Amplification of Sound by Gas Phase Reactions.

摘要

A four year study of sound propagation in chemically reacting mixtures has led to experimental observation of sound amplification. Photo-initiated C12-H2-inert gas reactions provided the energy for the amplification observed. Amplification experiments were conducted in two modes which we termed pulsed and cw. For the pulsed experiments, high intensity UV-flash lamps dissociated molecular chlorine at the start of the experiments and the C12-H2-Ar reactions quickly went to completion; amplification was observed for about 6 msec. The measured gain was 1.8 at 2 kHz compared to gain of 4 predicted by theory. The source of this difference has not been resolved completely. In cw experiments, low intensity UV-fluorescent lamps dissociated molecular chlorine continuously during the experiments, this extended the time over which amplification was observed to about 800 msec. Experiments were conducted for three C12-H2-SF6 mixtures and four frequencies, 1.0, 2.5, 4.0, and 6.5 kHz. Attenuation measurements were conducted for several C12-SF6- and H2-SF6 mixtures. These data were used to calculate vibrational relaxation times for SF6 in collisions with C12, H2, and SF6 molecules. The vibrational relaxation times were used to predict vibrational relaxation attenuation in C12-H2-SF6 mixtures used in cw amplification experiments.