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Two- and three-dimensional direct numerical simulation of spherical expanding flames

Titel Englisch Two- and three-dimensional direct numerical simulation of spherical expanding flames
Gesuchsteller/in Frouzakis Christos
Nummer 116669
Förderungsinstrument Projektförderung (Abt. I-III)
Forschungseinrichtung Institut für Energietechnik ETH Zürich
Hochschule ETH Zürich - ETHZ
Hauptdisziplin Fluiddynamik
Beginn/Ende 01.09.2007 - 31.08.2010
Bewilligter Betrag 145'550.00
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Keywords (10)

Direct numerical simulation; Sperical flame propagation; Hydrodynamics instability; Thermodiffusive instability; Cellular flames; Hydrogen combustion; combustion instabilities; premixed laminar flames; cellular flame; spectral element method

Lay Summary (Englisch)

Lay summary
Expanding premixed spherical flames are susceptible to different instability mechanisms resulting in transitions from stable laminar flame propagation, to unsteady flame cracking and cell formation, to cellular flame propagation, and, when the flame radius is large enough, self-turbulization of the flame even in flows that are initially quiescent.

The associated phenomena and the observed rich dynamics (formation of regular or chaotic cellular patterns, spiral waves on the flame surface, periodic and aperiodic pulsations) are of fundamental as well as of practical interest (e.g. spark ignition in an internal combustion engine).

In this project, we intend to study the effects of hydrodynamic, and thermodiffusive instabilities on the propagation of expanding premixed spherical flames using detailed numerical simulations. So far, numerical simulations have either assumed spherical symmetry, thus reducing the problem to one spatial dimension, or that the density is constant (thermodiffusive model), or considered the flame as a discontinuity in density (hydrodynamic model). Detailed multidimensional simulations coupling all flow and thermochemistry processes are scarce, and limited to single-step description of the kinetics and simple transport.

We plan to use direct numerical simulations to study expanding spherical flames in two and three spatial dimensions, considering both single-step and detailed chemistry, and full coupling of all relevant processes. Equi-diffusive (prone only to hydrodynamic instabilities) and diffusionally-imbalanced mixtures (prone to hydrodynamic as well as thermodiffusive instabilities) will be considered, aiming at simulating all the transitions from stable flame propagation to self-turbulization. Our parallel spectral element code based on high-order methods of low numerical diffusivity, and characterized by good scalability properties to a large number of processors, is well suited to address these issues. It will provide detailed information of the subprocesses and the instabilities involved that cannot be obtained by other means, and enhance our understanding of the associated phenomena.

Of particular importance for practical applications is also the detailed study of the propagation of hydrogen spherical flames.

Hydrogen is currently intensely investigated as an environmentally-friendly alternative fuel, or as an additive to hydrocarbon fuels for internal combustion engines in order to enhance flame stability at strongly diluted conditions.
Direktlink auf Lay Summary Letzte Aktualisierung: 21.02.2013

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