Reproducibility in the slow combustion of methane

1953 ◽  
Vol 49 ◽  
pp. 628 ◽  
Author(s):  
D. E. Hoare
Keyword(s):  

As a result of a variety of experiments it was suggested in 1928 that engine “knock” “appears to be due to inequality in the condition of the charge (in the engine cylinder) set up, particularly in regions of high pressure and temperature as in the neighbourhood of hot exhaust valves. This inequality provides regions of high energy containing molecules in high energy states where reaction can spread more quickly.” This view was a little vague, and was arrived at from indirect experimental evidence. It was with a view to obtaining more precise evidence that knock was occasioned in the flame as the result of processes of slow combustion occurring in the gaseous charge prior to its arrival that the present work was undertaken. Callendar and those working with him had simultaneously arrived at the conclusion that “knock” was occasioned in much the same manner, but they adopted the more definite view that peroxides of the hydrocarbons were formed and stored in the gas, and then suddenly detonated, so igniting a whole region of the gas simultaneously. This view had also been advanced by Moureu and Dufraisse.


Kinetic and analytical studies of the gaseous oxidation of aluminium trimethyl at ambient temperatures and at pressures well below those required for spontaneous ignition have shown that, in contrast to the oxidations of less electron-deficient metal alkyls, no peroxides can be detected and no volatile oxygenated organic compounds are formed. Methane, traces of hydrogen and a solid methoxymethyl compound of aluminium are the only products. The initial rate of reaction is approximately proportional to the first power of the alkyl pressure and to the square of the oxygen pressure; it is little influenced by temperature or by inert gases but is lowered by an increase in surface. The observed kinetic and analytical results can be accounted for in terms of a free radical chain mechanism in which termination takes place predominantly at the walls.


1997 ◽  
Vol 79 (8) ◽  
pp. 1515-1518 ◽  
Author(s):  
J. Maunuksela ◽  
M. Myllys ◽  
O.-P. Kähkönen ◽  
J. Timonen ◽  
N. Provatas ◽  
...  

A comprehensive theory of the combustion of hydrocarbons must describe in detail all the analytic and kinetic data. Up to the present no such theory has been proposed, for though the hydroxylation theory of Bone and his school has been very successful in the former field, it is inadequate in its original form to take account of the latter. In the present paper it is shown that a comparatively small modification, involving the introduction of the conception of chain propagation by free radicals, remedies the earlier deficiency and makes possible for the first time a detailed description of the widely varied phenomena of combustion. The work of Egerton, Hinshelwood, Haber, Semenoff and others has led to the recognition that both rapid and slow combustion are autocatalytic in character, the reaction being propagated through the gas from certain initial centres, so that from every centre started by the primary mechanism, a great many molecules of hydrocarbon are oxidized. The first attempt to interpret the chain character in terms of a concrete theory is embodied in the suggestion of Egerton who has extended the peroxidation theory of Callendar to include an energy-chain mechanism by way of which reactivity is handed on from the active products (peroxides) to new reactant molecules. This theory and its various modifications, however, is unsatisfactory in more than one kinetic aspect, the effect of inert gases in particular being the reverse of the deactivation to be expected for an “energy” chain. Moreover, the peroxidation theory is not reconcilable in all respects with the analytical data, for while the induction period has been interpreted as a period of peroxide building no evidence of any such peroxide formation at this stage has been established, nor is the induction period affected by the addition of any such bodies. There thus arises the need of some further attempt to bring the analytic and kinetic data into relation with one another and in the hypothesis developed below, which we shall call the “atomic chain hypothesis,” it is believed that we have a simple explana­tion which encompasses both the analytical and kinetic results in an adequate manner.


1932 ◽  
Vol 7 (6) ◽  
pp. 680-681 ◽  
Author(s):  
C. H. Bayley

A new type of slow-combustion gas pipette is described in which the combustible gas is admitted through a platinum jet and impinges directly on to the platinum spiral, thereby ensuring complete combustion and eliminating the danger of explosion.


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