Supercharging!!!!!

[spooky]

And this is just pure 'Thumper' pawn!!!!! 

Falcone_Compressore_500cc

Bill

i saw that bike in veenendaal classic races a few years ago,

[Propellor]

i thought that the spitfire merlin engines had a supercharger on them anyway?

They did.

Aircraft superchargers were about getting low altitude power at high altitude. The slave engine had a supercharger as well as driving one. The big blower fed air into the others as though at 20000 feet at 40000. The result is an aircraft with enough power to go to 50000 feet instead of running out of power at 22000.

Andy

Interesting.

I know next to nothing about aircraft but one might assume that as you get higher, because there is lower air density, you'd need less power to move through it. But I guess maybe there's also less of the stuff holding you up! So maybe you have to move faster (airspeed) just to stay up there? Is that how it works?

The rate at which you overcome gravity (climb rate) will presumably affect how much power you need as well, but if you're prepared to take your time you can do it on less power?

Cheers

[mthee]

This is a 1940's idea



The hump in the bottom of the Lancaster derivative contains a fifth Rolls Royce Merlin. This drives a roots blower of large proportions, whose output is directed into the carburettors of another 4 on the wings. A true plumbers nightmare, fortunately  overtaken by common sense and the jet age.

https://en.m.wikipedia.org/wiki/Avro_684

Maybe try a C90 motor blowing your XBR?

Andy

Met a gent today who used to be in the RAF and showed him this pic and discussion. He said he'd worked on the guns on a Lancaster for BBM day. His last role before leaving was involved with ejector seats - 0-62mph in 0.3 secs, generating 20G's. He said they used an explosive charge to get going! Glad to have him sorting out my son's specialised seating 

[SteveC#222]

This is a 1940's idea



The hump in the bottom of the Lancaster derivative contains a fifth Rolls Royce Merlin. This drives a roots blower of large proportions, whose output is directed into the carburettors of another 4 on the wings. A true plumbers nightmare, fortunately  overtaken by common sense and the jet age.

https://en.m.wikipedia.org/wiki/Avro_684

Maybe try a C90 motor blowing your XBR?

Andy

Met a gent today who used to be in the RAF and showed him this pic and discussion. He said he'd worked on the guns on a Lancaster for BBM day. His last role before leaving was involved with ejector seats - 0-62mph in 0.3 secs, generating 20G's. He said they used an explosive charge to get going! Glad to have him sorting out my son's specialised seating 

The De Havilland Mosquito had 2 supercharged Rolls Royce Merlin engine in a plane made mostly of Balsa and plywood! that's why it was the fastest thing in the skies up until the very end of WWII when the Germans developed the ME262 jet fighter.

Amazing plane the Mosquito - very much an unsung hero as it was the worlds first multi roll plane - bomber, fighter, reconnaissance and U-boat killer and also the worlds first stealth plane (sort of).

[Andy M]

If you take an Enfield Bullet to Everest base camp you'll end up pushing it up the hills.

At sea level you'll be getting the full 18 HP with a main jet designed to give a mixture fractionally richer than the 14:1 stochiometric set up, the chemical formula that results in all the hydrogens and carbons in the petrol reacting with the oxygens in the air to give water and carbon dioxide and monoxide. At a few thousand feet the air is thinner, less O2 in a given volume so you change the jet for a smaller one. The flow /  volume you can get in 498 cc's is fixed, so you get less HP. If you can cram in twice the volume of air to the same amount of petrol and keep tge jetting, you get the power back.

Andy

[Moto63]

Brilliantly explained.....in a way we mere mortals can understand...🛩🛩.thanks Andy

[Propellor]

Mass flow rate?

[Andy M]

Now you are getting beyond what a brake engineer has picked up from "the enemy"!

FI (as used by the dastardly hun) saves changing jets, but can still only drop the petrol to match the air. Having denser air by blower and intercooler gives it more options.

They also have drag as an important factor. A nice big air scoop as they had on the Typhoon and Mustang gives you air compressed by the forward motion, but it is a robbing Peter to pay Paul sort of set up. It alway amazed me at the lengths they eventually went to. The Sea Hornet, the lighter weight single seat Mosquito derivative had two stage (double impellor), two speed (driven by a gearbox at 10000 rpm) superchargers and the radiators burried in the wing.

After that they went Turbo-Compound; add fuel to a turbo charger exhaust flow side to make a sort of jet cum afterburner cum extra power compressor driver. They often caught fire!

The other interesting bit of Merlin technology was the exhausts. Fishtail pipes crossed over the block gave 10 mph extra. If the speed ratios to speed or power, that might be a whole 1 mph on a bike!

Andy

[Propellor]

Very interesting stuff Andy. 

I'm glad you mentioned the turbo compound types as I could have sworn I read about them as a kid in the days when I'd go to the city library once a week. I was beginning to think I'd imagined it.

The point I was making re mass flow is that it is the mass of air that is trapped in the combustion chamber that counts,  which is exactly what you're saying.  No?

 I suppose the number of atoms ultimately?

[JOOLZ]

What about the ultimate Merlin conversion the RR Crecy 2 stroke supercharged sleeve valved engine, designed as a sprint interceptor, they were going to put it in a Spitfire but eventually calculated it would tear the airframe apart, 5000+ hp plus almost 600lbs of thrust just from the exhausts....  https://en.wikipedia.org/wiki/Rolls-Royce_Crecy

[Propellor]

What about the ultimate Merlin conversion the RR Crecy 2 stroke supercharged sleeve valved engine, designed as a sprint interceptor, they were going to put it in a Spitfire but eventually calculated it would tear the airframe apart, 5000+ hp plus almost 600lbs of thrust just from the exhausts....  https://en.wikipedia.org/wiki/Rolls-Royce_Crecy

Hee hee.

What sort of thrust does 5000hp translate to at the prop?

Incidentally my "avatar" name is nothing to do with aircraft. Not directly anyhow.

[CrazyFrog]

Fascinating stuff this. You just don't get this quality of thread on other forums. 

[Andy M]

The point I was making re mass flow is that it is the mass of air that is trapped in the combustion chamber that counts,  which is exactly what you're saying.  No?

 I suppose the number of atoms ultimately?

Yes exactly, thin air has less mass and fewer atoms in a set volume, so less "reactive".

That Crecy 2-smoke (albiet without the smoke oil) is bonkers. 2000 Hp made propeller fighters almost supersonic, something that made the tail planes fall off. They took off on half throttle as otherwise the torque rolled them over (hence contra-rotating on the later and naval ones). Turning hard made G forces that knock you out. The plan must have been something like the ME-163, missile with a man in it, get up there before its too late sort of thing.

The quality of threads on here varies. I bet I can reduce the level of this one with half a dozen words;

Landrover, Weather presenter, camping stove, discuss

 

Andy

[CrazyFrog]

The quality of threads on here varies. I bet I can reduce the level of this one with half a dozen words;

Landrover, Weather presenter, camping stove, discuss

 

Andy

 

[Steve Lake]

and the griffon (latterly used in spitfires) had a 2 stage supercharger .. as used on the shackleton running 2 contrarotating 3 blade props... (also used on the Fairey Gannet but superceded with a turboprop), ... sorry... showin :(g my age