Designing a cooling system

Zoom2136 · #1 05-12-2010, 05:38 PM

Hi guys, I'm building a Cozy IV aircraft (a derivative of the Long EZ by Burt Rutan), and I plan on installing a liquid cooled engine. http://www.cozybuilders.org/

Why am I posting here?

Well you guys are probably among the most knowledgeable people about WWII era fighters that used liquid cooled engines (which is nowadays pretty much a lost art, most GA aircraft being powered by air-cooled piston engine). And also it's a nice change from this plane is uber... bla, bla, bla...

So I'm looking for BF-109 (or other liquid cooled engine fighter (P-51s, Spits, etc.)) pictures, plan, production diagram, etc. that show their radiator and ducting system (inlet construction, form and size of the ducting, radiator position/size, exit construction, etc.).

Regards,

dduff442 · #2 05-12-2010, 07:11 PM

This little diagram illustrates the channel in the Bf-109F radiator intake designed to draw the turbulent boundary layer airflow away from the radiator itself. It's taken from a US evaluation of the a/c which is on rapidsharehere.

dduff442

robtek · #3 05-12-2010, 07:16 PM

You might specialice on the He-100 or the He-177 prototype.
Those planes had a condensation cooling system.
When the water -steam - mix left the engine the water was separated and pumped
back to the water - inlet of the engine.
The separated steam was guided to surface-coolers, which were part of the upper planking of the wings where the lower temperatures (air-press reduction over the wing) helped to condensate the steam.
The condense-water then was brought back to the water - inlet of the engine.
The major point for this system is reduced drag, the malus that it is easily shot doesn't count here, me thinks.

baronWastelan · #4 05-13-2010, 12:02 AM

Looks like someone's already done the same project. This is linked from the web site www.cozybuilders.org/

http://www.eaa.org.za/projects/regob

Skoshi Tiger · #5 05-14-2010, 07:10 AM

There are a few designs that use high performance auto v8 and v6's modified for use in aircraft.

An Australian company makes scaled down reproductions of Spitfires. They supply optional aluminium radiators, ducting and fixings(including electric cowl flaps).

Check out http://www.supermarineaircraft.com/O...l%20Extras.htm

You never know you may be able adapt it to your project.

Cheers and all the best.

Thunderbolt56 · #6 05-14-2010, 12:10 PM

Very cool Zoom. I have a total of about 3 hours in a VariEZE from 2 short flights back in the 80's and, as I remember, it was a true pleasure to fly...almost idiot proof (no offense).

Keep us posted on your progress.

Zoom2136 · #7 05-14-2010, 02:15 PM

Quote:

Originally Posted by baronWastelan

Looks like someone's already done the same project. This is linked from the web site www.cozybuilders.org/

http://www.eaa.org.za/projects/regob

Yes but with so so results. By the way, I'll be using a mazda 13B turbo charged engine (aviation turbo, not the stock version)

A lot of poeple have installed water cooled engine but most have serious cooling issues. I'm trying to get as much info as possible in order to reduce the risk of ending up with a setup that will not work.

Most of the knowledge surrounding watercooling got lost after WWII, so this is why I'm looking here.

Thanks guys, keep it coming if you have more info, all is very appreciated.

erco · #8 05-14-2010, 03:04 PM

No doubt you've contacted your local EAA chapter, or even someone at technical, so assuming that, I'll offer that you can't go wrong lavishly copying the P-51 setup. There's never been a bad word about it; if properly done, it's drag-neutral (or nearly so); and it ought to fit nicely on the bottom of the aft fuselage which should keep the plumbing light and simple. See if you can find someone with a P-51 who'll let you have a close look. Or maybe get in touch with the guys building the Thunder Mustang, they ought to know how to build the Mustang cooling system.

Good Luck!

Post some pictures!

baronWastelan · #9 05-14-2010, 07:02 PM

Quote:

Originally Posted by Zoom2136

Yes but with so so results. By the way, I'll be using a mazda 13B turbo charged engine (aviation turbo, not the stock version)

A lot of poeple have installed water cooled engine but most have serious cooling issues. I'm trying to get as much info as possible in order to reduce the risk of ending up with a setup that will not work.

Most of the knowledge surrounding watercooling got lost after WWII, so this is why I'm looking here.

Thanks guys, keep it coming if you have more info, all is very appreciated.

Pusher with a liquid cooled engine is a proven design -- proven to never have adequate cooling. You could make history and be the 1st one to solve it.

SAAB tried:

Quote:

A total of 298 SAAB 21s were produced in five production batches. They served from 1946 to 1954.

Series aircraft were not without problems. Because of the propeller's placement, engine cooling proved to be inadequate, especially on the ground - a serious problem that was never really worked out.

http://www.ipmsstockholm.org/magazin...detail_j21.htm

Blackdog_kt · #10 05-15-2010, 04:30 PM

I'm not an engineer or anything (just a long time physics student), but that's interesting. I think it's logical that liquid cooling would be difficult in a pusher, because the radiator is in front of the airscrew and thus, it can't benefit from the airflow generated by the propeller.

If this would present problems, i guess it would be in low airspeed scenarios or on the ground, with cruise or high speed flight presenting less of a problem (more airspeed=more airflow through the radiator)

Of course, there were many liquid cooled aircraft where the rads where not directly behind the propeller, like the wing radiators of the 109 and the near-the-wing-center rad of the spit, but they both had a nose intake right behind the prop as well.

So, it all got me thinking and i've come up with a weird idea.

What came to mind was to use a normal, belly mounted radiator with some sort of airflow augmentation device. A small propeller/fan/turbine in front of or behind the radiator could be used to increase the airflow at the expense of some extra weight. Think of it as a P51 belly radiator with an attached fan.

Of course, if the fan stopped turning it would be worse than not having the fan at all, since the airflow would have to overcome the fan's resistance as well. So, it would either have to be a retractable device to be used during low airspeed segments of the flight (eg, taxi, takeoff and climb) or one that's constantly turning. A retractable one would impose space and weight penalties though.

So, it could be that the fan turned constantly, but its speed could be regulated by the pilot. Along things like carb heat and cowl flaps found in most piston engine systems, there could be an extra lever or spring loaded switch that would control the fan's speed. With today's electronics, it could be possible to have a servo governor mechanism or something like that, so that you would control the fan's RPM through a spring loaded switch that modulated its pitch for example.

When the oil temp went up, you would increase the fan's speed to generate more airflow. This would cool the oil as the heat would be absorbed by the radiator, increasing the temperature in the radiator as a result and lowering its cooling potential. So, when the radiator temp went up you would open the radiator flap to help that warm air escape.

So, why have a flap in the first place and not leave it wide open? You might be flying in a cold day and as you are climbing at high power and low airspeed the engine is getting warm, but if you leave the flap wide open it would cool the air way too much because of the low outside temp (oil needs to be somewhat warm, otherwise it won't flow well enough).

Finally, i don't know if it would work at all, but there's also two more issues about such an installation. We don't know the possible effect on the propeller. A small fan in the radiator assembly is still a mini-prop in front of the main prop, it could create problems with the airflow that goes through the prop.

The second is the placement of the airflow augmentation fan. Would it be best to have it in front of the radiator so that it pushes the air in, or have it behind the radiator so that it sucks air into it like a big vacuum cleaner? I think that placing the fan in front of the radiator would look too much like a turbine assembly and in those, the resulting air compression generates increased heat. Good for a turbine engine where you want to burn the air with some fuel, but not so good for a radiator that's supposed to be receiving cool air. I don't know if it would in fact work like a turbine and i'm not sure if placing the fan behind the radiator would negate such effects, but someone with a better knowledge of aeronautics could shed some light on this.