SUPPRESSION OF SUPERSONIC BLOCK JETS NOISE BY WATER INJECTION
The present work experimentally investigates an acoustic field of a supersonic block jet and suppression of the sound level by water injection. The jet is produced by a solid rocket motor. Water jets are injected to the combined jet along its perimeter at an angle 0◦ and 60◦. It is established that process of afterburning of fuel is capable to create discrete tone (screech) of the big amplitude and water injection at an angle 60◦ completely deletes this discrete tone. Wavelet transform showed a relation of frequency of discrete tone to pressure in a combustion chamber. It was determined that injection angle of 60◦ has greater effectiveness to reduce sound levels. Refs 12. Figs 6.