TY - JOUR
T1 - Stabilization and onset of oscillation of an edge-flame in the near-wake of a fuel injector
AU - Kurdyumov, Vadim N.
AU - Matalon, Moshe
N1 - Funding Information:
This work has been partially supported by the National Science foundation under Grant DMS-0405129. V.K. also acknowledges the support of the Spanish Government through the Ramón y Cajal Program and the MEC under Project ENE2005-09190-C4. M.M. also acknowledges the support of the United States Israel Binational Science Foundation under Grant 2004069.
PY - 2007
Y1 - 2007
N2 - The stabilization of an edge-flame in the near-wake of a fuel injector is discussed within the context of a diffusive-thermal model, but with a realistically computed flow. Although the boundary layer approximation can be used to describe the mixing process in the wake region, the velocity field in the immediate vicinity of the injector satisfies the full Navier-Stokes equations. The stabilization of the edge-flame and its dynamics are affected not only by diffusive-thermal effects, but also by the acceleration experienced by the fuel and oxidizer entrained into the mixing layer. The present calculations confirm an earlier prediction that edge-flame oscillations can be triggered by heat losses alone. Moreover, it is shown that when the intensity of the losses is excessive, oscillations can occur even when the Lewis numbers are less than one. New results are also obtained when examining the flame response to variations in Lewis numbers. For Lewis numbers that are not too large, there exists a minimum value of the Damkhler number D below which the edge-flame cannot be stabilized. The response curve, describing the standoff distance as a function of D is multi-valued and the turning point, which also coincides with the marginal stability state, identifies extinction or blowoff conditions. For D above this value, the edge-flame is steady and stable. For relatively large values of the Lewis number the response curve is monotonic. There is, however, a restricted range of states where the flame undergoes spontaneous oscillations with the edge-flame moving back and forth along the stoichiometric surface dragging behind it the trailing diffusion flame.
AB - The stabilization of an edge-flame in the near-wake of a fuel injector is discussed within the context of a diffusive-thermal model, but with a realistically computed flow. Although the boundary layer approximation can be used to describe the mixing process in the wake region, the velocity field in the immediate vicinity of the injector satisfies the full Navier-Stokes equations. The stabilization of the edge-flame and its dynamics are affected not only by diffusive-thermal effects, but also by the acceleration experienced by the fuel and oxidizer entrained into the mixing layer. The present calculations confirm an earlier prediction that edge-flame oscillations can be triggered by heat losses alone. Moreover, it is shown that when the intensity of the losses is excessive, oscillations can occur even when the Lewis numbers are less than one. New results are also obtained when examining the flame response to variations in Lewis numbers. For Lewis numbers that are not too large, there exists a minimum value of the Damkhler number D below which the edge-flame cannot be stabilized. The response curve, describing the standoff distance as a function of D is multi-valued and the turning point, which also coincides with the marginal stability state, identifies extinction or blowoff conditions. For D above this value, the edge-flame is steady and stable. For relatively large values of the Lewis number the response curve is monotonic. There is, however, a restricted range of states where the flame undergoes spontaneous oscillations with the edge-flame moving back and forth along the stoichiometric surface dragging behind it the trailing diffusion flame.
KW - Diffusion flame
KW - Diffusive-thermal
KW - Edge-flame
KW - Instabilities
KW - Oscillations
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U2 - 10.1016/j.proci.2006.07.248
DO - 10.1016/j.proci.2006.07.248
M3 - Conference article
AN - SCOPUS:34548745361
SN - 1540-7489
VL - 31 I
SP - 909
EP - 917
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 1
T2 - 31st International Symposium on Combustion
Y2 - 5 August 2006 through 11 August 2006
ER -