Swett, Clyde C., Jr., Donlon, Richard H.
An investigation was conducted to determine the effect of turbulence generated by different sizes of wire grid on the minimum spark-ignition energy of a flowing propane-air mixture. Test conditions were: pressure, 5 inches of mercury absolute; temperature, 80 degrees F; fuel-air ratio, 0.0835 (by weight); velocity, 50 to 250 feet per second; spark duration, 500 microseconds; and electrode spacing, 0.37 inch. The wire sizes of the turbulence promoters ranged from 0.006 to 0.105 inch in diameter and the promoters were located either 4-3/8 or 6-3/8 inches upstream of the spark electrodes. The investigation was conducted with turbulence having superimposed flow pulsations and duct resonance. The required ignition energy increased with wire size of the turbulence promoter and with gas velocity and decreased with distance from the promoter to the spark electrodes. The required ignition energy therefore increased with those factors that are reported to generate increased intensity of turbulence. At a velocity of 250 feet per second, three times more energy was required with the 0.105-inch wire-diameter promoter than with no promoter.
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