Gaseous Detonations. XV. Expansion Waves in Gaseous Detonations

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Abstract
The ultraviolet absorption spectrum of OH and the visible light emission profile in the rarefaction wave following a detonation in C2H2+H2+2O2 have been measured. Analysis of the absorption spectrum at an initial pressure of 60 mm Hg gives an average rotational temperature of 3164°K during the first 310 μsec. after the detonation wave front. The gas temperature calculated by using detonation theory and necessary thermodynamic data is 392°K higher than the experimental rotational temperature. The difference is very close to the difference of 350°K which has been predicted by T. C. James theoretically. The emission profiles demonstrated the presence of double waves at initial pressures higher than 90 mm and the appearance of these waves coincides with an increase in detonation velocity to that calculated using a ``frozen'' sound velocity. In expansion waves produced by bursting a thin diaphragm with the detonation wave, the emission intensity was found to be far higher than predicted and the velocity of the expanding gas and the shock wave ahead of it to be somewhat lower than expected.