New internal combustion engine 3x as efficient!

[zahc]

http://www.msnbc.msn.com/id/42460541/ns/technology_and_science-innovation/

I'm trying to figure out exactly what makes this different from a turbine engine. If making a series hybrid using one of these is economically feasible, then why isn't making a series hybrid with already-invented turbine engines feasible? A turbine engine would also run on diesel.

[dogmush]

It's different from a traditional turbine because it's radial flow as opposed to axial flow. Also wave rotors operate at significantly lower RPMs then your more conventional turbines. That's why it can be so much shorter.  I think you'll find this runs on diesel or kerosene as well, just because of the properties needed for shock wave ignition.  It's a neat idea (that has been around for a while).  If they can shrink it and make it cheap enough it could work for a generators, and hybrid car engines.  As I recall it's not great for any kind of conventional engine arraignment because it takes a while to change RPM's and idles pretty fast.  It's better suited to constant RPM/Load applications.

Also:

Michigan State's team of engineers hope to have a car-sized 25-kilowatt version of the prototype ready by the end of the year.

Yeah, that's 34 HP.  Not exactly "car sized"

[RocketMan]

A very interesting idea.  Being that MSU came up with it, maybe that will allow it to gain some traction in Detroit.  Less of a chance of it being derailed by the 'not invented here' syndrome.

[zahc]

34 horsepower is probably plenty for a series hybrid.

[AZRedhawk44]

34 hp is plenty for a light car at constant power.  Use stored battery power for brief acceleration and hill climbs.  A 125 hp vehicle doesn't use 125 hp all the time.  I hear it only takes 10% of typical engine capacity to maintain highway cruise speeds.  City driving would be more demanding due to more stop and go, but still only average 25% engine utilization I think.

[Northwoods]

Yeah, most cars are ridiculously over powered considering what they're being asked to do 95% of the time.  I know with both my pickup and sedan it's very rare for me to use more than 75% of the capacity of the engines, and typical use is more like 10-30%.  I my truck I can climb a steep grade with a fairly full bed at half throttle and maintain highway speeds.

[230RN]

I hope they can figure out a way to generate electricity directly off the spinning rotor,  like a homopolar generator.

Terry, 230RN

REF:
http://en.wikipedia.org/wiki/Homopolar_generator

CAVEAT:
No jokes about those white bears who live waaaay up north.

[drewtam]

From what I can gather from the internet...

Ignition is caused by the compression temp and pressure. This would lend itself to a diesel fuel or kerosene fuel (jet).

The compression is caused by the radial compressor. To achieve pressures and temps needed for compression ignition, there needs to be another 3-5 stages of compressors to get the right pressure ratio and temp ratio.

The claim of a "shockwave" is vague, perhaps they are referring to a detonation event initiated at the outer edge of the compressor wheel when the exhaust port is blocked (the area of highest temp and pressure) that may radiate inward. Intentional detonation would lend itself to using gasoline.

This design could also benefit additional turbo expansion.

Based on the information I can find so far, the claimed efficiencies appear exaggerated. In addition, the claimed thermal efficiencies for other combustion engines are intentionally made lower than actual practice in order to make this device look better.

[birdman]

Hmm.  3G as efficient?  Most automotive engines are 25-30+% efficient, so this one is 75-90%?  I call BS, assuming it's operating on EARTH, 75% would require combustion temperatures of 900-2700 C (and that's assuming Carnot efficiency), real heat engines (even constant volume PDE (that what I believe the detonation part they are alluding to is) driven stifling or turbo-rankine cycles, would require hot-side temps of 1200-3000degC or higher, beyond the steady-state temps realizable for those types of engines without efficiency sapping cooling (like high perf. Jets).  I bet they are comparing to REALLY crappy engines (like a Briggs 5hp, which is <20%), in which case, their claimed performance is not much better than highly turbocharged, miller-cycle advanced diesels with direct injection and stratified charge ignition. 

These kinds of "new engines" (see the "six stroke engine") pop up all the time--eventually things will move in that direction (jaguar concept car turbine-hybrid), but it doesn't help the cause when they make crazy claims.

As for generating electricity, simply incorporating perm. Magnets in the compressor rotor would work for a brushless generator, no need for the high external fields or brushes of a homopolar (which is not very impedance matched to the types of loads it would be used for--too low of a voltage).  In fact, motor speed alternators of this type are common in microturbines (and also in motorcycles)

Anyway, my $0.02

[HankB]

These kinds of "new engines" (see the "six stroke engine") pop up all the time . . .

I'm a skeptic.

I've seen all sorts of articles on "super efficient" engines with catchy names like the "Tri-Dyne" or "Smokey Yunick's Adiabatic Engine" or "New Scotch Yoke Design" over the years, as well as miracle gizmos like the "Fish Carburetor."

So far, it's all baloney. Now and then there will be a modest incremental improvement, but it's hard to make a MAJOR upgrade to a mature technology.

[birdman]

I'm a skeptic.

I've seen all sorts of articles on "super efficient" engines with catchy names like the "Tri-Dyne" or "Smokey Yunick's Adiabatic Engine" or "New Scotch Yoke Design" over the years, as well as miracle gizmos like the "Fish Carburetor."

So far, it's all baloney. Now and then there will be a modest incremental improvement, but it's hard to make a MAJOR upgrade to a mature technology.

I think we are in agreement...I think.
My point was that heat engines are just that, and thus limited by materials.  The highest thermodynamic efficiency I've ever seen on a heat engine of any scale was 50-60%, and that was a:
Very large (scale reduces proportional losses) very high pressure ratio, advanced turbine alloy gas turbine (to maximize hot side temperatures) with a water/steam rankine bottoming cycle with multiple reheat/superheat stages, and a very low turbine exit pressure...running on methane to get the max combustion temps as high as possible...and that folks, is as good as it gets. 

Well, unless you built a hydrogen fueled fueled stirling engine completely out of hafnium carbide and operated it in deep space...then you could theoretically get really high efficiencies...of course, it would cost you billions.  :)

[AJ Dual]

I hear that's actually what they want to do for next-gen RTG's. Ditch the thermocouples, and hook them up to as perfect a sterling engine as possible with NASA money, and unobtanium uber-low friction components. Opposing pistons to cancel torques on the spacecraft...

Realworld, the radial disk might get 50%, not that it isn't worth pursuing.

[drewtam]

I think they are quoting the 3x efficiency by playing shell games...

the wave engine coupled to an electric generator/hybrid
vs
a 20% thermal efficient gasoline (like a 1960's engine) with typical automatic transmission losses.

They are making final efficiency comparisons not thermal efficiency comparisons, and comparing apples and oranges drivetrain designs. Which makes me even more suspicious of the actual capabilities.


By the way, Birdman, large ship low speed diesels currently achieve approx 50% thermal efficiency at rated power.

[birdman]

Good call on the diesels...I think the ICCG turbines are still the highest, but I forgot the large diesels were that high.

RTG's with stirlings...funny you mention that, I've done a bunch of work with LANL and MSFC on space nuclear power systems with opposing piston stirlings, and other systems (google "SAFE reactor" or "heatpipe power system" for the ones I worked on)...RTG's have their place, but we are going to need to go to real reactors, not isotope heat sources, in the near future--we need more and more power for the spacecraft, and our supply of '238 is pretty limited (and it has the "dreaded" P word)

[AJ Dual]

It would be cool if they ever did send it to Epsilon Eridani. Do you really think the turbine in the Brayton would last 78,000 years? Magnetic bearings or something? More likely, either humanity will collect the probe for the Epsilon Eridani IV museum of Galactic history that had been there for 77,000 years, or the Earth will be empty of humans. 

More realistically in our lifetimes, I'm thinking that drill-sub for Europa we'll hopefully do someday sooner is going to need stuff like that.

I know the PuO2 has the best characteristics for RTG's, but as you say, there isn't much left. IIRC, going to a Thorium economy with MSR's would give us lots of PuO2 for spaceflight, I believe. Although my thoughts on "proliferation concerns" are "meh"... Bad actors are going to do what they do anyway.

[birdman]

I like how you think, oddly enough the system we were working on was for the interstellar precursor mission (1/3rd of a LY in <25-50yr).  The bearing were foil bearings...look them up, very clever design, and they last A WHILE (I think there is a test system somewhere they started in the 60's and it's still going)

With the above power system, Rigel kent /alpha cent is "only" 300-600yr away, within range of what we can design for (remember, we had mAny modern materials and machining methods 150-200 years ago, so we know what "can" last.

I agree though, sending people isn't gonna happen unless a. You have to because the ship returns for me. B. use some sort of Near-c or FTL

As for thorium...there isn't any (or much much less than normal) Pu made in a thorium cycle--a TH/U cycle uses an initial U235 fraction to breed U233 from thorium...no Pu, unless you use LEU for the U, or use Pu instead of U for the starter

It would be cool if they ever did send it to Epsilon Eridani. Do you really think the turbine in the Brayton would last 78,000 years? Magnetic bearings or something? More likely, either humanity will collect the probe for the Epsilon Eridani IV museum of Galactic history that had been there for 77,000 years, or the Earth will be empty of humans. 

More realistically in our lifetimes, I'm thinking that drill-sub for Europa we'll hopefully do someday sooner is going to need stuff like that.

I know the PuO2 has the best characteristics for RTG's, but as you say, there isn't much left. IIRC, going to a Thorium economy with MSR's would give us lots of PuO2 for spaceflight, I believe. Although my thoughts on "proliferation concerns" are "meh"... Bad actors are going to do what they do anyway.

[kgbsquirrel]

Those foil bearings are neat but you would have to enclose the entire rotating device in a pressurized vessel for it to work. How much weight/complexity/maintenance requirements will that add and also what is the minimum atmospheric pressure for operation (I'm thinking of the Apollo and Lunar modules which operated at 5 psi, would that be sufficient)?

[birdman]

Well, we were running a closed cycle gas turbine (closed brayton cycle) using a helium /xenon mix, so the bearings were fed off the compressor and the whole thing was sealed anyway.  With 3 redundant systems, we estimated a 20+ year life at full power, which is all we needed (20 years @ 1/1000 of a g acceleration)

[RoadKingLarry]

I hope they can figure out a way to generate electricity directly off the spinning rotor,  like a homopolar generator.

Terry, 230RN

REF:
http://en.wikipedia.org/wiki/Homopolar_generator

CAVEAT:
No jokes about those white bears who live waaaay up north.

Are Eskimos still fair game?