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NH3 slip, NOx emissions, and intermittent (OH∗, NH∗, NH2∗) species under bistable modes in non-premixed ammonia/hydrogen flames in a reverse-flow combustor

par Salah, Mohamed ;Kamal, Muhammad Mustafa ;Tarabet, Lyes;Parente, Alessandro
Référence International journal of hydrogen energy, 194, page (152374)
Publication Publié, 2025-12-01

Article révisé par les pairs

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Résumé :

Ammonia-hydrogen combustion offers a path to carbon-free power, yet its practical deployment is limited by high NOx emissions, unreacted NH3 slip, and a lack of high-fidelity optical data for validation in industrial combustors. This study experimentally investigates non-premixed NH3/H2 flames in a Stagnation Point Reverse Flow (SPRF) combustor, mapping stabilization regimes and characterizing multispecies chemiluminescence. Optical imaging of OH∗, NH∗, NH2∗, and exhaust analysis were conducted while varying hydrogen fraction, inlet conditions, and air-annulus geometry. The results reveal flame hysteresis, where identical inlet conditions yield bistable – attached and lifted – modes, each with distinct characteristics. Lifted flames exhibit improved NH3 conversion but higher NO emissions. OH∗ intensity monotonically increases with H2 content, providing a composition-robust signal, whereas NH∗ and NH2∗ display complex, mode-dependent behavior. NH∗/OH∗ emerges as a promising marker for fuel composition, whereas NH∗/NH2∗ or NH2∗/OH∗ qualitatively indicates stoichiometry. Reducing the air-annulus enhanced three-way (air-fuel-exhaust) mixing, mitigated NH3 slip at lower preheating temperatures, but raised NO, defining a controllable NO–NH3 trade-off.