Diffusion flame

About: Diffusion flame is a research topic. Over the lifetime, 9266 publications have been published within this topic receiving 233522 citations.

Blow-Out Stability of Gaseous Jet Diffusion Flames Part II: Effect of Cross Wind

Abstract: A non-dimensional stability curve that describes the blow-out stability of diffusion flames in a cross-wind, for different gases, has been established experimentally. For a given burner and a given gas, if the cross-wind speed is greater than a limiting value, a stable flame is not possible. For cross-wind speeds less than this limit, there are usually two blow-out limits which are on either side of the blow-out limit in still air.

Effects of turbulent structure and local concentrations on soot formation and combustion in C2H2 diffusion flames

Abstract: The present work is a continuation of previous work to study and model effects of turbulence on soot formation and combustion in turbulent flames. The main objectives have been to investigate effects of turbulent structure and of local chemical and thermodynamic conditions on soot formation and combustion. The following experimental conditions have been investigated for a free jet C2H2 diffusion flame: - Effects of variations of Reynolds number. - Effects of variable dilution of the fuel with nitrogen. - Effects of preheating of the fuel. - Effects of water—vapor addition to the fuel. Experimental results are given for mean quantities, fluctuations, the flatness factor and intermittency, and probability density distributions for the soot appearance. Based on a generalized eddy—dissipation concept, predictions were made for all experimental conditions. Variations of the Reynolds number had a strong effect on the amount of soot, with soot concentration increasing as the Reynolds number was reduced. Addition of nitrogen and water vapor to the fuel, as well as preheating the fuel, reduced the amount of soot. These observations could in general be accounted for by the mathematical model, taking into consideration the effects of changes of the turbulent structure due to the various input conditions.

Computational and experimental study of soot formation in a coflow, laminar ethylene diffusion flame

Abstract: A sooting, ethylene coflow diffusion flame has been studied both experimentally and computationally. The fuel is diluted with nitrogen and the flame is slightly fifted to minimize the effects of the burner. Both probe (thermocouple and gas-sampling techniques) and optical diagnostic methods (Rayleigh scattering and laser-induced incandescence) are used to measure the temperature, gas species, and soot volume fractions. A detailed soot growth model in which the equations for particle production are coupled to the flow and gaseous species conservation equations has been used to investigate soot formation in the flame. The two-dimensional system couples detailed transport and finite-rate chemistry in the gas phase with the aerosol equations in the sectional representation. The formulation includes detailed treatment of the transport, inception, surface growth, oxidation, and coalescence of soot particulates. Effects of thermal radiation and particle scrubbing of gas-phase growth and oxidation species are also included. Predictions and measurements of temperature, soot volume fractions, and selected species are compared over a range of heights and as a function of radius. The formation of benzene is primarily controlled by the recombination of propargyl radicals, and benzene production rates are found to limit the rate of inception, as well as the net rate of soot growth. The model predicted soot volume fractions well along the wings of the flame but underpredicted soot volume fractions by a factor of four along the centerline. Oxidation of particulates is dominated by reactions with hydroxyl radicals that attain levels approximately ten times higher than calculated equilibrium levels. Gas cooling effects due to radiative loss are shown to have a very significant effect on predicted temperatures.