ASA 127th Meeting M.I.T. 1994 June 6-10

4pEA6. The combustive sound source; basic principles.

Preston S. Wilson

Thomas G. Muir

Appl. Res. Lab., Univ. of Texas at Austin, P.O. Box 8029, Austin, TX 78713-8029

Janet L. Ellzey

Univ. of Texas at Austin, Austin, TX 78712

The combustive sound source (CSS) is a low-frequency underwater sound source that has appeared in several U.S. patents dating back to 1924, but until now, has not undergone extensive study. Combustible gases are introduced into a combustion chamber and ignited with a spark. The ensuing combustion produces a bubble of expanding gas which, in turn produces high-intensity, low-frequency acoustic pulses. It was observed that low-energy combustions produce several bubble pulses, while high-energy combustions produce a high-pressure first bubble pulse, and fewer, lower amplitude bubble pulses. The boundary between the two regimes was observed at 8900 j, for stoichiometric methane-oxygen (which corresponds to a volume of 0.75 liters at STP), ignited in an open-bottomed conical combustion chamber. A high-speed motion picture camera was used to observe the bubble produced at the boundary condition and pressure signatures were recorded. Behavior from both regimes was observed. For the high-energy case, the bubble motion observed on film is correlated with the measured pressure signature. For the low-energy case, bubble periods observed on film are compared to acoustically measured bubble periods. [Work supported by ONR.]