Gaseous phenomena induced by short-duration sparks at atmospheric pressure have been photographed during the first microseconds of their existence by a flash-schlieren technique. The growth of the heated gas domain (kernel) expanding from the spark discharge has been observed for air and argon. The kernel continues to expand rapidly, but subsonically, after the spark current ceases and after the shock wave separates. It develops further into a torus about the spark electrodes and eventually decays. The development of flame from a heated gas kernel in a flammable mixture is illustrated. Energy relationships for the expanding argon kernel are discussed.
The g~seo~s expansion from an electric spark is described in this paper in terms of ideal gas theory. The a.ssumptlOn IS mad~ ~~at a quantity of energy is injected into a small gas volume in an infinitesimally short time and that the 1~ltIal volume of gas then expands until it reaches the pre-spark pressure at an elevated temperature .. ~xpenmental results are ~:,~n for a condenser discharge illustrating the dependence of the pr~ssure e~Ulhbrated gas volume upon mltIal pressure and condenser energy. These results are interpreted usmg the Ideal gas model presented. The significance of this expansion to the problem of spark ignition in combustible gases is discussed.
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