Influence of Different Frequency Power Generators on Plasma Temperatures in the Ammonia Decomposition Process: OES-Based Temperature Profiling in a Gliding Arc
Michalina Perron, Tim Gehring, Mateusz Wiosna, Wojciech Gajewski, Michał MłotekAbstract
A gliding arc plasma reactor operated with highly concentrated ammonia (90 vol % NH3 in N2) was investigated using spatially resolved optical emission spectroscopy, electrical diagnostics, and gas chromatography. Fitting the N2 second positive system (310–360 nm) yielded rotational and vibrational temperature profiles along the arc for 50 Hz and Bipolar HV high-frequency (25–35 kHz) excitation. Results indicate local thermal equilibrium near ignition and a transition to nonequilibrium along the arc, which is a typical characteristic of a gliding arc. Bipolar HV kHz excitation produced higher vibrational temperatures, enhanced N2+ emission downstream, and substantially increased reaction rates localized in the discharge channel. It demonstrates improved energy concentration and higher ammonia conversion compared to 50 Hz, and promising potential for energy-efficient hydrogen recovery from ammonia.