Chuck_Harbert@arkwright.com wrote:
Paul, there has been a lot of good info presented in your newsletter, but
in the real world, where you're just trying to fit the HX into a fixed
limited area, it really is a big compromise that you hope will work. In my
case, I fit a turbo 20B (with H2O HX) inside the space of an IO360 (std
Velocity). They normally use underwing armpit air scoops (ducts) on each
side, but in my case, the HX is only accessable on one side. Using
empirical data from several articles (Contact, etc.), and talking with a
lot of other knowledgeable people, I decided on a HX size (supposedly good
for 400hp), and an enlarged armpit inlet duct (30% of HX area). I also
added an auto rad fan (old Mazda pickup) for ground cooling. So far the
engine heats up to 190 degF (160 thermostat) during static test runs (20
mins) w/o the prop and cowls attached. Oil temp is 180 (no fan).
I believe the inlet diffuser will effectively distribute the air to the HX,
but there is no outlet duct (because there is no room for it). The exit air
just dumps into the upper cowl. Since it is a pusher, I'm hoping that the
prop will pull the warm air from the cowl (HX, engine, turbo) and assist
the HX efficiency. Most of the planes I've seen using auto conversions
don't have designed exhaust ducts.
I'd be interested in other peoples experiences as to how they view what
I've done and how they've solved their similar cooling problems. Jeff, how
much efficiency will I lose w/o an exhaust duct? If necessary, I have the
ability to add an additional HX w/duct to the lower cowl, but obviously,
I'm hoping not to.
(Paul, you took some pictures when you visited. Are any available that you
could attach, so that they could picture what I'm doing? Thx)
I would suggest if you are planing on having that IVO prop suck air
out of there don't! My suggestion is build some foam and fiberglas
high angle of attack cuffs and glue them to the IVO prop hub.
The really big thing you got going for you is the intakes are
in a real high pressure area. Probably with a very thin boundry
layer to boot.
chukduct.jpg
PL
