Thought this was interesting, given the discussions of ducted fans:
http://www.aero-news.net/news/commair.cfm?ContentBlockID=1e59c2c5-8740-4f14-8ecd-20c5d5d37015&Dynamic=1
<http://www.aero-news.net/news/commair.cfm?ContentBlockID=1e59c2c5-8740-4f14-8ecd-20c5d5d37015&Dynamic=1>
For fuel efficiency, the jets look more and more like turboprops. Now
they're going to be gearing the bypass section.. If the customers
wouldn't complain, I'd think they'd just take the ducts off and go back
to propellers...
Regards,
Matt-
Matt,
In the early 90's I was on the commercial side and they had a rig that
per-dated this effort. I my memory is correct it was geared and had
essentially a multi-bladed (something like 11 bladed) constant speed prop in
the duct. It was made from a PW2000 core. I was told the thrust was much
more than anticipated (no I won't say) and other numbers were good. The
total package proof of concept was very heavy, but then again it was just
for running in the test cells, not on a wing. I am going to assume they gave
up on the CS-prop.
At the time the V.P. of Engineering was Dr. Ed Crow and he truly championed
the concept (geared fan). I got to meet him via sessions thye would have to
keep the employees up to date, and I liked him as leader and his take on
things. I believe he retired and is doing something at the college arena. In
my opinion it would be a tribute to him to get this on the wing and all the
others that have been working on it behind the scenes all these years.
Pratt has taken its lumps on the commercial side with not winning contracts
to get on the wing of the most recent launches, at it is not do to lack of
engineering prowess. The last time I had heard Boeing said they could make a
business case for their entry in the 787 competition, perhaps this will be a
home run for my old teammates back in East Hartford.
On taking off the ducts, customer perception would not allow it, and I am
not sure engineering wise it's a go. It has been a long time since I looked
at a graph in PW's Jet Engine Familiarization Book, but turboprops have a
sweet spot up to about 400mph (again if all the synapses are firin' ;-) ).
My Best,
Anthony
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