Of course. Being a pusher driver, I think of inlet
speeds in terms of the speed of the airplane. So does the fact that the inlet
is behind the prop give a much higher effective velocity?
Al,
I’m in the same boat (i.e. pusher configuration.)
As far as inlet speed, For my application it going to be pretty
close to my airspeed. For you tractor types, the inlet speed will be higher due
to the prop-blast. As a former skydiver and jump master, I can attest to the
physical effects of prop blast as one climbs out the open door of an aircraft
to experience it first hand. When you see the facial skin flapping on a 25 year
old, you know there is some additional airspeed at work there.
Prior to reading the links Ed sent me, I was thinking a straight
flare was going to take care of the diffuser layout. After researching these
sources and digging into some NACA papers from WWII, it becomes obvious that
the same considerations need to be applied to the diffuser as one would apply
to the wing airfoil to maintain laminar flow and avoid separation and the
associated turbulence in order to obtain the greatest benefit from the least
amount of drag.
As far as I can tell, thrust recovery in the P-51 is
legend. Never found anything in the way of proof that it really occurred.
The P-51 scoop is not a deviation into some new theory for my
airplane. Instead, it was the plans method.
……and yes, the ‘Meredith Effect’ is a
reality. (F. W. Meredith 1935)
Reference also: "Spitfire - The History" by
Morgan & Shacklady. Page 25
The exhaust from the P-51 scoop is travelling at a higher speed
than the inlet so from what I’ve read, that equates to thrust. I’m
not trying to build a ram-jet. The idea is to capitalize as much as possible of
the heat energy to cancel out the drag created by the scoop.
My research here is not a case of ‘the paralysis of
analysis.’ I spend a lot of time working on my project ‘Physically’.
I also spend a lot of time ‘thinking’ about the upcoming phases so
in effect while I’m sitting through one of those boring presentations at
work (that don’t involve me in the least) I’m mentally crunching numbers,
airfoils and the like.
….in the meantime, I believe I have a radiator core face
dimension to work with. I’m looking at some airfoil shapes that I have
available to me to determine if there is a possibility of using one of those
for the profile of my diffuser.
What the hell ……. I’m going to be snowed in
again within the next few hours (once this freezing rain turns to snow and the
winds kick up to 50+) soI should be able to get something done while I’m
waiting for the epoxy to cure.
Al ….. you said it best. Merry Christmas to all and a Happy
New Year to boot!
T Mann