Some open issues in premixed turbulent combustion

Abstract

The widely studied subject of premixed turbulent combustion is discussed, with particular attention to identification and review of controversial and unresolved fundamental issues having practical significance. Four such topics are discussed: (1) prediction of turbulent burning velocity (ST) in the flamelet regime, (2) the role of the velocity spectrum on ST, (3) the existence and properties of turbulent combustion with distributed reaction zones, and (4) quenching of flames by turbulence. Directions for future research are suggested.

Thin front propagation in steady and unsteady cellular flows

“…By fixing θ = 1 for x → −∞ and θ = 0 for x → ∞ the front propagates from left to right. It is natural to expect that the front speed can be expressed according to the following relation [7,25,26] …”

Front speed enhancement in cellular flows

“…Therefore, in the following, we consider the velocity field as given. This approximation, hardly tenable in the context of flame propagation in gases, is rather appropriate for chemical front propagation in some liquid solutions [2,[5][6][7]. Under these simplifying assumptions, the evolution of θ is described by…”

Front dynamics in turbulent media

“…4 Mainly due to its practical relevance in combustion processes, the subject has motivated numerous theoretical as well as experimental efforts. [5][6][7][8][9][10] The generic understanding coming from these studies is that the turbulent front velocity v T is larger than v 0 , to an extent which depends on the intensity and spatiotemporal correlations of the turbulent flow. Some other issues, however, such as velocity quenching effects, role of turbulent spectra remain somewhat more open.…”