University Sendai, Miyagi, Japan 1 Introduction Sustainble solutions are needed to be increasingly applied to the energy sector in order to prevent the detrimental effects of fossil fuels on the enviroment. Ammonia (NH3) is, recently, identified as a carbon free sustainable fuel, and anticipated as a hydrogen energy carrier because of the higher hydrogen capacity of 17.8% in weight. Nevertheless, much lower laminar burning velocity [1-2] and high fuel NO generation in the combustion, because NH3 contains nitrogen itself than that of conventional hydrocarbon fuels, hindered the use of NH3 as a commercial fuel. However, recent studies of Somarathne et al. [3-4] and Hayakawa et al. [5] have numerically and experimentally illustrated that by introducing swirl flow, and thereby making a recirculation near the downstream of swirler, NH3/air turbulent premixed flames have successfully achieved a stable combustion at the atmospheric pressure and various turbulent intensities at the initial mixture temperature of 500 K and 300 K. Moreover, the studies of [3-5] elucidated that fuel NO generation can be significantly reduced by using the rich flame condition and there is an equivalence ratio in rich flame condition in which NO and unburnt NH3 emissions are minimal and in a same order, and thus, this would be the best operating point for the selective catalytic NO emission reduction (SCR) process in the downstream. However, this specific equivalence ratio like to be depended on the initial mixture temperature and burner wall condition, and in the case of adiabatic wall and initial mixture temperature of 300 K and 500 K, the equivalence ratios were 1.15 and 1.2, [3-4] respectively, whereas in the case of isothermal wall and initial mixture temperature of 300 K, the specific equivalence ratio is 1.05 [5]. In addition, recently, NH3/air combustion power generation has been successfully realized using a 50 kW micro gas turbine at the National Institute of Advanced Science and Technology (AIST), Japan by Kurata et al. [6]. In the study of [6], stable turbulent non-premixed ammonia/air swirl flame has been achieved using a high swirling flow of air and a jet flow of NH3, nevertheless NO and unburnt NH3 emissions are still higher than that of the government environment regulations [7]. However, insights of the combustion and emission characteristics of non-premixed NH3/air flames in gas turbine combustors are still unclear. Besides, to the best of author’s knowledge, there is no any comprehensive study on turbulent NH3/air flames at high