SCAT15F
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Do GEnx Nacelle Chevrons Impact Thrust?

Wed Feb 06, 2013 12:00 am

I was noticing how for the GEnx-2b67, Boeing installed thrust (Boeing equivalent thrust?) is 66,500 lbs. GE rates the engine at 67,400 lbs.

Obviously, installed thrust is going to be less than for a bench test engine, BUT, how come Boeing installed/equivalent thrust for the CF6-80c2b8f on the 764 is 63,500 lbs and GE says it is only 62,100 lbs?

And for the PW4062 Boeing equivalent/installed thrust is 63,300 vs Pratt's info stating 62,000 lbs?

Makes me wonder if the GEnx nacelle chevrons actually reduce thrust slightly...
 
SPREE34
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RE: Do GEnx Nacelle Chevrons Impact Thrust?

Wed Feb 06, 2013 12:40 am

Don't know about your specific numbers given, but across the engine spectrum, there is a slight thrust loss where chevrons are used. It is small enough to be considered a worthy trade for meeting noise restrictions.

I don't have a link, but recall reading this in AW&ST, and another publication 2 or 3 years ago.
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LH707330
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RE: Do GEnx Nacelle Chevrons Impact Thrust?

Wed Feb 06, 2013 7:14 am

I've heard you lose about .25% from the drag penalty that the chevrons induce, but in exchange, the nacelles can be narrower for the same noise level, so there's a weight tradeoff. The A380's nacelles are oversized so they could make QC .5 approaches, and they paid for that ability in weight. The two approaches likely have their own respective optimal use cases, just as with any other engineering tradeoff.
 
cornutt
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RE: Do GEnx Nacelle Chevrons Impact Thrust?

Thu Feb 07, 2013 2:33 am

Huh... I've been calling those things "Jughead hats". Guess I'm showing my age.  Wow!
 
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HAWK21M
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RE: Do GEnx Nacelle Chevrons Impact Thrust?

Thu Feb 07, 2013 4:59 am

Quoting SCAT15F (Thread starter):
Obviously, installed thrust is going to be less than for a bench test engine

Pls Elaborate........
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SCAT15F
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RE: Do GEnx Nacelle Chevrons Impact Thrust?

Thu Feb 07, 2013 7:25 am

Quoting HAWK21M (Reply 4):

Well, if I remember correctly, a bench test engine run is usually conducted without the engine nacelle/cowling and in static conditions resulting in optimum airflow and optimum thrust. Installed thrust is typically(?) a little less depending on the nacelle inlet design/restriction.
 
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HAWK21M
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RE: Do GEnx Nacelle Chevrons Impact Thrust?

Sat Feb 09, 2013 11:12 am

Quoting SCAT15F (Reply 5):
Well, if I remember correctly, a bench test engine run is usually conducted without the engine nacelle/cowling and in static conditions resulting in optimum airflow and optimum thrust. Installed thrust is typically(?) a little less depending on the nacelle inlet design/restriction.

How would the thrust be affected if the Engine is run on a Stationary stand with not much relative wind.
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SCAT15F
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RE: Do GEnx Nacelle Chevrons Impact Thrust?

Sat Feb 09, 2013 6:00 pm

I think it is because there is no inlet cowling, but I could be wrong.

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