De Havilland Hornet & Turbocharger Idea

[KJ_Lesnick]

Could the DH Hornet accomodate a turbocharger in the engine-nacelle it had?  There didn't seem to be much room for the gears, and the engines.  I doubt a turbo could fit...

[PR19_Kit]

Why would a Hornet need a turbo?

It already had a socking great 2 stage supercharger anyway, and you're right about the lack of space too. The Hornet's R-R Merlin 130/131s were specially built to ensure their cross sesction was the minimum possible so they could be very closely cowled specifically for the Hornet.

[pyro-manic]

It's not as if the Hornet was lacking in power or performance, so what possible reason would there be for trying to fit a turbo?

[KJ_Lesnick]

It was a whiffie design I had for a long range US fighter that happened to be similar to the DH hornet.

[Hobbes]

Similar is certainly possible. The nacelle design changes a bit because you need more intake and exhaust tubing, but turbochargers aren't that big.

[The Wooksta!]

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.

[dogsbody]

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

[Hobbes]

From Wikipedia:

Also considered (for the Merlin 60 with 2-stge supercharger) was an exhaust-driven turbocharger but, although a lower fuel consumption was an advantage the added weight and the need to add extra ducting for the exhaust flow and waste-gates, meant that this option was rejected in favour of the two-stage supercharger.

From http://www.thunderboats.org/history/history0324.html

One of the significant differences between the Allison V-1710 and the Rolls-Royce Merlin was the Allison relied upon a GE turbocharger to maintain high power at altitude, while the Merlin used two speed (and eventually two stage) supercharging. GE was unable to produce the turbochargers in sufficient quantity to equip both bombers and fighters, so aside from the P-38 Lighting which was equipped with turbochargers, most Allison-equipped planes were limited to relatively low altitude operation -- under 20,000 ft.

Apparently GE was unable to sufficiently mitigate the power loss at high altitudes.

[rickshaw]

Sorry if I'm being obtuse but what is the difference between "super-charging" and "turbo-charging"?   And what is therefore a "turbo-super-charger"?

[perttime]

The term supercharger is often (usually?) used for "mechanical" chargers, where the engine mechanically runs a compressor that feeds the carb. In a turbocharger, you run the exhaust gases into a turbine that runs the compressor.

If the word "turbo" is present, it means turbocharging.

[Aircav]

This may help a little. 
http://en.wikipedia.org/wiki/Supercharger

[PR19_Kit]

To make life even more complicated, some engines, the Napier Nomad II in particular, had a turbo-charger that not only compressed the inlet air but was also connected mechanically to the output drive shaft via an infinitely variable ratio gearbox.  

Best of both worlds? We'll never know as it was only ever flown on the prototype Shackleton.

And it was a DIESEL!

[famvburg]

   IIRC, or understand it may be better, that's basically what the R-3350 Turbo Compound engines did.

[PR19_Kit]

Moved in from Spinners' thread.

The Hornet was a very compact aeroplane, even its engines were specially designed by R-R to have the smallest possible frontal area, but once the exhaust gases were outside the airframe they were gone, ejected clear of the cowlings and off into the wild blue yonder. If they'd had a turbo to wriggle through before escaping the turbo itself would have got very hot and that heat wouldn't be able to escape, it would have been right there in the wooden airframe.

The Vampire had a much bulkier fuselage and the hot engine and exhaust went down the middle with cooling air around it. Looking in the back of a Vampire's exhaust you can see the cooling duct round the outside of the jetpipe. Plus the Vampire didn't have so much emphasis on small frontal area.

[jcf]

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

The Power Recovery Turbines of the R-3350 Turbo-Compound were indeed mechanically connected
to the propeller drive. The Russians also had some large engines with PRTs.
http://www.enginehistory.org/Wright/Kuhns/CurtissWrightTC18/TurboCompounds.shtml