Study On Acoustic Radiation Mechanism Of Pyrotechnic Combustion And Enhancing Technology

In order to study the acoustic radiation mechanism of pyrotechnic combustion underwater, the relevant acoustic underwater sound source mechanism was analyzed, According to the foundation, the bubbles and thermal acoustic radiation mechanism of pyrotechnic combustion underwater and enhancement techniques will be explored.Firstly, based on bubbles acoustic radiation formed by the gas of Pyrotechnic combustion underwater, a equipment was designed which could remove the high-temperature solid particle of pyrotechnic combustion underwater to research the shape of nozzle bubbles and its acoustic radiation by using the high-speed photography and underwater acoustic instrument test systems. The results showed the bubbles acoustic radiation frequency formed by the gas of pyrotechnic combustion underwater was mainly centralized in the range of 0-1000Hz, of which the peak frequency was about 100 Hz.Secondly, the infrared thermometer was used to study the thermal acoustic radiation of pyrotechnic combustion underwater, which embodied different thermite. The results showed the acoustic radiation mechanism of pyrotechnic combustion underwater enhanced with the increase of thermite,the peak SPL of pyrotechnic combustion increased from 137 dB to 149 dB and the SPL in the range of 0～1000 Hz increased from 145 dB to 151dB,when the content of thermite increased from 0 to 10%.Afterward, the comparative research methods of pyrotechnic and compressed nitrogen was adopted to investigate the acoustic radiation characteristics of two different sound source in different volume flow by using the underwater acoustic test system. The results showed the acoustic radiation characteristics both of them were enhanced with the increase of gas flowing, but the SPL of underwater pyrotechnic combustion was higher at the same frequency than the compressed nitrogen source.Finally, combining with the sound radiation characteristics and mechanisms, different types, charges and mechanical devices of pyrotechnic combustion underwater were devised to enhance the sound radiation, which was produced by pyrotechnic combustion underwater.