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This work presents a numerical model to evaluate the energy deposition pathways activated during plasma-assisted ignition of a stoichiometric ammonia/air mixture at atmospheric conditions. To that end, zero-dimensional simulations are conducted of ignition by nanosecond repetitively pulsed discharges (NRPD), for which a detailed energy tracking is performed from the electrical input to the mechanisms that directly influence ignition. The analysis of the plasma energy deposition pathways is relevant to gain insight into complex plasma kinetic mechanisms and help optimize actuation strategies. Results show that the main pathways activated are: (i) slow-gas heating, (ii) fast-gas heating, (iii) dissociation of NH3 into NH2, (iv) dissociation of O2, and (v) dissociation of NH3 into NH. The exact proportion of energy deposited in each pathway is highly dependent on the reduced electric field profile, in particular the "down-slope" dominates the energy breakdown. The influence of the reduced electric field magnitude is studied for square pulses. The correlation between the various plasma energy deposition pathways and NOx emissions is quantified.
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Emissions and Dynamic Stability Improvements in Premixed CH4/NH3 Swirling Flames With Nanosecond Pulsed Plasmas
In this paper we explore the effects of nanosecond repetitively pulsed discharges (NRPD) on combustion instabilities and NOx emissions of CH4/NH3 flames, in a swirl-stabilized, 6 kW combustor. The combustor has a large dump plane ratio resulting in a turbulent flame with a single compact macrostructure across all operating conditions. Discharges are setup with a central pin-to-cylindrical-wall type electrode configuration with a discharge gap of 4.55 mm at the dump plane. For pure methane, instabilities occur at various frequencies and amplitudes, up to 1000 Pa. NPRD actuation was successful in suppressing instabilities across all conditions, with best reduction being as much as 23 dB. The discharge voltages ranged from 6-9 kV at a pulse rate of 9 kHz, equivalent to 5-12 mJ/pulse energies and plasma powers less than 99W. For pure CH4 flames, the NRPD actuation increased NOx emissions, but for high NH3/CH4 blends, the NRPD actuation reduced NOx emissions.
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- Award ID(s):
- 2339518
- PAR ID:
- 10568178
- Publisher / Repository:
- American Institute of Aeronautics and Astronautics
- Date Published:
- ISBN:
- 978-1-62410-716-0
- Format(s):
- Medium: X
- Location:
- Las Vegas, Nevada
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.2514/6.2024-3898
