Science/Engineering Question

[Thunderscreech]

So, I was thinking the other day about hybrid cars, and something occurred to me:
Given: A normal car engine uses pistons and crankshafts to transfer linear motion to rotary motion. On a normal car, this is the best system.

BUT: on a hybrid car, the engine and wheels are not in direct contact. Given that, wouldn't it be simpler to replace the normal engine for something like a gas turbine? After all, you're just turning an alternator to generate power, right?

[Thunderscreech]

I was not stoned when I came up with this. Really.

[iamlowsound]

So a turbine engine in a car? It has been done before, wasn't very efficient, but it was very fast.

lowsound

[Thunderscreech]

A turbine driving a hybrid car. The gas turbine spins the alternator.

[iamlowsound]

Originally Posted by Thunderscreech

A turbine driving a hybrid car. The gas turbine spins the alternator.

It would work, but I don't see any advantage over the conventional engine in the current hybrids.

lowsound

[fdeck]

I know exactly who to ask at my day job tomorrow. I have a colleague who understands the thermodynamic in's and out's of every possible engine. But first I will place a bet on his answer: Too expensive.

[hbarcat]

Here's your answer:

[hbarcat]

Get this book. It's the Bible of automotive engineering.

http://www.sae.org/technical/books/BOSCH7

[B.C.]

Originally Posted by fdeck

I know exactly who to ask at my day job tomorrow. I have a colleague who understands the thermodynamic in's and out's of every possible engine. But first I will place a bet on his answer: Too expensive.

I agree, plus I think efficiency might be a problem.

[T-Bird]

Hi.

2 problems.

The first one can be found out when looking at the fuel efficiency of a turbine engine. The advantage of a turbine engine is obviously that You can use any fuel you can throw into the chamber.

The second one can be found out if one takes a look at the availability of high speed alternators/generators or the technology and alternatively the size, weight and efficiency of the reduction gears needed for the matching.

Volvo had a turbine hybrid in testing stages in mid 90's IIRC when they developed a high speed generator.

If my memory serves me correctly from the Poly times when we were into these things more, 30kW is needed to sustain a speed of 100Km/h with a four wheel vehicle veighing 1000Kg and having "normal" aerodynamics.

Regards
Sam

[Solarmist]

Originally Posted by iamlowsound

So a turbine engine in a car? It has been done before, wasn't very efficient, but it was very fast.

lowsound

Just ask Batman

Seriously a turbine uses a lot of fuel running at a lot higher RPM

[i_got_a_mohawk]

Originally Posted by fdeck

I know exactly who to ask at my day job tomorrow. I have a colleague who understands the thermodynamic in's and out's of every possible engine. But first I will place a bet on his answer: Too expensive.

Sounds like a faily typical engineers answer.

[Jim Nazium]

Piston engines may not be the theoretically ideal design, but they've been refined and tweaked so much over the last hundred years that I don't think we'll see a replacement in cars any time soon. Just think how far they've come since the 70's: electronic ignition, variable valve timing, fuel injection, etc.

I read an article in Outside magazine once about a guy who proposed a radial piston engine for cars, claiming it would be more efficient. The engineer's response: "Will it start in minus 20 degree weather? Can it be rebuilt after 200 thousand miles? Can it be mass produced?"

[blizzard]

If you are looking at Hybrids, hydraulic hybrids seem to make much more sense than the petro-electric ones currently available.