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  1. #11
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    Hybrid w/turbine engine

    The comment on Volvo's Environmental Concept Car seems to be correct; unfortunately, I'm also having a tough time finding information on it. It was back from 1992/1993, so I'm sure we could do better these days, what with new research being done on micro power turbines (often used for onsite cogeneration of electricity for buildings, etc.). I think that a properly outfitted turbine (with regenerator and possibly intercooling and reheat) would be much more efficient than an Otto or Diesel cycle engine, and would certainly be more reliable. Cost, however, is another story. Maybe this is another case where the "law" of supply and demand would apply, though. For more on turbine efficiency, see: http://www.qrg.northwestern.edu/ther...d/brayton.html

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  3. #12
    Guest

    Hybrid w/turbine engine

    What about using the "rotary" style engine like the RX-8? Anyone got any numbers on how these engines are with respect to fuel efficiency and reliability?

  4. #13
    Guest

    Hybrid w/turbine engine

    Hyundai was experimenting with a gas turbine hybrid in their Santa Fe SUV back in 2000/2001 and promised that they would go into production with a similar system in their light commercial utility vehicles in 2002. Obviously, this never happened and the world is still waiting.

    GM also had a gas turbine hybrid version of their EV1 around the same time. Nothing came of it either.

  5. #14
    Guest

    Hybrid w/turbine engine

    As to turbine engines, they have a lower BSFC than 4-stroke piston engines, even at their most efficient ranges. As someone else already posted, even in aircraft, turbine engines are generally avoided for anything under 350 horsepower because you'll get better gas mileage from a piston engine.

    Where turbine engines shine is when you need to make huge power or desire extremely high reliability. I read one study that compared turbine and piston engines in aircraft and showed that turbine engines fail only 2% as often as piston engines. Granted, a lot of that is probably because most guys are only buying $15-30k piston engines and turbines are $75-500k and maintained better anyway, but still, the fact remains that turbine engines have lower BSFC even at peak, and their efficiency at low power percentages is horrible. A turbine engine at idle will use something like 20 times as much fuel as a piston engine at idle.

    As for Mazda's rotary engine, the easiest comparison there is between Mazda's 220hp RX8 and Honda's 240hp S2000. They both produce almost the same torque, power, and have nearly the same weight, but the S2000 gets dramatically better gas mileage. Rotary engines have much lower BSFC than piston engines. Why do you think piston engines are so common? Because they're extremely efficient, especially at light load.

    In the middle of 2006, new regulations will be in effect with regards to ULSD, aka Ultra-Low Sulpher Diesel. That will all but entirely eliminate the nasty smell from diesel and will pave the way for far better particulate traps on diesel powered vehicles making it possible to pass even California emissions with a diesel engine. Diesel has greater thermal content per gallon than gasoline (about 130,000 BTU versus 115,000 BTU for gasoline) and because diesel engines don't use a throttlebody, they have lower pumping losses and overall far higher total energy efficiency. Once the new regs are in effect, we'll see greater willingness for manufacturers to introduce non-smelly high tech diesels in America.

  6. #15
    Guest

    Hybrid w/turbine engine

    I would like to see a manufacturer use a small, and efficient, constant speed diesel engine coupled only to a generator which would charge a battery bank which powers a traction motor. It seems to me that the overall complexity of such a system would be far less than that of a hybrid since you would be dealing strictly with one propulsion system than two.

    Some common systems would have to reengineered to be run electrically: brake booster pump, power steering pump, etc. Heating and cooling could be done via a heat pump setup with an electric heater for extremely cold temps.

    The owner of such a car would also be able to plug the vehicle in at night (and perhaps at work) to supplement the charge thus reducing the need for the diesel alternator to run.

    All wheel drive (AWD) versions of this vehicle could easily be created by adding a second electric motor to the rear.

    In the event of a blackout, emergency power (and utility power by backs?) could come off of the battery bank via an inverter.

  7. #16
    Guest

    Hybrid w/turbine engine

    It is my understanding that turbines run in their optimal rpm efficiency constantly (like in hydrid applications) have a more effcient cycle than even diesel engines; especially with a regenerator. The proper sizing of a smaller turbine might be ideal for a hybrid, but two obstacles exist in their current manufacturing. Exotic metals may ultimately be replaced by gel-cast micro-fiber reinforced ceramics that can be mass produced to solve the first manufacturing/cost problems. The second problem is building a simple, efficient, and reliable small turbine. When you shrink the dimensions.. the reynolds numbers stay proportionally the same - therefore your tolerances have to be even tighter to maintain efficiency. Ask Dr. Williams of Williams Internationsl - he'll tell you the real problems.

  8. #17
    Guest

    Hybrid w/turbine engine

    The problems with making small turbines is one issue, the other problem is with fast rotating devices such as the turbine, in automobiles. That is the gyroscopic effect. Cars move around a lot and the gyroscope of the turbine rotor wants to remain at a fixed orientation in space, therefore the mounting has to fight to turn the turbine.

    Capstone is working very hard on both these problems but I don't know where they are with something suitable for the automobile environment yet.

    Flywheels also have this same kind of flywheel problem in vehicular applications.

  9. #18
    Guest

    Hybrid w/turbine engine

    Why not mount the turbine generator in a freely rotating way, so that the car does not have to "fight" the gyroscopic effects. Compare with cyroscopic compasses. It "only" need some clever design for cabels, fuel in and waste out though. But that can probably be solved by some smart guys.

    Maybe Turbine Hybrids are not a good idea, maybe they are. However the principle of choosing the most fuel efficient engine for generating electricity and then using the electricity (possibly via buffert batteries) to power electrical motors is sound IMO. Also, it should always be possible to plug in a hybrid, if the owner chooses to. In some countries there are 100% environmentally friendly power (nuclear + hydro) and users in those countries might prefer "fueling" with clean electricity.

    Cars like that would become "electric cars with internal powerplats for optional use", which is my dream car.


  10. #19
    Guest

    Hybrid w/turbine engine

    Magnus,

    Gimbals only handle the rotational problem, not bumping and motion -- but I'm sure they will help a lot.

    I agree that a plug-in hybrid is the answer for now.

    see
    www.pluginamerica.com
    www.calcars.org
    www.edrive.com

    There are many who share your vision.

  11. #20
    Guest

    Hybrid w/turbine engine

    Below are a couple of to the most recent use of a gas turbine in a car by a major auto manufacturer. The microturbine in this modified EV1 "series electric hybrid" runs at a constant optimal speed. It is a single-stage, single-shaft, recuperated gas turbine with a high-speed permanent magnet AC generator. Only the electric motor is connected to the drive train.

    http://www.evworld.com/archives/testdrives/gmshev.html

    http://www.evworld.com/archives/test...gmshev-dia.gif

    Small single-stage turbines are less efficient than the multi-stage versions used in most jets. However, multi-stage turbines are very expensive to build. When using a recuperator, and running at a constant speed micro turbines DO have better efficiency than a reciprocating ICE. In a series hybrid configuration the car could get up to 100 mpg using gasoline. It would also be able to run on any other fuel like alcohol, hydrogen, diesel or methane. The ability to use multiple fuels is a good reason alone to reconsider the use of the turbine in autos.


    Because the gasses in turbines reach such high temperatures most of the toxic compounds found in gas and diesel fuel are more thouroughly combusted and broken down. The turbine engine in the 65 Chrysler experimental turbine car was touted as a clean air engine. This was 5 years before the EPA was formed.

    http://www.allpar.com/mopar/turbine.html

    http://www.turbinecar.com/sia/sia57.htm

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