Mach Wave Elimination
A new method for quieting high-speed jets
(U.S. Patents 5590520 and 5916127)
MACH WAVE ELIMINATION (TMWE)
In this mode, the coflow is applied partially around the core exhaust, covering the downward and sideline directions. Typical arc angles of the coflow nozzle would be around 240 degrees. This arrangement has produced results superior to the annular (concentric) arrangement for two interrelated reasons:
(a) The noise reduction effort is concentrated in the direction that really matters, i.e., toward communities. Substantial reductions, on the order 15 dBA, are achievable with fan flow rates much less than in the annular case. The bypass ratios for TMWE have ranged as low as 0.7.
(b) most importantly, the core flow spreads faster than when it is fully enveloped by the fan flow. This minimizes the elongation of the noise source region and allows the fan stream to do its Mach wave elimination job very effectively.
TMWE has been tested using eccentric nozzles and most recently a nozzle similar to the one sketched above.
For noise measurements, see the section ACOUSTIC DATA
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