How is the oil cooling saga coming Al?
Paul Lamar
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Using sheet metal, I reshaped the upper wall of the duct, as shown in the
attached sketch. As well as reshaping, it was intended that it would also
reduce the bypass leakage at the top. Unfortunately, that new upper wall is
in three pieces, with some gaps between where the intermediate scoops
supports are located. I also did some closing of the gap at the bottom of
the cooler.
In further flight tests I measured the pressure at the face of the core
toward the top (at 'D'); which is about the same as at 'C', suggesting the
distribution over the face, at least at that location about 1/3 the length
from the inboard end, is fairly uniform.
I did further measurements of BL pressures in front of the scoop, and found
that the pressure at the surface (well, 1/8" away) is 3.0" and increases
rather quickly to about 8.5 - 9" moving away from the surface, but is still
only 8.5 - 9 at 1 1/8" away from the surface; the extremity of the scoop
opening. This suggests there is not a well formed BL, but a fair about of
turbulence over a greater distance from the surface. I think this can be
explained by the presence of the gear well doors a short distance in front
of the scoop.
While I had the manometer tubes in place, taped to the surface in front of
the scoop, I saw no improvement in the cooling from the changes; in fact
things seemed to get worse - climbing to 3000' on an 85F day brought the oil
temps to about 225F. I then removed the tubes and went flying again.
Starting with a warm engine, and 190F oil temp at the start of the takeoff
roll, I climbed at 1500 fpm to 2500' (TPA) and then about 1000 fpm to 4500',
where the oil temp peaked at about 217F.
Obviously having those tubes in, and in front of the scoop in recent flights
had made the problem worse. Level cruise at 5000 - 5200 rpm had the oil
temp around 210F - on the high side, but with the OAT then about 87F, not
too bad. Coolant temp was 185F. I plan some further work on sealing up the
air leakage around the cooler, and call it good for now. After all; without
cowl flaps or other means of control, if I made the cooling much better I'll
have to be concerned about the oil getting too cool when the OAT is 40F :-).
I won't be flying for awhile. Had my flight physical a couple of weeks ago.
Everything was fine; but it seems the FAA wants all kinds of info for a
review of a surgery I had a year and a half ago. I'm sure it will be
renewed, but it may take a month.
Meanwhile, I'm heading out of town on wheels for the next couple of weeks.
Please take me off the e-mail list until further notice.
Thanks,
Al
OK Al
Paul Lamar
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