Advantage of Wide Chord Fans.
Advantage of Wide Chord Fans.
(OP)
What are the advantages of a WCF?
I can think of;
- Fewer blades ---> saved weight.
- More damage resistant.
Are these correct and are there other advantages?
Thanks!
I can think of;
- Fewer blades ---> saved weight.
- More damage resistant.
Are these correct and are there other advantages?
Thanks!





RE: Advantage of Wide Chord Fans.
The weight one may be a red herring, because of the increased structural weight required for containment (sometimes kevlar is used, instead of steel, because of this).
RE: Advantage of Wide Chord Fans.
- Opportunity for hollow core at neutral axis.
- Potential lower cost, fewer blades.
Prior GE QCSEE fan dev engr.
RE: Advantage of Wide Chord Fans.
http://
scotty7: containment of a "deviant" fan blade is a serious issue. I worked with BMW/Rolls-Royce (BRR) on the BR710/BR715 engine. I worked on the accessory gearbox design. The gearbox housing had to maintain structural integrity (ie. not crack open and dump oil everywhere) for 30 seconds during a "blade out" condition. 30 seconds was the amount of time deemed necessary for an out-of-balance engine to stop shaking and come to a halt.
To test for a "blade out" condition, the engine was run up to max RPM (like during a take-off) and a fan blade was explosively separated from the rotor. I remember seeing the high speed test film of the fan blade being blown free and impacting the kevlar containment structure of the fan shroud. The kevlar composite containment structure was at least an inch thick and seemed as solid as a rock. But when that 40 inch diameter fan blade, spinning at about 15,000 rpm, came loose and hit that containment structure, it looked as though it was made of rubber. It contained the fan blade alright, but it sure "moved around" alot doing so.
I also recall a couple of years ago that a woman and her child were killed during a take-off of an MD-90 aircraft (it has fuselage mounted engines) when a fan blade separated from the engine and penetrated the fuselage.
To make a long story short, the less a fan blade weighs, the less destruction it will cause if it decides to come loose. A wide chord composite fan blade would seem beneficial in this regard.
RE: Advantage of Wide Chord Fans.
The containment tests must be really impressive! Are there any movies available on the internet? I'm not trying to be a "wise guy", but isn't the fan normally turning a lot slower than 15,000rpm?
Also, about the swept fan blades - is the idea to get a more elliptical loading on the blade? I read in Flight Intl that the swept blades 'transition the shock wave away from the tip toward the core'.
RE: Advantage of Wide Chord Fans.
A single WCFB will weigh more than a single narrow fan blade (but because there are fewer the shipset will probably be lighter). Therefore it is more energetic and requires heavier containment than a narrow blade. And if either gets out of the casing, I would not like to be in the way...
RE: Advantage of Wide Chord Fans.
http://www.msm.cam.ac.uk/phase-trans/2002/RR.html
Doesn't really show the rubber casing, but mighty impressive anyway.