Emission Characteristics of Turbulent Non-premixed CH4/NH3/air Swirl Flames through a Rich-Lean Gas Turbine-like Combustor at High Pressure

In this study, NO emission characteristics of turbulent non-premixed CH4/NH3/air flames (energy fraction of NH3 (ENH3) of 20%) in a rich-lean gas turbine like combustor were numerically studied using a large eddy simulation technique and detailed chemistry, and compared with CH4/air (in which thermal NO is dominant) and NH3/air (in which Fuel NO is dominant) flames. The study found that NO production in CH4/NH3/air flames is primarily dependent on OH concentration, like NH3/air flames, which confirmed that the NO is mainly fuel origin. Consequently, the study found that low NO emission in the order of 200 ppm can be achieved using a rich-lean combustor at primary zone global equivalence ratio of 1.4 owing to low OH concentration. However in lean and stoichiometric conditions, NO emissions from CH4/NH3/air flames were two times higher than those of NH3/air flames and ten times higher than those of CH4/air flames due to high OH concentration. In addition, CH4/NH3 mixing enhances the burning characteristics of NH3, and even until global equivalence ratio of 1.4, unburnt NH3 not get into the secondary stage from the primary stage.