Batmobile

[BodybyFisher]

Anyone care to guess miles per gallon on this>

http://www.youtube.com/watch?v=nZSBpFMWk-M

[Cadillac Jim]

Internal combustion turbine engines have a fuel consumption that varies far less with load than does that of piston engines. Fuel gph at idle will be something like 25% of fuel gph at full throttle. Another factor is that thrust is not a strong function of speed until speed approaches exhaust velocity.

With that background, you can see that fuel economy under lightly loaded conditions and low speed will be truly abysmal. Fuel economy in mpg is speed in mph divided by consumption rate in gph, so generally mpg is proportional to speed or at least increases with speed, something you see in piston engines up to cruising speed (which varies with the car, about 65 mph for a Northstar). And, fuel gph is proportional to engine size or maximum hp. Maximum hp would be achieved only at speeds unattainable in a wheeled vehicle except in exceptionally flat surfaces such as the Bonneville Salt Flats. So, you will need something like 1,000 hp or more to have a good-performing car in city driving.

To answer your question, I would say 1-2 mpg city, 5 mpg highway, for a thrust-powered car. I would say 5 mpg city, 10 mpg highway for a geared turbine power, like a turboprop aircraft engine, where the engine spins a turbine which turns a reduction gear that provides propulsion to the wheels. But the more I think about it I think these numbers are way too high.

[Texas Jim]

I don't know about the MPG....

But I would love to see that car in person...it is so cool.... :)

[Cadillac Jim]

In the movie it's presented as thrust-powered, which is appropriate to the far-out genre. All practical cars and motorcycles (yes, Jay Leno has a turbine-powered motorcycle!) use an output shaft and reduction gear with wheel-powered propulsion. For one thing, the turbine itself can be much smaller and give great performance and fuel economy that peeks above the decimal point on the mpg scale. For another, you can have a reverse gear. And, those within a half-block behind you don't have to have Kevlar MG Mittens over their cars to survive a takeoff from a traffic light by your car.

If you go to a hybrid, the turbine concept has even more practical potential, but in a full generator-electric configuration like the Chevy Volt, a turbine-powered generator has a very, very interesting potential. A fist-sized internal combustion turbine can provide enough generator power to support high performance; say, 200 hp, 50 hp per wheel. Good efficiency and economy is possible because the turbine will be run at load or not at all. The Volt generator engine has four settings: off, low, medium, and maximum power. The turbine could have three (off, idle/warmup/cool-down, and cruise) and offer high efficiency. It's principal disadvantage, other than initial cost, would be the higher electrical power needed to spin up the turbine for light-off; internal combustion turbine engines typically idle at 50,000 RPM and cruise at 100,000 RPM. But it could run on anything; it could run on generally available fuel such as ordinary diesel fuel, and efficiency in terms of fuel BTU to Watt-hours of battery power could be far higher than from an internal combustion piston engine. The catalytic converter would not necessarily be a problem because the turbine would be so small, and the output shaft turbines will decrease the exhaust velocity and temperature to manageable levels.

Don't tell me that these small turbines aren't practical. They sell them for model planes, albeit in thrust-powered configurations.

[BodybyFisher]

Here is a small turbine

[BodybyFisher]

Big boy's toy?

[WarrenJ]

On Chrysler's (admittedly long ago) experience with turbine powered cars:

"There were numerous functional challenges and limitations with the Turbine Cars, of which sluggish throttle response was the biggest. This is an inherent design limitation of turbines, as they need to spin up to over 40,000 rpm to develop full power. The Turbine Car had a one and a half second lag from first pressing the throttle. That could be considered dangerous; it certainly would by today's standards. Throttle lag was noticeable at higher speeds too. Performance was reasonable, about 12 seconds 0-60, but substantially less than if a 383 V8 were under that sleek hood. One extended test produced an average fuel economy of 11.5 mpg. Not terrible, but far from good. A comparably-quick conventional car at the time would be expected to achieve about 15 mpg."

http://www.thetrutha...e-turbine-cars/

[Cadillac Jim]

The Chrysler turbine prototypes were in the 1960's. Fifty years can provide a lot of progress. The problem is that most of that progress has been in piston engines. But, yet, the 11.5 mpg figure is impressive. The performance is not, but that was a choice in the size of the turbine.

The Chrysler prototypes used the turbine output shaft in gear reduction that drove a transmission to drive the wheels. Turbines are better suited to constant loads than to continuously varying loads. Thus driving a generator is a better use of a turbine. That leads us to a concept that modifies the Volt engine-generator-battery-controls-motors drive train by using a turbine instead of a piston engine. That concept has potential for excellent economy.

[Texas Jim]

The Chrysler turbine prototypes were in the 1960's. Fifty years can provide a lot of progress. The problem is that most of that progress has been in piston engines. But, yet, the 11.5 mpg figure is impressive. The performance is not, but that was a choice in the size of the turbine.

The Chrysler prototypes used the turbine output shaft in gear reduction that drove a transmission to drive the wheels. Turbines are better suited to constant loads than to continuously varying loads. Thus driving a generator is a better use of a turbine. That leads us to a concept that modifies the Volt engine-generator-battery-controls-motors drive train by using a turbine instead of a piston engine.

That concept has potential for excellent economy.

I would think that a really small turbine would power the generator to keep the batteries charged and use very little fuel while doing it.

It would be interesting to see what the economy would be with a setup like that.

[Cadillac Jim]

How efficient it would be would heavily depend on the design point and the execution. For a Tesla, you will need a larger turbine than for a Volt, for example. I would think that the public would be most interested in the 250 hp peak power at the wheels range in a mid-size four-door at a reasonable price, for example. The car companies would be more interested in a 350 hp peak power at the weels SUV because they would make more money. Green organizations and the Government would like to see something more efficient than the 1000 cc four cylinder that provides generator power in the Volt.

There are a lot of variables in defining a design for a turbine-to power a generator for a motor vehicle. Size, along with hp-hour per pound of fuel defines the maximum continuous horsepower. Insulation increases efficiency but increases turbine temperatures, size, weight, and cost. The gear reduction from the output turbine speed of about 50,000 rpm is a big item and there are trades of size, weight, and efficiency there. The generator design is another opportunity to trade size, weight, maximum peak and maximum sustained power, and cost. Heat dissipation and thermal design of the generator is a complex and critical item.

The fundamental concept of piston-engine powered generators with electrical motors for propulsion is really old. Diesel electric locomotives have been used in railways since the 1940s, the transition having begun ten years earlier. But there are fundamental differences: Diesel engines were chosen for fuel efficiency and versatility of fuel to burn, but are so heavy that the principal land vehicle use was railways until further development made them practical for large trucks and buses, then eventually for smaller and smaller cars, and ultimately the Mercedes 300D and such. Another more important fundamental difference is that the Diesel engines were designed to run at sustained half maximum load or higher. Batteries were not used in the earlier designs.

In our car, we design the battery maximum drain rate and the motors at each wheel for maximum peak horsepower, which is at least ten times the expected average horsepower for cruising. Higher sustained horsepower is needed for climbing steep grades at speed, but one major property of DC motors is that, for a given current and voltage, torque increases as RPM decreases, so that an economy vehicle will climb any legal grade, albeit far more slowly than a Tesla or even a Volt with a low battery and running on its engine.

[Texas Jim]

I had a 1979 Olds 88 with the diesel and a 1981 Seville with the diesel.

I know they were problematic to a lot of people, but I never had any issues with mine at all.

I did do a couple of tweaks to them to make them run better.

Turn the pump up, and LARGE, true dual, exhausts with a balance pipe.

The factory exhausts were real tiny, single exhausts.

The MPG on a long highway cruise at the speed limit was absolutely amazing.

My Darling Wife almost killed me when I traded her Seville for an L82 Corvette...

[WarrenJ]

Even a small turbine must move a very large air volume at high velocity. I wonder what's involved in quieting one of those critters? I'd imagine there would also be a substantial amount of mechanical noise as well . . . or could only my dog hear that?

EDIT: Is that why they stick their head out the window?