Microchronometric Schlieren Study of Gaseous Expansion from an Electric Spark

Abstract

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.