Exhaust silencer using water injection

This paper describes results from the development of a water injection noise control system applied
to an exhaust duct. A mist of water is introduced into an exhaust duct by injectors into the gas
ow
and is used to reduce the sound pressure level in the exhaust by several mechanisms, particularly
through the absorption of energy required for the evaporation of the water vapour. This noise
control method is investigated rstly with the aid of CFD software and then tested experimentally.
The results from the CFD showed that there are signicant reductions in temperature, pressure
and hence energy of the
ow. The experimental prototype injection system showed inconclusive
results due to systematic error. The instrumentation noise
oor in every test was approximately
100dB when the water injectors were activated. It is expected that the increase in the noise
oor
is created by the injected water causing vibrations in the pipe walls which is picked up by the
microphone. It is proposed that a water injection based noise attenuation device could be eective
with dierent implementation based on research theoretical results.