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Bill,
I don't think I have a problem getting air out of
the cowl. The exit area is greater than 3X the size of my inlets with no
restrictions. The inlet ducts and wedge diffusers tested very good on a bench
wind tunnel setup. But I need to review that data to make sure it's
close to my actual flight data. I really don't have any
other options for my radiator inlets other than a small enlargement. My
radiators are 2.75" thick and have a denser fin count than the
Griffin type Dennis and Tracy are flying. I expect Air Delta T to be better
than 81F.
Any difference in controlling the inlet air verses
traditional cowl flaps on the exit?
Bobby
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bill
Schertz
Sent: Saturday, July 11, 2009 12:07 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Water Spray Pump
Time I chimed in. I have been testing with short
flights trying to get my temps in line. I cannot stay at full throttle beyond
climbing to ~2500, at which point I throttle back to 5600 - 6000 rpm, and bring
the speed up to 110 knots. Temps then stabilize below 200 - 205.
As part of my diagnostics, I have always had a air
pressure differential measurement from my Blue Mountain (sigh) unit, and it
would indicate ~3 to max 4 inches of water pressure difference between the front
of the rad and behind it under the cowl.
For further information, I have installed a
temporary set of pressure probes that run to a manometer in the cabin. This has
told me the following:
1. The entrance to the rad is getting good pressure
6-7 inches water pressure, but
2. The exit is not functioning well enough, because
I get 3-4 inches pressure under the cowl.
My theory as to why this is difficult to fully cool
includes.
1. The cowl was designed for an air cooled engine,
rejecting heat at 350 cylinder head temperature, which is a bigger driving force
than we have.
2. I used the two cowl inlets in the original cowl
to supply the two rads.
3. I have a third entrance for the oil cooler, so I
have ~ 50% more airflow to get out of the cowl.
Bobby, I would install some manometers to see if it
is a problem getting the air in -- or out before you modify your
cowling.
Bill Schertz
KIS Cruiser #4045
N343BS
Phase I testing
----- Original Message -----
Sent: Saturday, July 11, 2009 10:44
AM
Subject: [FlyRotary] Water Spray Pump
Like Dennis I am
having to throttle back and reduce boost after reaching pattern altitude.
Flight testing this week showed I can stabilize my oil temp at 220F at 130
mph, 6400 rpm and 30" MP. Air Delta T after my radiators averaged
81F. This power setting gives a 600 fpm climb and about 185-190 HP. Not
very impressive for a RV10. My initial climb out was around 1000-1250 fpm
with OAT at 95F. Water temp stabilized at 200F. My oil to
water exchanger was transferring 43F to the water.
My total inlet
area is 58 sqin and 21% of core face. The numbers indicate that opening my
inlet area to 68 sqin or 25% should allow me to cool my full net 238
HP. Before starting major fiberglass work at 102 F I am thinking of
testing a super fine mist on the radiators. I would like to see what my
oil temps would be if I can drop the water temp by 10-20 degrees. The
pump information attached is a 15 bar pump and meets the specification for
continuous use and is safe to run dry. It's an espresso machine type pump but
does not have on\off time limitations. Other pumps like his have a 1/1 or
2/1 On/Off in minutes for cooling. If lowering my water temps to
180-185F has a positive effect on oil temps then I will open my radiator duct
this fall when it's cooler. Besides, I have another test for this pump. I
don't have an intercooler and having a 1 pound 15 bar pump will tempt me to
test manifold water injections after my super charger.
Bobby
RV-10 SC
Renesis.
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