TY - JOUR
T1 - Flow dynamics of laser-induced breakdown at a fuel–oxidizer interface and its effect on ignition
AU - Wang, Jonathan M.
AU - MacArt, Jonathan F.
AU - Freund, Jonathan B.
N1 - Funding Information:
We thank Alessandro Munafò, Andrea Alberti, and Marco Panesi for providing simulations of the laser-induced breakdown. We are also grateful to Jonathan E. Retter, Munetake Nishihara, and Gregory S. Elliott for providing experimental measurements. This material is based in part upon work supported by the Department of Energy, National Nuclear Security Administration, under Award Number DE-NA0002374.
Publisher Copyright:
© 2021
PY - 2021/7
Y1 - 2021/7
N2 - Motivated by experimental observations, we analyze the ignition dynamics following a laser-induced breakdown near a distinct fuel–oxidizer interface using detailed simulations of the flow following a model energy deposition. Cases simulated with a detailed H2-O2 combustion model show the dependence of ignition time, and its success or failure, on the post-breakdown kernel geometry. For asymmetric kernels, ignition can occur by ejections of hot gas that propagate several times the kernel size. The extreme conditions induced near the laser focus lead to near-complete dissociation, allowing heat release by radical recombination to be a primary mechanism by which the ejected gas maintains ignition temperatures as it advects. For kernels close to ehe interface, a pronounced hydrodynamic interaction between the density gradient and expanding kernel results in ignition-suppressing flow that repels hot gas away so completely in some cases that ignition fails. Mechanisms for a wide range of parameters are studied with a four-species reduced combustion model, and we show that this ignition-adverse flow response, particularly salient in hydrogen–oxygen cases, is absent for heavier fuels. For disparate fuel and oxidizer molecular weights, the varied flow response due to the breakdown location is a primary determinant of outcome.
AB - Motivated by experimental observations, we analyze the ignition dynamics following a laser-induced breakdown near a distinct fuel–oxidizer interface using detailed simulations of the flow following a model energy deposition. Cases simulated with a detailed H2-O2 combustion model show the dependence of ignition time, and its success or failure, on the post-breakdown kernel geometry. For asymmetric kernels, ignition can occur by ejections of hot gas that propagate several times the kernel size. The extreme conditions induced near the laser focus lead to near-complete dissociation, allowing heat release by radical recombination to be a primary mechanism by which the ejected gas maintains ignition temperatures as it advects. For kernels close to ehe interface, a pronounced hydrodynamic interaction between the density gradient and expanding kernel results in ignition-suppressing flow that repels hot gas away so completely in some cases that ignition fails. Mechanisms for a wide range of parameters are studied with a four-species reduced combustion model, and we show that this ignition-adverse flow response, particularly salient in hydrogen–oxygen cases, is absent for heavier fuels. For disparate fuel and oxidizer molecular weights, the varied flow response due to the breakdown location is a primary determinant of outcome.
KW - Hydrogen-oxygen ignition
KW - Ignition of heavy fuels
KW - Laser-induced ignition
KW - Nonpremixed forced ignition
KW - Reduced chemical modeling
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U2 - 10.1016/j.combustflame.2021.02.021
DO - 10.1016/j.combustflame.2021.02.021
M3 - Article
AN - SCOPUS:85103044189
SN - 0010-2180
VL - 229
JO - Combustion and Flame
JF - Combustion and Flame
M1 - 111375
ER -