Turbo Car... Will it work?

af_thefragile

Lately i've been thinking of designing a car powered by a turboshaft engine from a helicopter rather than a conventional piston engine.

Now a turbine engine has a lot of advantages over a piston engine.
Its much more efficient than a piston engine.
Its much lighter so better power to weight ratio.
It has much less moving parts hence can last much longer and is much more reliable.
It can run on pretty much any kind of fuel.
It doesn't need complex multi-ratio transmissions and clutches either.

The disadvantages are:
Its loud (but wouldn't be much louder than a racing car).
The exhaust would be pretty hot but this could be gotten around by good exhaust design with a heat exchanger which could then use the heat in some sorta combined cycle improving efficiency further.

And finally the major disadvantage is turbine engines have all their power at the high end of around 80k rpm. This leads to the problem of turbo lag from hell!
But maybe in something like a big sedan which is just cruising, this shouldn't be that much of a problem.



Well, anyway, Chrysler tried this back in the 60's and failed. That was mainly cuz petrol was hell of a lot cheaper back then so no was bothered.
Now with the serious pressure to move from the outdated piston engine, the turbine engine could be an answer...

The US army's M1A1 tank runs on a turboshaft engine and that works fine, so i think it should work just fine or maybe even better than a conventional piston engine in a car...

What do you guys think?
Will this be the next big thing or just a waste of time...??

vw4life

http://en.wikipedia.org/wiki/MTT_Turbine_SUPERBIKE

do it

Heroditas

af_thefragile wrote: »

The exhaust would be pretty hot but this could be gotten around by good exhaust design with a heat exchanger which could then use the heat in some sorta combined cycle improving efficiency further.

This would add a serious amount of weight to it though, wouldn't it?

Dartz

It's doable.

It burns a lot of fuel though, and noise regs will be a pain. Not just the exhaust, but the actual whine of the turbine blades themselves.

You really have to be clever with your exhaust, and even that won't kill the noise. engine bay will have to be soundproofed heavily too.

Best way would be to have it rear engined, leaving space for baffling in the exhausts to kill some of the noise, without running them under the passenger compartment and cooking the poor buggers inside. Also remember, turbines have poor torque, and run best at constant rpm, so you're best off using at least a CVT, if not a fully hydraulic, or turbo-electric powertrain./ Conventional mechanics while loose you efficiency.

Finally. No matter how cool. Afterburners are against the law. So no doing it in front of Gardaí.

I for one, would love a turbo-compound car engine. Massive efficency, since it recovers exhaust energy directly, and not as smug as a bloody Prickus.

Mr Benevolent

Actually turboshaft engines are a lot more inefficent in terms of miles per gallon. I've thought of it myself but there are a number of issues:

Noise reduction (turboshafts are LOUD)
Gearbox matching (they spin at between 10,000 and 20,000 rpm and will probably need a big CVT autobox, manual would never work)
Spoolup time (they take at least 5-7 seconds to spoolup due to fuelling issues)
Emissions (they spew out all sorts of crap)

Edit: Dartz beat me to it

Thought of some other issues:

The intake - it sucks in huge volumes of air at a ferocious rate. You can't just have a pipe under the bonnet - it'd inhale the whole engine.
Cost: The unit below (Innodyn) would cost about €20,000.

Now - solving the problems:

Easiest way to start is to power something like a stripped Mondeo platform with a turboshaft unit. The the unit best suit would probably be an Innodyn 165hp unit (Innodyn's website has disappeared for some reason).

Inlet: Best to have the inlet underneath the car with progressively finer filters (odd idea I know, but would save kids being sucked into the intake).

Gearbox matching: A big modified CVT box could do it

Spoolup: The Innodyn would spoolup in less time, maybe 3 seconds, so less problem there.

Noise: LOTS of soundproofing, maybe active noise cancelling etc.

Price: No way around this until ceramic bladed turboshafts come onto the market.

af_thefragile

Confab wrote: »

Actually turboshaft engines are a lot more inefficent in terms of miles per gallon. I've thought of it myself but there are a number of issues:

Noise reduction (turboshafts are LOUD)
Gearbox matching (they spin at between 10,000 and 20,000 rpm and will probably need a big CVT autobox, manual would never work)
Spoolup time (they take at least 5-7 seconds to spoolup due to fuelling issues)
Emissions (they spew out all sorts of crap)

Edit: Dartz beat me to it

Noise would definitely be an issue. It'ld need some serious noise insulation to get around and some clever exhaust design. Though maybe people can get used to the swooshing sound of the turbine like we've gotten to like the sound of big V8s and V12s...

Most turboshafts have a freepower turbine which rotates at a slower speed to the gas turbine that is run by the combustion. Basically they're like built in torque converters. But getting the power down onto the road efficiently would be an issue. It would need a CVT.

I don't think a few secs spooling up time should matter much for a sedan type of vehicle where once you've gotten going you're mostly cruising and fast throttle responsiveness wouldn't be that necessary. It could be a small trade off for the efficiency benefits.

And good turbine engines have a thermal efficiency of atleast 30% whereas piston engines struggle to reach above 25%. Then theoretically it should be cheaper to make a turbine engine than a piston engine as its far less complicated and has less parts.


Another thing that can be done is get the turbine to power a battery pack that powers an electric motor to run the vehicle. Like a hybrid. Would get rid of the 'getting the power form the turbine to the wheels' issue.
But efficiency could be lost or maybe the lack of complex transmission could improve it. But there's the added weight of the battery pack and electric motor.


I guess i should look into how the M1A1 tank works with the turbine engine to see how well it could work on a road car...

A recirculating exhaust through a heat exchanger feeding the intake could solve part of the high air intake issues.
I've noticed a couple of small Rolls Royce turboshaft engines have the exhaust going back into the intake.

kasper

why not leave it in the helicopter and fly all problems solved and no congestion

Mr Benevolent

kasper wrote: »

why not leave it in the helicopter and fly all problems solved and no congestion

Because helicopters are painfully expensive to fly and maintain

kasper

they cant be any more expensive to maintain than a car with a helicopter engine , its a lot easier to fly a helicopter than drive a car

Mr Benevolent

kasper wrote: »

its a lot easier to fly a helicopter than drive a car

:rolleyes:;)

CianRyan

kasper wrote: »

they cant be any more expensive to maintain than a car with a helicopter engine , its a lot easier to fly a helicopter than drive a car

Hahaha, ah god.

Fishtits

kasper wrote: »

its a lot easier to fly a helicopter than drive a car

As one who has attempted both, mastered neither, with the greatest respect, I'd suggest you revisit this nugget of wisdom...

af_thefragile

Helicopter is one of the most complex machine to fly. There are tons of controls you've gotta constantly keep adjusting to keep the thing in the air and stop it from falling out from the sky as unlike a plane or an autogyro, helicopters aren't aerodynamically designed to produce lift.

Almost anyone can drive a car on the other hand. Especially if its an automatic.



Anyway, back to the subject of the turbine car. I can see why its hasn't worked out so far.
Its the noise, the turbo lag and that turbine engines aren't designed for stop-start variable rpm like the piston engine is but to keep revving at a constant rpm.

But maybe if once you can find out a way to get around these problems, it could maybe work.
The biggest advantage of the turbine engine is that you can run it on any fuel very efficiently (especially with a combined cycle) which means it'ld be up to run on "green" and alternative bio fuels stuff too when we run out of petrol. And the long life would certainly make it more economical in the long run than too.

If we can find a way to get around the problems with turbine engine and make it work somehow. Then mass producing it would be much cheaper than piston engines as they're more simpler and have less parts.

So if anyone would like to contribute in trying to see if a turbine powered car that could be used for everyday use can be made, feel free!

sogood

kasper wrote: »

why not leave it in the helicopter and fly all problems solved and no congestion

And you'd have to mount your speakers on the outside and then invest in a good Wagner tape, maybe Ride of the Valkyrie?

Wibbs

Confab wrote: »

Because helicopters are painfully expensive to fly and maintain

... and crashes tend to be more consistently fatal.

FOGOFUNK

Turboshaft Spacewagon

Saab Ed

FOGOFUNK wrote: »

Turboshaft Spacewagon

I want one of these. Not much room left for the kids though and you wouldnt want to be walking behind it crossing a road at traffic lights . I wonder what John Gormless would make of it aswell. Whats the Co2 on this John???!!! :eek: