Considerations pertaining to spherical-vessel combustion

Abstract

Certain considerations bearing on the interpretation of measured flame speed and pressure rise rates during combustion in a spherical vessel are treated in this paper. 1. A. The relation between the pressure rise and the fraction of the charge burnt as the wave traverses the vessel is involved in the evaluation of laminar burning velocity. New considerations are presented show that under the conditions of measurement the relation given by Flamm and Mache is equivalent to the equation n = (P − P i)/P iγ u (E− 1) where E is the expansion ratio for constant-pressure burning at P i, the initial pressure, and n is the fraction burnt. 2. B. An experimental technique has been developed to determine approximate empirical values of the expansion ratios for gases passing through a laminar combustion wave. 3. C. New data have been obtained over a range of sub-atmospheric and supra-atmospheric pressures to show that the pressure dependence of the burning velocity can be positive. However, a previous correlation of pressure exponents with only the burning velocity was found to be an oversimplification of the situation. 4. D. Observations were made of peak pressures and end pressures after cooling resulting from the combustion of very rich hydrogen-air mixtures at initial pressures of a half to three atmospheres. Observed values were within a few per cent of theoretical values based on assumed thermochemical equilibrium in the burnt gas.