Swett, Clyde C , Jr
December 18, 1951
The effect of electrode spacing, configuration, and material on the energy required for ignition of a propane-air mixture at a pressure of 3 inches mercury absolute was determined. The energy required decreased and then increased as the spacing was increased; a minimum occurred at a spacing of 0.65 inch. Small-diameter electrodes required less energy than large-diameter electrodes if the spacing was less than optimum; at the spacing of 0.65 inch no differences were observed. Glow discharges required more energy for ignition than the arc-glow discharges; with glow discharges the effect of electrode material was negligible. A determination of the energy distribution along the discharge showed one-third to one-half of the energy to be concentrated in a small region near the cathode and the remainder uniformly distributed across the spark gap. Long duration (600-microsec) sparks required much less energy than the short-duration (1-microsec) sparks.
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