The interaction of flame curvature and stretch, part 1: The concave premixed flame

Effects of fresh gas velocity and thermal expansion on the structure of a Bunsen flame tip

“…8) does not level off for large Lí, and even seems to increase linearly with U at the largest valúes of the thermal expansión y for which a solution has been computed. Such linear increase would mean that the curvature V • n tends to a constant valué for large Lí, a result suggested by Echekki and Mungal [16] on the basis of their experiments with a slot burner and later rationalized by Poinsot et al [17] from a heuristic extensión of the result (14).…”

“…This quantity fully characterizes the response of the fíame to small curvature and strain. It was first introduced by Markstein [8] as a phenomenological constant and has been subsequently computed using asymptotic methods for small valúes of the quantity in parentheses in (14). For the case of a single overall Arrhenius reaction, it is [9][10][11]24]…”

“…In an analysis of strongly curved ñames carried out using the thermodiffusive model with an artificial velocity field for which an analytic solution exists, Mikolaitis [14,15] found that a conveniently defined fíame velocity depends separately and nonlinearly on the strain rate and the curvature of the fíame. Echekki and Mungal [16] and Poinsot et al [17] proposed a heuristic modification of the definition of fíame stretch in which the factor U L multiplying the curvature of the fíame is replaced by the velocity of the curved and strained fíame, and found that the modified relation between velocity, curvature and strain rate, which is no longer linear, compares well with their numerical and experimental results for fíame tips of large curvature.…”

Analysis of flame curvature evolution in a turbulent premixed bluff body burner

“…Clavin and Joulin [3] examined the stability of highly wrinkled premixed flames. Activation energy asymptotics were used to examine concave and convex premixed flames with a radius of curvature comparable to the thickness of the preheat zone [4,5], aiming to analyse the statistical behaviour of flame stretch and its influence on flame propagation. Based on two-dimensional [6,8,[10][11][12][13][14][15]23] and three-dimensional [7, 16-20, 22, 24, 26, 27, 29] Direct Numerical Simulation (DNS), it has been shown that local flame curvature significantly affects the statistical behaviours of displacement speed S d = |∇c| −1 (Dc/Dt) (where c is the reaction progress variable) and its components for both statistically planar [10-18, 22-24, 26, 27, 31] and statistically spherical flames [19,20,29,36].…”

Theory of non-adiabatic conical spray premixed flames with non-unity Lewis number

“…Nevertheless, some effort has been made to investigate the interaction of the flame curvature and stretch stabilization mechanism of inverted Bunsen flames (positively curved flames) [15][16][17][18][19]. Mikolatis [20,21] investigated the interaction of flame curvature and stretch with positive and negative curvatures and reported that the flame speed is strongly dependent on flame curvature in the presence of Nomenclature Dimensional quantities B 0 pre-exponential factor C 0 PG specific heat of gaseous mixture…”