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Meredith Effect


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#11 NeoConShooter

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Posted 08 May 2012 - 01:57 AM

It very much did.

The air came in a narrow slot, was expanded to go through the cooling matrix (ie the engine) and then exited through an adjustable nozzle.


The flaps were there to stop airflow at high speed. The slower the plane was going, the wider they opened. Exactly the oposite of what would be required if it did use the Meredeth Effect.

#12 Wuzak

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Posted 08 May 2012 - 02:24 AM

The flaps were there to stop airflow at high speed. The slower the plane was going, the wider they opened. Exactly the oposite of what would be required if it did use the Meredeth Effect.


You are incorrect.

The flap position is not dependent on the aircraft's speed.The flaps are used to control teh mass airflow of air through the engine.

At low speed and low power the flaps would probably be closed because there isn't much cooling required.

At WEP at high speed the flaps may need to be open as the engine temperatures, especially the cylinder head temperature, may become too high otherwise.

From wiki:

The cowling enhanced speed through drag reduction and utilising the heat of the engine to generate thrust.



#13 GregP

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Posted 08 May 2012 - 02:37 AM

You don't stop the airflow through a NACA duct or it creates a drag point, exactly the same as if a jet intake were too large and air werr to be both flowing into and back out of the inlet, as on the Bell YP-59A Airacomet.

The flaps might slow the flow through the NACA duct but they certainly won't stop it entirely without adverse drag penalties.

What do you think, Flo and Drgondog and Wuzak?

Guess we posted at the same time, huh Wuzak? Thoufg we said essentially the wame thing, I like Wuzak's wording better than my own.

Edited by GregP, 08 May 2012 - 02:42 AM.


#14 Wuzak

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Posted 08 May 2012 - 02:52 AM

Looks like it Greg.

I was thhinking about the P-51's situation. I'm quite sure that the best thrust from the radiator occurs when the flap is closed.

As I said before, Joe Smith admitted that the exit of the radiator ducts on the Spitfire were too large - not maxmising the potential thrust and causing over-cooling in some situations.

I've wondered if the Spitfire XIV would have been faster had it been given the same style radiators as the Spiteful (which are like the Bf109's).

On radials when the cowl flaps are closed there is still an air path - it is just smaller than when they are open. The flaps also must have soem effect on drag when they are open.

#15 NeoConShooter

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Posted 08 May 2012 - 03:09 AM

You are incorrect.

The flap position is not dependent on the aircraft's speed.Yes it does!The flaps are used to control teh mass airflow of air through the engine.True.

At low speed and low power the flaps would probably be closed because there isn't much cooling required.Major mistake! The flaps will be all the way open because at low speed there is not enough air to cool the engine at idle.

At WEP at high speed the flaps may need to be open as the engine temperatures, especially the cylinder head temperature, may become too high otherwise.Wrong again! At high speed there is so much air that the engine will not reach the right temperature for correct operation. By closing the flaps, more air is spilled out side the cowling.

From wiki:


Again, you know what they say about Wiki?

#16 GregP

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Posted 08 May 2012 - 03:36 AM

The P-51 radiator does not produce thrust; that is a myth. What it does is reduce the cooling drag. In the case of the P-51, it can eliminate most, but not all the cooling drag. So the P-51 flies as though the raduiator is mostly not there. It isn't thrust, it is drag reduction. There cannot BE a positive thrust from the P-51 radiator.

There might be from the Republic Rainbow exhaust system, but that is NOT a cooling system producing thrust, that is exhaust thrust, which is possible and several aircraft have taken advantage of it.

Radiators will never produce thrust, only more or less drag.

Neo is so wrong below that I don't really know where to start. I seriously wonder if he hasd ever operated an air-cooled piston engine in an aircraft. I think he is Gaston or a close cousin. Maybe he is The Pipe. Hello, The Pipe here. Remember him? He was about to start posting in third person when he mysteriously disappeared. Maybe he is back.

At low speed and low power, such as when you are gliding toward landing on final or coming down base, the cooling flaps are usually mostly closed, and your ramblings won't change that. As you increase power and the temperature rises, the cooling flaps are progressively opened to keep the temperatures in the green. If you open the cooling flaps at low power, you usually shock-cool the engine and it gets expensive due to cracked cylinders. Better stay away from aircraft with air-cooled engines Neo. You'll buy a few before you are done, if you fly them the way you post. Best stick with the engine manufacturer's recommendations in the pilot's operating handbook.

Edited by GregP, 08 May 2012 - 03:48 AM.


#17 Wuzak

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Posted 08 May 2012 - 03:47 AM



Again, you know what they say about Wiki?


Yep, it's a better source than your memory!

#18 Edgar Brooks

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Posted 08 May 2012 - 06:49 AM

Again, you know what they say about Wiki?

What people say about Wiki is immaterial; the flap(s) on the radiators opened as the coolant got hotter (with increased engine revolutions and speed,) and closed as things cooled down when the aircraft slowed. On early aircraft, with a single radiator, the flap was opened by the pilot, as he saw the coolant temperature rise, then closed as he slowed.
On the twin-radiator airframes, the flaps opened automatically by a temperature-controlled microswitch; the Mk.IX's temperature setting was 115C, which was what it was supposed to reach (and no higher) in cruise. During take-off, climb, and combat, the temperature was expected to rise above that, and the flaps opened.

#19 NeoConShooter

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Posted 15 May 2012 - 12:59 AM

You don't stop the airflow through a NACA duct or it creates a drag point, exactly the same as if a jet intake were too large and air werr to be both flowing into and back out of the inlet, as on the Bell YP-59A Airacomet.

The flaps might slow the flow through the NACA duct but they certainly won't stop it entirely without adverse drag penalties.

What do you think, Flo and Drgondog and Wuzak?

Guess we posted at the same time, huh Wuzak? Thoufg we said essentially the wame thing, I like Wuzak's wording better than my own.


It works by forcing air to go outside the cowl instead of through it.

#20 NeoConShooter

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Posted 15 May 2012 - 01:12 AM

The P-51 radiator does not produce thrust; that is a myth. What it does is reduce the cooling drag. In the case of the P-51, it can eliminate most, but not all the cooling drag. So the P-51 flies as though the raduiator is mostly not there. It isn't thrust, it is drag reduction. There cannot BE a positive thrust from the P-51 radiator.
True!
There might be from the Republic Rainbow exhaust system, but that is NOT a cooling system producing thrust, that is exhaust thrust, which is possible and several aircraft have taken advantage of it.
No. The Republic Rainbow developed thrust because the engine was cooled by fan air that was drawn in through a small opening, slowed and heated by the cooling fins where it expanded, was then mixed with the exhaust to provide over 200 pounds of thrust through a small opening.
Radiators will never produce thrust, only more or less drag.
Unless the air it uses is forched through it by a fan.
Neo is so wrong below that I don't really know where to start. I seriously wonder if he hasd ever operated an air-cooled piston engine in an aircraft. I think he is Gaston or a close cousin. Maybe he is The Pipe. Hello, The Pipe here. Remember him? He was about to start posting in third person when he mysteriously disappeared. Maybe he is back.

At low speed and low power, such as when you are gliding toward landing on final or coming down base, the cooling flaps are usually mostly closed, and your ramblings won't change that. As you increase power and the temperature rises, the cooling flaps are progressively opened to keep the temperatures in the green. If you open the cooling flaps at low power, you usually shock-cool the engine and it gets expensive due to cracked cylinders. Better stay away from aircraft with air-cooled engines Neo. You'll buy a few before you are done, if you fly them the way you post. Best stick with the engine manufacturer's recommendations in the pilot's operating handbook.

I do and would. But if you watch films of P-47s from WW-II, the flaps are closed at high speed and open on take off. Same-o, same-o for film of Zeros taking off from the carriers before PH!




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