Wave Disc Engine/Generator for Series Hybrids

[NeilBlanchard]

Hello,

This is a new one on me:

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

Researchers from Michigan State University have been awarded $2.5 million from the Department of Energy’s ARPA-E program 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.

(emphasis is mine)

Here's a picture of the main parts:

[dcb]

not sure where 5 times more efficient comes from, as the comments say it would be more than %100 efficient then. But an interesting configuration though.

[Christ]

Noticed that myself. Did the gov't just fund over-unity studies?

[Rokeby]

I read the linked article but the references to intermixed diesel, turbine and
two-cycle pressure wave scavenging has my head spinning.

I'm not entirely sure how this device works. I take it that the useful output
is the rotation of the disk (at what rpm?) Just how does that occur?

At the point of ignition, the now pressurized charge seems to be contained
in a fixed volume, then the disc rotation opens the exhaust port.
Is it a matter of every action -- the release of the exhaust -- has an equal
and opposite reaction -- force applied to the disk causing it to spin?

I also take it that the boundary between the new incoming charge and the
old burned charge in the open chambers is maintained by a moving
pressure wave. Very subtle.

Am I even close to understanding what's happening here?

[dcb]

ignoring the shockwave bit, it seems very two stroke-esque, the intake and exhaust ports are open at the same time. *maybe* then can get it to run cleanly at a very specific rpm/load.

But, then again, this is basically a turbine, the only torque being generated seems to be from the gasses escaping out the exhaust port, and what keeps them from blowing back up the intake instead is beyond me at the moment, or why it should be better than a normal turbine with a distinct combustion section.

[NeilBlanchard]

Yes, I think that is how it works.

Someone on another forum found an interview where they explained the "5X" number: in a series hybrid vehicle, this engine is 5X more efficient than an SUV, and it is 3.5X more efficient that a current parallel hybrid. Only a bit more helpful, but still pretty vague...

[Rokeby]

Originally Posted by dcb

ignoring the shockwave bit, it seems very two stroke-esque, the intake and
exhaust ports are open at the same time. *maybe* then can get it to run
cleanly at a very specific rpm/load.

Two-strokesque for sure. Both the intake and exhaust ports are not only
open at the same time, they are open all the time! However, for any
particular combustion chamber, only one port is open at a specific point in
the disk's rotation.

But, then again, this is basically a turbine, the only torque being generated
seems to be from the gasses escaping out the exhaust port, and what keeps
them from blowing back up the intake instead is beyond me at the moment,
or why it should be better than a normal turbine with a distinct combustion
section.

Yes, like a turbine, it has a single moving part, the disk. The operational
RPM range would be strictly regulated by the velocity of
propagation/reflection of the pressure wave across the chamber. That
velocity may not be constant due temperature, pressure, and density
variations in the chamber.

I suspect that the efficiency of the the device is a function of the sealing of
the chamber inner and outer ends in the brief rotational period between
ignition and exhaust of the hot gases. The difficulty is probably keeping the
sealing device(s) from dragging throughout the disk's rotation.
(Thinking of a Wankel's wipers/seals.)

Does this device require metered/premixed lubricant to be added to the
intake air stream?

A fascinating device that clearly shows thinking outside the proverbial box,
in this case the cylindrical box of the piston/cylinder, a turbine's
cylindrical combustion space, or the two-strokes twisted, essentially
cylindrical exhaust tract.

[jamesqf]

Originally Posted by NeilBlanchard

YSomeone on another forum found an interview where they explained the "5X" number: in a series hybrid vehicle, this engine is 5X more efficient than an SUV, and it is 3.5X more efficient that a current parallel hybrid. Only a bit more helpful, but still pretty vague...

I'd think a lot of that has to be a comparison against "normal" IC engine use, where it's operating far from the max BSFC. Now if you put the engine in a Volt-like hybrid where it's always running at max efficiency, the numbers would be different.

What puzzled me most was the claimed reduction in CO2: that's a fixed relation with fuel burn, so the number should be exactly the same as efficiency increase.

[Rokeby]

Since reading the OP, I've been wondering just how big the device is...
as big as a birthday cake... a tea cup... a 35mm film canister?

There is a similar thread running on CleanMPG. In it the poster, Brick, gives
a link for a research summary on what I take to be an earlier version, 2005,
of a similar device.

Some key phrases that give a fuzzy indication of its size:

"micro turbo engine," "micro scale"

"Wave disk can be formed as two parts etched together..."

"The electric motor-generator can be imprinted in the case parts
containing ports and in one of parts forming a wave disk..."

"All the presented below results correspond to the case of heat release
steam equal 800 W and disk rotational speed equal 176 500 rpm.

I'm now thinking that these devices are the size of a dime, or a shirt button,
or even the head of a pin. Seems like the air filtration requirements would be rather strict... Not "For off-road use only"

The thread at CleanMPG:

MSU receives $2.5 million DOE award to build advanced hybrid engine - CleanMPG Forums

[dcb]

FYI, The OP link says it is for autos and is "About the size of a large cooking pot"