liquid cooling info

[airguy]

While doing some research on the cooling system used by the Galloping Ghost P51 racer at Reno, I ran across this interesting piece about designing radiators for liquid-cooled aircraft engines. It has some good info and some good literature references, I thought you guys might find it interesting.

http://protonet.org/doc/Liquid_cooling_5_LTR.pdf

[TSwezey]

Great info and he probably put that liquid cooled stuff in my brain back when I was one of his students in 1983 and 1984.

[elippse]

There were also articles in several issues of Contact! magazine. Check out their back issues on their site, contactmagazine.com, such as #45 which devotes 8 pages by Hans Mayer to the duct designs on many American, English, and German WWII planes. Also #62 on radiators, and #53 on the Mustang cooling by J.L. Atwood, former president of North American. Contact! has a wealth of info on liquid-cooled engines, including augmented cooling, a real treasure-trove of info!

[JDanno]

Todd,
You an Aggie?
My Dad graduated there in 1958 with Phd. Physics. It was still male only then. Dan

Originally Posted by TSwezey

Great info and he probably put that liquid cooled stuff in my brain back when I was one of his students in 1983 and 1984.

[rv6ejguy]

The protonet article is one of the best I've read on cooling and it takes a few reads for it all to sink in. This was published in Contact! many years ago. If you apply the knowledge here on rad placement and duct shape, chances are things will cool well.

Hoerner's book is probably the best published on this subject with actual testing.

The Hans Mayer articles draw some erroneous conclusions and have some questionable information in my view although some of the information is useful. The high diffusion angle depicted in his drawings would doubtless cause serious separation within the duct even with a guide vane.

[pierre smith]

Originally Posted by rv6ejguy

...... The high diffusion angle depicted in his drawings would doubtless cause serious separation within the duct even with a guide vane.

....inside the upper chamber shelf, leading to the radiator on his P-51. Would this not be an appropriate place for VG's?

Thanks,

[TSwezey]

Originally Posted by JDanno

Todd,
You an Aggie?
My Dad graduated there in 1958 with Phd. Physics. It was still male only then. Dan

Class of '86, Corps of Cadets, BS Aerospace Engineering

[TSwezey]

Originally Posted by pierre smith

....inside the upper chamber shelf, leading to the radiator on his P-51. Would this not be an appropriate place for VG's?

Thanks,

Pierre I don't have a clue about any of that but Ross might know. Not knowing the flow it would probably best be tested in a wind tunnel.

[rv6ejguy]

Guide vanes are more effective in gently turning the air within a duct without turbulence. Studies after the war found most under wing submerged rad setups had serious flow separation and consequently higher drag and less cooling.

High divergent angles are usually bad but we are limited by practical duct lengths in most aircraft to diverge airflow gently- yet another compromise.

With regards to Galloping Ghost at Reno with the boil off/ loss type cooling system eliminating the rad, this has been tried before many years ago and it made no difference in speed. The modified P51 rad ducts like Strega and Voodoo have been highly refined so that they offer no net drag and possibly even some net thrust with the high speeds and spray bar water being injected.

Despite the less than good press on the P40 rad setup, tests during WW2 with ventral rads like the P51 had always showed a clear loss in speed over the under engine setup on this airframe. There are many factors in play here.

[SHIPCHIEF]

I had read somewhere that Curtiss tried a P-51 type radiator on the P-40, but it did not work for them.
P-40's certainly were fast in a straight line or a dive. I have seen one fly with a P-51 at an airshow. It was during the pull-out with a turn that the P-40 lost energy while the P-51 retained more. I don't think that had much to do with the cooling layout, but rather the wing's span loading and airfoil efficiency in a high lift situation.
But back to the cooling; When I began to realize that mounting the cooling system aft of the wing spar required carrying the weight of all that tubing and the coolant therein, I went back to the chin radiator.
As for a boil off cooling system, you are back to the excess weight problem; how can you carry enough total loss coolant to offset the weight penalty of a radiator over the course of any kind of trip?
Add to that, can you dependably get coolant at any airport where you might land?
What about coolant chemicals? plain water leads to corrosion inside your expensive engine, so total loss expensive chemicals is out too.
When you look at the whole airplane, Simple and Light are the best way to go. Never forget that.
Alternative engines still have to measure up to the power output, power to weight ratio, fuel consumption, usability and relaibility of traditional aircraft engines.
Lately I've been trying to understand "Plume Drag". That's the drag caused by the air exiting your aircraft, from leaks around the canopy, rudder cables, engine cooling air etc. Perhaps the Galloping Ghost's cooling system suffers from that instead of traditional radiator form drag? Sometimes you trade one kind of problem for another. That's OK if you're looking for a challenge.
I'm not building a alternative engine because I think Lycoming makes a bad engine.