Experimental and Numerical Study of NH₃/CH₄ Counterflow Premixed and Non-premixed Flames for Various NH₃ Mixing Ratios

Abstract

Ammonia is a promising sustainable fuel, however, its low reactivity creates challenges in industrial applications. In this study, ammonia/methane mixtures were considered for premixed and non-premixed counterflow flames. The extinction stretch rate was measured over a wide range of ammonia/methane mixing ratios and compared to 1D numerical results from four different mechanisms. Additionally, for counterflow premixed twin flames, quantitative analysis based on the comparison of experimental and numerical FWHM of OH and NO profiles was performed. Results showed that in premixed flames, all the mechanisms investigated were inadequate for predicting the extinction stretch rate, specifically for lean flames. In non-premixed flames, Okafor's mechanism was accurately predicting the extinction stretch rate. For the FWHM analysis, the numerical mechanisms overpredicted both OH and NO apparition in the flame, except for Tian's mechanism which underpredicted OH apparition. GRI Mech 3.0 performed well for small quantities of ammonia but failed to reproduce the pure ammonia case.Okafor's and UCSD mechanisms gave better predictions of experimental trends, though overestimated both OH and NO apparition. In the FWHM analysis of both OH and NO, the lower R 2 values in the lean region suggest that the lean region should be the focus for mechanism improvement.

Study of the Combined Effect of Ammonia Addition and Air Coflow Velocity on a Non-premixed Methane Jet Flame Stabilization

“…Demonstration of gas turbine power generation (Kurata et al, 2019) are encouraging but some challenges remain for industrial usage due to NOx emission and stabilization issues. The first one has been the subject of several works, including fundamental studies on the NOx production for ammonia, methane, or their blends (Zieba et al, 2009;Li et al, 2013;Hayakawa et al, 2015), the validation of the associated chemistry (Han et al, 2019;Okafor et al, 2018;Colson et al, 2020), and practical strategies for industrial burners, such as the rich-lean strategy (Kurata et al, 2019;Okafor et al, 2019). The stabilization issue was examined for premixed ammonia/air flame by Hayakawa et al (2017) in a swirl burner configuration, but fundamental aspects of ammonia and ammonia blend flames stabilization still need to be considered.…”

Numerical Analysis on the Evolution of NH2 in Ammonia/hydrogen Swirling Flames and Detailed Sensitivity Analysis under Elevated Conditions

“…For the case of Okafor's model, although it has shown very good resolution in other experimental campaigns, the impact of different hydrodynamics and reaction ratios affect the final results, thus still requiring further improvements out of the scope of this work. Recently, Colson et al (2020) showed how the resolution of existing mechanisms is still inaccurate for certain premixed ammonia-based blends. Thus, only the points T2/P2 and T3/P3 (refer to Table 1) were used for CFD analysis.…”

Humidified ammonia/hydrogen RQL combustion in a trigeneration gas turbine cycle

“…years). Consequently, works on the use of methane-ammonia [17,18], Coke Oven Gas-ammonia [19], ammonia-hydrogen [20][21][22] and pure ammonia [23][24][25] have been undertaken, in an attempt to assess the feasibility of ammonia as a means of reducing/eliminating carbon in gas turbine power production. Most studies have focused on the complex reaction mechanisms, flame structures and technical challenges of using the molecule for these means of energy generation.…”