Mach Wave Elimination
A new method for quieting high-speed jets
(U.S. Patents 5590520 and 5916127)


THE CONCEPT

EXPERIMENTAL SETUP

ACOUSTIC DATA

APPLICATION TO AEROENGINES

TECHNOLOGY EXCHANGE

FUTURE PLANS

SPONSORSHIP

PUBLICATIONS

PUBLICITY & AWARDS

TMWE:   JETS WITH ARCUATE COFLOW
Sound Pressure Level spectra

Very-far-field measurements (r/D=200) performed without anechoic chamber

Jet: Mach 1.5, 700 m/s
Coflow: Mach 0.95, 360 m/s, bypass ratio=1.7

polar_angle.jpg (1539 bytes) azimuth_angle.jpg (2389 bytes)

tmwe_arc_spl_comp1.jpg (46587 bytes)

Concentrating on the 100-kHz frequency  (this corresponds to 1200 Hz in an engine with 1-m exhaust, hence is weighed heavily in the PNL metric), the noise reduction is:  20 dB at 0-deg. azimuth;  20 dB at 45-deg. azimuth ( the two spectra pratcially overlap); and  12 dB at 60-deg azimuth.  We are hopeful that more refined  designs will give good performance up to 90-deg. azimuth

In a multi-engine application, there may an optimum placement of the coflow nozzle (not necessarily vertical as shown above) that maximizes the reduction in both take-off noise and sideline noise.

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