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Al,
I think that you should pursue one problem at a
time until you have exhausted the chance of any improvement on that
front.
You have too many variables and you are not
eliminating any in these tests. You are merely making unknown possible
improvements/detriments to lots of problems all at once.
From what I can tell, you should be getting more
static pressure at the core than you are even with the BL problem and the wall
being a non-ideal shape (as you stated). This could be due to leakage, or it
could be due to separation and duct stall due to the boundary layer ingestion
problem. There is no way to know for sure with the info you have.
I am not convinced by the 9 in of water 5/8 from
the surface that you should get 6 in at the cooler face. Absent a methodical
rake test from the wing out to below the scoop, and all along the
front of the scoop it is impossible to make much of conclusion from one
point of data. What is it at .25 in from the surface, along the entire length?
If 1/4 of your duct has slow boundary layer air going into it (which
unfortunately is the poorly contoured surface of the duct) you may have a
disaster for flow inside the duct. If the flow separates from the top wall, the
unseparated high energy flow will not diffuse properly. What is happening
at the end of the duct towards the wheel well? All unknown variables.
First order of business is eliminate ANY chance of
leakage past the cooler. Eliminate this variable first. This includes the area
near the tanks where there is no core, only tubes. This should be sealed up
completely as well as the perimeter of the core. Then retest with no other
changes. Make sure you use the same location for your manometer and use foam
around the end of the tube. That way your data will be apples to
apples.
Once armed with this info you can proceed to the
next step. If it were me, I would fix the duct contour (no gaps in the
metal allowed) and then retest. Then I think I would try a mixing
divider vane in the inlet before the change in curvature. That way the
high energy air is mixed with the low energy air BEFORE it has
to begin diffusion. If this fails I would move on to sealing the gear
door and external VGs
Forget about quick fixes and start killing rats
until you find the one causing the majority of the problem. Right now you are
only "wounding" or perhaps missing "the" rat all together while flailing at them
with a big blunt instrument. Get out the rifle and kill them (verifiably,
unquestionably dead) one by one until the problem is solved.
;-)
I hate rats.
Monty
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