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  #1  
Old 01-26-2006, 02:01 PM
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Default p51 style scoop

From what little i have seen - sounds like they got it right. I didn't realize that it was both an entrance and an exit! only good for liquid cooling

wait - maybe good for intercooling!! have to ponder that a one
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Old 01-26-2006, 03:12 PM
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The P51 scoop routed all rad, intercooler and oil cooler air through there and controlled the exit air with various doors. Nice low drag setup.
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Old 01-26-2006, 03:23 PM
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Buly's MASSIVE P51 scoop was Paul Lamar's recommendation. It feeds plenums for the rad and oil coolers. No cowl flap doors. Like Greg Richter's monster cowl scoops, I'm thinking "brick wall at 170 kts".

(But he'll definately get all the girls at fly-ins ).
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Old 01-26-2006, 03:24 PM
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Quote:
Originally Posted by rv6ejguy
Nice low drag setup.
carmichael in the arnold video implied that the p51 set up was the bect that can be had

maybe that is the way to go for the intercoolers!
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Old 01-26-2006, 03:27 PM
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Quote:
Originally Posted by John Slade
Buly's MASSIVE P51 scoop was Paul Lamar's recommendation. It feeds plenums for the rad and oil coolers. No cowl flap doors. Like Greg Richter's monster cowl scoops, I'm thinking "brick wall at 170 kts".

(But he'll definately get all the girls at fly-ins ).
i don't think feeding plenums for stuff is a P51 scoop. i think it has to be both the inlet and outlet with pretty straight flow though to be a "P51" style scoop.

I thin feeding plenums and routing the air to the areas would qualify it a just a scoop
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Old 01-26-2006, 03:33 PM
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Quote:
i think it has to be both the inlet and outlet with pretty straight flow though to be a "P51" style scoop.
Really? Doesn't the original P51 scoop (in a P51 Mustang) channel the air through 180 degree turn and then forward toward the engine?
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Old 01-26-2006, 03:34 PM
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not the drawing i saw - thats what i thought before the drawing
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Old 01-26-2006, 04:35 PM
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Quote:
Originally Posted by John Slade
Really? Doesn't the original P51 scoop (in a P51 Mustang) channel the air through 180 degree turn and then forward toward the engine?
Not sure which "scoop" you're refering to here. The P51 used a scoop just below the engine to feed air to the Merlin V12, and then a large scoop below the belly, for the radiator & turbochargers.
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  #9  
Old 01-26-2006, 05:13 PM
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Quote:
Originally Posted by ShaleDC
then a large scoop below the belly, for the radiator & turbochargers.
this must be the one that is touted in the video as being da best possible, lowest drag, cooling device.
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  #10  
Old 01-26-2006, 05:20 PM
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Of course the P51 was supercharged, not turboed and used a liquid to air intercooler system just like the Spitfire. Supercharger inlet air was taken below the spinner. This went through two supercharger stages (both centrifugal) then was passed off (very hot) to a heat exchanger at the rear of the engine. A pump circulated coolant to the rear scoop area to a bigger heat exchanger mounted above the engine coolant radiator where this heat was given up to the air.

The P51 was one of the first aircraft to have the cooling system integrated INTO the airframe, not ONTO it. My analysis of of rad inlet area, volume, area placement, duct shape and length vs. installed hp shows that the P51 has a very efficient system. Likewise the Daimler Benz powered FW 190 D series and TA 152s with the ring radiators was also very efficient. The Dehavilland Hornet with 2070 hp Merlins and leading edge rads also had very favorable rad areas and volumes per unit hp. These aircraft could often pull rated power up to nearly 30,000 feet so their cooling in the climb at these altitudes is truly impressive. Believe me, this is not easy to do with a low drag penalty.

When it comes to cooling drag and liquid cooled engines there are some pretty wild theories out there today in the experimental world. Bottom line, the heat exchanger is a restriction to airflow. Any time you turn air, there is an energy loss. If you turn it sharply, expand it quickly over short distances or converge it too quickly, there are much higher losses. The closer to freestream velocity you discharge the cooling air, the less drag you are likely to have. The frontal area of a scoop may cause far less drag than flush inlets feeding a convoluted path past all kinds of drag producing structures under the cowling and exiting its air into less than ideal conditions.

Just about every current liquid cooled experimental breaks these rules and suffers high drag as a result. Airflow management on entry, diffusion and exit through the cooling system is critical to performance and low drag. I have found one example of a really good setup powered by a 4.3 Chev uses a P51 style scoop on a Velo. Only 32 square inches of inlet area, 126 square inches of rad face area and 315 cubic inches of matrix volume. This easily cooled a 230hp engine. Impressive.

A lot can be learned here from WWII documentation. This was state of the art for liquid cooled aircraft engines, most of which has never been exceeded to this day. These guys were very clever.
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Old 01-26-2006, 06:38 PM
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yeah - all thos turns. I'ma thinkin Ima gonna get my cooling air from the top of the cowling and bend the air down.

getting the air from in front of the jugs and cramming it into a box plenum that changes the direction 90 degrees and then another 90 below the engine just seems - bendy.

I got a look at the p51 scoops for my two intercoolers in the wing root.

straight through

30% of total drag is cooling drag - gotta look - have some thoughts churnin in my head on how to take the airbend it in gradually opening runners from the top to the cylenders, between each intake runner - lookin good in my head
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Old 01-26-2006, 07:40 PM
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Even the air cooled cert type engines can benefit from airflow management. There was a good article in Kitplanes a couple years back on a Lyco powered Mustang II or similar (memory failing slowly but surely). Through round inlets, a full plenum, with sealed exit curved to direct air out the cowl flapped, reshaped and sized, belly exit duct instead of thudding into the firewall, this fellow picked up something like 15 knots. That's freeeee. (well a lota work).

With pushers, there is the interaction of the cooling air with the prop and possibly impacting its performance. Be interesting to tuft one in flight and vid it.
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Old 01-26-2006, 08:31 PM
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Well, at this point i'm seperating the cooling between jugs/oil cooler and intercoolers.

i'm picturing intake like tubes (a backwards oval funel) from the top of cowl down to between each cylendar and the reverse on the other side.

on the intercoolers - mmmm gotta look at small p51 style in the wing root.

the naca just for combustion air and turbo and general under cowl cooling.

don't know where I'll end up - gotta think before i do - gotta understand before i go, gotta want a lot to get a little - gotta go in the shop now

I'ma lucky man - gatta alota gottas
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Old 01-26-2006, 10:09 PM
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i know it looks obvious, but air flow is air flow, wether it be in the intake manifold, exhaust, cooling, wings, fuse, internal heating system - smooth flow and gradual changes, reduces drag and increases performance

ima gettin a handle on it
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Old 01-27-2006, 01:26 AM
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The P51 I saw had 2 flaps at the back of the scoop.
One large and low on the back of the scoop, the other smaller and higher. Both were open for ground operations, like taxying, the big one closed for takeoff, and it seems both were closed for airborne operations. I didn't see any places in the fuselage where exiting air would go, but then I didn't really get a chance to look too closely.
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