How to properly turbo-supercharge the P-39 Airacobra.

phx,

More like a single pipe steam heating system, but don't tell the patent examiners.

Caution- only competent adults beyond this point!

If you want to make one, get a 3 or 4 foot length of 3/8 inch diameter copper refrigeration tubing- solder one end closed and install a refrigerant Schrader valve on the other. Have your local refrigeration shop pressure check it, then pull a vacuum, and inject about one half to three quarters fluid ounce of whatever automotive Freon they have available (R-12 if they have any). Incline the charged tube up and down to be certain that the tube is not filled and the liquid has plenty of volume to slosh around in. The liquid phase should only occupy the bottom foot or so of the internal volume, with saturated vapor above. You now have a Heat Pipe, or isothermal tube.

Submerge about 6-inches of the far end in boiling water and hold upright by the opposite end. In a matter of seconds the tube will be too hot to hold, while a solid rod of copper or even silver of the same dimensions would not even be warm. Naturally, one would not experiment with hot, high pressure devices and boiling water without taking endless precautions, wearing protective gear, not pointing an end at your head (in case the soldering or brazing was not professional grade), etc.

I had one of these tubes around for years, and people were amazed at the performance.

Dynasoar
 
right as it says on the tin.
Water tube boilers have water in the tubes. Fire tube... yep, hot gas/fire;)
Yeah, I kinda figured.:) I've never needed to know.;)
Flash boilers are a type of water tube
That I didn't know. Thx.:cool:
If you want to make one
I really, really don't.:openedeyewink: I'm happy to study diagrams & think, "Those guys were smart!":) Or imagine how to describe a better one with 100yr or so of development behind it. But actually build one?:eek: As Harry Callahan famously said, "A man's got to know his limitations."
 
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I see I missed a lot while I've been toiling away on my P-38 thread...

There are several ways to reduce or cancel the risk of ingestion of the exhaust
Since we're talking about turbo-charging the P-39 the issue of exhaust gasses being ingested by the engine air scoop become moot because the exhaust will first travel back to through the turbine and then exit under low pressure aft of the entire installation. No deflectors or fancy exhaust arrangements needed.
Whether the air-to-air or water-to-air intercooler is probably a moot point, I'm okay with whatever works.
Air-to-air is nice for its light weight and simplicity but if you were to use a liquid-to-air intercooler you can install the liquid radiator in pair with the engine coolant radiator and leverage the Meredith Effect for both. Then you have the intercooler itself, which will be smaller than an air-to-air intercooler for the same cooling value, that can be installed directly in line between the turbocharger and the engine, simplifying the duct work and making for an overall more compact turbo installation.
 
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Since we're talking about turbo-charging the P-39 the issue of exhaust gasses being ingested by the engine air scoop become moot because the exhaust will first travel back to through the turbine and then exit under low pressure aft of the entire installation. No deflectors or fancy exhaust arrangements needed.

That post of mine was for the OTL P-39s, sorry for misunderstanding.

Air-to-air is nice for its light weight and simplicity but if you were to use a liquid-to-air intercooler you can install the liquid radiator in pair with the engine coolant radiator and leverage the Meredith Effect for both. Then you have the intercooler itself, which will be smaller than an air-to-air intercooler for the same cooling value, that can be installed directly in line between the turbocharger and the engine, simplifying the duct work and making for an overall more compact turbo installation.

Meredith effect is great if you can re-design the respective parts of the aircraft in suitable manner. If not, the intercooler's raditor is left sticking in the airstream (= more drag), like it was the case on the Spitfires outfitted with 2-stage engines.
The air-to-air intercooler can also be done either 'right' or 'wrong', depending on many factors.
 
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Here is a very rough concept. It isn't to scale and hard to see but I'll explain it a little.
upload_2017-9-27_16-14-27.png

The red lines are the exhaust. They run down to the turbine, mounted in the bottom of the fuselage just behind the wings. The light blue lines are the intake (re-positioned to the left side at about 10-11 o'clock) and this goes down directly to the compressor. The dark red is the charged air duct up to the liquid-to-air intercooler (purple block--this could be moved deeper inside the fuselage but I thought that with it mounted high you could add a second air-intake on the right side to allow some airflow over the inter-cooler if needed). The pink line is the cooled air duct to the carburetor and engine mounted S/C. Under the engine are the radiators (big black blocks). The inlet for the rads is still in the LE root but the duct is redesigned to allow a fast expansion of the air to slow it down and improve cooling efficiency. The hot air outlet form the rads no longer exits out the bottom (the exit flap is still on the drawing through) but instead is split into two ducts which direct it to narrow outlets on the lower sides of the fuselage just above the trailing edge faring (green rectangle). With some careful designing I think you may be able to get a slight Meredith Effect with this, although it may require an expansion of the radiator section and/or a re-designed inlet scoop for them.
 
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