Hi
Bobby,
The theory I have
read indicates that once your open area has passed 25-30% of your core area,
that from that point on - exit area dominates. In other words, it does not
make much difference how much more you enlarge your inlet area if the air
can not get out. Air pressure simply builds under the cowl in back of
the core and restricts further enhancement of thorough flow. That is
if I understood what I read correctly.
Ed
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bobby J. Hughes
Sent: Saturday, July 11, 2009 3:52
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Water Spray
Pump
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.
--
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