De Havilland Hornet & Turbocharger Idea

[KJ_Lesnick]

Hobbes

How big would it make everything?

To avoid diverting this topic, feel free to send me a PM

[wuzak]

If I remember it correctly, the Merlin didn't take well to turbo-charging. Unfortunately, I don't remember where I read this. I just got home from work and haven't had time to go through all my refs yet.

Others most likely know more.



Chris

I don't think the Merlin was ever tried with turbo, so we can't really know if it "took" to turbocharging.

Rolls-Royce had experimented with turbochargers on the Condor (IIRC) in the late 1920s. They came to the conclusion that the exhaust thrust was more valuable at altitude than the extra power.

WW2 era aero engine turbosuperchargers were also designed to maintain backpressure levels in the exhaust as if they vented directly to the atmosphere, though the reality was slightly more backpressure than normal. The air delivered to the engine was at sea level pressure - so no actual boosting of the engine by the turbo.

[wuzak]

IIRC, the turbocharger is between the engine and the firewall with the ducting from the wing leading edge.

RR had designed the engines for the Hornet with all the ancilliaries behind it, so the cross section would be as small as possible.  The Hornet was designed around the engines.  One nacelle is an inch(!) longer than the other to accomodate the gear to ensure the prop rotates in the opposite direction to the other.

The Merlin 131 (the LH rotation engine) wasn't any longer than the Merlin 130 (RH rotating engine).



The main gear on the prop shaft is the same for both versions. The reduction ratio is slightly different - 0.420:1 for the 130/RH engine and 0.422:1 for the 131/LH engine.

The biggest change between the 130 series and earlier Merlins was the adoption of the downdraft carburettor in place of the updraft carburettor.

[wuzak]

Perhaps something along the lines of the post-war Hispano-Suiza 12B 40 with H.S. 600 turbo-compressor:
http://www.flightglobal.com/pdfarchive/view/1949/1949%20-%201398.html

That is a very interesting project. Slightly more advanced than the Allison V-1710-E27 (-127) turbocompound.



The problem the Allison had was that the turbine could not withstand the exhaust temperatures. Had the project continued the turbine (based on that from a C-series turbo) would have been replaced wih an air cooled version.

The concept also reminds me of the XP-67, though that didn't have compounding. Instead the turbocharger was mounted with its shaft horizontal, and the exhaust and wastegate exhaust were pumped directly out the rear.

http://www.warbirdsresourcegroup.org/URG/images/xp67-7.jpg

[KJ_Lesnick]

Anybody

To help me visualize a modified DH-103 nacelle with a turbo in it could anybody do a really crude drawing of where the turbo and all that junk would fit in a way that would work and be as compact as possible and realistic for the time?

wuzak

Rolls-Royce had experimented with turbochargers on the Condor (IIRC) in the late 1920s. They came to the conclusion that the exhaust thrust was more valuable at altitude than the extra power.

I didn't know the turbos produced any significant exhaust thrust?  Did this segue into jets?

[eatthis]

Anybody

To help me visualize a modified DH-103 nacelle with a turbo in it could anybody do a really crude drawing of where the turbo and all that junk would fit in a way that would work and be as compact as possible and realistic for the time?

wuzak

Rolls-Royce had experimented with turbochargers on the Condor (IIRC) in the late 1920s. They came to the conclusion that the exhaust thrust was more valuable at altitude than the extra power.

I didn't know the turbos produced any significant exhaust thrust?  Did this segue into jets?

from readin that id say the turbo REDUCED exhaust thrust (which tallies with what i know about turbos)

[The Wooksta!]

I got the 'extra inch on a Hornet engine' from a posting by John Adams on Britmodeller.  If there's one person I trust implicitly about anything British and aeronautical, it's him.

[wuzak]

wuzak

Rolls-Royce had experimented with turbochargers on the Condor (IIRC) in the late 1920s. They came to the conclusion that the exhaust thrust was more valuable at altitude than the extra power.

I didn't know the turbos produced any significant exhaust thrust?  Did this segue into jets?

That's not what I said.

Rolls-Royce preferred to have the exhaust thrust which was available when not using a turbo. They spent some time on improving ejector exhausts for that reason.

[KJ_Lesnick]

wuzak

That's not what I said.

Rolls-Royce preferred to have the exhaust thrust which was available when not using a turbo. They spent some time on improving ejector exhausts for that reason.

I'm sorry, I totally misunderstood what you said.  Hence the confusion.

[Hobbes]

That's interesting, because the thrust from the Merlin's exhausts wasn't all that much.  The Merlin is listed as up to 150 lbs of thrust which gave it 241 net hp from the exhaust. (from "The Rolls-Royce Crecy" by Nahum, Foster-Pegg and Birch)

[wagnersm]

Could it also be metallurgy? 

Turbos require "advanced high-temperature metals in the turbine" to quote Wikipedia.   Something that the article mentions limited use.

Could gear driven supercharging also have been simpler to implement? 

Steve

[wuzak]

That's interesting, because the thrust from the Merlin's exhausts wasn't all that much.  The Merlin is listed as up to 150 lbs of thrust which gave it 241 net hp from the exhaust. (from "The Rolls-Royce Crecy" by Nahum, Foster-Pegg and Birch)

I know, it doesn't sound like much.

But consider the Mosquito B.IV.

When they changed from the "saxophone" exhaust to ejector stubs the gain was 10-15mph.

http://www.wwiiaircraftperformance.org/mosquito/dk290-b.pdf

Also, the equivalent power is dependent on the plane's speed. That is, ejector exhausts are more effective for faster moving aircraft than for slower ones. The Mosquito gained more than the Lancaster.

Turbo installations are much heavier than the supercharged ones. They also add drag through extra cooling requirements, as well as the drag from the need to create lift to carry the extra weight.

And consider that as the altitude increases the efficiency of the prop decreases.

[Hobbes]

Could it also be metallurgy? 

Turbos require "advanced high-temperature metals in the turbine" to quote Wikipedia.   Something that the article mentions limited use.

Could gear driven supercharging also have been simpler to implement? 

Yes. I think this was mentioned earlier in the thread, but superchargers generally run at much lower rpm so the forces acting on the blades are much smaller. Also superchargers don't need an impeller in the exhaust.

[KJ_Lesnick]

While this is an old post, it is based on an idea I'm thinking of again...

That being said, I'm wondering about what aircraft had compact layouts (turbocharging)?

I can readily think of the P-38, Hawker Typhoon, F7F Tigercat

[kitnut617]

While this is an old post, it is based on an idea I'm thinking of again...

That being said, I'm wondering about what aircraft had compact layouts (turbocharging)?

I can readily think of the P-38, Hawker Typhoon, F7F Tigercat

Erm! Hawker Typhoon --    I don't think so ---