190V-18

[Krusty]

It wasn't that big a departure in practical application. A number of Germans told of how you could just run at higher settings all the time without fear of overheating. It was frigidly cold, if you recall, and that helps cool things down a lot more than the thinner less efficient air.

So I have no doubt you may have quite a basis in fact and truth, but in practicality I have never heard of any plane in WW2 that had problems cooling at very high alts, or any special "pressurized" liquid cooling system in any of the planes that did it.

[morfiend]

 IIRC,the P38 had issues with too much cooling at higher alts in European theater.







   

[kilo2]

Got home, nope not in the ebert book, the piece I remember seeing high altitude discussion, stemmed from the the use of MW-50 to alt, then switching to GM-1.  Had something to do with engine cooling, that is why it was stuck in my mind at the time.  

There is much more to this, air pressure having a lot to do with the ability of a heat exchanger to "exchange heat".  Lots of stuff is out there on air cooled engines, but I am having a hard time find specifics on high altitude radiator design, inlet design, and exhaust design.  The radiator has to be larger because although colder, the atmosphere is not as efficient at heat transfer (giant math stuff, nearly over my head)

http://digital.library.unt.edu/ark:/67531/metadc61946/m1/10/

Bear in mind this paper discusses air cooled engines at altitude, but the concept of heat transfer also will apply to liquid cooling if you substitute the cylinder head design and interior cowl design for radiator design.  

Part of making massive power is massive cooling.  There are drag engines that make 7000HP out of less than 700 Cu in, but only for 4 seconds or so.  Making 1000HP for hours, now that is cool, literally.  

The GM-1 system was pressurized to turn the gas into a liquid I think when this happens the gas super cools to -127F. It helped with cooling

[Krusty]

Actually I think the GM when combusted created more oxygen in the cylinder, thus giving more power up where there wasn't enough power even with a super charger. GM-1 was basically nitrous oxide for street rods today.

[dirtdart]

Officially leaving my field (geological engineering) and opening a can of worms. My point is the air at altitude does not have the ability to act as a heat transfer to the extent lower altitude atmosphere is able to. Despite very low temperatures if the engines design was not developed with high altitude operations in mind there may have been cooling problems. At least that is what I got from the article I attached, which covered radial engine cooling at high altitudes.

A chart I would l love to see is the horsepower of the 213 at 35k. I am curious what the loss in hp is in comparison to sea level. Again if there are any aero guys who want to get into thermodynamics I would enjoy the read .... Lesson

[Krusty]

As in.... Jumo 213?



Note I put the Spit14 in there as well. I don't believe anything special was done to the cooling design other than making the radiators slightly deeper because of the higher-powered engine. That wasn't a HF version of it, either, just a basic F.XIV.

[oakranger]

As in.... Jumo 213?

(Image removed from quote.)

Note I put the Spit14 in there as well. I don't believe anything special was done to the cooling design other than making the radiators slightly deeper because of the higher-powered engine. That wasn't a HF version of it, either, just a basic F.XIV.

Intresting

[dirtdart]

On the chart, speed does not equal HP.  What HP is the 213 generating at 35K?  

Speed can have more to do with aerodynamic efficiency than HP.  Part of that aerodynamic efficiency is how to manage the larger cooling requirements (surface area=drag).  The question on these charts is:  Is the disparity in speed a result of aerodynamic efficiency, or the ability to cool the engine effectively to operate in a higher HP range at altitude?

An analogy:

When I cool my beer wort, if I slow the flow of water, the wort chills faster, than if I accelerate the flow of water though the chiller.  The reason, a greater amount of heat transfer takes place between the water and the wort, because there is more time for it to occur.  At altitude, there is a great deal less in terms of particles to effect this heat transfer.  Just because it is cold does not equal heat transfer.  Think of the temperature of the ISS on the sunny side vice the shade side { http://science.nasa.gov/science-news/science-at-nasa/2001/ast21mar_1/ }, both exist in a vacuum and extremely cold "outside" temperatures, yet the sunny side can overheat becasue there is nothing for the heat to transfer to.  

As discussed earlier, it was these design considerations I find fasinating.  I really wish I knew more about the math behind them.  The engineering decisions between say radiator area creating drag, vice enhancing cooling and enabling more HP.  Pick one if you know what I mean.  

[kilo2]

1580 HP at 3,000 Rpm my book has this listed for Climb to alt and Combat for the jumo 213 E/E1 that was in 152s.

[morfiend]

 Dirt,

  try looking up the BV 155,it has a unique cooling system.






   

[dirtdart]

There is just a teaser (one page or so) in the Messerschmitt book I mentioned earlier.  It sure was a neat looking, and huge plane.  My current love affair is with the JU-288.  I have already built one scale model of it, as a proof of concept, now I need to make it a bit bigger and a bit more detailed.  Read up on the engines in that biscuit, not the BMWs, the Jumos..... 

Another interesting aspect of high altitude flight is propeller design.  Another discussion completely.   

[smoe]

Everyone here needs to take a thermodynamics engineering course. It's the one class I consider the most pratical in real world engineering. It's the study of how heat and energy work.

And how come no one mentioned anything about the radiator fluid used? This had to be used to decrease the freezing/increase the boiling point temperatures.

[Mace2004]

The P51 is a good example of dealing with the problems of high-altitude cooling.  The scoop has a relatively small opening which expands in front of the radiator.  This expansion slows the air and increases its pressure as it passes through the radiator and improves cooling at high altitude and speed.  The remainder of the duct then converges which reaccelerates the air to the exit at the rear to approximately the same speed and pressure as the local airflow.  This alone reduces drag but there is also the expansion of the air heated by the radiator which actually offsets even more of the cooling drag.  You could consider it a primative ram jet.  The overall cooling system still adds drag but only a fraction of the drag created by more conventional designs while providing an efficient cooling system.

[oakranger]

The P51 is a good example of dealing with the problems of high-altitude cooling.  The scoop has a relatively small opening which expands in front of the radiator.  This expansion slows the air and increases its pressure as it passes through the radiator and improves cooling at high altitude and speed.  The remainder of the duct then converges which reaccelerates the air to the exit at the rear to approximately the same speed and pressure as the local airflow.  This alone reduces drag but there is also the expansion of the air heated by the radiator which actually offsets even more of the cooling drag.  You could consider it a primative ram jet.  The overall cooling system still adds drag but only a fraction of the drag created by more conventional designs while providing an efficient cooling system.

Would this concept be similar, but improvement to what the SR-71 engine answer?

[Krusty]

Mace: The P-51 design actually created THRUST. The thrust overcame the drag of the radiator to begin with, for a very nice design... Essentially a drag-free radiator scoop! Not necessarily designed for high-alt. Designed for general use. It wasn't the only one like this. The MiG-3 also had a very similar design.

Dirtdart: Yes, but the speed charts are a good indicator of how much HP you're making. I've shown you a nearly linear increase up to that peak power. The question was related to LOSS in power and I was showing only a steady GAIN all the way up to FTH instead. Look at... let's see... ah-ha! The perfect example: P-40F and P-40N:



...just to illustrate my point. These are the same airframe but with different engines. From this I can tell where they make the most power, and that at 18K the Merlin is making a helluva lot more power on 2nd speed of its supercharger than the -N's single speed can make. This speed drop is a direct correlation to the loss in power above FTH.

So the chart is helpful for getting an idea of the power curve. Though it isn't a specific number (Kilo posted one, let's use that), it does give a good idea.


I never said I'd spell it out, just gave an idea.