What's With Annular Radiators?

[sequoiaranger]

We all know that the Junkers Jumo-engined Fw-190 D had a mean-looking nose containing an inline, liquid-cooled engine, but had a "round" radiator in front of the engine instead of the traditional boxy, underslung ones found on the fuselage or wings of seemingly ALL other liquid-cooled-engine aircraft. Same with the Ju-88. Why?

Was there something special about Junkers Jumo engines that lent themselves to annular radiators? Why wouldn't other aircraft/engines follow suit if it were such a good idea? I know of an annular radiator on a Bf-209 V5 (Daimler-Benz engine) but the aircraft, or the radiator scheme, never became operational. Or was the annular radiator thing just a "one-off" concept that worked reasonably well?

Why didn't we see an annular radiator on Stukas, Yak-9's, Mustangs, or even Spitfires?? 

[Annular radiators on Spitfires? Now THERE is a whiff not tried before! BLASPHEMY you say? 
Any takers?  PS--remember to put the exhausts up higher if you do---Jumos and DB's were INVERTED-V engines!]

[pyro-manic]

What about the Avro Shackleton? It had Griffon engines with annular radiators. Perhaps for ease of maintenance? You can remove the whole engine + cooling system as a unit, rather than having to de-plumb the engine from the radiator system before you can change it.

[sequoiaranger]

>It had Griffon engines with annular radiators.<

I'm pretty sure the radiators did NOT go 360 degrees around the engine, but rather a "smile" through about 180 degrees. In other words, merely a modified "chin" radiator. But it was "closer" to an annular radiator than many others.

[pyro-manic]

You may be right.

It seems Hawker tried an annular radiator for the Tempest:

http://www.hawkertempest.se/AnnularRadiator.htm

Also, this forum post has a photo of a DB603 with annular radiator, from a Heinkel 219 nightfighter.

[sequoiaranger]

Thanks. Yes, I was aware of the Tempest experiment. Seems that, except for the Jumo 211/213 engines, the experiments with annular radiators were failures, or at least never bore fruit on operational aircraft. Funny that both the He-111 and Ju-88 used Junkers Jumo 211 engines, yet had different radiator systems. They both seemed to work, but the question still remains why the concept had such limited use worldwide.

[sequoiaranger]

This heavy-bomber (maybe more accurately a VERY heavy dive-bomber!) had the "coupled" DB-606/610 liquid-cooled engines in a large, circular housing, and had annular radiators. The He-177 was indeed an "operational aircraft" but largely unsuccessful, largely as a result of engine overheating and fires (so maybe the annular radiator wasn't such a good thing here!).

[kitnut617]

I think it was more to do with having a common nacelle which either a radial or the inline plus annular radiator could be attached to with minimal hassle.  IIRC, they appeared at about the same time that things had turned against Germany and they were having to streamline production as much as possible.

[jcf]

Do 335 used an annular radiator on the forward DB 603.

Junkers use of annular radiators made their self-contained 'power-egg' concept workable,
it decreased both airframe manufacture and field repair times.

[Gondor]

The whole Annular Radiator was probably partially used as an  attempt to streamline the aircraft, less bulk of a rectangular lump or a radiator hanging under a chine or wing. Though I could be wrong.

Gondor

[Weaver]

I always thought the fundamental idea was to reduce cross-sectional area by putting the radiator in front of the engine instead of next to it, essentially an update on the WWI-style installations seen on aircraft like the Fokker D VII, the Bristol Fighter or the SE5a. the downside is getting a clean air exit from the radiator of course, although I daresay design experience with radial engine cowlings helped there.

[sequoiaranger]

>The whole Annular Radiator was probably partially used as an  attempt to streamline the aircraft, less bulk of a rectangular lump or a radiator hanging under a chine or wing. Though I could be wrong.<

I don't think you are wrong. Sounds like a good idea, IF IT WORKS. Certainly all aircraft manufacturers looked for ways to streamline their aircraft and still cool their engines (the fastest aircraft in the world at the time, the He-100, suffered engine overheating due to its small, "streamlined" radiator).

The question then becomes, WHY did only the Germans use this "innovation" if in fact it really was one? Most good ideas found their way into all aircraft. The Ju-88 was used very early in the war, but no Allied aircraft "copied" and used the annular radiator idea. Methinks it wasn't such a "hot" idea (forgive the pun) after all.

[Maverick]

Altho I'm not a techically qualified person regarding this issue, there's no real reason that the annular radiator technology wasn't a sound concept.  There were quite a few designs during the war that were successful in various technical areas that weren't necessarily copied by the 'other side'. 

The various wing fold designs from carrier owner nations are a case in point.  Each nation, and to some extent individual aircraft companies, had their own designs for the concept of folded wings but there didn't seem to be any reason to suggest that they tried to copy each other's designs.

Reading wartime accounts of the 190D suggested that there were thoughts that it was a 'long nosed' model of the baseline radial 190.  It was only later that it was realised that there were inline exhaust stacks which meant it wasn't a radial at all.  Given the guessing & second guessing that was prevalent during the war, I can't say I'm surprised that some aircraft went down different design paths that were still successfully developed and employed.

Regards,

Mav

[Weaver]

Another factor is that the thrust (pardon the pun) of Allied radiator development seemed to be to compensate for the extra drag by having thrust-producing variable exhaust flaps, rather than avoiding it in the first place.

Although they're not strictly "annular", you could argue that some chin radiators, as on the P-40 for example, were along the same line of thinking as the Dora, since they're tucked up close around the narrow bottom end of  V-engine. Actually, that might be an explanation for the German enthusiasm for the fully annular radiator: with their inverted-V engines, a "chin" intake wrapped around the crankcase would actually be on top, blocking the pilot's view, so the fully circular option was the better one.

[sideshowbob9]

In addition to the Tempest previously mentioned, the annular Sabre was trialled on a Warwick as well.

Also the Curtiss Y1O-26 (a modified O-1E) trialled a "nose" radiator for it's V-1570.

I have several models planned with annular radiators. I like the look.

Edit:

[GTX]

Of course some sick, twisted individual might do a ducted spinner/annular radiator Spiteful...



But of course that would be just silly .

Regards,

Greg