A couple of engine designs 3

[GregLocock]

The Scuderi engine may appear at the SAE show in April.

Previous thread thread71-163878

Claimed advantages

http://www.scuderigroup.com/technology/theory_of_operation/summary_of_gains.html

Major Parameter Involved In Effecting BTE

Potential Increase In Points of BTE (Percentage Increase Over 33.2 Point Baseline)
1) Increased burn rates 5 points BTE (15% increase)
2) Use of ceramics to insulate the power piston and cylinder from heat losses due to the faster burn rates. 2 points BTE (6% increase)
3) Being able to run lean without the need for a three-way catalytic converter (TWC) 1 point BTE (3% increase)
4) Advanced piston motion features resulting from the second computer study, which allows more time for the power piston to build pressure during combustion. 1.4 points BTE (4% increase)
Total potential gains identified 9.4 points BTE (28% increase) (BTE from 33.2% to 42.6%)


The final report of the Southwest Research Institutes' computerized study is available upon request, provided the requesting party signs a non-disclosure agreement with the Scuderi Group, LLC.

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Commentary
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Note that the study is not based on hardware testing, that doesn't invalidate it but it is likely that the claimed improvements are greater than can be achieved by realistic working engines. There is no guarantee that the engine baseline (33.2%) is a valid starting point, the baseline engine may have its own advantages that are negated by the split cycle technology.

1) I don't see why burn rate is a good thing in itself. Diesels have a fairly slow burn rate and yet they are efficient.

2) Never seems to come true (it is important though)

3) Interesting, why does eliminating the 3WC help? I assume that means you can move into lean burn, but that militates aginst (1)


The following items are not mentioned in the table. They would all tend to reduce the efficiency of the engine.

5) Friction in additional piston and conrod rings and bearings

6) Pumping losses in transfer port

7) Friction in additional valve gear

8) Irreversible heat transfer effects in pumping operations

Incidentally, real SI IC engines with 38.4% (independently measured) efficiency are known technology.


Secondly there is this little beauty, sadly it seems defunct, if only they'd put as much thought into the engine as they have into the website

http://www.mce-5.com/introduction/index.htm

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[MikeHalloran]

The flows in the Scuderi engine remind me of those in something Triumph Motorcycles came up with in their death throes many years ago, a twin with stepped pistons that supercharged each other. I'd expect both to have odd heat/ differential expansion problems that could take a while to iron out. Triumpn ran out of time. Scuderi needs someone with deep pockets, and those are in short supply just now.



Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

It simply looks to me like a reciprocating piston supercharger.

I think they were in use before the start of last century, but due to lack of efficiency were discarded in preference for roots blowers, centrifugal blowers and turbochargers.

Re their claims, I think I agree with Greg.

1) I am not sure why the fuel would burn faster, but if (and that's a big IF) it did, later ignition but still optimal peak pressure timing means less pressure build up against the rising piston for equal pressure against the descending piston.

2) As far as I know, ceramics can be used on any piston engine. They are not used for reasons of durability and cost. I can't see where this engine would be different in that regard.

3) I absolutely agree, the TWC has no bearing on BTE. Lean burn only yields an improvement to a point. Once you can effectively burn all the fuel fairly close to TDC, less fuel means less power, not more thermal efficiency.
Bottom line, extra moving parts, cost, weight and friction for no real gains at best.



Regards
Pat
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[TDIMeister]

The claimed BTE improvement for each stated change is incredibly optimistic.

Furthermore, no internal combustion engine technology will pass Tier 2 Bin 5 automotive emissions limits (especially the NOx component) without some form of either a three-way catalyst or oxidation-cat + lean-NOx trap for lean-burn engines, no matter how clean the engine-out emissions are. Furthermore, rapid combustion and cylinder insulation are keywords for NOx emissions increasing. This is the bane of engine development.

Scuderi is not seen with a lot of respect in engine development circles. I was at the Engine Expo 2008 in Stuttgart in May of last year, and Scuderi had a prominent booth near the front of the main hall adjacent to the seminar stage. Several high-ups at engine development companies that I happened to stand next to whispered amongst ourselves that Scuderi is little more than a company run by a family with deep pockets derived from a whole bunch of different ventures; engines was just a pet dream of one of the family patriarchs. Their JVs with Ricardo and Bosch for the development of the air hybrid engine were brilliant strategy on all sides. Ricardo and Bosch gets to make money with little hope of the engine actually going anywhere, just like many ideas that come to development houses the likes of Ricardo, AVL, Mahle (formerly Cosworth Engineering), FEV, Lotus Engineering and Porsche Engineering. Scuderi buys in Ricardo and Bosch credibility among investors (who are the ones bankrolling everything) by having their names on the same line as their air-hybrid engine, and they also buy proper development expertise (Scuderi themselves don't; they're a company of a little over a dozen staff, mostly family members, with backgrounds in law and finance) They (Scuderi) are convinced their engine works; few others in the industry do.

 

[ivymike]

I wouldn't say that no tech. could possibly meet tier 2 bin 5 w/o aftertreatment. There are developmental stationary engine technologies which can beat those NOx levels by a factor of 2 or more (depending on how you convert from g/hp.hr to g/mi). There was a 2006 paper on hydrogen-assisted lean operation (HALO) where the authors got a small natural gas engine down to about 0.05g/hp-hr NOx. Admittedly, the load acceptance and power density might not be adequate for mobile operation, but perhaps a bit of dev't for a mobile application could sort that out.

 

[TDIMeister]

Scuderi's stated primary target for their air-hybrid engine is for mobile automotive applications, so within that context I considered T2B5/LEV II. For stationary and industrial appplications, other regulations apply but are nonetheless becoming evermore stringent particularly on NOx. An automotive application with T2B5 NOx limit of 0.05 g/mile over 120,000 miles requires a further order of magnitude reduction below 0.05g/hp·hr, and this over a wide load/speed range and highly transient operation, both banes to NOx formation.

I would really appreciate if you could share the title or source of that 2006 paper you allude to.

 

[TDIMeister]

My take on the claims (I do have literature to support but will take time to dig up and assemble; I include what I can right off the top of my head):
1) Increased burn rates 5 points BTE (15% increase)
Gains of this magnitude are customary in HCCI/CAI found in literature, but represent the ideal. VW's GCI (Gasoline Compression Ignition) saw a 15% decrease in BSFC from 371 to 315 g/kWh @ 2 bar BMEP / 2000 RPM. But at the current state-state-of-the art, HCCI/CAI cannot be done over the entire operating map but is restricted to a narrow range of moderate speed and load. Source: The GCI Combustion Process from Volkswagen, MTZ 04|2008.


2) Use of ceramics to insulate the power piston and cylinder from heat losses due to the faster burn rates. 2 points BTE (6% increase)
Numerous research from the 70s and 80s suggest this magnitude of efficiency improvement is possible. However, the problem that couldn't be resolved was NOx emissions going through the roof; reduced volumetric efficiency due to fresh charge heating; increased thermal stress (solvable); and extra cost of ceramic/coated components (any OEM's deal killer).


3) Being able to run lean without the need for a three-way catalytic converter (TWC) 1 point BTE (3% increase)
I agree with Greg Locock's hypothesis that the improvement stems from running lean. This magnitude of BTE increase is reasonable but neglects the reality of NOx in the current emissions regulatory environment.


4) Advanced piston motion features resulting from the second computer study, which allows more time for the power piston to build pressure during combustion. 1.4 points BTE (4% increase)
Research into sinusoidal motion cranktrains serve as a reference benchmark to aim for as the ideal. Some increase in BTE have been seen. However, it is entire possible to design a combustion system to achieve as close to a constant volume process as possible to get similar indicator diagram results using fancy cranktrain kinematics. However, doing so drives NOx once again through the roof, and additionally increases peak cylinder pressures and combustion noise.

So while all the above gains have precedent in other research, they are highly idealised and not at all realistic, feasible nor necessary desirable (e.g. noise and cost) as series production development goals or for meeting customer demands.
Total potential gains identified 9.4 points BTE (28% increase) (BTE from 33.2% to 42.6%)
Efficiency gains are NEVER simple additive stack-ups of individual improvements.

 

[ivymike]

NOx limit of 0.05 g/mile over 120,000 miles requires a further order of magnitude reduction below 0.05g/hp·hr

how many hp-hr does it take to go 120,000mi? If you were to average 25mph and 25hp, then 0.05g/hp-hr would equal .05g/mi over 120,000mi. to require another order of magnitude reduction using 25mph average, you'd have to average 250hp, yeah? That sounds a bit too pessimistic to me.

http://www.osti.gov/bridge/servlets/purl/885936-5UDKxt/885936.PDF

looks like the figure was 0.07g/hp-hr at 8% (by LHV) H2

 

[ivymike]

BTW, that level is very impressive for stationary SI engines (industrial, gas compression, etc), where the federal NOx limit is currently 2g/hp-hr, dropping to 1g/hp-hr next year. Some nonattainment areas have limited the emissions to 0.5g/hp-hr or even 0.15g/hp-hr via permit requirements. There might be some spots CA (?) that are even lower, but if there are I'm not aware of them.

 

[TDIMeister]

Mike, thank you very much for the link. I don't want to veer the discussion away too far from Greg's original intent to discuss the Scuderi engine, but I think it's appropriate and relevant to discuss the topic of NOx that tails in with the paper you linked to. However, I think a detailed discussion about that paper in a separate thread would be interesting.

First of all, this is a response to my assertion that there is no ICE technology that will meet Tier 2 Bin 5 regulations without exhaust aftertreatment. My professional engine development experience is in a mostly automotive paradigm (although I did work in a stint developing a locomotive Diesel), so I want to keep the discussion on automotive, not stationary applications, and along with that automotive emissions limits and testing procedures. This is in keeping with Scuderi's stated target application market.

I continue to stand by my position that there is no ICE technology that will meet Tier 2 Bin 5 regulations without exhaust aftertreatment, end stop. The paper you alluded to, and many papers of their kind, study on one or a very small number of operating points, and this on a steady-state test bench on highly controlled and rigorous boundary conditions. In the case of the paper you refer to, it's 1800 RPM at baseline rated IMEP. There, the engine under investigation is a 5.4L Ford V8 engine with a baseline rated power of 54 kW, which the author says is representative of the size and output of natural gas stationary gen-sets. Fine.

However, the stated 0.07 g/HP·h BSNOx figure represents the best point at that one operating point, and a steady-state point at that. There have been lots of attempts to extrapolate and predict emissions in a transient drive cycle out of a limited number of discrete, steady-state operating points (and I have been involved in research with my employer on this very thing). So far, suffice it to say the models have been inadequate. It is to date very difficult to correlate discrete steady-state emissions data in g/HP·h into a continuous transient test such as a driving cycle like FTP-75/NEDC, and the correlation deteriorates with fewer operating points. But some patterns and trends emerge. I didn't go and do a detailed calculation to come to the conclusion that 0.07 g/HP·h BSNOx will not meet T2B5 of 0.05 g/mile on a driving cycle; rather, from working experience in emissions calibration and having a knowledge of some typical BSNOx figures at discrete operating points of compliant vehicles, I assess that one needs to go substantially better than 0.07 g/HP·h BSNOx to meet T2B5 if no aftertreatment is used.

Back to Scuderi. If the claims of not requiring aftertreatment holds any water, it would require at least a comparable BSNOx as in the paper above over much more than a single operating point. Nothing in the technology that Scuderi offers suggests to be able to do that (e.g. HALO).

As for the 120,000 mile thing, that is merely the EPA's durability requirement on the engine and aftertreatment system. All this means is that the engine and aftertreatment system must remain at a functional level such that the regulated emissions remain under the respective limits when tested over a specific driving cycle. An engine that just squeaks by under the limits when tested new is unlikely to comply at 120,000 miles, so the development process has to leave substantial margin and also account for every conceivable usage scenario.

And there's where the difference emerges between invention and the stark reality of development. IMO many companies touting the next great engine is rich on the former but lacking on the latter.

 

[Lou Scannon]

Well said, TDI.

 

[JSteve2]

Looks like a Miller cycle, only with more delicate and expensive hardware. Efficiencies are quoted at the ideals, and even for that don't end up achieving much more than other optimized products. I think the Atkinson cycle Prius runs about 38% thermal efficiency. Super-charging with super-fast combustion should lead to increased NOx, unless the timing retard is significant, in which case their efficiency will not be that good.

Probably, as suggested above, this is just a delicate lab mock up that would be difficult to convert to a robust real application.

 

[SomptingGuy]

This is an odd page on their site:

http://www.scuderigroup.com/patent/patent_portfolio.html

The bit that starts with "Advantages to licensing" descibes all the benefits to the Scuderi people (95% profits, etc). Why would they want to share this with potential customers.


I wonder how many people will license the technology and build engines?

- Steve

 

[JSteve2]

I'm pretty sure the licensing page is directed to would-be investors, although future customers of course can see it. Interesting that they state they are protected for "at least" the next 20 years, when of course that should be "at most" the next 20 years depending on filing dates, etc.

 

[patprimmer]

Unless I missed something, any home mechanic could rig up a simple test rig by linking two engines at the crank on a one to one drive by whatever method and running a pipe from the exhaust port on one to the inlet port on the other.

Regards
Pat
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[BrianPetersen]

Pat, it's not quite that simple, because the transfer from one to the other happens at the maximum cylinder pressure, which is not very easy to do (!).

 

[patprimmer]

So it would need some custom made cams or valve control devices to simply prove the principle. Beyond the home mechanic, but still probably a lot cheaper than their website to set up and produce real test results.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[tbuelna]

BrianPetersen hit the nail on the head. The reason I would be skeptical of Scuderi's efficiency claims is because (unless I'm missing something) of the high flow, valving and blow-down losses that occur during the transfer of the compressed working gas from one cylinder, past a valve and into a transfer port, past another valve with very poor flow characteristics (due to its high operating frequencies), and then finally partially expanding into a combustion space.

On the other hand, I might partially believe the low NOx claims, since the initial charge temperature in the combustion cylinder at the start of combustion could be lower than a conventional recip. engine. That would help with NOx.

I can also see issues with thermal loads in the combustion cylinders. Having nothing but combustion and exhaust events, with no intake or overlap flows in your cylinder, would put very high thermal loads on the piston, rings, liner, exhaust valves and exhaust valve seats.

Finally, there would also be minor issues like vibrations arising from the unequal pressure forces acting on the pistons of of the opposing cylinder banks.

Regards,
Terry

 

[Lou Scannon]

If they really wanted to promote their concept based on its technical merit, wouldn't they be illustrating the cycle in P-V and T-S diagrams, using measured or at least modeled data?

 

[BrianPetersen]

The people that they are really interested in attracting probably don't know what any of that means.