victech
Posts: 541
Joined: Sun Jun 11, 2000 9:46 am

777 Engine Questions

Sun Jun 11, 2000 10:16 am

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.
 
dash8
Posts: 389
Joined: Sat Aug 27, 2005 8:23 am

RE: 777 Engine Questions

Sun Jun 18, 2000 12:18 pm

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.
 
dnalor
Posts: 346
Joined: Fri Mar 10, 2000 7:58 pm

RE: 777 Engine Questions

Sun Jun 18, 2000 7:33 pm

Wonder if he means Cubic Feet per Minute, the way induction systems are rated in cars.
 
victech
Posts: 541
Joined: Sun Jun 11, 2000 9:46 am

RE: 777 Engine Questions

Sun Jun 18, 2000 8:23 pm

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.
 
TOP
Posts: 250
Joined: Wed May 10, 2000 5:22 am

RE: 777 Engine Questions

Mon Jun 19, 2000 1:55 am

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


Stephan

Duisburg,
GERMANY
 
victech
Posts: 541
Joined: Sun Jun 11, 2000 9:46 am

RE: 777 Engine Questions

Mon Jun 19, 2000 10:21 am

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.
 
TOP
Posts: 250
Joined: Wed May 10, 2000 5:22 am

RE: 777 Engine Questions

Tue Jun 20, 2000 12:25 am

These values are per second and not per minute!



Stephan

Duisburg,
GERMANY
 
victech
Posts: 541
Joined: Sun Jun 11, 2000 9:46 am

RE: 777 Engine Questions

Tue Jun 20, 2000 2:54 am

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.
 
TOP
Posts: 250
Joined: Wed May 10, 2000 5:22 am

RE: 777 Engine Questions

Tue Jun 20, 2000 4:23 am

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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