Measurements of Hydrocarbon Concentrations in the Exhaust Products from a Spherical Combustion Bomb

Total hydrocarbon concentrations in the exhaust products from a constant volume heated spherical combustion bomb have been measured using a flame ionization detector. Results were obtained for methane-air and propane-air mixtures as a function of equivalence ratio, initial pressure, wall temperature and inert gas diluent fraction. Although an effort was made to eliminate all crevice volumes and wall contamination, the results indicate that at initial pressures greater than 1 atmosphere, most of the hydrocarbon came from a crevice which was not perfectly sealed. At initial pressures less than 1 atmosphere, it was possible to correct for this and obtain an estimate of the hydrocarbon mass in the quench layer. For an equivalence ratio of unity and no diluent, the hydrocarbon mass per unit wall area was ≤0.02 μg/cm². This is only 2% of the value predicted by a theorectical model used to correlate standoff distances on a flat flame burner and suggests virtually complete post-quench oxidation of the quench layer as suggested by Lavoie and co-workers. For nonzero diluent fractions, the wall hydrocarbon concentration increased substantially.