'Mute' button for jets explored

Monday, July 5, 2004
'Mute' button for jets explored


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By Carrie Spencer
The Associated Press


COLUMBUS - The latest, most advanced jet engines have seemingly simple
zigzags cut around the metal exhaust nozzle to control noise.

A mechanical engineer who helped in the years of research leading to that
idea is trying to replace it with an aircraft mute button.

Ohio State University professor Mohammad Samimy and associate professor
Igor Adamovich have shown that they can change the patterns of exhaust
turbulence - one of the main causes of aircraft noise - with high-voltage
electric current.

Unlike the metal cutouts, the current can be switched off when the noise
reduction isn't needed, saving fuel, said Samimy and Joseph Grady, project
manager for engine noise reduction at NASA Glenn Research Center.

"When you're up six miles in the air, you don't care how much noise you're
making," Grady said.

Airports spend tens of millions of dollars buying and soundproofing nearby
homes because of noise. It also keeps airlines from scheduling night
flights that might lead to lower fares. Meanwhile, residential areas are
creeping closer to military bases, which then deal with more noise
complaints.

Commercial aircraft today are four times quieter than they were in the
1970s, and Cleveland-based NASA Glenn is sponsoring several studies with a
goal of halving the noise heard around airports by 2008 and cutting it in
half again by 2020.

Samimy's research, supported by $100,000 from NASA, is one of four or five
ideas being considered for the longer-term goal, Grady said.

The next step is taking it from lab simulation to testing on a scale model
engine and then the real thing. Samimy said he's not comfortable guessing
at how much the device would reduce noise.

"It looks encouraging and it passed the first hurdle," Grady said.

Cincinnati-based GE Aircraft Engines uses the new zigzag nozzles, which
encourage outside air to mix with the exhaust and reduce the roaring noise
from blobs of air slamming against each other at high pressures and
temperatures. They're an important part of meeting the 2008 goal, Grady
said.

But the technique reduces thrust, burning more fuel for the whole flight.
If Samimy's concept works, the engines could be quieted only during
takeoff and landing.

"What we'd like to do is what I guess professor Samimy is doing, which is
turn the effect on at will and off at will," said Mike Benzakein, general
manager of advanced engineering at GEAE.

GE is also exploring "smart" metals that can change shape with temperature
and a University of Cincinnati study on shooting small jets of air into
the exhaust, Benzakein said.

"Five years from now we'll probably have to pick a concept," he said.

Industry experts said Samimy's idea could be 10 to 15 years from appearing
in airports, if it makes it at all. Samimy is hoping for four to five
years.

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On the Net:

http://rclsgi.eng.ohio-state.edu/7/8.../GDTL/GDTL.htm




http://www.enquirer.com/editions/200...c_loc1qui.html

Monday, July 5, 2004
'Mute' button for jets explored


Cold mike?