> > How about let's change the idea up, to air cool a rotary without
> > cooling
> > fans?
> >
> > Let's posit that we have an air-cooled rotary engine with no water
> > jacket. Instead, on the outside of the engine, fins radiate from both
> > the sides and the ends of the engine, to cool it like the barrel of an
> > old radial piston engine is cooled. The fins are positioned and
> > oriented so that air flow is optimized for appropriate cooling and for
> > air flow in, through, and out of the engine compartment.
> >
> > No cooling fans, such as the Midwest/Diamond or Porsche engines are
> > needed, so no power is drained, no unnecessary fuel is used.
> >
> > Such an air cooled rotary engine would certainly be physically bigger
> > than its water cooled counterpart, but would not the air cooled rotary
> > be smaller overall than the water cooled engine and its attendant
> > radiators, hoses, etc.?
> >
> > Would not such an air cooled rotary engine be lighter, simpler, more
> > efficient, more reliable than its water cooled counterpart? How would
> > we know that it would be or would not be? How would we know that we
> > knew?
> >
> > Let us also posit that each fin, where appropriate, has within it a
> > properly-engineered heat sink. Heat sinks have no moving parts, so they
> > would be reliable. Perhaps heat sink technology could siphon the heat
> > out from the center housing into fins projecting into the air stream,
> > so
> > that even the center housing could be cooled.
> >
> > Would using a technology like a heat sink increase the cooling
> > effectiveness of each fin? Would not heat sink technology make such air
> > cooling more efficient? Could such technology help cool a rotary
> > engine enough? Again, how would we know that it would or would not and
> > how would we know that we knew?
> >
> > I would certainly like to hear your thoughts about this. I expect I
> > will ask of you all, when you post, a lot of questions. Why? Not
> > because I am trying to be argumentative, but because I do not know all
> > the answers and I know I do not know. :-)
> >
> > Les Nordman :-)
> >
> > I understand. Good idea. I think you mean heat pipe rather than heat
> > sink.
> > I think it can be made to work. Got a couple of million lying around
> > you are not using? :)
> >
> > Paul Lamar ...No rotor no motor.
> >
> >
> > I dealt with this same scenario on a electric car motor. The original
> > idea was to do cast fins. The casting looked like a vintage Ducati. As
> > it turned out, the area on the cast fins was very limited due to the
> > wall thickness of the casting. The fins need to be a certain thickness
> > in order to get the molten metal to flow.
> >
> > They ended up using a corrugated fin. This gave something like two to
> > three times the cooling area but looked ugly. The fins were similar to
> > the link below, but it was able to flex and adhere around the OD of the
> > motor.
> >
> >
http://www.fs-thermalmanagement.com/html/products_radiacal1_fabfin.htm
> >
> > Early 80's 2-stroke engines used to be air cooled. They were able to
> > build to higher tolerance once they went to water cooling. Much of this
> > has to do with the unevenness of air cooling. It is tough to get rid of
> > a hot spot if air does not flow in that air due to an engine mount.
> >
> > A mars rover thermal engineer once explained to me that heat was like
> > electricity. To get it to flow you need a large potential
difference. It
> > wants to travel down a good conductor. The larger the cross sectional
> > area the better. When you have two different materials or a air gap
this
> > creates a resistance. He also said the prediction of how it travels is
> > pretty much black magic. There are just to many variables.
> >
> > Bill S
> >
> >
> > What's the big deal about trying to air cool a Mazda? Liquid cooling
> allows you to put the heat exchanger
> > where it causes the least drag. Liquid cooling also allows the engine
> to be
> > more compact and probably lighter as well as have higher specific
outputs
> > because of superior heat rejection. I think we have enough to do
getting
> > these things accepted as normal, everyday aircraft engines not
> experimental
> > projects.
> >
> > Steve Brazil
>
> Dear Steve Brazil:
>
> What
_is_ the big deal about trying air cool a Mazda? Not to create
> more trouble for the far-flung, small, lonely band of intrepid
> installers of 13b's, 20a's, and Renesis engines in their aircraft,
> trying to carve out, seemingly alone, legitimacy and respect from an
> ignorant, hidebound conservative aviation community and regulators! My
> reasons and questions I list below. :-)
>
> My post is an exploration, asking "what if?"; pushing the boundaries of
> our thought; gathering the community of rotary aviation engine-lovers
> away, for a little while, from the daily beat-down grind of getting our
> rotaries accepted, into a calm, safe harbor of thought and imagination,
> so that we whose minds have been unshackled from Piston Prison can look
> at what might be.
> I have some questions in response to your post.
>
> You wrote: "Air cooling is NOT necessarily better."
>
> I totally agree. If, in the final analysis, cooling a rotary engine
> with liquid is better than cooling a rotary engine with air, that will
> be great! We will have explored. We will know more! And knowing is
> always better than not knowing. :-)
>
> You wrote: "You can't transfer heat with a gas as efficiently as you
> can with a fluid."
>
> Great information! How much more efficient is a fluid in tranferring
> heat than a gas, more specifically, air? How was that measured?
>
> Might not new technologies such as the heat PIPE (thanks, Mr. Lamar!)
> overcome air's inherent inefficencies? New ideas, new technologies and
> new tools have come along since Continental and Lycoming ossified their
> engine designs in the last millenium. Using those new ideas,
> technologies and tools, could we not cool a rotary engine with air as
> efficiently as, or more efficiently than, the same engine cooled with a
> liquid? How would we know if we could or could not unless we first
> asked the questions?
>
> You wrote: "Liquid cooling allows you to put the heat exchanger where
> it causes the least drag."
>
> I am all for having the least drag. So how do we know that air cooling
> cannot cause the least drag of the two cooling schemes in question? How
> do we know we know?
>
> You wrote: "Liquid cooling also allows the engine to be more compact
> and probably lighter as well as have higher specific outputs because of
> superior heat rejection."
>
> Can you help me here, please? I am not clear what you mean. Do you mean:
>
> A. Liquid cooling allows the engine:
> 1. (definitely) to be more compact
> 2. probably lighter
> 3. (definitely) have higher specific outputs
>
> or
>
> B. Liquid cooling allows the engine:
> 1. (definitely) to be more compact
> 2. probably lighter
> 3. probably have higher specific outputs
>
> I added the word "definitely" to heighten the contrast. Which do you
> mean? Or do you mean something else, something that I did not catch?
>
> Cooling the engine with liquid definitely makes just the engine itself
> more compact than the same engine cooled by air! I agreed with you in
> my first post: "Such an air cooled rotary engine would certainly be
> physically bigger than its water cooled counterpart . . . " My question
> to the forum is: "would not the air cooled rotary be smaller, lighter,
> and more reliable
_overall_ (taking the entire aircraft into account)
> than the water cooled engine
_and_ its attendant radiators, hoses, etc.?"
>
> You wrote: "I think we have enough to do getting these things accepted
> as normal, everyday aircraft engines not experimental projects."
>
> Yes: the Blinkered, the Blind, and the Professionally Scared in aviation
> make it terribly difficult for you to gain acceptance for your rotary
> engine as a Real Engine. Your fellow rotary aviators here on this forum
> are slogging down the same road as you. Heck, my brother is going
> through exactly the same kind of ordeal as you, at his job at Boeing.
> You are not alone.
>
> Steve, if it is too much for you, that's okay. Just opt out of the air
> cooling exploration. I will still be leading the cheerleaders for you
> and all the rotary aviators fighting for acceptance. :-)
>
> Also, if it was okay for Dr. Felix Wankel could have a dream in 1920
> about a rotating engine, and that dream ended up with the rotary engine
> in 1950, certainly it is okay post a question in the AREN newsletter
> about improving the rotary engine, isn't it? Can't the newsletter do
> both: help us with our here-and-now slog
_and_ allow part of our mental
> energies to mull the possibilities of improving these wonderful
engines? :-)
>
> Yours,
>
> Les Nordman :-)
>
> The problem is money Les. Unless you can come up with the money, to
> do the R&D and manufacturing, air cooling the rotary is a moot point.
>
> If you want to do something, manufacture and sell complete bolt on
intakes systems
> for RX7 and RX8 engines. Other than motor mounts (well handled now by
Jerry Hey).
> Complete bolt on intakes systems remains the largest stumbling block
for most people.
>
> Also a firewall forward package for one or two popular RV models
package less the engine
> would also sell IMHO. Let people get their own engine. So far people
that have tried
> it priced it at an unrealistic level as they attempted to tune and
supply the engine.
> Tuning the engine is unnecessary as a stock engine will work fine for
about 185 or so HP.
> Also there are many companies that can supply engines. The right
price for a good
> firewall forward package could be at $5000 including all high quality
plumbing
> and oil cooler and water rad.
>
> Paul Lamar ...No rotor no motor.
Dear Mr. Lamar:
Ah! I get it now. The Newsletter exists to discuss and solve the
issues and problems of real people, who are spending their real sweat,
brains, tools, and money on real projects. I need to be
_here_, be
_real_, be
_now_. If I don't have the money to actually do the project,
the ideas I come up with are moot.
Cool. :-)
Now, you could have just dismissed me for being a head-in-the-clouds,
over-intellectual dilettante, but you did not. You gave me not one,
but two ideas for projects that meet real, pressing needs, projects that
could really be built and be priced for real people. You helped me.
In fact, every one of the posts responding to my questions have been
enlightening, instructive and helpful. For that, I am deeply
grateful. You guys on this newsletter are great people. :-)
Since I do not yet have the money to research, develop and manufacture
air-cooled rotary engines, I shall drop the topic.
Thanks for continuing to let me be a part of you all, a part of this. :-)
Gratefully yours,
Les Nordman :-)
I, supect that air cooling the Rotary. Will not become a garage
type project for the enthusiast untill nano type materials become
more developed and widely available. The way fiberglass and carbonfiber
started showing up in the home built market, it would be more profitable
to come up with a way to shrink the heat exchanger to better fit aircraft
cowls and still be as effective as a large flat automotive type how about
a square duct heat exchanger it could run from the high pressure zone in
front of the cowl opening to a lower pressure zone like where most people
mount the muffler now maybe a small fan could Be used to improve efficiency
I would draw it but I'm still at the stick figure stage in the drawing
department so I will spare every body the agony .
Clifton
The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site.
http://www.rotaryeng.net
Copyright 1998-2007 All world wide rights reserved.