videns
Posts: 132
Joined: Thu Mar 18, 2004 3:28 pm

Engine Pylon And Bypass Airflow

Sun Apr 17, 2005 2:13 pm

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?
 
Mr Spaceman
Posts: 2723
Joined: Thu Mar 15, 2001 5:09 am

RE: Engine Pylon And Bypass Airflow

Mon Apr 18, 2005 12:49 am

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)


View Large View Medium
Click here for bigger photo!

Photo © Stuart Lawson
View Large View Medium
Click here for bigger photo!

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)


View Large View Medium
Click here for bigger photo!

Photo © Carlos De La Fuente
View Large View Medium
Click here for bigger photo!

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.


View Large View Medium
Click here for bigger photo!

Photo © Michael Van Bosch
View Large View Medium
Click here for bigger photo!

Photo © Alexandru Magurean



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


View Large View Medium
Click here for bigger photo!

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!


View Large View Medium
Click here for bigger photo!

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"
 
FinningleyMech
Posts: 26
Joined: Fri Sep 10, 2004 4:02 am

RE: Engine Pylon And Bypass Airflow

Mon Apr 18, 2005 2:29 am

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
 
tinpusher007
Posts: 890
Joined: Wed Feb 09, 2005 2:03 am

RE: Engine Pylon And Bypass Airflow

Mon Apr 18, 2005 6:51 am

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."

Who is online

Users browsing this forum: CandleFlight, Horstroad and 24 guests