What is the area at the opening of
the scoop? What is the area at the face of the cooler? Does the
area of the duct increase at all points after the entrance?
The opening of the scoop is
14.5" by 4.25" or 61.625 SQ. IN. The duct does open up to the
cores, although it is only about 12" from the opening to the junction
of the 2 cores, which are in a shallow "V".
Steve;
My analysis of air
flow required for 200 hp climb at 120 kts on a 95F day, and a very effective
scoop is 65 sq.in. inlet area – just for the coolant rads. Another
25 sq. in. inlet for the oil cooler. This is more than typically needed
for cruise, but it’s a tradeoff.
Another idea is to remove the oil cooler altogether from the main scoop, and
add an additional scoop for the oil cooler. This would leave more air for
the radiators, but be higher drag. At this point, I guess I could settle
for cool and slower.
The pressure recovery
of your scoop/core configuration is difficult to predict, but may be OK for the
coolant cores. It seems an additional scoop for the oil cooler is the way
to go if you can find a way to configure it. Better a little more drag
than not being able to take off without overheating.
FWIW,
Al
It does seem very likely that you
are going to have some trapped air if you don’t have a bleed at the
highest point. You may need to add a threaded bung and a petcock valve;
or as I refer, a small o-ring plug that is drilled with a small port into the
bottom and then out the side at the top of threads and just below the o-ring.
Just loosen the plug about a turn while you are filling until all the air
is out.
I agree. I've
ordered an AN-16 elbow to redo the turn out of the thermostat housing.
I'm going to drill a hole and tap it, in the side of the fitting for a plug.
Are you able to get a timing light
on the mark? Set up the timing according to Tracy’s
specs.
I did set it with a
timing light, but it was pretty close to the static setting. I couldn't
really adjust it with the RPM's above 3000, so I subtracted the 4 degree from
it, and set the timing for 1500 RPM's at 21 degrees BTDC. I hope that
this is right.
Steve
Subject:
[FlyRotary] Re: Still high temperature
and I
agree that it appears to be insufficient cooling. Since others are
running the evaporator cores with no trouble. I assume that the issue is
air flow. John Slade seems to have no trouble with his temperatures, and
has the identical plane and scoop. Actually I've added a front end to my
scoop to get outside the boundary layer, but still have high temperatures.
I have a
P-51 style scoop that I had put on earlier with the old cooling system. I
removed it when it didn't improve the cooling, but the old set up I think was
beyond help. Maybe I should try it with the new set up.
I was
also wondering about any other factors causing excessive heat from the engine,
like timing. I haven't tried to retard the timing any, but I know that in
piston engines, if you get the timing too advanced, it can result in allot of
heat.
-----Original
Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net]On Behalf
Of Al Gietzen
Sent: Sunday,
September 19, 2004 3:28 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Still
high temperature
The high temps are indicating
insufficient cooling capacity ( I guess that’s obvious); which means
insufficient air flow or too little heat exchange area. If others are
getting adequate cooling at the same power with the same cores, then it is air
flow. As I recall, you are no longer running the coolers in series, but
there still may be a pressure recovery issue with your scoop, or just too small
an opening; more like the first.
After a few runs it seems that the
air should be purged. Do you have a means of checking (confirming your
temps to be sure there isn’t some boiling going on?
Al
Subject: [FlyRotary] Still high temperature
I would appreciate input to a problem that I
have. I just overhauled the
engine, and reworked the cooling system. I'm now
using the A/C evaporator
cores for radiators. The problem I'm having is,
that when I take it up, I'm
seeing coolant and oil temperature of about 210 degrees.
That is climbing
to pattern, leveling off, and throttling back to low
power. The oil stays
pretty much where it is, and the coolant come down
just a couple of degrees.
When throttle back to land, the coolant and oil both
come down to about 180
at touchdown. I taxi back to the hanger and shut
down with oil and coolant
about 190-195, but after shut down, I get all sorts of
gurgling noises from
the header tank, which is fed by the tap on the side
of the thermostat
housing. The gurgling noises go on for 5-6
minutes, which would seem like
the engine is overheated, but while hot, it doesn't
seem overly hot. The
other end of the header tank feeds coolant to the
turbo, so maybe the hot
water is coming from it ? Maybe my header tank should
be fed differently ?
Also at this time, after a short flight, there is only
a couple of cups of
additional coolant in the overflow tank.
I assume that the higher than desired coolant
temperature, and the gurgling
noise are related. I pulled the water pump off
today to double check it,
and all seems OK. The pump only has about 10
hours on it. When I run it on
the ground, and feel the radiators after shutdown,
they are uniformly hot.
I put a furnace blower pointed at the scoop, and I'm
getting very even
airflow through the radiators. The oil cooler,
on the other hand, has about
75% of the air going through the middle of the cooler,
so I'm going to have
to add some deflectors in the plenum to push more air
to the outside. That
seems to be a less significant issue at the present.
Any thoughts ?
Steve Brooks
Cozy MKIV
Turbo rotary
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