Gas samples have been withdrawn from laminar atmospheric-pressure propane-air flat flames using an uncooled quartz probe with a 0.1 mm diameter orifice. The samples (60 torr total pressure) are analyzed by gas chromatography for all C11,-C44, hydrocarbons, CO1C02, N2, and 02. The Quartz probe is movable vertically, allowing measurement of the concentrations of stable molecules as a function of height above the burner with vertical resolution better than 0.2 mm. During lean (#x3A6;=0.6-0.9) operation, intermediate hydrocarbon products (C2H2, C2H4, C3H6, CH4) are seen in the luminous zone at concentrations of 200-2000 ppm. All hydrocarbons decrease to below I ppm within 0.25 mm above the top of the luminous zone. When the flame is rich (#x3A6;= 1.2-1.4), a peak in the intermediate hydrocarbons is again seen in the luminous zone, but the decay rates of C2H2and CH4in the post-luminous zone are much slower. These species are present at concentrations of 100-1000 ppm several mm beyond the luminous zone for #x3A6;1.3. Their decay rates are critically dependent on both #x3A6; and the temperature of the flame, which is controlled by the cold gas flow rate. These results are important in gaining a better understanding of pollutant generation in premixed flames such as those found in internal combustion engines.
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