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Do GEnx Nacelle Chevrons Impact Thrust?  
User currently offlineSCAT15F From United States of America, joined Feb 2007, 402 posts, RR: 0
Posted (1 year 2 months 1 week 4 days 10 hours ago) and read 2733 times:

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...

7 replies: All unread, jump to last
 
User currently offlineSPREE34 From United States of America, joined Jun 2004, 2195 posts, RR: 9
Reply 1, posted (1 year 2 months 1 week 4 days 9 hours ago) and read 2715 times:

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.



I don't understand everything I don't know about this.
User currently offlineLH707330 From United States of America, joined Jun 2012, 593 posts, RR: 0
Reply 2, posted (1 year 2 months 1 week 4 days 3 hours ago) and read 2542 times:

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.

User currently offlinecornutt From United States of America, joined Jan 2013, 338 posts, RR: 1
Reply 3, posted (1 year 2 months 1 week 3 days 7 hours ago) and read 2205 times:

Huh... I've been calling those things "Jughead hats". Guess I'm showing my age.  Wow!

User currently offlineHAWK21M From India, joined Jan 2001, 31572 posts, RR: 57
Reply 4, posted (1 year 2 months 1 week 3 days 5 hours ago) and read 2135 times:

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

Pls Elaborate........



Think of the brighter side!
User currently offlineSCAT15F From United States of America, joined Feb 2007, 402 posts, RR: 0
Reply 5, posted (1 year 2 months 1 week 3 days 3 hours ago) and read 2109 times:

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.


User currently offlineHAWK21M From India, joined Jan 2001, 31572 posts, RR: 57
Reply 6, posted (1 year 2 months 1 week 23 hours ago) and read 1810 times:

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.



Think of the brighter side!
User currently offlineSCAT15F From United States of America, joined Feb 2007, 402 posts, RR: 0
Reply 7, posted (1 year 2 months 1 week 16 hours ago) and read 1758 times:

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

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