Acoustic Measurements for a Pulse Detonation Engine

The acoustic environment of a pulse detonation engine was measured. The engine consisted of one to four detonation tubes which were detonated at 20 or 40 Hertz. Fill fractions and equivalence ratios of 1 and 0.5 were tested. All of the testing was conducted in a test cell which was not acoustically treated. Measurements were made near the exit of the tubes and up to a distance 12 feet. Time histories and narrow band spectral analysis were generated. Comparisons of sampling frequencies of 200K and 20K were conducted. Numerous potential noise suppression approaches were evaluated. The results indicate that a very high level pulse is generated near the exit of the tubes but tends to decrease in amplitude fairly quickly with distance since the higher frequency energy dissipates in the atmosphere.