Thread: New Product Change Sun 10 blade 70mm
View Single Post
Old Oct 11, 2012, 10:30 PM
PeterVRC is offline
Find More Posts by PeterVRC
Registered User
Australia, VIC, Melbourne
Joined Nov 2006
13,934 Posts
CS10 again:
I believe it does not like low FSA because it is already compressing air 'excessively' with a large (or typical) FSA even.
It is only a very small distance, but it might even already be excessive within the shroud! I wouldn't think so though. It more fits in that the shroud is ok still by then - not sure why, maybe as it is such a small time that it is within that distance - thus bench testing is still looking good, but in a plane, over the much longer ducting distance, it matters more.... and thus why their performance is worse than low blade count.

I mention 'swept area'.... I guess when I say that it means the area covered, but I also mean the whole picture of what that fan 'grabs... blade profile, pitch etc too. The whole 'chunk of air' it grabs - for all those factors totalled. (There is probably a better word to call that total?)
And it would seem they just made a fan total that is somewhat 'amiss' in design perfection.... thus having these spin-off issues. In part giving better torque.... but a bit less efficient... lower efflux.... too much back-pressure (and thus sensitivity to more)

Which might all be totally FINE if that is what you need to do to get torque.... but it seems to me the level of it is excessive, and not required in most planes it will be used in. Most are more suited to having speed (efflux speed) instead. But this poor design can't cope with the typical 'convert flow to efflux by lowering FSA exhaust ratio' (again due to the pressure issue).
And again, they probably never designed anything to do anything... they probably COPIED stuff, not specifically or accurately to be a perfect copy of something, without true understanding and just ended up with this resultant!
PeterVRC is offline Find More Posts by PeterVRC
Reply With Quote