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Abstract
Three effects found during the measurement of oxides of nitrogen produced by liquid fuel diffusion flames are reported. In each experiment a diffusion flame at one atmosphere pressure was formed around a horizontal fuel wetted cylinder. In the first experiment a porous metal cylinder of 5.2 mm diameter was wetted by normal heptane and placed in a low velocity stream of ambient air. Soot escaping from the turbulent wake of the diffusion flame was deposited on the surfaces of a large collection system located above the flame. This collection system drew in all of the flame products plus some entrained ambient air. The soot was found to give off NO slowly at ambient temperature and more rapidly when healed. The NO from the soot amounted to 20 percent of the gas phase NO produced by the flame. In the second experiment, a quartz microprobe was used to take gas samples along a horizontal line perpendicular to the cylinder axis. The cause of high NO leadings indicated by the chemiluminescent analyzer for samples taken near the liquid surface was traced to sensitivity of the analyzer to pyrolysis products. In the third experiment, the fuel wetted surface was a horizontal moving thread. It was found that the presence of unburned hydrocarbons in the air around the flame promoted the conversion of NO to NO2 without changing the total amount of NOx produced.