Topic
Diffusion flame
About: Diffusion flame is a research topic. Over the lifetime, 9266 publications have been published within this topic receiving 233522 citations.
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01 Jan 2000
TL;DR: In this article, the results obtained for the unconditionally filtered scalar dissipation rate are qualitatively compared with general observations of scalar mixing from experiments in non-reactive and reactive jets.
Abstract: Predictions of scalar mixing and the scalar dissipation rate from large-eddy simulations of a piloted nonpremixed methane/air diffusion flame (Sandia flame D) using the Lagrangian-type flamelet model are presented. The results obtained for the unconditionally filtered scalar dissipation rate are qualitatively compared with general observations of scalar mixing from experiments in non-reactive and reactive jets. In agreement with experimental data, provided the reaction zone has an inward direction, regions of high scalar dissipation rate are organized in layerlike structures, inwardly inclined to the mean flow and aligned with the instantaneous reaction zone. The analysis of single-point time records of the mixture fraction reveals ramplike structures, which have also been observed experimentally and are believed to indicate large-scale turbulent structures. The probability density function (pdf) of the instantaneous resolved scalar dissipation rate at stoichiometric mixture evaluated at cross sections normal to the the nozzle axis is shown to be described accurately by a lognormal pdf with σ=1. A new model for the conditionally averaged scalar dissipation rate has been proposed and is shown to account for local deviations from the simple mixing layer structure. The stabilizing effect of the pilot flame in the present configuration is also discussed. Finally, the influence of the resolved fluctuations of the scalar dissipation rate on the flame structure is investigated, revealing only a weak influence on temperature and nitric oxide predictions. However, the model requires further refinement for situations in which local extinction events become important.
142 citations
TL;DR: In this paper, the structure and propagation of a methanol (CH3OH)-air triple flame were studied using direct numerical simulations (DNS) and a mixture fraction-temperature phase plane description of the triple flame structure was proposed to highlight some interesting features in partially premixed combustion.
141 citations
TL;DR: In this article, the transition from CH4/H2 mixtures to periodic oscillations was investigated under acoustically coupled and uncoupled conditions in a 50kW swirl stabilized combustor.
141 citations
TL;DR: In this paper, the effect of the preferential molecular diffusion and the Lewis number on the average reaction rate was investigated for two sets of flames: turbulent pressurized Bunsen flames, where hydrogen content and pressure is varied (from CNRS Orleans), and highly turbulent combustor flames where the hydrogen content is varied.
141 citations
TL;DR: In this paper, the structure of unconfined lean premixed methane-air flames stabilized on an axisymmetric bluff body has been examined for conditions increasingly closer to blowoff and during the blow-off event.
141 citations