Why not use turbine engines in cars?

[cjl]

When nothing matters (cost, efficiency) besides power density, turbines are sometimes the way to go. Honeywell AGT1500, 1500 HP, 2750 lb-ft torque.

Although even in that application, their use is questionable. Most modern main battle tanks use diesel instead, and the fuel efficiency advantage of diesel is fairly significant.

 

[mheslep]

Although even in that application, their use is questionable. Most modern main battle tanks use diesel instead, and the fuel efficiency advantage of diesel is fairly significant.

Yes, and all other battle tanks have significantly less HP than the US Abrams 1500 HP with 45 mph road speed. Russian T-90 950 HP; British Challenger 2, 1200 HP, 37 mph-road, etc.

Yes this comes at an efficiency penalty which the US improvises around with a large fuel logistics tail. One of the more dramatic illustrations of the trade off was the 2003 Iraq invasion and tank assault on Baghdad. There, US tank companies passed through heavy opposition with slight casualties and drove at speed over concrete barriers and down the highway into Hussein's palace in a single day. Once in the compound they were also without resupply and in danger of running out of fuel by the second day. The subsequent resupply column had much greater difficulty with its many fuel tankers and suffered many casualties.

The Abrams was at one point eventually equipped with simple Big Box store portable generators to enable efficient operation at halt, i.e. with the fuel guzzling turbine off.

 

[Nugatory]

A gas turbine powered car would really have to be designed specially to make best use of engine characteristics . Coupling a gas turbine to a conventional piston engine clutch, gearbox , drive shaft and differential to get power to the wheels is definitely not best way to do things .

A case in point: A half-century ago (late 1960's) gas turbines made a short-lived appearance in American Indianapolis-car racing, before the rulemakers outlawed them. Once they couldn't be used in racing, some were sold for pennies on the dollar ("Hey! Want to buy a white elephant?"), and one of these was transplanted into an automatic-transmission street car (Chevy Corvette) a few years later... The thing idled at 70 mph.

 

[rollingstein]

The crux of the matter seems that we modern cars the key battle we are seeing is an efficiency battle and not a power, weight or thrust challenge. Ok, the losses reduce with weight somewhat but modern piston engines are pretty light anyways and there's other weight cutting targets in a car.

So far as I understand, the selling point of turbines is their massive power to weight ratio. Not their inherent fuel efficiency.

Ergo, I don't see what the motivation would be to fit a turbine to a car.

As a practical matter, if turbine technology does advance in any specific way that makes it more suitable for vehicular sources I'd expect the trickle down to be from larger vehices first. i.e. You'd see more widespread adoption in something like train engines where the thrust levels are much larger and gearboxing is not an issue since they typically drive electric motors anyways for traction.

I knew GE had a bunch of turbine running locos in the 60's but they never really caught on. And till a turbine makes sense for a train I see no reason it will for a car.

In niche uses like the Abrams Tank (i.e. huge power requirement, efficiency a secondary concern, space comes at a premium, ease of maintenance needed, robustness) yes we do see turbines.

Even in shipboard applications although there's some turbine use but if they really got efficient you'd see the Emma Maersk run its props on turbines instead of that huge monstor of a piston engine.

 

[cjl]

A case in point: A half-century ago (late 1960's) gas turbines made a short-lived appearance in American Indianapolis-car racing, before the rulemakers outlawed them. Once they couldn't be used in racing, some were sold for pennies on the dollar ("Hey! Want to buy a white elephant?"), and one of these was transplanted into an automatic-transmission street car (Chevy Corvette) a few years later... The thing idled at 70 mph.

In racing, you also wouldn't have the part-throttle efficiency to worry about as much either. Turbines are fairly efficient at wide open throttle, and idle/low-throttle fuel efficiency is largely irrelevant for a racecar. I'm a bit disappointed that they're outlawed, honestly - I'd love to see what F1 or IndyCar racecars could do if they were relatively unrestricted in design, but I understand why that isn't the case...

The crux of the matter seems that we modern cars the key battle we are seeing is an efficiency battle and not a power, weight or thrust challenge. Ok, the losses reduce with weight somewhat but modern piston engines are pretty light anyways and there's other weight cutting targets in a car.

So far as I understand, the selling point of turbines is their massive power to weight ratio. Not their inherent fuel efficiency.

Ergo, I don't see what the motivation would be to fit a turbine to a car.

As a practical matter, if turbine technology does advance in any specific way that makes it more suitable for vehicular sources I'd expect the trickle down to be from larger vehices first. i.e. You'd see more widespread adoption in something like train engines where the thrust levels are much larger and gearboxing is not an issue since they typically drive electric motors anyways for traction.

I knew GE had a bunch of turbine running locos in the 60's but they never really caught on. And till a turbine makes sense for a train I see no reason it will for a car.

In niche uses like the Abrams Tank (i.e. huge power requirement, efficiency a secondary concern, space comes at a premium, ease of maintenance needed, robustness) yes we do see turbines.

Even in shipboard applications although there's some turbine use but if they really got efficient you'd see the Emma Maersk run its props on turbines instead of that huge monstor of a piston engine.

I agree with this - especially in situations like highway trucks and trains. Large ships probably won't go away from slow-speed 2 stroke turbodiesels anytime soon, since they're so efficient (I believe they're well over 50% thermal efficiency right now) and can burn such low grade fuel, but if turbines become both somewhat lower cost than they are currently and more efficient than medium and high speed 4 stroke turbodiesels, I'd expect to see trains and trucks adopting them en masse, far before they become cost effective for cars.

 

[HowlerMonkey]

Turbines don't scale down very well as do many other things.

 

[mheslep]

Turbines don't scale down very well as do many other things.

There has been remarkable progress in this area in recent years. See the subject of microturbines.

 

[HowlerMonkey]

Then we need to see a BSFC map of a microturbine VS one for...let's say... a toyota prius for comparison.

Interestingly, none of the microturbine manufacturers seems to have one.

They're great for stationary power/heat production especially where heat is needed but the 25% I see from them get's diluted by the figures they assign to the heat production.

Since this is an automobile forum, I would guess the original poster was referring to a car and not a large bus or stationary power plant.

 

[mheslep]

No mfn, of any size of turbine, is going to bother with BSFC plots given a turbine runs nominally at 10,000 rpm and not the 1000 to 4500 rpm of an internal combustion engine.

 

[cjl]

No mfn, of any size of turbine, is going to bother with BSFC plots given a turbine runs nominally at 10,000 rpm and not the 1000 to 4500 rpm of an internal combustion engine.

Turbine manufacturers care a lot about efficiency, and the RPM a turbine runs at is highly dependent on which part of the turbine and the design of the turbine - the core will be spinning at 9-10krpm or more, but on a turboshaft engine, the power turbine can be spinning much, much slower than that. In addition, why does it matter if it's spinning twice as fast as an IC engine - you can gear it differently to achieve the same output shaft speed if you want. RPM is not the primary problem with turbines for small vehicle applications.

 

[mheslep]

In addition, why does it matter if it's spinning twice as fast as an IC engine - you can gear it differently to achieve the same output shaft speed if you want.

Very high RPM with affordable and reliable gearing is a very difficult mechanical engineering problem. Tolerance requirements, materials limits, MTBF, all become problematic.

Pratt and Whitney just in the last few years stepped into the gear box no-mans-land with turbines, but even with that breakthrough I doubt that tech is anywhere near the at-speed gear changes required of an automobile power plant. So far the only practical approach seems to be using the turbine to drive a generator to charge batteries, either on or off.

 

[cjl]

Yes, but 10k isn't really all that high. It's less than a factor of 2 higher than existing car engines (hell, it's barely higher than some of them - a lot of high performance engines rev to 8-9krpm), and for the same horsepower, the torque requirements are lower on a higher revving engine (which makes the engineering problem significantly easier). If we were talking about gearing a 250krpm engine here, that would be different, but 10k isn't really much of an engineering challenge at all.

 

[NTW]

Chrysler tested a few turbine prototype cars, in the late 50s or early 60s. They designed a rather compact power unit, but the already low efficiency of that small-sized gas turbine was made even worse by the low working temperatures forced by the simplified design, intended for mass production. Rotating regenerators were incorporated in order to improve mileage, but those prototypes were real gas-guzzlers, even much more than equivalent cars of the time...

 

[Baluncore]

Using the turbine to generate electricity for use in motors does work and can be very fuel efficient.

Electric drive is relatively easy to implement .
Electric drive also fits in well with hybrid technology vehicle designs .

Kozy and Nidum have the right ideas.
Electric power is the obvious way that vehicle technology will go. Any conceivable mechanical drive with a variable speed turbine will be inefficient in a vehicle that stops and starts in city traffic. That was discovered 50 years ago.

In my opinion we will not see turbines in cars again until they are used to boost or charge the batteries of an electric vehicle. They will be there to extend the range. That way they could be autonomous and only run rarely, but then at maximum efficiency. The weight, space and cost reduction in batteries required would more than offset the use of a micro-turbine, alternator and fuel supply.