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Engine Pylon And Bypass Airflow  
User currently offlineVidens From Argentina, joined Mar 2004, 133 posts, RR: 0
Posted (9 years 4 months 2 weeks 2 days 10 hours ago) and read 3069 times:

How much does the engine pylon on modern jets affect the airflow coming out of the engine?
What's the actual pylon's effect on airflow?
Are there any sections inside the engine (besides the mounting points) designed considering the disturbance the pylon creates on the airflow?

Any answers, or related comments appreciated,
v


Travel? Why would i travel if I can watch it on TV?
3 replies: All unread, jump to last
 
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Reply 1, posted (9 years 4 months 2 weeks 1 day 23 hours ago) and read 2782 times:

Hello Videns.

After taking into account the different types of engine cowlings & exhaust pipes, and the different pylon designs and mounting configurations ......... my guess would be that the affect of disturbance on both the hot core gases and the by-pass airflow (as mentioned in your topic's title), would be between none and .000005%. Big grin

I'm going to try to read your mind a bit!

If you were to look at the first 2 photos of the B747 & B767 below, you might be wondering about whether or not the pylon affects the bypass airflow because the by-pass air exits the engine beside the pylon .... several feet ahead of the pylon's trailing edge. In this case, the pylon may actually help the by-pass airflow (not disturb it), by straightening it out a bit ... just a guess. (engine types anyone? - RB211, PW4000, CFM, GE)


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Photo © Stuart Lawson
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Photo © Miguel Snoep



The situation in the case above wouldn't be an issue on airliners with engines that have one full length cowling with both the by-pass air and hot core gases exiting from the same single jet pipe ....... like the engines on the B757 & A320 in these 2 photos. (engine types anyone? - RB211, PW4000, CFM, GE)


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Photo © Carlos De La Fuente
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Photo © Carsten Blümel



I don't believe the engine/pylon designs of some older clasics with their low by-pass engines would cause any airflow disturbance problems ...... such as on the DC-8 & 737-2.


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Photo © Michael Van Bosch
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Photo © Alexandru Magurean



I think airliners with aft/side mounted engines are exempt from this issue too ..... such as the ERJ-145.


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Photo © Justin Wood



>> You asked ......... "Are there any sections inside the engine (besides the mounting points) designed considering the disturbance the pylon creates on the airflow?"

I don't know, but I don't think so. On a side note, the jet engines on MD-80s have guide vanes inside the intake infront of the fan which I believe are for re-directing the intake air to make the fan more efficient ..... but that's got nothing to do with your questions. Sorry!


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Photo © Bruce Leibowitz



Finally, if by saying ..."the disturbance the pylon creates on the airflow", you are talking about any "turbulence" that is created by the pylons, on any airliner regardless of the engine/pylon mounting design, then I would have to say ...... I doubt it!

By the time any turbulence caused by the pylon reached the by-pass & hot core airflow behind the engine, the airflow's work (thrust!) would have already been done ...... thus there would be no disturbance affect.

Just my thoughts. Big grin

Chris  Smile



"Just a minute while I re-invent myself"
User currently offlineFinningleyMech From United Kingdom, joined Sep 2004, 27 posts, RR: 0
Reply 2, posted (9 years 4 months 2 weeks 1 day 22 hours ago) and read 2759 times:

The Bypass air on modern engines actually travels through 2 "C-ducts", which as im sure you can imagine are C shaped. This means that there are two areas, such as ( ) the top and the bottom where there is no bypass airflow.

I know this is a simple reply, but i think you get the idea.



Unofficial A.net Finningley Rep
User currently offlineTinPusher007 From United States of America, joined Feb 2005, 977 posts, RR: 1
Reply 3, posted (9 years 4 months 2 weeks 1 day 17 hours ago) and read 2729 times:

Quoting Mr Spaceman (Reply 1):
(engine types anyone? - RB211, PW4000, CFM, GE)

The KLM 744 and the Sobelair 767 have GE CF-6's...while the 757 is using RR RB211'S and the A320 is using the IAE V2500



"Flying isn't inherently dangerous...but very unforgiving of carelessness, incapacity or neglect."
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