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Investigation of ignition by composite sparks under high turbulence intensity conditions

Authors
Journal
Symposium (International) on Combustion
0082-0784
Publisher
Elsevier
Publication Date
Volume
24
Issue
1
Identifiers
DOI: 10.1016/s0082-0784(06)80210-9

Abstract

In order to clarify the mechanism of ignition process by composite sparks under high turbulence intensity conditions, flame kernel development was observed and the effects of turbulence intensity and energy distribution of composite sparks on the minimum ignition energy were studied, using an ignition device which could vary energies of a capacitance component and the following glow discharge (subsequent component) independently. Mutual collision of jets emanating from four nozzles fitted on a combustion chamber provided turbulent fields with minimum, mean flow near the spark gap. Turbulence intensity ranges from 2.53 m/s to 9.87 m/s. In addition, a numerical simulation was made to study the mechanism of flame kernel development in its early stages. The experimental results indicate that the intitial stages of flame kernel development are the same as those in laminar conditions. Transformation of the laminar flame kernel into a turbulent flame kernel occurs earlier as turbulence intensity increases. The calculated results suggest that this tendency is associated with a degree of suppression of turbulence by a spherical shock wave initiated at the first onset of spark. Ignition ability was found to be much improved by the addition of the subsequent component to the capacitance component. This effect was pronounced in the case of turbulent mixtures of high intensity.

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