Are Liquid Cooled Aircraft Engines Possible?

[airguy]

Originally Posted by Yukon

I can't believe anybody with any technical savy would fund such a business plan.

Really? With fuel bumping $5 to $6 for Jet A at many locations, you still don't see that this application has market potential? Obviously SOMEone does - because it's happening.

By the way - it's not technical savvy that will drive this application - it's marketing savvy. Technical savvy will make it work, but only marketing savvy can make it sell - regardless of how well it works. You don't have to build a better mousetrap - just build a better sales brochure.

[Mike S]

Originally Posted by Yukon

Well Ross, my post said " none in US commercial use" so I am not sure what your point is. I don't know what a Canadair airliner looks like, so I can't really speak to foreign applications.

Well, if you click the link in Kevins post (#40), you will see what the airliner looks like, and see that it was used commercially in the U.S..

As well as the other aircraft I mentioned in an earlier post.

Liquid cooled commercial aircraft seem to have not been common, or overly popular, but they were used.

[Yukon]

Originally Posted by Mike S

Well, if you click the link in Kevins post (#40), you will see what the airliner looks like, and see that it was used commercially in the U.S..

As well as the other aircraft I mentioned in an earlier post.

Liquid cooled commercial aircraft seem to have not been common, or overly popular, but they were used.

Mike,

That's a re-engined C-54, and I still maintain it was not operated by any US air carrier. At least that's what the article says.

[Yukon]

David,

Glad to hear you are enjoying your Subie. Maybe one day the sun will be blotted out with Subie-powered RV's!

[CNEJR]

Right, I can hardly wait.

[captbilly]

Originally Posted by szicree

Something I've been wondering about lately is whether it might be possible with the right materials (perhaps not yet invented) to make a piston engine that requires no cooling. I have no engineering knowledge whatsoever (obviously) but figure that perhaps the internals could be made of something that doesn't so readily soak up heat. Maybe?

It can be done with a diesel but it is essentially impossible with a spark ignition engine. In a spark ignition engine the combustion chamber (including the top of the piston) must be cool enough to not cause detonation when the fuel air mixture is compressed. The only way to do this on a spark ignition engine is to provide some sort of cooling (either liquid or air). Of course with adequate octane and some cooling through the cylinder head and piston (from the oil spash) it would be possible to make an operable spark ignition engine with no cooling fins or liquid cooling system, but it would either require extremely low compression ratio, incredibly high octane, extremely rich mixture, extremely retarded ignition, or some mixture of all of these.

In a diesel there is essentially no problem with making an uncooled engine. The hotter the better for burning the fuel as it is injected into the engine. The only issue would be materials that could withstand the temperatures (probably not a insurmountable problem) and lubrication of the piston at these extremely high temperatures (a bit more difficult). At some point the temperature of the engine would rise to the point where some heat would be removed from the combustion area to the surrounding area (engine compartment) so I suppose it really isn't precisely true that the engine would truely have no cooling system, it just wouldn't have much of a cooling system. If the engine truely operated at the combustion temperature then there is no material on earth that could withstand the heat and pressure inside of a diesel or gasoline engine, so I suppose there would be some requirement to move some heat out of the combustion area.

I do believe that such an engine has been built, partially using ceramics, but it would seem that none have made it to production status. I could certainly see a diesel using pistons made of metals other than aluminum, that could operate at temperatures high enough that very little cooling would be required, but again, the problem of a lubricant that can operate at those temperatures becomes a serious problem.

[rv6ejguy]

Many modern SI engines use direct injection so detonation would not be an issue in this context. Witness the over 12 to CRs on some of these engines operating on pump fuel.

[Andy_RR]

Ross, Gasoline DI gives you a knock/detonation advantage, but it doesn't remove the problem entirely.

Re: un-cooled engines - there have been numerous attempts - google "adiabatic engine" for a few links. The Cummins/TACOM military diesel project is/was one example. Lubrication of the ring-pack is the major headache.

BTW, many automotive engines have a cooling system "limp-home" mode where they go into an "eight-stroke" mode if the cooling system has failed. I think the GM Northstar engine was capable of this, as were many of the Ford engines. I know from my work that the Ford EEC-V has the control strategy to do this. This is a quasi-adiabatic concept, albeit not a very high power density one!

A