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=1e59c2c5-874
0-4f14-8ecd-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
FYI... 787 chose GE and Rolls Engines. But The performance #'s Pratt is
taunting for the geared fan is very impressive... The question is can
they build it and meet their targets. We will see.
Regards,
Mike Collier
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