Ignition delays for mixtures of ethane,, n-butane, isobutane, hydro¬gen, or propane with oxygen and nitrogen were measured using a flow system with two experimental procedures. Delays were measured in the temperature ranges 571° to 733℃ for ethane, 444° to 715℃ for n-butane, 564° to 713℃ for isobutane, 594° to 652℃ for hydrogen, and 540° to 681℃ for propane. The effect of fuel concentration was measured for all fuels, and delays were inversely, proportional to fuel concentration to the 0.6 to 1.7 power. The effect of oxygen concentration was measured for propane and the butanes, and) in general, delays decreased slightly with increasing oxygen concentration. However, at very low temperatures, for n-butane, the dependence on oxygen concentration increased. The two pro-cedures gave different absolute values for the delays, but the trends were the same by either method. From the variation of delay with temper¬ature at constant fuel and oxygen concentration, apparent activation energies were calculated.
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