Drag of annular/drum radiator

[spicmart]

How do drag, efficiency and thrust (Meredith effect?) of annular/drum radiators
,that were preferred by the Germans late in the war, compare to
other radiator designs of both friend and foe?

 

[drgondog]

No data that I am aware of to derive calculated values, nor wind tunnel test data. Absent these data speculation and arm waving are about all that is left.

 

[tomo pauk]

You might want to take a look here:

tempest | 1946 | 1441 | Flight Archive

 

[jim]

That is a very interesting question that i have asked in several forums without clear response
I also wonder if Bf 109K would benefit, drag wise, from an annular radiator
What i do know is that every late war german aircraft had such radiators . Also while Me 410A had underwing radiators , future variants would replace them with annular radiators. Of course that does not mean nessecary lower drag. Main German motivation in mid/late war was not performance but easy production, easy repairs and general simplification , very often with significant performance penalty

 

[Shortround6]

The annular radiator certainly makes a power egg easier to design. I doubt that you can really get the Meredith effect to work to the full extent using an annular radiator. Not enough room for the defuser in front of the radiator elements. Not to say that some good annular radiators were not built.

 

[tomo pauk]

That is a very interesting question that i have asked in several forums without clear response
I also wonder if Bf 109K would benefit, drag wise, from an annular radiator
What i do know is that every late war german aircraft had such radiators . Also while Me 410A had underwing radiators , future variants would replace them with annular radiators. Of course that does not mean nessecary lower drag. Main German motivation in mid/late war was not performance but easy production, easy repairs and general simplification , very often with significant performance penalty

Reading the pdf from Flight archive, the drag was reduced by 8.8% vs. standard Tempest V, the speed going up 11-14 mph.
We can only wonder how much faster would be the 'plain' Bf-109 and Spitfire with annular radiators, wheel well covers and fully retractable tail wheel (though some versions were incorporating the last two items). For the Spitfire, the annular radiator system perhaps might not be such a good thing, going with under-prop layout seem like a more plausible idea.

The Tempest I was another speedy bird, faster than Tempest V due to it's leading edge radiators.

 

[spicmart]

Thanks Tomo for the link. I am going to read it later.

I think to remember an article somewhere that stated the Fw 190D as surprisingly aerodynamic, much more so than its radial engined sibling and also more than the Spitfire with its large underwing radiators.

Apparently leading edge radiators also seemed to be a good (better?) solution.

Tomo, why do you mean that an annular radiator does not suit the Spitfire?
Maybe because of the ground clearance of the propeller?

Does anybody has the speed difference between the leading edge radiator equipped Tempests and the other versions so that one can compare?

 

[tomo pauk]

Tempest I was managing 466mph at 24500 ft, and, after 'tweaking the airframe finish" (presumably including sealing the gaps, etc) and mounting the different tailplane, it was capable to do 472 mph. The Tempest I did not have the cannons, that was giving maybe 10 mph? The Tempest V (ie. the 'regular' type, with beard radiator) was making 432 mph at 18400 ft. The altitude gap (6000 ft) kinda skews the comparison.

The Spitfire have had, in difference against inverted V engines, radials, or Napier Sabre, raised thrust line. If one fits annular radiator 'around' the prop shaft, it would mess the pilot's view, since the upper edge of the radiator cowling would be placed notably above the engine cowling. It would certainly mess up the air flow, while adding to the fuselage width. Not much an issue with airframes tailored to wider engines (Fw-190, Typhoon/Tempest), Spitfire was of thin fuselage.

The Fw-190D introduction of liquid cooled engine enabled the 'new' plane's front part to be far more streamlined, no surprises there. The annular radiator enabled the transformation to be as seamless as possible.

 

[spicmart]

Just read the section from the link Tomo gave about the trials with the different radiators, so I have some questions:
Did the german power eggs have sliding gills as they seem to offer less drag than hinged gills?
Not sure if I get it right (english is not my native language) but is it that the chart gives the annular/drum radiator a lot less drag compared to the other cooling designs?

A successful exchange of a inline engine with an annular one on a fighter was the Ki-100.
The Ki-61's fuslelage was designed to accommodate an inline engine afaik.

 

[riacrato]

No, the typical German annular radiators did not have sliding gills. For them, there will be more increase in drag as the radiator opens when compared to this design.

Ki-100 was a radial engined fighter... doesn't count

 

[tomo pauk]

Just read the section from the link Tomo gave about the trials with the different radiators, so I have some questions:
Did the german power eggs have sliding gills as they seem to offer less drag than hinged gills?
Not sure if I get it right (english is not my native language) but is it that the chart gives the annular/drum radiator a lot less drag compared to the other cooling designs?

Riarcato answered the 1st question. The cooling drag, with energy recovery (=hot radiator?) is claimed to be 13% of Tempest V total drag, and only 4.5% with annular one. The table does show that it should make less drag than other radiator set-ups in use.
Maybe someone (Bill?) can chip in with data about P-51 cooling drag?

A successful exchange of a inline engine with an annular one on a fighter was the Ki-100.
The Ki-61's fuslelage was designed to accommodate an inline engine afaik.

The Ki-61 airframe was adopted for radial engine, resulting in Ki-100.

 

[spicmart]

Riarcato answered the 1st question. The cooling drag, with energy recovery (=hot radiator?) is claimed to be 13% of Tempest V total drag, and only 4.5% with annular one. The table does show that it should make less drag than other radiator set-ups in use.

That's what I wanted to know in the first place: that the annular installation was more aerodynamic than the other lay-outs, something that one would not assume at first view (leading edge).
I guess that the ventral radiator of the P-51 was the most effective as it also provided considerably more thrust than others.

The Ki-61 airframe was adopted for radial engine, resulting in Ki-100.

I guess that's what I meant.
I just wanted to say that the Ki-61 was tailored to take an inline engine as propulsion so it had a fuselage as thin as the Spitfire's
yet it could be modified to take a radial engine and thus become the Ki-100.
Could be done with a the Spit airframe also.

 

[GregP]

Here's a Messerschmitt 109 with a radial. It was supposed to have flown quite well.

View attachment 228478

 

[tomo pauk]

Both Ki 100 and La-5 were giving away some streamlining in order to receive engines of more power, Soviets have also installed the ASh-82 on the modified Yak-3.
In Spitfire's case, there is no gain in engine power.

Anyway, I've cobbled this one some time ago, P-40 with annular radiator. In order to do the same to the Spitfire, I'll need Readie's permission

 

[Aozora]

Here's a Messerschmitt 109 with a radial. It was supposed to have flown quite well.

View attachment 228478

Reggiane Re 1009...

Found this somewhere:

 

[davebender]

Also makes the aircraft more damage resistant. Engine block protects radiator from rear shots and coolant lines are very short. Hits in wing or fuselage (except engine compartment) will not cause a coolant leak.

 

[bobbysocks]

Here's a Messerschmitt 109 with a radial.....

View attachment 228478

and a tear drop canopy...the eppenage and wings look 109 but the fuse looks completely redone..

 

[GregP]

Well I suppose it would HAVE to be largely redone to mount a radial anyway, but they DID make one with the standard Me 109 canopy enclosure.

 

[bada]

Here's a Messerschmitt 109 with a radial. It was supposed to have flown quite well.

View attachment 228478

for further details about this monstruosity see
Me-109X

 

[razor1uk]

Also with the annular rad' cooled power egg, less coolant pipework and hence coolant; lowering the 'wet' installed 'ready to use' weight further than those installations that didn't have nose mounted cooling.

That Daimler/Jumo-ised Warharwk looks more like a Dewotine project than a Curtis now Tomo...