Proceedings of the Symposium on Combustion最新文献

Recent theories of hydrocarbon oxidation have been critically compared. The evidence favors monovalent radical chains. The assumption of intermediate formation of peroxides and of sensitization of peroxide dissociation by condensation with aldehyde proves to be fruitful in explaining varied phenomena, such as the low-temperature reactivity of higher hydrocarbons and the high-pressure oxidation of methane and ethane. The implications of the chain theory in interpreting the experimental results have been discussed. The necessity of revising Norrish and Foord's steady-state treatment has been pointed out. The question of thermal versus branchedchain explosions in methane remains open, with some experimental evidence favoring the latter.

After considering the most likely factors which may influence the measurement and calculation of gas temperatures in an engine during combustion and expansion, there appears to be reasonable agreement between measured and calculated results if (1) temperatures are measured by means of the line-reversal method with suitable corrections for the effect of temperature gradients in the gases, and (2) temperatures are calculated on the basis of thermodynamic analysis, assuming thermal and chemical equilibrium, including the effects of variable specific heat of the gases and dissociation, based on the most recent thermal and chemical data, and correcting for heat loss during combustion.

Analyses of the products of the slow combustion of propane in oxygen by flow and static methods have been made.

Peroxides are found only when the surface does not destroy them too fast to prevent their detection. In the vapor state hydrogen peroxide appears tobe mainly present and dihydroxymethyl peroxide in the condensate.

Propylene is formed early in the reaction, possibly from the aldehydes which initiate the reaction.

Methyl alcohol and aldehydes appear to be formed by the same chain process.

Flame temperatures were measured by the sodium line-reversal method along the vertical axis of centrally (partially) colored Méker flames for mixtures of natural gas with air and oxygen. For air mixtures the vertical temperature gradient above the cones is positive. The temperature range and length of the positive gradient depend upon space velocity and mixture composition. In oxygen mixtures the maximum temperature is found immediately above the cones, and the vertical gradient is a uniform negative gradient for several centimeters.

The maximum observed temperatures in air mixtures show the greatest deviation from the theoretical near the stoichiometric point, being about 20° to 40°C lower. The maximum temperatures of oxygen mixtures on the average slightly exceed the theoretical. The results are explained on the basis of heat losses, particularly to the grid, and the excitation lag in oxygen mixtures.

The thermal and the chemiluminescence theories of the radiant energy from flame are discussed and the conclusion is reached that the emission is very largely chemiluminescence. New experimental evidence on the radiation from the carbon monoxide flame is in agreement with this conclusion.

The study of the radiant energy from flames offers a line of approach to the problems of catalysis of the processes of combustion, and this is illustrated by reference to experimental work on the catalysis of the carbon monoxide flame by hydrogen. It is concluded that the action of hydrogen is twofold in character. It acts as a catalyst in the chemical sense when the hydrogen percentage exceeds 0.02, and as a conserver of chemical energy within the flame throughout the whole range of concentrations up to 2 per cent. The latter type of catalysis is termed “energo-thermic,” and in the above example it is concluded that either the proton or the electron is the effective agent. The chemical energy is conserved within the flame by collisions between protons or electrons and the newly formed products of the combustion process.