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Hi All, Over the last several weeks there has be discussion on use of different radiators, and size of cowl openings for cooling. Has anyone read "How to Cool Your Wankel" by Paul Lamar? Some valid points are made. I am not an engineer and do not know all the formulas. Measuring air flow over the coolant system seem to be a key. Variables would include take-off speed of the aircraft and average in flight speed. Slow air speed and the angle of attack in take-off greatly affects air flow through the system. This is the greatest concern regarding cooling and should be considered in the shape of cowl openings,
radiator positioning, and ducting. This book is at the least a good reference in considering the size of the radiator for cooling and gives a recommendation for folding a radiator in half with minimal changes in the cooling ability.
I understand Paul has offended many in his past discussions on the rotary engine. Unfortunately, this might make the consideration of his recommendations difficult.
I am currently working on the wiring of my panel with hopes of starting my 13B rotary engine this coming year. This engine is mounted to a Zenith Ch801 where both take-off and top air speeds will by slow. My take-off my angle of attack will also by high. As I have studied ducting the radiator, all aircraft designers have decided to recommend anterior cowl openings and duct the exit air to flow under the aircraft. A more efficient design would have intake air entering the bottom anterior of the the cowl and to pass through the radiator. As this air is heated by the radiator it rises and should exit the top sides of the cowl. No one has done that because of the risk of engine oil on the windshield.
As Ben Haase has mentioned, he had difficulty with cooling and only the bent edge of his diffuser made the difference. As I begin to fly my plane we will find out if my cooling system is effective. At that time I will get back with my cooling results. Ken Johnson
If there are
From: Charlie E <ceengland7@gmail.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Wednesday, October 24, 2012 8:00 AM
Subject: [FlyRotary] Re: flow path in conventional radiator
OK, actual: 13.75" H between tanks, ~14.25" W including protective rails on sides, 2.25" thick protective rails (actual core slightly less). So slightly under 440 cu in.
17.75 bottom of tank to top of filler cap. 14.5 max width. 2.5 max thick. Mount studs ~1" on bottom.
Charlie
Sent from my iPhone
It came from CX Racing; I'm pretty sure
that this is it:
http://www.ebay.com/itm/290600743649?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
I wrote the actual core dimensions on the rad, but they are now
covered with protective tape for making the duct. IIRC, the core
is roughly 14x14x2 1/2, around 450 cu in. (Yes, I know that the
math doesn't 'multiply up'.) Don't trust the numbers in the link;
I think that they include the tanks. I picked it based on having a
bit more than 2/3 of Tracy's core volume (2 rotor vs 3 rotor).
I'll try to get you the actual core dimensions tomorrow.
Thanks for the feedback on the flyin. I learned a lot, too, &
we had a great time hosting. Y'all were wonderful house guests.
Tupper's already asking about doing one 'next year'.
Charlie
On 10/23/2012 06:53 PM, DALE HARVEY wrote:
Hi Charlie, what size is your rad and where did you get it? I
will have the same set-up as you pretty much.
Dale Harvey
PS. thanks for having a great fly-in, got some good ideas!
To: flyrotary@lancaironline.net
Date: Tue, 23 Oct 2012 09:27:04 -0500
From: ceengland7@gmail.com
Subject: [FlyRotary] Re: flow path in conventional radiator
Here are a couple of low res
images (list limits on size; if bigger are needed, I'll send
in separate emails). Basically the same config as Tracy's
-8, except a downflow rad instead of crossflow dual pass.
Bottom of rad is several inches below bottom of engine; top
is roughly even with or slightly above the water pump
height.
I can see Mark's point about reversing the flow in this
configuration; if coolant drops below the level of the rad's
top tank, the pump will be sucking air. In a coolant loss
situation, it might only buy a couple of minutes, but could
still be the difference between a safe/unsafe landing spot.
If I move the pressure cap to the swirl pot, there really
isn't any reason to reverse the flow.
Charlie
On 10/23/2012 05:44 AM, Mark Steitle wrote:
Bill,
Since Charlie hasn't posted any pictures or sketches of
his design, I was referencing more what you'll find in
auto installations than in a/c. Still the principles are
the same, namely that the coolant naturally flows to the
bottom and air goes to the top. If it gets low enough,
the pump will begin sucking air and will soon loose prime.
This will happen much quicker if you're drawing off the
upper tank. Of course, if the radiator is located below
the engine it will take longer for this to happen than if
it is beside the engine because the air pocket will be
inside the engine rather than in the radiator. If you
have a coolant leak in flight, you'll benefit from more
time to get on the ground rather than less.
I don't see where it makes any difference which tank
you return the coolant to, but when supplying the
pump, any air will risk loss of prime. So, it makes sense
to me to draw from the bottom and return to the top. At
least that's how I understand it.
In the end its Charlie's decision.
Mark
On Mon, Oct 22, 2012 at 11:10
PM, Bill Schertz <wschertz@comcast.net>
wrote:
I guess that I don’t understand this
(Mark’s) comment. I am assuming that the
radiator is lower than the water pump in any
circumstance, since in general it is either
below the engine, or on the side like Tracy’s.
The Mazda pump is very high, and any loss of
coolant will cause loss of prime if air gets
in the pump, but whether the outlet of the
pump goes to the bottom of the radiator, or
the top, I don’t see the difference. What am I
missing?
Bill Schertz
KIS Cruiser #4045
N343BS
Phase one testing Completed
Sent: Monday, October 22, 2012
6:25 PM
Subject: [FlyRotary] Re:
flow path in conventional radiator
Charlie,
So, with the bottom-up flow what what
happens if you get a little low on
coolant? My guess is the pump will
start pumping air along with the
coolant, and eventually loose prime
altogether and the remaining coolant
will stop flowing, followed shortly by a
catastrophic boil-over. This may be why
auto makers favor the top-down flow
design. The Mazda's water pump is
already very high up on the engine. I
wouldn't want to aggravate this even
more. Also, the cross-flow design
doesn't suffer this failure mode,
assuming you draw from the lower hole.
Mark S.
On Mon, Oct
22, 2012 at 2:05 PM, Bill Schertz <wschertz@comcast.net>
wrote:
Charlie, I am using two
evap cores in parallel, with
system pressure limited to
10 psi on the expansion
bottle. When the engine is
running, the pressure
measured at the inlet to the
cores (exit of the pump) is
a function of RPM and can
rise to as much as 20 psi
(10 psi over system pressure
in the expansion bottle).
Having the flow enter the
bottom of the radiator and
out the top, then going to
the inlet of the pump sounds
like a good way to avoid
problems.
Bill
Schertz
KIS Cruiser #4045
N343BS
Phase one testing Completed
Sent:
Monday, October 22,
2012 1:06 PM
Subject:
[FlyRotary] Re: flow
path in conventional
radiator
Unless
there is a serious
restriction through
the radiator I can't
imagine there would be
anything greater then
1 psi over system
pressure caused by
pump output. As for
the reverse flow, ie,
bottom to top,,, It's
called counter flow,
and yes it can work.
My set up has worked
flawlessly for 500
hours and I use the
Moroso swirl /
pressure tank and a
air bleed line from
the output of the
radiator... About 3
minutes into this
video shows my set
up.....
http://www.youtube.com/watch?v=rCNnEgRkdXc&context=C3e091d3ADOEgsToPDskKmHo69I6bUDuoBHd5YSUfu
Ben
Haas
www.haaspowerair.com
To: flyrotary@lancaironline.net
Date: Mon, 22 Oct
2012 12:40:11 -0500
From: ceengland7@gmail.com
Subject: [FlyRotary]
flow path in
conventional
radiator
I've
been
doing research
on radiators,
& my 1st 'experiment'
will be a conventionally
configured
radiator
(downflow
design) with
inlet &
pressure cap
on top. In
reading about
issues with
conventional
radiators, a
common
complaint is
pressure
venting due to
the water pump
+ system
pressure
exceeding the
cap's
rating. Crossflow
types like the
Sirocco
are supposed
to avoid this
because the
cap is at the
mid-point in
the flow
through the
rad, which
drops some of
the pressure
seen by the
cap.
Here's
my question:
Is there
any reason a
conventional
rad can't be
fed from the
bottom,
instead of the
top? This would
achieve
similar effect
as the
crossflow cap
location (all
the way to the
end of the
flow path)
& any air
could be
vented
using the
existing
fittings. I'm
also considering
the removal of
the spring
loaded seal,
& moving
the pressure
cap function
to a separate
swirl
can. By doing
this, the existing
over-pressure
port could function
as the air
removal port
in the top
tank of the
radiator.
What
am I missing?
Thanks,
Charlie
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