From: "Stephen Izett stephen.izett@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Re: Cooling Issues
Date: Sat, 30 Dec 2017 16:05:31 +0800
References: <list-10493361@logan.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
In-Reply-To: <list-10493361@logan.com>
Message-Id: <86B0AF2A-7389-4841-A283-6FAE3362640D@gmail.com>

Hi Steve & Lynn
I got a moment today so went to the hangar and:=20
1. Measured the right cheek inlet.
Fudged due to shape I now think its total area is 22 in^2 and I=E2=80=99m =
currently using 18 in^2 due to the air feed to coils and alt.
So there is a possible 20+% available but not sure what the inlet will =
do close to the spinner.
2. I hung some wool in front of the cowl cheek as Lynn suggested. One at =
each end about an inch in and another in the middle.
The outside piece was clearly blowing or sucked into the diffuser. The =
middle one was barely wanting to go in, and the one closest to the =
spinner was all over the shop.
At an OAT of 90F the water out of the engine got to 225F in 10 minutes. =
2000 engine rpm fine pitch.

Thanks for the info on pressures at 2400rpm.
I=E2=80=99ll be very interested to see what I=E2=80=99m getting inside =
the diffusers.=20
The cowl was pretty much zero at 2000rpm and then -0.5 inch H2O at about =
6000rpm.


Steve Izett


> On 30 Dec 2017, at 3:32 pm, Steven W. Boese SBoese@uwyo.edu =
<flyrotary@lancaironline.net> wrote:
>=20
> Steve,
>=20
> The test stand load was a 3 blade Warp Drive HP prop.  The =
engine-reduction drive assembly was mounted such that it was free to =
rotate on an axis collinear with the engine eccentric shaft but the =
rotation was constrained by a load cell.  The load cell measured the =
torque which, along with the prop RPM, allowed the HP to be calculated.
>=20
> The prop blast supplied the cooling air to the radiator and oil cooler =
ducts.  The pressure on each side of the heat exchanger core was =
measured using piccolo tubes across the core.  The piccolo tube holes =
were 1/16" dia  at a 1" spacing.  The holes were oriented perpendicular =
to the air flow through the core.  Each piccolo tube was connected to =
one side of a differential pressure transducer while the other side of =
the transducer was open to the atmosphere.  It would have been possible =
to measure the delta P directly using just one differential pressure =
transducer for each core, but I was interested in the absolute pressures =
as well as the delta P.
>=20
> The same setup was used in the plane to measure the pressure at the =
inlet side of the core of GM AC evaporator cores used as radiators =
behind short ducts with stock cowl nostril inlets.  In flight, the =
pressure at the core face was about 80% of the pressure measured by the =
airframe pitot tube.  With an in flight pitot pressure of about 10  =
"H2O, the pressure in front of each radiator core was about 8 "H2O and =
the pressure inside the upper cowl (not near the radiators or cowl =
outlet) was about 4 "H2O, all relative to the airframe static source.  =
During stationary  run up with a prop RPM of 2400, the pressure =
recovered at the left radiator core was about 1.8 "H2O while the =
pressure at the right radiator core was about 1.5 "H2O.  Overheating at =
ide or while taxiing was normally not a problem.  Take off and climb =
cooling was marginal at OAT over 70 deg while cooling at cruise was =
good.  I have since changed to a belly scoop system with much improved =
take off and climb cooling. =20
>=20
> I don't know of a convention for expressing inlet area with respect to =
the lip shape.  An inlet duct divergent area change from 16.5 sq in to =
27 sq in in a short distance indicated the potential for air flow =
separation from the duct wall and turbulence in the duct at the air flow =
velocities likely to be generated in flight.  =46rom your additional =
description, this would not seem to be a concern.
>=20
> Steve Boese
> RV6A, 1986 13B NA, RD1A, EC2
>=20
>=20
> =20
> From: Rotary motors in aircraft <flyrotary@lancaironline.net> on =
behalf of Stephen Izett =
stephen.izett@gmail.com<flyrotary@lancaironline.net>
> Sent: Friday, December 29, 2017 6:44 PM
> To: Rotary motors in aircraft
> Subject: [FlyRotary] Re: Cooling Issues
> =20
> Hi Steve
>=20
> I took a moment and estimated the total duct scaled from the drawing =
as being about 18.5 in^2 (Prop Flange is I think 6 in)
> Then I have taken away 2 in^2 for feeding the coils/alternator.
> It=E2=80=99s that 2 in^2 I=E2=80=99ll redeem for water cooling and =
move the coiling air for the coils/alternator.
> I just realised to that I should probably be feeding the coils and =
alternator from diffused (slowed) air and not from free stream air.
>=20
> I=E2=80=99ve always measured from the inside minimum neck of the entry =
and not included the lips. What is the convention?
> You appear to have measured from the outside of the flange which I =
measure to be about 27 inch^2.
>=20
> I=E2=80=99ve wondered how effective the inlet area right against the =
prop spinner will be at cruise.=20
>=20
> Steve