Radiator designs

[wuzak]

What was the power used for those speeds?

Sabre II was 2200-2400hp max.
Sabre IV was 2400hp max.
Sabre VII was 3000hp max.

I don't know at what altitudes those powers were. I am quite sure that is not the power at the top speed altitude.

I think, but am not certain, that the IV was tuned for higher altitude than the II. Not sure with the VII.

 

[tomo pauk]

Sabre IIB was making 2045 HP at 13700 ft, Sabre VII was at 2760 HP at 12450 ft. All second gear, maximum/combat power, 5 min duration. With ram that would be around 19000 ft, at least the Tempest V was fastest at that altitude. So the Tempest with Sabre VII will be having some 35% more power at about the same altitude, raising the question how much actually the annular radiator helped to achieve the 40 mph speed advantage.

The Sabre IV was to turn 4000 rpm, the power should be indeed better than for Sabre IIB, but at all altitudes. Seem like the power was about the same as Sabre VII?

 

[Aozora]

Sabre IIB was making 2045 HP at 13700 ft, Sabre VII was at 2760 HP at 12450 ft. All second gear, maximum/combat power, 5 min duration. With ram that would be around 19000 ft, at least the Tempest V was fastest at that altitude. So the Tempest with Sabre VII will be having some 35% more power at about the same altitude, raising the question how much actually the annular radiator helped to achieve the 40 mph speed advantage.

The Sabre IV was to turn 4000 rpm, the power should be indeed better than for Sabre IIB, but at all altitudes. Seem like the power was about the same as Sabre VII?

I don't think that claims were being made about the annular radiator improving the Tempest's top speed by 40 mph - Napier were more interested in testing the installation, with an added bonus of testing the newest Sabre variant.

Sabre VII specifications:

From:
View attachment Napier Sabre VII Flight 1945 a.pdf

 

[tomo pauk]

Thanks for the docu. The SR6's question was, however:

"Probably the best results it would be possible to find would be for the Tempest since it seems to have used at least 3 different radiators on the same airframe using essentially the same engine, reducing other factors to a minimum."

Unfortunatelly, the Sabre IIB was of significantly less power than the IV and VII, hence we are ill able to deduce just how much a different radiator played the role in speed gain.

 

[Aozora]

Thanks for the docu. The SR6's question was, however:

"Probably the best results it would be possible to find would be for the Tempest since it seems to have used at least 3 different radiators on the same airframe using essentially the same engine, reducing other factors to a minimum."

Unfortunatelly, the Sabre IIB was of significantly less power than the IV and VII, hence we are ill able to deduce just how much a different radiator played the role in speed gain.

Agreed, it would be difficult to make any real comparison. The "next best" variant was the Tempest VI with a 2,340 hp Sabre V and carburettor air intakes in the wing-root leading edges; top speed 438 mph @17,800 ft vs Tempest V 426 mph @ 18,500 ft @ 2,180 hp (Thomas The Typhoon Tempest Story), so an extra 160 hp = roughly 12 mph?

Another factor are the redesigned exhaust stacks on the annular installation - there's no mention about whether they have any effect.

 

[Shortround6]

I would venture to say that you could use the cube law to "estimate" power required for the faster versions compared to the base line Tempest and then see how far off the actual planes were. Some of the discrepancy could be attributed to the radiator installation.

A whole lot better than trying to compare planes with different wings, airfoils, sized fuselages, engines, and tails and trying to figure out if the radiators were doing anything for drag.

 

[Aozora]

I would venture to say that you could use the cube law to "estimate" power required for the faster versions compared to the base line Tempest and then see how far off the actual planes were. Some of the discrepancy could be attributed to the radiator installation.

A whole lot better than trying to compare planes with different wings, airfoils, sized fuselages, engines, and tails and trying to figure out if the radiators were doing anything for drag.

Aw heck, be fair - start talking about "cube law" and all my brain sees is:

 

[OldSkeptic]

Were the leading edge radiators not getting just as much 'troubled air' than the annular ones closer to the spinners' center ?

(Further from the propeller axis, would they have gotten a 'cleaner air' ? or not ? Thanks the more scare presence of the prop's paddle through space (in a given time frame) in the outer region, as the (similar) relative aera section covered in a given time was done so more through radial speed... and little matter presence than near the axis, where one found lower actual speed but more 'obstructive' or 'effective' matter presence of the paddle...)

(the relative aeras travelled by the padde were the same but by the axis the overall scale of the scheme was smaller...)

Yet that same paddle in the outer ring was much more air blasting than at the near-axis region.

Some questions being easier to ask than to answer.

Rationnaly, could anyone explain why a leading edge radiator situated behind the outter ring of the propeller, blasting at its full might, might be getting a 'cleaner air' than the annular radiotor situated by the axis region of the same propeller, producing much weaker 'air trouble' but, hm, 'taking more place' ??????

The advantage is depth. You can reduce effects of the turbulent/accelerated air from the propeller if you have a deep enough radiator intake (and it is shaped properly), slowing and smoothing the airflow.
At the wing root, you have a lot of room. Naturally structural issues come into play in doing that. But you could use most of the wing area, giving that very deep intake required.

You just don't have the room in an annular one, so the intake airflow will be suboptimal and you have the issue of exhausting the hot air to give thrust. A chin one can, naturally, be made larger, but it is debatable whether you can make it long enough.

 

[tomo pauk]

I would venture to say that you could use the cube law to "estimate" power required for the faster versions compared to the base line Tempest and then see how far off the actual planes were. Some of the discrepancy could be attributed to the radiator installation.

A whole lot better than trying to compare planes with different wings, airfoils, sized fuselages, engines, and tails and trying to figure out if the radiators were doing anything for drag.

Right all the way.
Let's see how I'm good at that. I'll take a cube root from 2045 and from 2670 HP. That makes 12.693 and 13.873. The ratio between these two values is 1:1,092964316. Now I'll multiply the ratio with 435, arriving at 475 mph, or 10 mph more than Sabre VII-powered Tempest achieved.
What I'm missing here?

 

[Aozora]

Right all the way.
Let's see how I'm good at that. I'll take a cube root from 2045 and from 2670 HP. That makes 12.693 and 13.873. The ratio between these two values is 1:1,092964316. Now I'll multiply the ratio with 435, arriving at 475 mph, or 10 mph more than Sabre VII-powered Tempest achieved.
What I'm missing here?

I have a top speed for the Sabre IIB Tempest V of 426 mph x 1.092964316 = 465 mph...

 

[tomo pauk]

This ADC gives 435 mph: here.

 

[swampyankee]

For minimum overall drag, a radiator needs to have the airflow slowed before it goes through the radiator core, then accelerated up to whatever velocity is present at the radiator exit. While short efficient diffusers are possible -- they were and probably are an active area of research for use with high-bypass turbofans (shorter => lighter less skin friction rag) -- they are not that easy, and may have severe losses off-design.

Of course, annular radiators do benefit from the aerodynamic work done to improve the cooling drag of radial engines, as a radiator causes the same sort of pressure drop as a radial engine's finning.

 

[Maxrobot1]

How efficient was the radiator system used by the Bell P39 and P-63?
That design seems to be unique.

 

[Aozora]

This ADC gives 435 mph: here.

This one says 427 mph http://www.wwiiaircraftperformance.org/tempest/tempest-v-ads-sabre-IIa.jpg with the Sabre IIA with 2,180 hp; however this test with the IIA shows 435 mph http://www.wwiiaircraftperformance.org/tempest/tempest-hawkerchart.jpg so, yeah 430+ mph

Anyway, it would seem that the annular radiator didn't seem to instill much of a performance advantage, plus it would be interesting to see the data.

 

[GregP]

One can argue about a lot of qualities of the Concorde, but being fuel efficient probably isn't one of it's strong points.

At best economy supersonic cruise the Condorde burns 46.85 pounds per mile.

A Boeing 747 burns 30 pounds per mile at 550 mph.

So the Concorde burns more than 50+% more fuel per mile than a 747 to go fast. Not a bad tradeoff, but also not more efficient than a typical modern jetliner that isn't supersonic. If I were on a business trip, making the crossing in 3.5 hours versus 8 hours for non-supersonic flight might well be worth the extra cost, depending on the business.

I think they were silly to retire it after a crash not attributable to a Concorde design flaw. Perhaps Aerospatiale's and BAE's decision to stop supporting it's maintenance was the real reason after all. If they made some new Concordes today, I'd say they would have people waiting in line for the chance to save that much time and avoid jet-lag, but maybe not. It might depend on the cost of a ticket.

I heard a Concorde Captain speak once and he said that if a Concorde left London for JFK runway 31L, the alternate could be pretty much anywhere on the eastern seaboard of North America. But, once he was halfway across or more, the alternate was runway 31R.

 

[tomo pauk]

How efficient was the radiator system used by the Bell P39 and P-63?
That design seems to be unique.

The 'Prestone' cooler seem to be designed after Merredit's effect 'rules', the oil cooler less so. The P-39Q, without wing guns, was been able to beat 400 mph mark at ~10000 ft, using ~1420 HP there. The P-51A was some 10-15 mph faster on same HP and altitude. The best P-40 (early P-40N, lighter and 'cleaner' than most of others) was clocked at 378 mph under similar conditions; the direct comparison must take into account that P-40 did not featured fully covered undercarriage, and the wing area was some 10% less for P-39 vs. P-40 and P-51. P-39 was also lighter than P-51, but not than early P-40N.
The Soviet Yak-3 was about as fast as such a P-39Q, on some 100 HP less, the Yak being far smaller and lighter. Not sure about the Bf-109F, the G-1 was capable for 360-370 mph at 10000 ft and with 1400 PS. The Spitfire V was good for 360 mph at 11000 ft, ~1450 HP used (standard supercharger).

The P-63 seem also decent, about 400 mph at ~25000 ft on 1125 HP. The Cd0 for the P-39 was staed at 0.0217, the P-63 at 0.203. P-51 was far better at 0.0176, the single-stage Spitfires were at 0.0213-0.218, the Bf-109F and early G's seem to be at 0.22-0.23 (corrections welcomed), the 109Es and late Gs were worse. Date for US fighters is from 'America's hundred thousands', the British data is from AVIA table.
The P-40 was at 0.242, yet it was significantly faster than Hurricane with Cd0 of around 0.25, and in the ballpark with Spitfire, Bf-109 or most of Yaks (not -3) when on similar weight, same horsepower and altitude. Go figure.

 

[nuuumannn]

Perhaps Aerospatiale's and BAE's decision to stop supporting it's maintenance was the real reason after all.

It was cost. Airbus has the rights to the design and that firm decided that it would no longer support the aircraft owing to the expense. Both Air France and BA agreed it was too expensive, although BA held out for a bit longer than AF, retiring theirs in October 2003. There were enthusiasts that hoped there would still be at least one flying for the 100th anniversary of the Wright's first powered flight in December that year, but BA and Airbus stuck to their guns, sadly and with no sense of nostalgia or history.

 

[BarnOwlLover]

Sorry to revive this thread, but one of the weirdest designs I may've seen (other than the Curtiss XP-37) was what may've been used on (if it was actually built, that is) the Bellanca 17-110 and 20-115. Only pics (or illustrations, rather) I found were in this topic on page 2 of this thread at Secret Projects:

US Piston Engined Fighter Projects

From William Douglas Clark.

www.secretprojects.co.uk

They don't show a lot of details (and there was no ventral illustrations), but they do show what appears to be a ducted spinner, that's also rather small compared to what early FW190s and experimental Hawker Tempests used.

 

[pbehn]

As far as I am aware, the only quick engine change module (QEC) developed in the UK was for the Merlin XX as used on the Beafighter and Lancaster.

I dont think the idea was a QEC module, but to have the possibility to swap power unit supplier if an engine factory was bombed out of use. So the Lanc MK II had Hercules engines. The Halifax used both and a few Beaufighters had Merlins.