Nanosecond pulsed plasmas have been demonstrated, both experimentally and numerically, to be beneficial for ignition, mainly through gas heating (at different timescales) and radical seeding. However, most studies focus on specific gas conditions, and little work has been done to understand how plasma performance is affected by fuel and oxygen content, at different gas temperatures and deposited energies. This is relevant to map the performance envelope of plasma-assisted combustion across different regimes, spanning from fuel-lean to fuel-rich operation, as well as oxygen-rich to oxygen-vitiated conditions, of interest to different industries. This work presents a computational effort to address a large parametric exploration of combustion environments and map out the actuation authority of plasmas under different conditions. The work uses a zero-dimensional plasma-combustion kinetics solver developed in-house to study the ignition of CH4/O2/N2 mixtures with plasma assistance. A main contribution of the study is the detailed tracking of the energy, from the electrical input all the way to the thermal and kinetic effects that result in combustion enhancement. This extends prior works that focus on the first step of the energy transfer: from the electrical input to the electron-impact processes. Independent of the composition, four pathways stand out: (i) vibrational-translational relaxation, (ii) fast gas heating, (iii) O2 dissociation, and (iv) CH4 dissociation. Results show that the activated energy pathways are highly dependent on gas state, composition, and pulse shape, and can explain the observed range in performance regarding ignition enhancement. The approach can be used to calculate the fractional energy deposition into the main pathways for any mixture or composition, including new fuels, and can be a valuable tool to construct phenomenological models of the plasma across combustion environments.
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A physics-based ignition model with detailed chemical kinetics for live fuel burning studies
This work presents a computationally inexpensive framework for modeling combined pyrolysis and gas-phase combustion of general vegetative fuels, which improves on existing solvers by incorporating detailed chemical kinetics and predicts the ignition behavior. The main motivation for this work is capturing the burning behavior of live wildland fuels, which can differ from those of dead fuels. Existing models are unable to accurately predict the ignition time and temperature variations for the live fuel cases. The kinetics model used here accounts for the non-primary constituents of fuels, or “extractives”, which are expected to play a role in this distinct behavior. Validation studies show that the developed model is a promising tool for understanding the effects of fuel chemistry and spatial variation on ignition and fuel burning behavior. Case studies using the tool suggest that variations in ignition time can be explained by combined effects of variables such as moisture content, initial composition, and density.
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- Award ID(s):
- 1931592
- PAR ID:
- 10511924
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Combustion and Flame
- Volume:
- 265
- Issue:
- C
- ISSN:
- 0010-2180
- Page Range / eLocation ID:
- 113487
- Subject(s) / Keyword(s):
- Wildland fire live fuels pyrolysis
- Format(s):
- Medium: X Size: 2.4MB Other: pdf
- Size(s):
- 2.4MB
- Sponsoring Org:
- National Science Foundation
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