Drag of annular/drum radiator

[Reluctant Poster]

Just look at Reno Unlimited`s, thats been won by annular air cooled (effectively no different to a water cooled annular) and belly scoop systems (p51),
and planes like Sea Fury`s which have both leading edge and annular cooling systems at once.

Sea Furies only win when the P-51s are not entered. Streg and Voodoo are much faster although Rare Bear was just as fast. That being said I wouldn't use Reno as an example. The aircraft are far, far removed from practicality.

 

[Reluctant Poster]

Rolls Royce didn't think their powerplant installation was any different from a leading edge radiator in terms of drag. From "The Merlin in Perspective" by Alec Harvey-Bailey

"The same Mosquito was subsequently fitted with Rolls-Royce powerplants with chin radiators. Tests before and after conversion using the same Merlin 23 engines and propellers showed no measurable difference in performance at the same all up weight. On calibration test flights the speed was 378 mph true at 18,000 ft at a weight of 18,400 lb."

 

[spicmart]

Here's a fact in the report that should not be overlooked:

"With an annular radiator the power plant weight is 180 lb. heavier than with the underslung type,..."

That is a big difference and would have an effect on performance, negating some of the drag benefits and reducing rate of climb. It is also moved the c of g forward 2 1/4 in which might require counter balancing (think P-39 nose armor.....or maybe not). Note that the chin radiator is already well forward on the Tempest, for the Hornet moving the radiator from the leading edge to the front of the engine would result in a much greater c of g shift.

Here it is said that the Tempest with annular radiator at least appears to be better at the climb than its counterpart with underslung radiator, but concrete climb times haven't been recorded.

 

[Reluctant Poster]

Here it is said that the Tempest with annular radiator at least appears to be better at the climb than its counterpart with underslung radiator, but concrete climb times haven't been recorded.

Standing tall amongst pygmies. The underslung radiator was not an exemplar of good aerodynamic design. It was a holdover from the Typhoon adopted as an expedient to get the Tempest into production ASAP. The Mark I Tempest was much faster and climbed quicker according to this website:

Mark I

hawkertempest.se

I don't know if the numbers quoted represent a true apples to apples comparison.
Also note from the pictures that the leading edge radiators stand proud of the wing and are not buried as the Hornets are. The report you posted discusses the problems with the Tempest I radiator installation and notes a much lower drag leading edge installation is possible

 

[Deleted member 68059]

Rolls Royce didn't think their powerplant installation was any different from a leading edge radiator in terms of drag. From "The Merlin in Perspective" by Alec Harvey-Bailey

"The same Mosquito was subsequently fitted with Rolls-Royce powerplants with chin radiators. Tests before and after conversion using the same Merlin 23 engines and propellers showed no measurable difference in performance at the same all up weight. On calibration test flights the speed was 378 mph true at 18,000 ft at a weight of 18,400 lb."

Whoops just remmbered I had this stuff, will have a read through and report back.

 

[Deleted member 68059]

Curses, my photo of the comparison graph is so blurry I cant see a damn thing.

However, it DID say that the main problem with the leading-edge radiator installation for this prototype Napier fighter was that the required radiator size combined
with the very thin wing desired, meant that putting in the leading edge radiator meant compromising the profile, as a "Bump" would be needed. So it may well be that
as with most proposals, some things work well in some planes, and less well in others.

 

[pbehn]

Something a bit confusing for me here, wiki says that an annular radiator was tried on the Typhoon, so the same thing on a Tempest is covering old ground "
One Typhoon, R8694, was used by Napier for trials with the more powerful Sabre IV, cooled using an annular radiator and driving a four-bladed propeller. The new engine and radiator arrangement required substantial modifications to the forward fuselage and engine bearer structures. Although a maximum speed of 452 mph (727 km/h) was claimed by Napier, it was decided that the modifications would not be worthwhile, mainly because of the promising development of the Tempest, and because the disruption to Typhoon production would not be sufficiently outweighed by any benefit achieved.[79]​[80]"​

 

[Reluctant Poster]

Something a bit confusing for me here, wiki says that an annular radiator was tried on the Typhoon, so the same thing on a Tempest is covering old ground "
One Typhoon, R8694, was used by Napier for trials with the more powerful Sabre IV, cooled using an annular radiator and driving a four-bladed propeller. The new engine and radiator arrangement required substantial modifications to the forward fuselage and engine bearer structures. Although a maximum speed of 452 mph (727 km/h) was claimed by Napier, it was decided that the modifications would not be worthwhile, mainly because of the promising development of the Tempest, and because the disruption to Typhoon production would not be sufficiently outweighed by any benefit achieved.[79]​[80]"​

If it truly did 452, which I doubt, it would be faster than the Tempest. That Sabre IV must have pumped out 4000 hp to move the brick like Typhoon that quickly The disruption to production had to be less than for the Tempest which also had a new forward fuselage plus a new wing. It would seem to be a no brainer to modify the engine bearers rather than build a new wing.
Also note that 40 mph speed increase is an incredible improvement, it would put the Typhoon in a whole new category.

 

[pbehn]

If it truly did 452 which I doubt, it would be faster than the Tempest. That Sabre IV must have pumped out 4000 hp to get the brick like Typhoon that quick. The disruption to production had to be less than the new wing and lover fuselage for the Tempest.w

I think Napier were the UKs version of Bell, a lot of fanciful BHP and speed figures. The new wing and fuselage were for the Tempest which was really a better Typhoon, as I understand it the Typhoon for ground attack was good enough so they just wanted as many as possible. They werent made in the same factory.

 

[ThomasP]

In my notes I have the Typhoon R8694 fitted with a Sabre VI engine and the annular radiator with cooling fan.

I have never been able to find any authoritative data on the power curve for this setup.

re annular radiator tests on the Tempest

Apparently there were several variants of annular radiator tested.

ww2aircraft thread at "Hawker Tempest V production batches"

 

[Reluctant Poster]

In my notes I have the Typhoon R8694 fitted with a Sabre VI engine and the annular radiator with cooling fan.

I have never been able to find any authoritative data on the power curve for this setup.
View attachment 674235


re annular radiator tests on the Tempest

Apparently there were several variants of annular radiator tested.
View attachment 674237

ww2aircraft thread at "Hawker Tempest V production batches"

More pictures of the Typhoon annular radiator installation previously posted in the forum

Hawker Typhoon wet day

Never heard of it, many thanks

ww2aircraft.net

An brief history of the Sabre is here:

Napier Sabre

www.hawkertempest.se

"Napier and Hawker experimented with annular radiators using various Sabre IIB engines installed on a Typhoon IB (R8694) and a Tempest V (EJ518)"
This indicates that R8694 was fitted with Sabre IIBs. I find it intriguing that according to the Wiki reference the annular Typhoon was faster than the annular Tempest.

 

[Reluctant Poster]

Curses, my photo of the comparison graph is so blurry I cant see a damn thing.

However, it DID say that the main problem with the leading-edge radiator installation for this prototype Napier fighter was that the required radiator size combined
with the very thin wing desired, meant that putting in the leading edge radiator meant compromising the profile, as a "Bump" would be needed. So it may well be that
as with most proposals, some things work well in some planes, and less well in others.

View attachment 674198

The Fairy Firefly went from a chin radiator to a rather protruding leading edge system. I wonder if there any performance comparison between the two installations was ever done.

 

[Shortround6]

Exactly what is a leading edge system?

Inlets, radiator matrix and outlet/s all have to be forward of the forward wing spar?

Inlets and radiator matrix have to be forward of the wing spar, with outlet/s behind the forward spar?

Inlets have to be forward of the wing spar, with and radiator matrix outlet/s behind the forward spar?

If you are trying to cram all three in front of the spar and exit the cooling air above or below the the spar it seems like the turn may be fairly tight?

Obviously you have less frontal area than a chin radiator but the speed changes in the airflow may not be as good as as a good ventral radiator.
A lot depends on the airflow through the ducts in addition to the size of the frontal area?

 

[Reluctant Poster]

Exactly what is a leading edge system?

Inlets, radiator matrix and outlet/s all have to be forward of the forward wing spar?

Inlets and radiator matrix have to be forward of the wing spar, with outlet/s behind the forward spar?

Inlets have to be forward of the wing spar, with and radiator matrix outlet/s behind the forward spar?

If you are trying to cram all three in front of the spar and exit the cooling air above or below the the spar it seems like the turn may be fairly tight?

Obviously you have less frontal area than a chin radiator but the speed changes in the airflow may not be as good as as a good ventral radiator.
A lot depends on the airflow through the ducts in addition to the size of the frontal area?

According to the report posted by spicmart the Tempest I had to locate everything forward of the front spar which was less than ideal. The Firefly installation is well forward of the front spar but appears to have much more space.

 

[pbehn]

Exactly what is a leading edge system?

Inlets, radiator matrix and outlet/s all have to be forward of the forward wing spar?

Inlets and radiator matrix have to be forward of the wing spar, with outlet/s behind the forward spar?

Inlets have to be forward of the wing spar, with and radiator matrix outlet/s behind the forward spar?

If you are trying to cram all three in front of the spar and exit the cooling air above or below the the spar it seems like the turn may be fairly tight?

Obviously you have less frontal area than a chin radiator but the speed changes in the airflow may not be as good as as a good ventral radiator.
A lot depends on the airflow through the ducts in addition to the size of the frontal area?

First of all what is it cooling? The Mosquito Hornet had everything in the wing leading edge, while the leading edge set up quoted by Napier was for a P&W R2800 so that can only be for oil and any intercooler ancilaries?

 

[spicmart]

The sliding ring cowl configuration does not add drag unlike the ones with hinged, articulated gills, including the leading edge system with its single flap outlet.

 

[Reluctant Poster]

First of all what is it cooling? The Mosquito Hornet had everything in the wing leading edge, while the leading edge set up quoted by Napier was for a P&W R2800 so that can only be for oil and any intercooler ancilaries?

The leading edge set up was for a Tempest I.

 

[pbehn]

The leading edge set up was for a Tempest I.
View attachment 674405

In the article posted by Spicmart post #26 the engine is a P&W R2800

 

[Reluctant Poster]

In the article posted by Spicmart post #26 the engine is a P&W R2800

No its not. The table in the flight article is the same table I excerpted rom the original report. Nowhere in the Flight article does it state that the drag data is for the PW 2800. In fact the table does include the drag data for the Centaurus Tempest. The R-2800 is only mentioned towards the end of the article in a weight comparison.

 

[elbmc1969]

The sliding ring cowl configuration does not add drag unlike the ones with hinged, articulated gills, including the leading edge system with its single flap outlet.

Is that based on test results?