An experimental and theoretical investigation of free turbulent premixed flames propagating in isotropic turbulence at neutrally stable preferential diffusion conditions is described. Experiments were limited to the wrinkled thin laminar ftamelet regime and involved mixtures of hydrogen, air, and nitrogen ignited within a fan-stirred combustion chamber. Measurements included flame tomography fo...

Large eddy simulations in a wall bounded domain are conducted in order to study the kinematic structure of premixed turbulent flame. The linear model presents a prospect of isolating the effects of each of the physical mechanisms that underly turbulent combustion. In the present study, we investigate the flame structure in the absence of thermodyamic effects such as heat release using this mode...

Simulations of forced ignition in a non-premixed laminar counterflow are used to study the effect of the strain rate on ignition success. A one dimensional calculation is performed, using detailed methane chemical kinetics, and treating the ignition event as an instantaneous heat release. Ignition success is seen to depend on the mixture composition and spark location, resulting in lean and ric...

Stereoscopic particle image velocimetry and planar laser induced fluorescence measurements of hydroxyl radical are simultaneously applied to measure, respectively, local turbulence intensities and flame front position in premixed ethylene-air flames stabilized on a bluff body. Three different equivalence ratios, 0.55, 0.63, and 0.7, and three different Reynolds numbers, 14 000, 17 000, and 21 0...

A turbulent lifted slot-jet flame is studied using direct numerical simulation (DNS). A single step chemistry model is employed with a mixture-fraction dependent activation energy to quantitatively reproduce the dependence of laminar burning rate on equivalence ratio that is typical of hydrocarbon fuels. It is observed that the leading flame edge exhibits a single branch close to the stoichiome...

The propagation speed of a thin premixed flame disturbed by an unsteady fluid flow of a larger scale is considered. The flame may also have a general shape but the reaction zone is assumed to be thin compared to the flame thickness. Unlike in preceding publications, the presented asymptotic analysis is performed for a general, multi-step reaction mechanism and, at the same time, the flame front...

Edge flames were investigated in a methane/O2/N2 counterflow diffusion flame burner. In a typical experiment, a stable counterflow diffusion flame in an axysymmetric configuration was perturbed by lowering the relevant Damköhler number slightly below the extinction value, Daext. As a result, the flame extinguished in the vicinity of the burner axis where conditions were uniform. An edge flame e...

This paper describes an analysis of acoustic wave scattering by turbulent premixed flames with moving, convoluted fronts that have random and possibly fractal characteristics. Such interactions play a role in the characteristic unsteadiness observed in turbulent combustion processes. The problem is posed with an integral formulation of the wave equation and assumes that the smallest scales of f...

The dynamic behavior of freely propagating premixed flames with large Lewis numbers was computationally simulated using a sixth-order central difference scheme and non-reflective boundary conditions. Results in the linear stage of the instability growth show that the growth rate dramatically decreases with increasing Lewis number and that the large activation energy excites the pulsating instab...