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777 Engine Questions  
User currently offlineVictech From United States of America, joined Jun 2000, 546 posts, RR: 2
Posted (14 years 6 months 3 weeks 2 days 2 hours ago) and read 2051 times:

Hello, I have two question about 777 engines. One, can anyone tell me the average CFM of the engine at cruise? And two, someone told me that at takeoff in semi-humid conditions, the engine will form a cloud from the outer metal rim to the 1st compressor fan. Is that true?  

Thanks,
Victor.

8 replies: All unread, jump to last
 
User currently offlineDash8 From New Zealand, joined Aug 2005, 6 posts, RR: 0
Reply 1, posted (14 years 6 months 2 weeks 2 days ago) and read 1838 times:

1. Don't know what CFM means.

2. It's true. Caused by accelerating airstream. Faster stream means reduced local pressure. Which means colder temperature, which means a lower dewpoint (temperature at which water in gas state condenses to fluid). Because of this excess water vapour in the air will become visible as a greyish cloud.


p.s. If at No1 you mean fuel consumption?
It's about 15,000 pound per hour.


User currently offlineDnalor From Australia, joined Mar 2000, 369 posts, RR: 0
Reply 2, posted (14 years 6 months 2 weeks 1 day 17 hours ago) and read 1822 times:

Wonder if he means Cubic Feet per Minute, the way induction systems are rated in cars.


User currently offlineVictech From United States of America, joined Jun 2000, 546 posts, RR: 2
Reply 3, posted (14 years 6 months 2 weeks 1 day 16 hours ago) and read 1818 times:

Dash8, thanks for the clarification on the cloud question, I guess I'm not remembering my physical science classes as well as I should. As to CFM, yes, I was asking for how many Cubic Feet per Minute the engine "sucks in" while at cruise.

Thanks.


User currently offlineTOP From Germany, joined May 2000, 264 posts, RR: 0
Reply 4, posted (14 years 6 months 2 weeks 1 day 11 hours ago) and read 1804 times:

Hello Victech,
the (max.) air mass flow of the PW4098 is about 1270 kg/s.


Stephan

Duisburg,
GERMANY


User currently offlineVictech From United States of America, joined Jun 2000, 546 posts, RR: 2
Reply 5, posted (14 years 6 months 2 weeks 1 day 2 hours ago) and read 1797 times:

Thanks for that info, now if I remember correctly, one cubic meter of air is 1.3kg. Therefore, that's about 983 cublic meters per minute; so about 34,714 CFM or 259,758 GPM of air. Please correct my math if it is off.

User currently offlineTOP From Germany, joined May 2000, 264 posts, RR: 0
Reply 6, posted (14 years 6 months 2 weeks 12 hours ago) and read 1772 times:

These values are per second and not per minute!



Stephan

Duisburg,
GERMANY


User currently offlineVictech From United States of America, joined Jun 2000, 546 posts, RR: 2
Reply 7, posted (14 years 6 months 2 weeks 10 hours ago) and read 1768 times:

Woops! In that case, that's 2,082,840 CFM - which is, wow, a heck of a lot of air. But on the other hand, only about 25-30% of that will ever see the combuster.

User currently offlineTOP From Germany, joined May 2000, 264 posts, RR: 0
Reply 8, posted (14 years 6 months 2 weeks 8 hours ago) and read 1771 times:

To be precise, only 17% of the whole air goes to the combustion chamber (PW4098).
PW4084: ~15%

More interesting data you can find here:

http://www.boeing.com/assocproducts/aircompat


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