Wave disk engines to make hybrid vehicles cheaper, more efficient

Wave disk engines to make hybrid vehicles cheaper, more efficient

Summary: Researchers from Michigan State University and the Warsaw Institute of Technology are developing a wave disk engine and electricity generator that promises to be five times more efficient than traditional auto engines in electricity production, 20% lighter, and 30% cheaper to manufacture.

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Researchers from Michigan State University and the Warsaw Institute of Technology are developing a wave disk engine and electricity generator that promises to be five times more efficient than traditional auto engines in electricity production, 20% lighter, and 30% cheaper to manufacture.

Possible technical realization of the wave-disk engine idea (Credit: Piechna, et al)

The new hyper-efficient engine is about the size of a large cooking pot, and could replace current backup generator technology of plug-in hybrid electric vehicles, according to Green Car Congress.

The idea may not be far-fetched as the team, led by Norbert Müller, an associate professor of mechanical engineering, has recently been awarded $2.5 million from the Department of Energy’s ARPA-E program to begin work on a vehicle-size wave disc engine/generator that could be ready in two years.

How do wave rotor engines work?

The wave disk engine is a new implementation of wave rotor technology (think micro turbines).  The first successful realization of a wave rotor was developed in the mid-1950s.

Wave rotors (also called pressure wave machines or pressure exchangers) are unsteady-flow devices that utilize shock waves to transfer energy directly between a high-energy fluid to a low-energy fluid, thereby increasing both temperature and pressure of the low-energy fluid.

According to a paper published by the MUS and Warsaw scientists in 2004, wave rotor technology can enhance cycle power and efficiency, plus possibly reduce the overall size, weight and cost. It allows a higher cycle peak temperature without need for a cooling system. Additionally, the rotational speed of a wave rotor is low compared with turbo-machines, resulting in low material stresses.

The new wave disk has a leg up on earlier wave rotor implementation that were mainly axial flow. In axial-flow configurations pure scavenging (the process of returning the hot compressed air back to the turbine) is a challenging task. Although it's possible to achieve a full scavenging process for both through and reverse-flow configurations, the solutions lead to more complex configurations.

The wave disc technology, however, uses a radial and circumferential flow, which can substantially improve the scavenging process by using centrifugal forces. Compared with straight channels, curved channels provide a greater length for the same disc diameter, which can be important to obtain certain wave travel times for tuning.  (Another paper, published in December 2008, explores this topic in detail.)

Previous research by the MSU team led them to position the combustion process internally in the wave rotor, thereby simplifying porting between the turbo-compressor and the wave disc “enormously”. That led to a proposed concept of a Radial Internal Combustion Wave Rotor—the precursor to the wave disk engine.

Now, with the wave disk engine, Norbert Müller's goal is to: "Enable hyper-efficient hybrid vehicles to meet consumer needs for a 500-mile driving range, lower vehicle prices, full-size utility, improved highway performance and very low operating costs. The WDG [wave disk generator] also can reduce carbon dioxide emissions by as much as 95 percent in comparison to modern internal combustion vehicle engines."

View the video below to hear Norbert Müller describe his wave disk generator.

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14 comments
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  • internal combustion is around 30% to 40% efficient


    Existing internal combustion engines of the otto-cycle family are in the region of 30% to 40% thermal efficiency.

    AC electric motors/generators are above 90% efficient.

    Exactly what process, motor, generator or engine are these guys claiming a 5x improvement on?
    spark555
    • I had the same question

      It is not clear at all what the heck this device is supposed to do.
      Economister
    • 5X more effecient in ELECTRICITY production ...

      The typical automotive engine wastes a lot of the produced energy in running accessories (EI: alternator, water pump, cooling fan, etc) so the net available power to generate propulsion electricity is much lower. This engine does not appear to need these accessories and can thus convert more of the available power directly to electricity.
      I do concur that the 5X figure is either wishfull thinking or a theoretical figure.
      kd5auq
    • 30%? not 10%, as NPR says?

      the CarTalk guys hosted a Nova program recently that gave the internal combustion engine a 10% efficiency rating and backed it up with their calculations. I don't know what an 'otto-cycle' engine is but a typical car engine is much less efficient than you state here. What's my error?
      Geedavey
    • Little optimistic

      A modern gasoline engine has eff range of 18-24%. 18 being a typical 2 valve wedge engine and 24 being a 4 valve computer controlled engine. Add 2% if turbocharged. A diesel is about 32% aspirated and 34% turbo diesel. The Wartsilla ship container turbo diesel is about 56% efficient due to its size. The larger and more simple the IC, the more efficient it is. Same goes for electric. 150hp electric motors are about 95% efficient. Small one about 30 hp are in the 70% range.

      5 times efficient is probably promotional or they are comparing it to a Tin Lizzy. By the way those efficiencies are at the flywheel. Gears drop this even further.
      osreinstall
      • To get 56%......

        I believe you need to extract heat energy from the engine coolant and exhaust and use that for other purposes, such as space heating, domestic water heating etc. No diesel cycle can get 56% without that.
        Economister
        • Yes they can.

          At 105 rpm with around 109,000 hp it was built with efficiency in mind. As you get larger in size the efficiency goes up. It is a turbocharged 2 stroke with heat recovery. All industrial diesels and turbines have heat recovery to boost efficiency.

          http://www.viperalley.com/forum/anything-goes/74738-wartsila-sulzer-rta96-c.html

          http://www.youtube.com/watch?v=jXHvY-zY9hA

          http://www.wartsila.com/,en,press,0,,8F51527F-00A3-4C5F-ABEA-B543789ACA1B,,,.htm
          osreinstall
          • Well I'll be damned

            You learn something new (almost) every day. I guess my knowledge is a bit dated.

            I wonder if I can do a quick swap into my F350. Just put in some slightly stiffer springs? How does 35mpg sound? You would all be SOOOO jealous. ;-)

            Economister
          • I think the upper catwalk will take out the traffic lights.

            You can always put a prop where the truck nuts are. Then no one will screw with you. ;)
            osreinstall
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  • RE: Wave disk engines to make hybrid vehicles cheaper, more efficient

    It would require an encyclopedia simply to list all the turbine applications developed over the past century. What turbines continue to dislike, however, is speed alterations. Change their speed and you lose much of their efficiency. That's one major problem with this work-in-progress that they are trying to address.

    The larger problem for automobiles, though, isn't with the prime mover, but with storage. Look under your hood, and the culprit will look right back at you. So while turbines have slowly improved over the decades, the battery really hasn't; at least it hasn't in sizes large enough to be useful on the Interstate. We like to pretend this problem doesn't exist and edge around it with hybrids or press releases. But it always reaches out and bites us.

    Having watched battery technology stagnate for more years than I care to admit, I'd guess we have a better chance of discovering a way to acquire alternating current at highway speeds.
    nikacat
    • Power generation is on or off

      That's an added efficiency. The turbine likes to go a constant speed to the batteries act like a temporary cache for electricity. While we're sitting in traffic the battery stores the extra energy we'll need to start from a stop. Currently, not only do we have to expend this energy, but we're wasting the energy that the engine burns while sitting still. This is how hybrids make their mark. The capacity of the batteries is a moot point since there is a power generator onboard that creates the electricity. The plus that nobody seems to be acknowledging is the separation of the need for torque from speed. The generator needs the speed while the wheels need the torque. Since there is no combustion lag in the conversion of energy to torque in an electric engine, the car will smoke the combustion engine off the line (and in distance, but that's not really a differentiator if the electric). Really, the fallacy are the ads of open roads with no traffic where an car can go at a nice constant speed.
      happyharry_z
    • So don't vary the turbine, vary the motor.

      a high-output diesel wave turbine driving a generator using a battery bank as a temporary storage/buffer system sending power to four independent coffee-can-sized electric wheel motors ought to kick ass. And you wouldn't need to recharge at a fill-up if the turbine is powerful enough to run the car at cruising speed.
      Geedavey
      • You just described a locomotive.

        They have been around for years and now the hybrid is all the rage. The first diesel over electric were WW1 U-Boats with massive battery banks. Those MAN Diesels were also steady rpm. The propeller was always driven by the electric motor. Wheels should always be driven by a motor and this gets rid of a gearbox.
        osreinstall