Joint Aircraft Survivability Program Final Test Report for the Acoustic Fire Suppression Project JASP-TR-14-05

Report No. ARL-TR-7802
Authors: Adam Friedman; Brent T Mills; Ed Habtour
Date/Pages: September 2016; 38 pages
Abstract: The Joint Aircraft Survivability Program (JASP)-V-14-05 was a collaborative, 3-year Joint Aircraft Survivability (Joint Live Fire-Air) project to develop a lightweight, low-power, acoustic, fire-suppression system. This report documents the background, mechanisms research, and prototype development for JASP-V-14-05. We found that the strongest influence on the flame�s mass flux was the magnitude of oscillatory air movement experienced by the flame. Acoustic perturbations were imposed on flames to determine acoustic extinction criterion. Using the data collected, a model was developed that characterized the acoustic conditions required to cause flame extinction. The model was based on the ratio of an acoustic Nusselt Number to the Spalding B Number of the fuel, and it was found that at the minimum speaker power required to cause extinction this ratio was a constant. Furthermore, we found that at conditions where the ratio was below this constant, a flame could still exist at conditions where the ratio was greater than or equal to this constant, flame extinction always occurred. These data were then used to design criteria for a prototype carbon nanotube (CNT) thermoacoustic speaker. Of the 3 designs fabricated, none of the CNT thermoacoustic speakers were capable of producing over 100-dB sound pressure level below 100 Hz and could not extinguish the flame. Additional research and development with CNT thermoacoustic speakers is required before the technology is suitable for acoustic flame extinction at low frequencies.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2016