A Shock-Tube Study on the Combustion Process of Hydrocarbon Fuels : 1st Report; Observations of Ignition and Decomposition Reaction with the Colliding-Shock Apparatus

Abstract

This study constitutes a part of the attempt to clarify the process of ignition of general higher hydrocarbon fuels following a suddn homogeneous heating. A special shock-tube device was constructed in which two plane shock waves of equal strengths collide with each other in the observation plane to form a stagnant region of controlled temperature and pressure free the cooling effects in the test gas. The oxidation reaction of butane-oxygen mixtures and the decomposition reaction (in the absence of oxygen) of butane were observed. Especially, the heat absorption rate in the latter reaction at various temperatures was determined in situ from pressure and (interferometric) density recordings, and the corresponding decomposition rate constant was deduced. The ignition delays of butane-oxygen mixtures were measured with much better time resolution than in the previous incident-shock study (with an overall agreement with the previous data) but a randomness in the appearance of ignition spots was observed which constituted a source of the scatter in the data. The half life of butane subject to thermal decomposition was demonstrated to be shorter than the ignition delay below about 1100°K, but to become longer than the latter above this temperature. these findings are considered to help in the modelling of the ignition mechanism of hydrocarbon fuels.