turbine hybrid

[beef_bourito]

Hybrids today are not true hybrids, they're electrically assisted gasoline engine. what do you people think about building a turbine-electric hybrid where the turbine is constantly running at a low speed, turning a generator, the generator stores energy in batteries or capacitors, then that goes to electric motors.

The turbine could keep spinning and would increase speed if the batteries were running dangerously low, it could also shut off if the batteries were full.

The problems that i think could have a bad impact on this system are: 1) sound, turbines are generally loud, i could probably have exhaust gases running through mufflers but the intake sound is still there. this might not be as much of a problem if i only use a 50hp or so engine because it wont be breathing in as much air. 2) the output shaft, how could i run an output shaft through the exhaust tube without creating a leak (emissions would be bad eh?). if this isn't feasible, i could probably run it off the compressor, this could cause some unwanted resistance and vibrations but that is to be seen. 3) the strength of the electric motor, i heard that some electric motors have so much torque that they can brake the output shaft, controlling this would be a minor problem but would probably be regulated. 4) heat, turbines get hot and this can pose problems.

help and comments will be appreciated, i plan on doing this in university as an extra credit project.

[MagicRat]

Interesting post.

There are lots of gas turbine engines that drive machines using rotating shafts, instead of relying on thrust alone.

FYI most commercial jet aircraft do not receive their electrical power from the big jet engines that you see hanging off the wing or the fuselage.

They use a really neat little gas turbine engine at the rear that exclusively drives a generator. You do not see it because its inside the fuselage (body) of the plane.

Often they drive a DC (often 12 volt) generator, and in smaller planes, like the DeHavilland Dash 8
http://flyaow.com/planes/dh1aircraftspecifications.htm
They are small enough to fit under the hood of a car, generator included.

Gas turbines are quite efficient when used at a constant speed and power output, which is why they are good in planes and ships.

Certainly a hybrid mechanism would allow a small, low power turbine to work at a near -constant output, with the battery absorbing then supplying extra power when needed.

IMO this would be most efficient for big trucks going down the highway.

However, electric generaltor do suffer from induction losses, so it would be helpful to have the turbine engine drive the wheels as well as a generaltor, to reduce such losses.

As for noise and heat, yes its a problem, but Chrysler effectively solved these engineering problems more than 40 years ago with their gas turbine cars.
http://www.aardvark.co.nz/pjet/chrysler.shtml

[mazdatech177]

and if you have the turbine engine at a constant speed driving your wheels you may want to look at a trans setup much like a snowmobile... i think honda experimented with a constant velocity trans. dont know if that helps any... an interesting idea you got, sounds kinda pricey though

[Reed]

there are a few cars that have constant velocity trannys but they are all low powered cause those cvt's cant take a lot of power. turboshaft engines are used probably more commonly than gas turbines for propulsion.


oh and APUs in aircraft are generally used to provide compressed air to start the engines and for ground power when the engines are not running. they are generally not used in flight.

[beef_bourito]

I got back to thinking about the problem with the output shaft and was wondering if i could use engine thrust to turn the turbine of a turbocharger and use that output shaft to turn the generator. would this be less efficient than hooking up a generator to the front or hooking up a gearbox to the front with some reduction gears or cvt? I plan on running this on diesel fuel, higher btu's than gasoline and should yield better mileage. also, how many joules of energy are in one gallon of diesel, this could allow me to calculate how much fuel i would need to burn at 100% efficiency and then I could adjust it from there, it would just help me with my starting point.

One more thing, there are turbochargers with variable vanes, how are these controled, would it be possible to control them from an external source? I'd like to be able to control the thrust without revving the engine higher, this would be for a thrust oriented project, or for a car/bike for more torque.

I'd like to make a few projects with turbine engines, they interest me, I'd like to make a boat as well and use a cvt to control the speed before the gearbox, this would allow me to run the turbine at high revolutions in neutral without destroying the gearbox. That wouldn't be for a while because of the cost of parts, I'd start off with something small and cheap, like a small propane turbocharger turbine engine, then move on to diesel, then move on to a straight-through turbine engine, with funding from something of course i can't afford the stuff required.

I am planning on doing this in university with the help of other engineering students, such as electrical engineering students, software engineering students for the programming of various components, there might be more but these are the ones i see as necessary.

[454Casull]

I'm too tired to read everything but I do know that Garrett's electrically-assisted turbo can be used as a generator when boost isn't required.

[454Casull]

I'm too tired to read everything but I do know that Garrett's electrically-assisted turbo can be used as a generator when boost isn't required.

[CBFryman]

Diesel
130,000 BTU/Gal

1 BTU = 1,055 joules

and for future reference

1hp = 746w (joules/sec)

So 1 gal of Diesle Contains aprox 137150000 joules.