Application of Hartmann Acoustic Generator in Source of Underwater Pyrotechnic Combustion

Abstract

In order to investigate acoustic radiation characteristics of underwater pyrotechnic combustion, Hartmann acoustic generator was applied and its main structural parameters effecting acoustic radiation characteristics were studied by using underwater acoustic measurement system. Experimental studies have shown that, when Hartmann acoustic generator was applied, the sound pressure level of underwater pyrotechnic combustion increased significantly because of the strengthening of turbulence degree. The distance between the nozzle and the resonant cavity is an important factor of affecting acoustic radiation characteristics of Hartmann acoustic generator. When the resonant cavity was placed in the unstable pressure area, it could stimulate strong sound waves. On account of the resistance of the water, the combustion products speed of reaching resonant cavity drooped and the collision strength between the feedback combustion products and the newly generated products reduced. So when the distance was larger, the SPL(sound pressure level) was smaller. The SPL of underwater pyrotechnic combustion increased and the acoustic frequency moved to the low frequency with the depth of resonant cavity increased, which is consistent with the acoustic characteristics of Hartmann acoustic generator applied in air.