MilitaryAttractions
Airman
- 66
- Feb 7, 2013
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Here's the intercooler arrangementI'm interested in learning more about the XP-39 prototype that used a turbocharger. I'm told that the additional equipment (intercoolers and exhaust manifolds I guess) created too much drag. Does anyone have any more information on this? Any pictures and diagrams that show the system in detail?
- Air is drawn in through a pair of ducts on the lower fuselage (at what point fuel is introduced does not appear to be made)
- Presumable air-fuel mixture flows through the turbocharger and is compressed
- Presumable air-fuel mixture then flows through the supercharger air-cooler, which is mounted inside a duct on the aircraft's right side; airflow through the duct carries away the heat from the airflow before it is directed into the V-1710's single-stage supercharger (not shown, but present)
the XP-39 used 4 pipes.7.Airflow escapes the aircraft through the bottom (I'm not sure whether it is through four exhaust pathways, one, or some number between).
On the bright side it doesn't seem to require air purely for inter-cooling (most aircraft with inter-coolers draw air from another source, route it through the intercooler, and then get rid of it), though from what I was told, you need around 3 times the amount of airflow for cooling than just the carburetor
On the bright side it doesn't seem to require air purely for inter-cooling (most aircraft with inter-coolers draw air from another source, route it through the intercooler, and then get rid of it), though from what I was told, you need around 3 times the amount of airflow for cooling than just the carburetor
Not sure what you mean here, the XP-39 used an air to air intercooler. Unfortunately it was nowhere near big enough. Especially for climbing. Best climb speed for most fighters was under 1/2 of max speed and that means 1/2 the cooling air per minute going through the inter-cooler.
So the fuel was mixed in at that point?All in error except the last line. The carburetor was mounted on the engine driven supercharger.
For the exhaust? Weird...the XP-39 used 4 pipes
The airflow path way seemed to be from the underside to the turbo, through the cooler...Not sure what you mean here, the XP-39 used an air to air intercooler. Unfortunately it was nowhere near big enough. Especially for climbing.
I thought the airflow increased to the square of velocity?Best climb speed for most fighters was under 1/2 of max speed and that means 1/2 the cooling air per minute going through the inter-cooler.
I figured the airflow to the engine was drawn in through the cold air ducts, then was compressed by the turbo, then went through the cooler, and to the engine: I was under the impression that most coolers that were air-to-air drew in air from the outside, ran it through the structures in the cooler (which would carry away the heat), so as airflow went across them, it would be cooled down...What are you talking about?
The intercooler duct feeds only the intercooler.
You'd fix that with a flap right?The intercooler undercooled at climb speeds but overcooled at high speeds.
I figured the airflow to the engine was drawn in through the cold air ducts, then was compressed by the turbo, then went through the cooler, and to the engine: I was under the impression that most coolers that were air-to-air drew in air from the outside, ran it through the structures in the cooler (which would carry away the heat), so as airflow went across them, it would be cooled down...
n the bright side it doesn't seem to require air purely for inter-cooling (most aircraft with inter-coolers draw air from another source, route it through the intercooler, and then get rid of it), though from what I was told, you need around 3 times the amount of airflow for cooling than just the carburetor
You'd fix that with a flap right?
I made a guess looking at the diagram (kind of followed the path of where the flow would go)Which is correct, but not what you said
The other source is the outside air, which is routed through the inetrcooler.
So the solution would have been to put a diverter in place; then enlarge the cooler, and draw additional cooling air for this task; then add flap to control the airflowThe size of the intercooler is possibly too small, the control mechanism (most likely an outlet flap) would open up to allow cooling at low speed and high power, and then close down to make sure the airflow is the right amount and not too much.
The intercooler air came from the cold-air intake? If so, I'm guessing 3/4 went to cooling and the remaining 1/4 to the engine?
So the solution would have been to put a diverter in place; then enlarge the cooler, and draw additional cooling air for this task; then add flap to control the airflow
the XP-39 used 4 pipes.
For the exhaust? Weird...
YesThe cold air intakes were shown in the diagram you presented facing forward and feeding the turbo.
YesThe intercooler was mounted to the side at the rear of the engine.
I see that airflow went through the intercooler duct from front to back, but I was under the impression that most intercoolers would tap air from another location (say the wing's leading edge), and route it through the air-passageways in the duct, so that when the airflow from the first stage of supercharging flows through the intercooler on it's way to the engine, it's cooled down before being compressed by a second stage...The intercooler had its own duct. I don't believe that the intake air for the turbo came from that duct, and the diagram seems to confirm this.
A separation between the airframe and duct to remove turbulent airflow.Diverter?
YupA properly shaped duct would help - a divergent duct leading to the intercooler and a convergent duct after the intercooler with a adjustable door to control the mass flow.
Yes, though the P-38's scoops look like they'd be decent candidates too.Like the radiator ducts of the Mustang. Or even the Spitfire (which had a two position outlet).
The left and right side formed one duct which fed the turbo?Note that the XP-37 had a different set-up, although it and the XP-39 used the same turbo, at least originally. The turbo was mounted under the engine, as in the XP-39, but the exhaust was ducted forward to the front of the engine by a single header on each side, after which the right hand header crossed over the nose case (the long nose case) to meet the left hand header and form a single exhaust, which went down to the turbo.
That's interesting!Note also that the exhaust arrangement was left to the airframe manufacturers.
I see that airflow went through the intercooler duct from front to back, but I was under the impression that most intercoolers would tap air from another location (say the wing's leading edge), and route it through the air-passageways in the duct, so that when the airflow from the first stage of supercharging flows through the intercooler on it's way to the engine, it's cooled down before being compressed by a second stage...
Diverter?
A separation between the airframe and duct to remove turbulent airflow.