"Silencer" system for Jet Engines

[jenat-lai]

Article here


Washington, June 24(ANI):

Researchers at the Ohio State university have developed a new silencer technology that creates electrical arcs to control turbulence in engine exhaust airflow responsible for engine noise.

According to Mohammad Samimy who developed it, the pilot could turn the plasma actuators on and off with the flip of aswitch, reducing noise around commercial airports or military airstrips.

He along with his colleague, Igor Adamovich demonstrated the technology in a series of laboratory tests where they used laser light to illuminate a simulated engine exhaust stream, and studied how different arrangements of actuators affected the flow.

They tested the actuators using two types of air streams, one simulating the exhaust from a commercial aircraft, and the other simulating that of a high-speed military aircraft. The tests showed that the plasma actuators succeeded in manipulating turbulence structures in the airflow.

The most important factor in silencing an aircraft during takeoff when the jet engine is the loudest, is controlling exhaust airflow, Samimy said. The high-speed airflow provides thrust for the plane, and also creates most of the noise.

"One has to reduce the noise while not adversely affecting the thrust - that is the challenge. When the development of the actuators is complete, they will meet the challenge," he said.

Plasma actuators developed for noise mitigation could also provide an additional level of stealth for modern military aircraft, Samimy said.

[Admiral Valdemar]

Interesting, but the problem for supersonic aircraft still persists much like trying to silence supersonic rifle rounds. This, if practical, would really help with future air congestion at least.

[LordShaithis]

Plasma actuators developed for noise mitigation could also provide an additional level of stealth for modern military aircraft, Samimy said.

As opposed to slapping them on an Me262, right? Was this reporter trying to hit his word-quota like a schoolkid writing an essay?

[Sarevok]

This technology could be useful in reducing noise pollution around airports. Modifications for reducing engine noise may well be worth the cost if they can reduce noise substantialy.

[The Kernel]

Interesting, but the problem for supersonic aircraft still persists much like trying to silence supersonic rifle rounds. This, if practical, would really help with future air congestion at least.

The noise factor is hardly the biggest problem holding back supersonic transport though.

[Vympel]

I wonder how cheap it is. If it's cheaper than simply getting quiter engines, the Russian commercial Il-76 fleet won't need to be completely re-engined with new engines to comply with Western noise standards- though they do have other benefits (more thrust, more fuel efficient).

Oh well, it probably won't be viable for years anyway, if at all.

[jenat-lai]

The problem I see with it, is that there is still a large amount of noise from the air being thrust out the back of the engine at high temperature and speed. a similar effect to thunder. You can make the mechanical part of the engine quieter, but that thunder-like noise is always going to remain as it is a biproduct of creating thrust. And thrust is the only thing that keeps the aircraft moving forward at speed. And moving forward at speed is the only thing that produces lift, and lift is the only thing that makes aircraft fly. Thus if you want your aircraft to fly (of course you do ) then the sound of the air movement (which is actually quite loud, for instance, on a landing 767, 70% of the volume is the sound of the air interacting with the physical aircraft (it's landing gear, flaps, wings, fuselage etc)... and if you know 767's you know theyre not exactly quiet when landing. LOL.

[jenat-lai]

The problem I see with it, is that there is still a large amount of noise from the air being thrust out the back of the engine at high temperature and speed. a similar effect to thunder. You can make the mechanical part of the engine quieter, but that thunder-like noise is always going to remain as it is a biproduct of creating thrust. And thrust is the only thing that keeps the aircraft moving forward at speed. And moving forward at speed is the only thing that produces lift, and lift is the only thing that makes aircraft fly. Thus if you want your aircraft to fly (of course you do ) then the sound of the air movement (which is actually quite loud, for instance, on a landing 767, 70% of the volume is the sound of the air interacting with the physical aircraft (it's landing gear, flaps, wings, fuselage etc)... and if you know 767's you know theyre not exactly quiet when landing. LOL.

er I forgot to complete that scentence... Anyway cheaper ways of making quieter engines is always a plus. Aircraft are always criticized in the media for being to loud etc creating curfews at airports and so on. By reducing the noise they make to that more like a large truck in volume, will give airlines and airports more flexibility of when to operate etc.

[Crown]

Interesting, but the problem for supersonic aircraft still persists much like trying to silence supersonic rifle rounds. This, if practical, would really help with future air congestion at least.

Actually the problem with supersonic aircraft is that if this functions the way I think it does, it has the potential to stuff up the flow at the rear of the engine so bad, that it will cause blow back and a massive surge (engines loses all power). Something you definetly don't want during take-off.

It sounds like a pie in the sky kind of thing, it would be 'nice' but as he said himself at the moment thrust is being sacrificed ... you can't do that during take-off. Ever.

[Admiral Valdemar]

Interesting, but the problem for supersonic aircraft still persists much like trying to silence supersonic rifle rounds. This, if practical, would really help with future air congestion at least.

The noise factor is hardly the biggest problem holding back supersonic transport though.

It is, however, a major one. The reason Concorde never took off, so to speak, was not only due to cost because of the engineering budget it needed and fuel etc, but because no one liked 110 people going Mach 2+ above their heads. It was, to say the least, loud. So much so that numerous flight lanes were verboten. Can't reap the rewards of fast air travel if you can't fly anywhere.

[MKSheppard]

It was, to say the least, loud. So much so that numerous flight lanes were verboten. Can't reap the rewards of fast air travel if you can't fly anywhere.

They should have flown at 80,000 feet then, the only noise on the
ground, would have been an omnious rumble

[The Kernel]

It is, however, a major one. The reason Concorde never took off, so to speak, was not only due to cost because of the engineering budget it needed and fuel etc, but because no one liked 110 people going Mach 2+ above their heads. It was, to say the least, loud. So much so that numerous flight lanes were verboten. Can't reap the rewards of fast air travel if you can't fly anywhere.

The main reason why the Concorde wasn't a success was because its fuel consumption and maintinence costs were in the stratosphere. Now, it's possible that these costs might be lowered somewhat (especially with higher capacity SST planes) but its never going to be cheap enough to replace subsonic flight, even on long runs.

And as for the noise issue, supersonic flight makes the most sense on the extremely long legs such as the Pacific and Atlantic runs where the noise issue is moot. Sure, a way to bring the noise down would allow a supersonic plane to have a greater number of routes, but that isn't what's stopping supersonic flight from taking off. It simply isn't economical enough, even with the initial plane costs completely discounted.

[J]

Anything to make planes quieter would be very welcome for me. My home is now right under an airlane thanks to the new airport terminal, though thankfully the planes are limited to the daytime so far.

[phongn]

I live under the flightpath of KPIE and some noise reduction would be nice. It's not the most heavily-used airport but they've been getting more business and are expanding their runway to handle charter flights from Europe.

[Beowulf]

I happen to live under the flight path of an airport, and military jets are frikkin loud... it's mostly daytime flights, luckily...

[jenat-lai]

I live about 5 miles offsett the approach path for runway 07 at YSSY, Sydney International. The airport is buisy, but the runway 07, or it's recipricol 25, isn't utilzed that much. That said I don't mind aircraft noise from where I live that much, but if I lived in a suburb which got aircraft directly overhead at below 1000ft I would probably like the idea of quieter aircraft. As it is though, Sydney only gets 727's rarely, and the occasional drop-in of Travolta's 707. Beyond that, the odd RAAF F-111 a couple times a year, most aircraft are modern quiet times. The most regular loud aircraft we have is the 747 varients, particularly the flights direct to America or Europe running at max takeoff weight, still fairly low and at high thrust settings/low derates