Comparison of ideal and actual combustion temperatures and pressures: Anomalous effects; Gas vibrations

In moist hydrogen-oxygen mixtures diluted with argon, helium, or excess hydrogen, explosion pressures are found that agree with the theoretical pressures calculated from band spectroscopic data. In dry mixtures the observed pressures are lower, possibly owing to heat loss by luminescence radiation. In moist mixtures diluted with nitrogen or excess oxygen the pressures are higher. This has been ascribed to the time-dependence of specific heats, called excitation lag. This excitation lag has been linked to gas vibrations which appear early in the explosion. The results with carbon monoxide-oxygen and with acetylene-oxygen mixtures can also be interpreted by heat loss and excitation lag. If a small amount of hydrogen is added to carbon monoxide-oxygen mixtures the heat loss appears to be reduced considerably, probably owing to the shorter duration of the explosion. Excellent agreement is found between experimental and theoretical explosion pressures in ozone-oxygen mixtures. An explanation of the absence of excitation lag in the latter is proposed. Measurements of expansion ratios in soap-bubble explosions of carbon monoxide-oxygen mixtures and flame temperatures by the line-reversal method of coal gas-air mixtures show a trend similar to explosion pressures in hydrogen-oxygen and carbon monoxide-oxygen mixtures.