Hyper Charging

[Stephen H]

hey all

in the book "model jet engines" by Thomas Kamps there is a part in it about hyper charging, using a turbo as a turbine and car turbo at once... i dont have the book so i was wondering if someone could scan just the bit on hyper charging for me..

also if anyone else knows anything about it i would be really interested!

Stephen

[mk]

There goes my gun...

Translating the whole text would be too much of work now, but you'll get the idea.

[Stephen H]

thanks heaps for that, i have read it before but couldnt remember totally how it works!!

[Bruno Ogorelec]

This is a good layout for a turboshaft. But, why have the turbine combustor at all? The piston engine is already a pretty good combustor. You should have the crankshaft geared to the turbine output shaft.

That way you have the best of both worlds -- the greater thermal efficiency of the turbine and the broader spread of usable RPM and the quick response of the piston engine. Some wonderful aero engines have been built this way.

Keith Duckworth -- the most successful car racing engine designer of all time -- once said it would make the perfect car racing engine.

[skyfrog]

Hi Bruno,

Why do we need this extra combustor ?

After digested what the book has said, I understand that there are two reasons to do this.

1. When the piston engine is idling, valve h is opened, fuel is injected into the CC and burned, the turbocharger is then driven by this CC temporarily, so the RPM of turbocharger is maintained at high speed. Thus we have high charging pressure available. Once we need the power the engine could deliver the power with zero lag.

2. High torque can be obtained even the piston engine is at low speed.

I have no idea of who's gonna need such powerful engine.

[mk]

Exactly, Horace.

The target is the avoidance of a turbo chargers "(power) hole phase" during accleration of the coupled piston engine.

IMO, with a geared -- and thereof "tight" or "unclutched" -- crankshaft-to-turboshaft connection you'd get a kind of negative feedback (during accleration through the "hole phase").
Having a "loose" or "clutched" connection, respecively the combustor should give you a kind of positive feedback (during accleration through the "hole phase").

Seems to me like rally cars would be first choice for such a device. High torque values from low RPM numbers to higher ones are a must for them.
Eventually -- I don't know exactly -- Audi, Lancia, etc. might have used this trick in the "wild years" until turbo chargers got banned.

[edit] Yeah! Taxi drivers! I didn't flush my mind, because it is about eight months ago I sit in a taxi the last time.[/edit]

[Johansson]

Turbo lag can more easily be avoided by injecting nitrous oxide into the engine at full throttle. A big shot can, beside increase HP and torque, double the amount of exhaust gasses and thereby instantly spool up the turbocharger, and when the turbo is at full charge the nitrous solenoid valve closes to make the bottle last longer.

It would be fun anyway to have a gas-turbine under the hood, it would probably sound pretty cool...

//Anders

[leo]

I think this system Is never used in racing because with a well designed exhaust system turbo lag is easily avoided, and the extra fuel consumption could be a problem in racing cars.
I build 4 autocross cars with turbochargers in the ninety eighties, and turbo lag was never a problem, the trick is to lead the pulses from every exhaust port directly to the turbine housing, instead collected them in a exhaust manifold and then feed it into the turbine housing.

[steve]

This reminded me of the Naiper Nomad engine that I just happened to see (and photograph) on display at the new National Air and Space Museum. What a remarkable piece of engineering!

I also got pics of a merlin and an alison if anyone wants to see them!