Experimental Investigation of the Structure and NO Emissions from Swirling Lean Premixed NH3/CH4/Air Flames and Their Correlation with OH

Ammonia/methane fuel blends have gathered interest asa promisingsolution for the development of a low-carbon energy system. In thatpursuit, this work focused on the effects of turbulent intensity (u & PRIME; = 1.3-2.6 m/s), ammonia contents (X NH3 = 0.0-1.0), and equivalenceratios (& phi; = 0.5-0.9) on the flame structure and NO emissionsof bluff-body swirl-stabilized premixed flames of ammonia/methane/airas well as their links to hydroxyl planar laser-induced fluorescence(OH-PLIF) intensity. Three swirling flame shapes are distinguished,which are jointly determined by the ammonia content and equivalenceratio. The normalized OH-PLIF intensity (I average/S L) of all X NH3 , u & PRIME;, and & phi; can be collapsedwell onto one unified correlation as a function of the normalizedturbulent intensity u & PRIME;/S L. The flame surface density (FSD, marked as & sigma;) of confinedswirling flames was rarely reported before, and the FSD in a V shapeincreases obviously when transiting to a M shape as the ammonia contentreduces. The turbulent flame area ratio (A T/A L) derived from the FSD is increasingas u & PRIME;/S L increases;however, it decreases first and then increases as & phi; increases.Then, a new description of the link between NO, OH, and X NH3 was provided, which improves the correlationperformance more than the previous studies only considering the linkbetween NO and OH.

Automated summary

This study focuses on the effects of turbulent intensity, ammonia content, and equivalence ratio on the flame structure and NO emissions of ammonia/methane/air flames, as well as their links to OH-PLIF intensity. It is found that the flame shape is determined by the ammonia content and equivalence ratio, and a unified correlation between turbulent intensity and OH-PLIF intensity is proposed. A new description of the link between NO, OH, and ammonia content is provided, improving the correlation performance.