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

Abstract

Ammonia/hydrogen blends have received some attention toward the development of new technologies focused on gas turbine combustion systems, as doping of hydrogen in ammonia enhances flame speed and stability while decreasing ignition energy. One of the challenges of these blends relies on the appropriate computational modeling of their combustion properties in combination with the complex hydrodynamics inherent to flow control techniques such as swirling flows, which are known to be the main method of flame stabilization in current gas turbines. Moreover, it is well-known that large reaction kinetic models are difficult to employ in these computational analyses, thus increasing the difficulty of obtaining reliable methods for the design of new combustors. Therefore, this research analyses a reduced chemical reaction mechanism, namely Okafor's mechanism, comparing its performance and accuracy against obtained experiments. Emission measurements and non-intrusive laser techniques (LDA) were employed to validate models running on CHEMKIN-PRO flow reactors and RANS Complex Chemistry. Once validated, the study identified the main contributors and reaction kinetics of NH 2 and NO consumption, hence evaluating the process via production rates and sensitivity analysis of various important reactions. The results depicted positive correlation between NH 2 formation and heat release, N 2 , H 2 O, N 2 O, NH, NNH, NO, O formation, whereas NH 3 , N 2 H 3 and NO 2 have shown negative correlation. Statistical correlations supported these findings but unfortunately were inconclusive to the impacts of vorticity and turbulence over the production/consumption of amidogen. Sensitivity analysis has shown NH 2 radicals and atomic N to be the main contributors of NO formation in the flame zone, although most of the NO formed in the flame zone shown to be consumed at the postflame zone due to the presence of NH x radicals and atomic N.

Numerical Simulation of Turbulent Premixed CH4-H2 Flames in a High Pressure Swirl Burner for Gas Turbine Applications

“…State-of-the-art imaging techniques have revealed new insights into HPGSB flame behaviors and interactions. Chemiluminescence methods effectively visualize key intermediates like OH* and CH* radicals to identify stability limits, heat release patterns, and combustion phases (Mashruk et al 2023;Kurji et al 2016;. High-speed imaging shows elevated pressures enhance efficiency while saturated fuels increase soot and NOx through detailed flame structure analysis (Kurji et al 2016;Buffi et al 2017;Marsh et al 2017).…”

“…Significant high pressure burners research has centered on alternative fuels including ammonia, hydrogen, syngas and biogas .Studies show blending ammonia with methane or hydrogen can substantially reduce NOx versus pure methane combustion, but higher ammonia fractions increase CO and UHC due to decreased flame temperatures (Valera-Medina et al 2015;Mashruk et al 2023;Pugh et al 2021;Xiao et al 2017). The addition of water vapor enhances combustion of carbonaceous fuels through widening stability limits, increasing flame speeds, and reducing emissions Pugh et al 2019;.…”

“…The addition of water vapor enhances combustion of carbonaceous fuels through widening stability limits, increasing flame speeds, and reducing emissions Pugh et al 2019;. Optical diagnostics have provided details on the combustion behaviors, efficiencies, and emissions of these mixtures (Mashruk et al 2023;Marsh et al 2017). The feasibility of 100% ammonia combustion has been analyzed (Bagdanavicius et al 2013).…”

Experimental and numerical analyses of nitrogen oxides formation in a high ammonia-low hydrogen blend using a tangential swirl burner

“…In the present study, Ansys CHEMKIN-Pro [33] was applied for all numerical simulations to calculate the concentration of NOX emissions. Based on the previous studies [31,[34][35][36], a chemical reactor network (CRN) was improved for better predictions of emissions from the combustion zone, as illustrated in Fig. 3.…”

Simultaneous measurements of NH2 and major species and temperature with a novel excitation scheme in ammonia combustion at atmospheric pressure

“…NH2 is of particular importance for NH3 chemistry as it is the initial product of the NH3 decompositions, and it plays a key role in NO X formation/consumption [6] and flame propagation [7].…”