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Michigan State University Receives $2.5M ARPA-E Award to Build Wave Disc Engine/Generator for Series Hybrid Applications

Schematic model of a wave disk engine, showing combustion and shockwaves within the channels. Source: MSU. Click to enlarge.

Researchers from Michigan State University have been awarded $2.5 million from the Department of Energy’s ARPA-E program (earlier post) to complete its prototype development of a new gasoline-fueled wave disc 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.

The wave disc engine, a new implementation of wave rotor technology, was earlier developed by the Michigan State group in collaboration with researchers from the Warsaw Institute of Technology. About the size of a large cooking pot, the novel, hyper-efficient engine could replace current engine/generator technologies for plug-in hybrid electric vehicles.

The award will allow a team of MSU engineers and scientists, led by Norbert Müller, an associate professor of mechanical engineering, to begin working toward producing a vehicle-size wave disc engine/generator during the next two years, building on existing modeling, analysis and lab experimentation they have already completed.

Our 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 also can reduce carbon dioxide emissions by as much as 95 percent in comparison to modern internal combustion vehicle engines.

—Norbert Müller

The Wave Disc Engine. The wave disc engine is a new implementation of wave rotor technology (also called Pressure Wave Machines or Pressure Exchangers). Wave rotors 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. Wave rotor technology has shown a significant potential for performance improvement of thermodynamic cycles.

Hyprex pressure wave charger. Source: Swissauto Wenko. Click to enlarge.

Wave rotor technology has been explored since 1906, although its first significant application was in 1940 by Brown Boveri Company (BBC, today ABB) which used it as a high pressure stage for a gas turbine locomotive engine. In 1986, Mazda introduced the Mazda 626 Cappela model, which had a 2-liter diesel engine equipped with a Comprex wave rotor (from BBC) used as a supercharger. Mazda produced 150,000 Comprex diesel cars. Other car manufacturers including Opel, Mercedes, Peugeot and Ferrari used the Comprex. Swissauto Wenko AG of Switzerland produces a modern version of the Comprex—the Hyprex—designed for small gasoline engines.

Earlier wave rotor implementation were mainly axial flow. In axial-flow configurations, noted Müller and co-authors in a 2004 paper, pure scavenging is a challenging task. Although it is 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.

This 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. With curved channels also the angle against the radius can be changed freely. This allows modulating of the inflow direction acting accelerating component of the centrifugal force and also to choose the inlet and outlet angle independently.

The latter enables independent matching with the flow direction through the stationary inlet and outlet ports or the use of a freely chosen incidence angle for a self-driving configuration. Furthermore, curved channels may be more effective for self-propelling and work extraction in the case of a wave turbine or work input for additional compression, analogous to the principle of turbomachines.

—Piechna et al. (2004)

The earlier MSU investigations of wave rotor and radial wave rotor technology were exploring gas turbine applications in addition to supercharging or refrigeration. In a gas turbine application, the team noted, positioning the combustion process internally in the wave rotor could simplify porting between the turbo-compressor and the wave disc “enormously”. This led to a proposed concept of a Radial Internal Combustion Wave Rotor—the precursor to the wave disc engine.

Piechna   Early concept of an internal combustion wave disc engine. The fuel supplies (green) are located at the inner inlet port. The mixture in the channel is ignited either by a stationary igniter acting through holes in the channel (yellow) or by rotating electrical igniters activated only in a certain angular position of the mixture-filled channel.

The air-fuel mixture can be radially stratified. Combustion starts in the central part of the channel, where the fuel/air mixture is rich and flame propagates to inner and outer end of the cell. Since heat release increases pressure inside the channel, opening the outer channel end generates an outflow of the exhaust gases. For curved channels, torque is given to the disc during the flow scavenging.

This can be used for self-driven rotation or for external work extraction through a shaft or a generator. The outflow of the burned gases can induce an inflow of air and air-fuel mixture into the channels, refilling and cooling the cell before the cycle starts again.

Source: Piechna, 2004. Click to enlarge.




Not a lot of money, and a decent school is doing the research...hopefully some "Piled higher & Deeper" students can actually generate some meaningful & useful information for industry, rather than come up with a bucnh of fluff & have their degrees paid for.


5x more efficient. The Volt will use a normal 4 cyl engine to generate electricity. Should be about 35% efficient. So these guys are targeting 175%?


5x more efficient could refer to it using 1/5 the fuel, or producing 5 times the power from the same size configuration.


Standing on your head from the southern hemisphere, It could mean 1/5th the inefficiencies of convention.
That would be ~60% losses div by 5 so 12% losses?
I'm still trying to figure how dogs do what doggies do.

Roger Pham

This is a very clever idea. Combining the standing wave pressure with the centrifugal pressure of the centrifugal compressor create higher pressures than possible with just a single stage of compressor, or with a straight-tube standing wave like in the tuned pipe of a 2-cycle engine. Then, by having combustion right within the compressor simulate the cycles of a Diesel engine or Otto engine. The intermittent combustion with cooling by intake air allows for higher peak combustion temperature without expensive nickel alloy as would be required for conventional gas turbines. This is like a marriage or a cross breed between a piston Diesel-cycle engine and a turbine engine, with combined advantages of both: The smooth running and higher power to weight ratio of a turbine combined with the low cost and higher efficiency of a Diesel engine, minus all the complicated valves and cooling system and lubrication systems.

The disadvantage would be that this disk wave engine can only operate at a very narrow range of rpm that enable a standing wave in order to maximize efficiency. Therefore, it can only be used to generate electricity. Furthermore, the intermittent combustion at higher peak temperatures would introduce the emission problems similar to Diesel engines: NOx, PM, HC and CO.

The 5-folds increase in efficiency over that of an auto engine is either hype or typographical error. It's efficiency cannot exceed that of a Diesel engine, having to operate within the same thermodynamic principle/cycle and suffering from the similar losses such as leakage at the edges of the blades, heat transfer loss, and heat loss in the exhaust. Still, we can expect the efficiency to be significantly higher than that of a gas turbine at comparable output.


The only recent application of these type engines appear to be as supercharger on a producton run of early Mazda cappelas and same on industrial engines. The operating term is wave disk (charging).

This Co. took over Comprex in '98, but no longer appear to be involved in any manufacture. They seem to have some rather nice loking ICE motors in the market place.

Geothermal power is thought a possible fit, otherwise Various similar resigns from the early 18th century -Tesla (Nicola) based disc rotary turbines ) to todays 'air engines' or 'detonation engine' (in concept.)


5 times less *frictional* lose sounds about right.
Talk about guessing games.


Perhaps they meant 5x specific power density? Frictional losses will definitely be significantly lower than a traditional piston engine. Hope they manage to pull this off as it seems it would be an ideal genset for a PHEV: cheap, light, power dense, and efficient.


If one assumes 5 times the energy density and 1/5 the cost, if could make a better flex fuel genset for future PHEVs, if it can be developed fast enough.


Isn’t this thing is just a turbocharger substitute, not an engine?

These pressure exchange superchargers are NOT new and have always OFFERED improvements (higher efficiencies, etc.) than a turbocharger but have not delivered.

Maybe modern computing power will be able to control the rpm to better optimize the "Pressure Exchange" – maybe not.
Maybe this manifestation is more efficient, - maybe not.

When they claim a five fold improvement in an old technology,their credibility usually drops 5 fold for me.

I am getting the impression that universities are not very motivated to monitor the claims made by various departments or students.


This gasoline electric generator is way better then the GM volt electric generator. The electric generator of the volt is just an approximation made with bolt-on innadapted old fart 4 cyl engine, LOL. I always knew that for an electric generator it take a compact engine spinning in his efficiency zone. It will do 5x mpg then the volt and drive better because of fewer weight. Im curious to see some other designs too for electric cars.
Just a battery for a car is not a solution. It take a battery + small inboard electric generator.

One other possible design is a hydraulic fluid motor car
with a diesel or gasoline pump/engine, it accumulate pressure in a hydraulic reservoir and that drive the motors, it can do 130 mpg.

It's the most inportant invention needed now,, small inboard gasoline or diesel electric or pressure generators for furur green car with 100 mpg and more. This wave disk seem perfect, im already interrested to buy.


@ a. b.
Whether this could perform as a hydraulic pump depends on its RPM and torque at peak efficiency w/acceptable emissions. Hydrostatic heavy equipment seems to run a diesel at mid rpm's maybe 2000 to 2500??
Other posts have shown hydraulic accumulation to be potentially more efficient than generating electricity.
I don't think hydrostatic drive is capable of powering a car at freeway speeds. However my knowledge of this is limited.


The most recent details on Volt's 1.4L genset is it will operate at variable 1200 to 4000 RPMs and from a 30% to 100% load. According to Volt engineers this allows better control in charge sustaining mode. And they are trying to limit mechanical vibration for "comfort." So this type engine might need further modification to best meet the demands of a real world HEV.

It would make a good genset for marine house battery banks or portable APUs.

Kevin Cameron

I'm very skeptical about Müller's claims for this device:

1) Whatever the shape and configuration of the rotor vanes, no torque can be generated unless there's a correspondingly large angular momentum imparted to the exhaust gas in the opposite direction. Getting a lot of angular momentum from exhaust gas means that the velocity must be large. High exhaust velocity implies a lot of kinetic energy remaining in the gas which implies a lot of wasted energy.

2) I don't see how it can match a more conventional turbine which is doing well to achieve even half the efficiency of a piston engine in the small sizes Müller proposes. From the description and drawings, combustion would occur at about half the rotor's radius which means that the pressure ratio would be about half that available from a conventional centrifugal compressor of the same size and RPM. Pressure ratio is the prime predictor of a turbine engine's efficiency. On top of that is the above mentioned limitation in converting heat energy to rotation.

3) The over-the-top performance claim (5X efficiency) is a red flag. Such statements are typical of both fraudsters and those without sufficient technical knowledge to correctly analyze their ideas. If the claim was a 20% improvement, it would hold my interest better.

If there was some practical way to do it, I'd give you 5 to one odds that no such engine will ever achieve even 40% efficiency.


I still say it is just a "turbocharger" not an engine.

The angled vanes can only rotate the disk weakly - they could not provide significant power.

A turbo charger can be considered a turbine engine but can then only provide thrust (or drive drive a turbine).

This thing makes NO sense as presented here.

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