Fins on Engine Cowling
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Fins on Engine Cowling
Hi,
Have alook at this picture:
http://www.airliners.net/photo/Lufthansa/Airbus-A340-642/0596750/M/
Here is mentioned that these fins are used to reduce turbulence, I would like to know more about these devices and why they put them on engine cowlings? Is there any major source of turbulence around the engines AND Does this method affect the noise (thanks toolowtoofast ) polution made by the plane?( I heard this somewhere but still unsure about the truth?)
Does Boeing use the sameway?
Have alook at this picture:
http://www.airliners.net/photo/Lufthansa/Airbus-A340-642/0596750/M/
Here is mentioned that these fins are used to reduce turbulence, I would like to know more about these devices and why they put them on engine cowlings? Is there any major source of turbulence around the engines AND Does this method affect the noise (thanks toolowtoofast ) polution made by the plane?( I heard this somewhere but still unsure about the truth?)
Does Boeing use the sameway?
Last edited by mmrassi; 17th Aug 2008 at 07:56.
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The "fins" (or "strakes") are really vortex generators, and are an important part of high AOA aerodynamics for the wing. I recall on the DC-10 they reduced the stall speed perhaps 10 kt. or more. They are your friends.
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Indeed they are vortex generators, and usually vortex generators are uses to put some energy back to the boundary layer, in this case they act exactly at the pods (engine to wing fixing), avoiding the area just behind the pods to become turbulent at high AOA. i.e., during takeoff, approach and landing
Indeed they are vortex generators, and usually vortex generators are uses to put some energy back to the boundary layer, in this case they act exactly at the pods (engine to wing fixing), avoiding the area just behind the pods to become turbulent at high AOA. i.e., during takeoff, approach and landing
Take one off, and you suffer a performance penalty.
If memory serves me right it's about 4-6 tonnes on both the 737 (CFM) and A319 (CFM).......
M
If memory serves me right it's about 4-6 tonnes on both the 737 (CFM) and A319 (CFM).......
M
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vortex generators delays the separation of airflow( profile )arround the airframe thereby reducing the drag which is created when the airflow separates from the skin.
nothing to do with turbulance as your post indicates.
see book MECHENICS OF FLIGHT BY A.C. CERMODE
it explains allmost all aspects of air.
theory of flight
good luck
nothing to do with turbulance as your post indicates.
see book MECHENICS OF FLIGHT BY A.C. CERMODE
it explains allmost all aspects of air.
theory of flight
good luck
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The picture is a little misleading to the actual angle of the vanes as the engine cowling is up.
I think the vanes are used to produce a stabilising force to stop the engines from vibrating/moving too much, as well as acting as vortex generators.
I think the vanes are used to produce a stabilising force to stop the engines from vibrating/moving too much, as well as acting as vortex generators.
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They are there to compensate for the cut out in the leading edge devices caused by the engine pylons. As well as the obvious reduction in slat span, the cut out affects the three-dimensional lift distribution. As the LE devices have a critical role in defining CLmax, this accounts for the effect on stall-speed (and hence weight).
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Just to add the main use is for high AOA and pre stall characteristics, if you look majority are only installed inboard only, because fan cowls can be fitted either side of an engine it can be un-noticed defect. I think some a/c such as an A319 may have fins either side though.
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if you look majority are only installed inboard only, because fan cowls can be fitted either side of an engine it can be un-noticed defect. I think some a/c such as an A319 may have fins either side though.
This extra engine strake together with several modifications on the leading and trailing edge of the aircraft enables you approach about 6kt to 7kt slower than the standard aircraft.
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Have seen pictures one or two 737s with the cowlings mixed up so two vortex generators on one engine and none on the other or maybe it might have been with one on each nacelle but on the wrong side.
I think Boeing may have modified the cowlings at this stage to prevent this.
I think Boeing may have modified the cowlings at this stage to prevent this.
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Two on either side and none on the other, is a bit odd, on day in one airline I have flown with maintenance put them on the other side the boeing rep went mad, I think that it is better tol look into the CDL to check that it is normal configuration
Two on either side and none on the other, is a bit odd, on day in one airline I have flown with maintenance put them on the other side the boeing rep went mad, I think that it is better tol look into the CDL to check that it is normal configuration
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Kijangnim
Warm greeting
Turbulence I was referring to mmrassi”s post not yours. I did not read or reply to your post.
Vortex generators are always fitted on the upper side of lift generating surfaces ,at an angle to the airflow to generate vortex and delay separation of air on the upper side of the wing ,this increases the lift generated by the wing.
Vortex generator increases the lift/performance, doesn’t reduce drag.
In this picture the small fin on the engine cowl is bifurcating the the airflow and optimizing its distribution around the pillion and the wing, by directing more towards lift producing surface and less towards pillion.
Thereby generating better performance .
Fin position, angle ,size & shape is the result of extensive wind tunnel tests. (NO GRAB)
There is no need to create vortex ahead of aerofoil.
that’s why this fin is not called vortex generator.
Other aspects
Could be this small metal piece is the waist left over after the a/c was complete and manufacturer thought of some cosmetic work around the engines.
And When it breaks manufacturer can sell new one for exorbitant amount as spares.
or to make pilot work harder while doing the walk around
Warm greeting
Turbulence I was referring to mmrassi”s post not yours. I did not read or reply to your post.
Vortex generators are always fitted on the upper side of lift generating surfaces ,at an angle to the airflow to generate vortex and delay separation of air on the upper side of the wing ,this increases the lift generated by the wing.
Vortex generator increases the lift/performance, doesn’t reduce drag.
In this picture the small fin on the engine cowl is bifurcating the the airflow and optimizing its distribution around the pillion and the wing, by directing more towards lift producing surface and less towards pillion.
Thereby generating better performance .
Fin position, angle ,size & shape is the result of extensive wind tunnel tests. (NO GRAB)
There is no need to create vortex ahead of aerofoil.
that’s why this fin is not called vortex generator.
Other aspects
Could be this small metal piece is the waist left over after the a/c was complete and manufacturer thought of some cosmetic work around the engines.
And When it breaks manufacturer can sell new one for exorbitant amount as spares.
or to make pilot work harder while doing the walk around
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Thanks for this discussion about an interesting example of a vortex generator!
Ever looked at a Concorde?
There are two 'vortex generators/chines/strakes' (whatever you want to call them) on the forward fuselage, roughly under the cockpit windows.
They don't look prepossessing at all, but they really "stick down'' the airflow over the entire top of the fuselage, even at quite high angles of attack, and prevent the lower part of the vertical tail ending up in a highly turbulent airflow. It's one of the reasons the Concorde vertical tail isn't all that big, compared to some subsonics, even if she lands at a higher angle of attack.
And an interesting snippet: they were already in place for the first flight of the first prototype in 1969.....
CJ
Ever looked at a Concorde?
There are two 'vortex generators/chines/strakes' (whatever you want to call them) on the forward fuselage, roughly under the cockpit windows.
They don't look prepossessing at all, but they really "stick down'' the airflow over the entire top of the fuselage, even at quite high angles of attack, and prevent the lower part of the vertical tail ending up in a highly turbulent airflow. It's one of the reasons the Concorde vertical tail isn't all that big, compared to some subsonics, even if she lands at a higher angle of attack.
And an interesting snippet: they were already in place for the first flight of the first prototype in 1969.....
CJ
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Ever looked at a Concorde?
There are two 'vortex generators/chines/strakes' (whatever you want to call them) on the forward fuselage, roughly under the cockpit windows.
There are two 'vortex generators/chines/strakes' (whatever you want to call them) on the forward fuselage, roughly under the cockpit windows.