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Bypass Ratio  
User currently offlineBryan Becker From United States of America, joined Mar 2001, 333 posts, RR: 0
Posted (13 years 7 months 1 week 1 day 14 hours ago) and read 1976 times:

I would like to know what thismeans I know what bypass is but how do you read this?

4.9-to-1 and 6-to-1,

Does that mean for every 4.9lb's of air sucked in only 1 pound goes through the engine and the rest go through the bypass? please help me on this!!!!!!!!!!!! Smile


-BryanBecker Big thumbs up

15 replies: All unread, jump to last
 
User currently offlineFlyf15 From , joined Dec 1969, posts, RR:
Reply 1, posted (13 years 7 months 1 week 1 day 13 hours ago) and read 1911 times:

You're correct.

User currently offlineAero42 From United States of America, joined Oct 2000, 18 posts, RR: 0
Reply 2, posted (13 years 7 months 1 week 1 day 9 hours ago) and read 1900 times:

Bypass ratio is the area ratio's the bypass area to the jet intake area. A 4.9 to 1 bypass ratio would mean that the area of the bypass on an engine is 4.9 times that of the area of the jet intake.

User currently offlineAvt007 From Canada, joined Jul 2000, 2132 posts, RR: 5
Reply 3, posted (13 years 7 months 1 week 1 day 8 hours ago) and read 1889 times:

Just to be picky, 4.9 lb would go through the bypass, and 1 lb through the core, totalling 5.9 lb.  Smile

User currently offlineAaron atp From United States of America, joined Mar 2000, 533 posts, RR: 2
Reply 4, posted (13 years 7 months 1 week 1 day 5 hours ago) and read 1881 times:

if you really want to be picky, it is 4.9 & 1 slugs of air, not pounds. It's a ratio of mass, not weight.

aaron
-I put new AA birdstrike pictures at hawke.50megs.com tonight if anyone cares to see blood, guts, and aircraft damage


User currently offlineAaron atp From United States of America, joined Mar 2000, 533 posts, RR: 2
Reply 5, posted (13 years 7 months 1 week 1 day 5 hours ago) and read 1867 times:

>>>Bypass ratio is the area ratio's the bypass area to the jet intake area. A 4.9 to 1 bypass ratio would mean that the area of the bypass on an engine is 4.9 times that of the area of the jet intake. <<<

Is that what they are teaching at CalPoly?

is that going to be the average frontal surface area? ...or just at the beginning of the duct?


aaron



User currently offline310_engineer From Belgium, joined Dec 2000, 165 posts, RR: 0
Reply 6, posted (13 years 7 months 1 week 14 hours ago) and read 1855 times:


Bypass ratio = secondary airflow / primary airflow


User currently offlineAaron atp From United States of America, joined Mar 2000, 533 posts, RR: 2
Reply 7, posted (13 years 7 months 1 week 13 hours ago) and read 1856 times:

310 engineer, my last post was an attempt at sarcasm. Apparently the aerospace engineering program at CalPoly is a bit lacking.

wtf are they teaching these kids?

http://www.airliners.net/discussions/profile.main?username=Aero42

aaron





User currently offlineTop Gun From Canada, joined May 1999, 101 posts, RR: 2
Reply 8, posted (13 years 7 months 1 week 7 hours ago) and read 1829 times:

To give you an idea of what sort of ratio is out there, the 777's GE90's are aprox. 8:1 (units). An older turbo jet is 1:1 (JT8D's as on the 737-200's) not to create confusion that is not a bypass engine.

A turbo fan is a Bypass
A turbo jet is not.


User currently offlineAria From Iran, joined Oct 2007, 0 posts, RR: 0
Reply 9, posted (13 years 7 months 1 week 6 hours ago) and read 1831 times:

Aaron atp:

Hello....thank God someone out there knows all the answers to everything....now I can sleep at night knowing that the next generation will be taken care of...
Aria


User currently offlineAaron atp From United States of America, joined Mar 2000, 533 posts, RR: 2
Reply 10, posted (13 years 7 months 1 week 6 hours ago) and read 1827 times:

I thank god for that too... After all, if enough of those impressionable daytona beach kids were to read that second reply to the original post, we could convince the world engineering community to amend the definition of bypass-ratio based on popular belief of the ignorant-masses.

Maybe we could even get them to present a working play-doh scale model of a GE-90 to the Royal Aeronautical Society as a basis for this bold new theorem.

have a nice evening and I'm sure you will sleep well.


aaron


User currently offlineNorthStarDC4M From Canada, joined Apr 2000, 3056 posts, RR: 36
Reply 11, posted (13 years 7 months 1 week 5 hours ago) and read 1820 times:
AIRLINERS.NET CREW
CHAT OPERATOR

just to correct Aria....

Turbojets have a 0 to 1 ratio.. no bypass at all... Acting devilish

Early low ratio turbofans like the JT3D, Conway etc had ratios of 1 to 1 or less ( Convays were .4 to 1)

 Insane

Wasnt till the C-5 and 747 program the High Ratio Bypass (4 to 1 or greater) really took off, mostly because there simply wasnt the demand for engines that size... and if you didnt need the power.. heck gas was cheap  Smokin cool and noise didnt matter much  Big thumbs up so buy a spey or jt8d or whatever.... Wink/being sarcastic



Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety.
User currently offline310_engineer From Belgium, joined Dec 2000, 165 posts, RR: 0
Reply 12, posted (13 years 7 months 5 days 16 hours ago) and read 1802 times:

Top gun

FYI JT8D Is not a turbojet but a low bypass turbofan


User currently offlineTop Gun From Canada, joined May 1999, 101 posts, RR: 2
Reply 13, posted (13 years 7 months 5 days 6 hours ago) and read 1790 times:

I'm sorry I was shooting my mouth of again and infact the JT8D's are Bypass. Silly me.

User currently offline310_engineer From Belgium, joined Dec 2000, 165 posts, RR: 0
Reply 14, posted (13 years 7 months 4 days 19 hours ago) and read 1786 times:

You are forgiven
 Big thumbs up


User currently offlineTimz From United States of America, joined Sep 1999, 6895 posts, RR: 7
Reply 15, posted (13 years 7 months 4 days 19 hours ago) and read 1804 times:

The term "turbojet" is used in the NOAA DP and STAR charts (if nowhere else) referring to jets in general. We fans like to suppose there are no turbojet airliners out there (except the Concorde) but we might get outvoted.

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