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#1 gruntguru

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Posted 08 December 2014 - 22:58

Dedicated Exhaust Gas Recirculation. The test engine (at SwRI) is a four cylinder with the entire exhaust from one cylinder being recirculated to the intake. The EGR generating cylinder is run rich which reforms some of the fuel to H2 and CO. The combination of 25% (cooled) EGR and the reformed fuel products has enabled 14:1 CR, low emissions and 42% BTE from the NA test engine. PSA will implement a turbo version by 2018 - you would expect even higher TE.

 

http://www.greencarc...r-20130204.html

 

It is difficult to say whether this technology would benefit an F1 PU. The big question would be - do the benefits carry over to a lean burn environment. (The DEGR system described runs at stoichiometric with 3 way cat.)

 

 



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#2 Kelpiecross

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Posted 10 December 2014 - 02:16


How would this engine compare to a conventional engine with a 14:1 CR Atkinson Cycle (by LIVC)?

#3 gruntguru

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Posted 10 December 2014 - 03:40

I guess it may have similar part throttle pumping efficiency ie higher manifold pressure due to the 25% egr as opposed to say 25% mixture rebreathing in the LIVC engine. At higher revs the VE of the LIVC would improve but it would be more knock prone and have higher NOx emissions at all speeds.



#4 manolis

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Posted 10 December 2014 - 05:39

Hello Gruntguru.

It seems like Honda’s Activated Radical Combustion 2-stroke project

exp11.gif

wherein a good part of the burnt gas was, at partial load, not allowed to exit from the cylinder. It could run, at some conditions, without a spark. An experimental 400cc motorcycle was at Paris-Dakar race.


According Terrence Alger of SwRI:
"the lab currently has a 2.0-liter engine running as a full D-EGR engine from idle to full load"

It is strange that they use full D-EGR at full load. Reasonable question would be: what is the peak power from their 2.0-liter naturally aspirating engine?


From Green Car Congress:

“In the inaugural study reported in an SAE paper in 2009 (2009-01-0694), SwRI ran a 4-cylinder engine with cylinder 1 exhausting directly to the intake manifold, leading to a constant 25% EGR level.”

“The new engines, due to be available in PSA vehicles by 2018, will consume 10% less fuel than their predecessors across all uses, according to PSA.”

While the improvements they claim are so significant, they proceed towards production very slowly.


Other reasonable questions:

Are things better or worse in the case of a 3-cylinder (33% D-EGR), or of a 5-cylinder (20% D-EGR), or of a six cylinder (17 or 33% D-EGR).

How the different conditions the D-EGR cylinder operates affect the engine? (reliability, smoothness / vibrations).

Thanks
Manolis Pattakos

#5 gruntguru

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Posted 10 December 2014 - 23:36

In round terms you would expect the peak power to be 75% compared to the same engine without DEGR since 25% of the intake flow is EGR. This is offset somewhat by the higher efficiency - if 10% better, the power would be 82.5% of normal.

 

The article lists "misfire and stability; control; boosting; and design and materials" as challenges for the technology. If these challenges still exist at the 25% EGR level, it is probable they have discounted higher ratios. OTOH the benefits no doubt diminish as EGR percentage is decreased.



#6 desmo

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Posted 11 December 2014 - 03:55

Specific outputs are really pretty meaningless in the real world though.  Efficiency, cost and packaging are all far more important.



#7 kikiturbo2

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Posted 11 December 2014 - 10:18


While the improvements they claim are so significant, they proceed towards production very slowly.


 behh

 

Engines are one of the most complicated systems in a motor vehicle and ones with the biggest ammount of logistics involved behind the scenes. When a manufacturer developes a line of engines it is not that easy to just drop everything and switch to something else quickly... also there are other issues like endurance testing.. etc...

 

Unless you are VW and your engines go POP on a regular bassis.. then you just throw it out of production after 2 years and make a new one.. :)



#8 TDIMeister

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Posted 11 December 2014 - 20:49

The problem I have with DEGR is two-fold (I might add more as I think them up while typing this).  First, you take a normal inline, 4-stroke 4-cylinder engine architecture.  You leave one cylinder (I'll arbitrarily choose #1) out of making any power and you get a firing order of x-3-4-2-x-3-4-2... and firing intervals of 360-180-180-360-180-180...  As a practical matter, the NVH characteristics will be like a 4-cylinder engine running on only 3; we've all probably had experiences of this - rough and simply icky sounding and nothing you can do can right this because of the funky firing and exhaust intervals.  The second challenge with which to deal is the torsional harmonics of the now uneven firing order.

 

I think there are other, more elegant solutions... one might be to set up the crankshaft to have 120° pins on the 3 firing cylinders so that it's just like a normal 3-cylinder, then the question is how to deal with the balancing of the lone cylinder, ostensibly attached on the same crankshaft?  Yet another solution that might work better is a 3- or 5-cylinder engine wherein the middle cylinder supplies the DEGR and the other remaining cylinders are arranged as even-fire inline-2 or inline 4s, respectively; in the former case, the DEGR cylinder is at 180 degree phase to the other 2 cylinders and in the latter, the DEGR cylinder is in the same phase as one of the other pair of cylinders but the masses are in such a way that primary force balance like in an inline-4 is maintained.



#9 gruntguru

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Posted 11 December 2014 - 21:35

The four cylinders all make (similar) power.



#10 TDIMeister

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Posted 11 December 2014 - 21:42

OK, I see it now.  My bad.  I seized on this and made an error of conclusion.  I took it to mean that chemical reformation is exclusive of combustion per se.  I don't see for a moment how DEGR would then be different or better to take exhaust from just one cylinder and feeds it back to the remainder instead of taking EGR from the complete pool of exhaust gases from all cylinders in the manifold. 

 

 

The D-EGR concept also combines the high efficiency potential of in-cylinder gasoline reformation. Under D-EGR, excess fuel is sent to the cylinder dedicated to producing the recirculated gases, the hydrogen (H2) content of which then increases. The reformate along with the EGR is distributed to the other cylinders. The resulting H2 levels increases EGR tolerance; increases knock resistance (i.e., higher compression ratios); reduces emissions; and improves fuel consumption.

 

I still don't like the implications on exhaust note and the uneven pulses that will arrive at the turbocharger turbine.  


Edited by TDIMeister, 11 December 2014 - 21:44.


#11 TDIMeister

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Posted 11 December 2014 - 22:01

This opens up a whole new avenue of discussion: Why would one waste the packaging space, weight and complexity of dedicating one cylinder to producing EGR/reformate when one can and should use a dedicated reactor/reformer (with ostensibly no moving parts), where one can much more finely tailor and control the produced species for the objectives of in-cylinder dilution and combustion enhancement?

 

Also, when I hear of running one cylinder perpetually rich, I think of fuel wash-down into the cylinder and engine oil and all the other negative impacts.  I have met Terry Alger at conferences before and I highly respect the work that he and SWRI does.  But my intuition leads me to think that this approach is not going anywhere far but may be a springboard for future developments.



#12 Greg Locock

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Posted 11 December 2014 - 22:21

It takes about 7 years to get a clean sheet engine into production, for a big company, about the same as a clean sheet transmission. Of that about 4 years is actual recognisable work, the rest is waiting!



#13 gruntguru

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Posted 12 December 2014 - 00:37

TDIM, I assume the "rich" cylinder is not rich enough for bore washing etc. Bore washing implies high levels of unburned HC - this concept seeks to produce CO and H2 but not HC.

 

Obvious advantages of the proposed architecture include precise, fixed EGR metering and controllable reformer - all without a control system, metering valve, external reformer etc. I don't see a weight penalty?


Edited by gruntguru, 12 December 2014 - 04:16.


#14 TDIMeister

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Posted 12 December 2014 - 03:19

I'm revising to go back to my original position.  The cylinder must make power or not.  Combustion or reformation.  It cannot be both.  Partial oxidation reforming of a hydrocarbon to form hydrogen produces only a fraction of exothermicity as conventional, complete combustion, meaning the one cylinder dedicated to the job will be putting out much less power than the rest, not likely enough to overcome the friction associated with that cylinder, with all the implications of my original post.  The weight penalty is thus to carry along an extra cylinder and all of its extra bits to accommodate it - longer and more material for the block, crankshaft, valvetrain, etc.) rather than having all cylinders firing so-to-speak.

 

Striking the extremely fine chemical equilibrium to get only CO and H2 but no HC is all but impossible and would require a catalyst and a continuous process - like in a dedicated reformer - and not intermittent like in an engine cylinder.



#15 gruntguru

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Posted 12 December 2014 - 04:24

The EGR cylinder is simply run rich - perhaps 0.9. Not at all unusual in SI engines you would agree. The other three cylinders would need to run 1.0 to give 1.0 at the cat and tailpipe. Power will be very similar, perhaps 3% or 4% higher in the rich cylinder.

 

Some HC would be produced of course (and burned in the lean cylinders) but you are not in a bore-washing situation - even if the rich cylinder ran at say 0.8



#16 Canuck

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Posted 12 December 2014 - 06:20

It takes about 7 years to get a clean sheet engine into production, for a big company, about the same as a clean sheet transmission. Of that about 4 years is actual recognisable work, the rest is waiting!

As a cog in a very large corporate machine. I'm impressed with just three years of waiting in a seven year cycle. There is nothing so slow as a well processed and procedured company.

#17 imaginesix

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Posted 12 December 2014 - 07:23

As a cog in a very large corporate machine. I'm impressed with just three years of waiting in a seven year cycle. There is nothing so slow as a well processed and procedured company.

On the other hand, how often do they have to throw out the results and start again from scratch?

#18 TDIMeister

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Posted 12 December 2014 - 13:09

I don't have a problem with the concept if all the DEGR cylinder is doing is operating at some percentage rich of stoichiometric, but it's a misnomer then to call the product of its exhaust "reformate" and its overall process reformation, which is a precise and well-defined chemical process; the products of rich combustion are very well known and yes, HC makes a substantial part of it.  But we don't actually know what's the mechanics behind SWRI's concept, do we?  The GCC article is very sparse on details.  I'll do some more digging.

 

4gaschart.gif


Edited by TDIMeister, 12 December 2014 - 13:12.


#19 TDIMeister

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Posted 12 December 2014 - 13:23

OK, the key is post-injection:

http://www.google.co...s/US20140196702

 

 

1. A method of controlling the ignitability of the charge provided to combustion cylinders of an internal combustion engine, the engine having an ignition system and an exhaust gas recirculation (EGR) loop such that at least one of the combustion cylinders is an EGR cylinder that generates an EGR stream carried only by the EGR loop, and in which the charge is a mixture of air, fuel and recirculated exhaust, comprising:

receiving combustibility data representing the current ignitability of the charge;
determining whether the energy of the ignition system is sufficient to ignite the charge; and
if the current energy of the ignition system is not sufficient to ignite the charge, increasing the amount of hydrogen in the EGR stream.
2. The method of claim 1, wherein the step of increasing the amount of hydrogen in the EGR stream is performed by providing a more rich air-fuel ratio to one or more of the EGR cylinder(s).
3. The method of claim 1, wherein the step of increasing the amount of hydrogen in the EGR stream is performed by providing post-combustion fuel injection to one or more of the EGR cylinder(s) for one or more engine cycles.
4. The method of claim 1, wherein the step of increasing the amount of hydrogen in the EGR stream is performed by injecting hydrogen into the EGR stream.
5. The method of claim 1, wherein the step of increasing the amount of hydrogen in the EGR stream is performed by injecting fuel into the EGR stream and using a reformer catalyst to generate hydrogen from this injected fuel.
6. The method of claim 1, wherein the combustibility data comprises the quantity delivered to the cylinders of one or more of the following: air, fuel and/or recirculated exhaust.
7. The method of claim 6, wherein the combustibility data further comprises data representing the in-cylinder pressure and/or temperature.
8. The method of claim 1, wherein the step of increasing the amount of hydrogen is performed by providing a calculated increase in hydrogen.
9. The method of claim 1, wherein the step of increasing the amount of hydrogen is performed by increasing the hydrogen incrementally until ignitability is achieved.


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#20 gruntguru

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Posted 12 December 2014 - 23:32

Interesting, thanks TDIM.

 

Post injection appears to be an optional strategy required for higher loads etc. It seems that the steps for increasing the hydrogen are claims 1, 2, 3, 5 in that order of priority. (Claim 4 requires a hydrogen supply).

 

The only reason for using a dedicated cylinder for EGR production is to allow that cylinder to be run rich, which seems to be the case even when "post cylinder" enrichment is employed (strategies 4 and 5).



#21 GdB

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Posted 20 December 2014 - 02:52

Dedicated Exhaust Gas Recirculation. The test engine (at SwRI) is a four cylinder with the entire exhaust from one cylinder being recirculated to the intake. The EGR generating cylinder is run rich which reforms some of the fuel to H2 and CO. The combination of 25% (cooled) EGR and the reformed fuel products has enabled 14:1 CR, low emissions and 42% BTE from the NA test engine. PSA will implement a turbo version by 2018 - you would expect even higher TE.

 

http://www.greencarc...r-20130204.html

 

It is difficult to say whether this technology would benefit an F1 PU. The big question would be - do the benefits carry over to a lean burn environment. (The DEGR system described runs at stoichiometric with 3 way cat.)

 

 

I definitely believe an F1 PU with D-EGR would have a big race advantage.  

The 1.6L spec with MGU powered compressor is ideal for D-EGR application.  MGU-H eliminates any turbo lag issues.
10% more efficient = 10% more power with limited fuel!  
Also maybe a bit more power is available by using higher energy content fuel with lower octane.
Seems almost weight neutral
Higher intercooler temperatures might be an issue or not.  Maybe more cooling drag.  Seems the same air flow will allow more heat loss with a hotter intercooler.

It's particularly interesting how Honda is taking an extra year to develop their PU.  Extra time to try D-EGR?  Also the different exhaust tone is a clue.

We will not know until we get clear views of exhaust manifolds on both sides of the PU.

PSAD_EGR.png



#22 GdB

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Posted 20 December 2014 - 02:56

A D-EGR motorcycle engine would also be interesting to get lots of power without the horrible MPG due to throttling losses.

600’s getting MPG in the 40’s seems terrible.



#23 TDIMeister

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Posted 20 December 2014 - 19:03

Not going to happen in F1.  Very unlikely to happen in motorcycles either.



#24 gruntguru

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Posted 21 December 2014 - 23:41

Agreed. While the benefits are impressive on emission regulated engines with stoichiometric exhaust, I doubt there is any efficiency benefit for lean engines like F1.

 

Motorcycles? I don't think throttling losses is the biggest issue addressed by DEGR nor is it the biggest issue hampering motorcycle fuel economy.



#25 TDIMeister

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Posted 22 December 2014 - 00:16

F1 engines are decidedly not lean burn.



#26 gruntguru

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Posted 22 December 2014 - 01:45

My best guess is 40% excess air. What's yours?



#27 TDIMeister

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Posted 22 December 2014 - 01:51

Lambda 0.8-1.  It's not a guess.  ;)

 

Edit: Somewhat >1 only on overrun.


Edited by TDIMeister, 22 December 2014 - 01:53.


#28 gruntguru

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Posted 22 December 2014 - 02:25

A pity it's not a guess.

 

It is probably time to start a new topic.


Edited by gruntguru, 22 December 2014 - 03:40.