We derive analytical expressions for the burning rate of a flame propagating in a prescribed steady parallel flow whose scale is much smaller than the laminar flame thickness. In this specific context, the asymptotic results can be viewed as an analytical test of Damköhler’s hypothesis relating to the influence of the small scales in the flow on the flame; the increase in the effective diffusio...

At a density near a few ×10 g cm, the subsonic burning in a Type Ia supernova enters the distributed regime (high Karlovitz number). In this regime, turbulence disrupts the internal structure of the flame, and so the idea of laminar burning propagated by conduction is no longer valid. The nature of the burning in this distributed regime depends on the turbulent Damköhler number (DaT ), which st...

Nomenclature CR,CI = empirical constants C = speed of sound, m/s D = Van-Driest damping function E = specific total energy f = frequency, Hz G = level-set variable hf,i = heat of formation of species i at reference condition k = turbulent kinetic energy lF = laminar flame thickness, m l = inner-layer flame thickness, m n = unit vector normal to flame front p = pressure Pr = Prandtl number q = r...

Ignition and flame spread above liquid fuels initially below the flashpoint temperature are studied. Opposed air flow to the flame spread due to forced and=or natural convection is considered. Unsteady computations are performed in order to study the ignition event and to describe both uniform and pulsating flame spread. Pools of finite width and length are studied in air channels of prescribed...

The speed of propagation of a premixed turbulent flame correlates with the intensity of the turbulence encountered by the flame. One consequence of this property is that premixed flames in both laboratory experiments and practical combustors require some type of stabilization mechanism to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity t...

A simplified model describing acoustically-generated parametric instability in a spherical chamber is developed for quasi-one-dimensional, low-Mach flames. We demonstrate how sound waves generated by a centrally-ignited, outwardly-propagating accelerating flamefront can be incorporated into a theory of self-similar flame acceleration in free space developed previously. Being reflected from the ...

High-fidelity multi-scale simulation tools are critically important for examining energy conversion processes in which the coupling of complex chemical kinetics, molecular transport, continuum mixing and acoustics play important roles. The objectives of this thesis are: (i) to develop a state-of-the-art numerical approach to capture the wide spectra of spatio-temporal scales associated with rea...

This study has assessed the validity of the commercially available turbulent flame speed models within ANSYS Fluent as applied to hydrogen/methane/air combustion, with 5 different fuel compositions considered from 100% methane to 100% hydrogen. It was found that existing turbulent flame speed models were capable of producing accurate predictions up to 60% hydrogen with the Zimont model being th...

Steady premixed flames subjected to space-periodic steady forcing are studied via inhomogeneous Michelson-Sivashinsky (MS) and then Burgers equations. For both, the flame slope is posited to comprise contributions from complex poles to locate, and from a base-slope profile chosen in three classes (pairs of cotangents, single-sine functions or sums thereof). Base-slope-dependent equations for th...

This paper describes the non-linear dynamics of premixed flames responding to harmonic velocity disturbances. It extends a prior computational study which determined the key parameters influencing the nonlinear flame characteristics. It was shown that the linear and nonlinear characteristics of the flame dynamics were controlled by the superposition of two sources of flame disturbances: those o...