Reposting a thread that got buried in the Unicorn "stuff" - D-EGR engine
 

More information surfaced on GCC. It is a very interesting solution indeed.

Green Car Congress: SwRI develops D-EGR demonstrator highlighting fuel-efficient, cost-effective engine; 10% and above fuel economy improvements

meh, very band-aidy. Reminds me of emissions era carbs, where the obvious answer is already available, plus a hydrogen gimmick.

Lots of talk about reducing costs and efficiency and complexity, not seeing it.

I wonder if they tried running this engine without the hydrogen gimmick.

I can't view the videos at work but, the reason for adding hydrogen to the air/fuel mix is that it speeds up the flame propagation. Adding high amounts of EGR to the air/fuel mixture slows down the flame speed. The same thing happens in a lean burn engine. The hydrogen speeds it back up and prevents misfiring as one of the linked articles state.

Green Car Congress: PSA to commercialize SwRI-developed Dedicated-EGR technology in high-efficiency gasoline engines by 2018


Just because it is hydrogen doesn't mean its unicorn poo. There is a partial truth that hydrogen is beneficial, you just have to apply it correctly. You also have to produce it efficiently if you're doing so onboard.

Wonder how it compares to SkyActiv? SkyActiv already uses cooled EGR, proper exhaust scavenging and direct injection to achieve ultra-high compression and low consumption... though 11.7 is still pretty high, considering they're using this on a turbocharged engine...

Daox, my point isn't that it is unicornian, but that there proposal (use a dedicated cylinder for reforming gasses and dedicated egr) is enormously more complicated than direct injection compression ignition and has less gain. You gain flame speed and ignition reliability by increasing pressure as well, as opposed to on-the-fly alchemy. I know what hydrogen does, but there are other ways to do that.

It would be akin to saying feedback carbs should be the primary focus of discussion, here, in 2014.

I'm not disagreeing, just explaining to those who don't know.

The problem with adding hydrogen always seems to be finding a good way to generate it.

Atkinson and Miller cycle engines already made this sort of obsolete... in the 80's.

They're not adding external hydrogen, they're feeding excess fuel into that one cylinder, which then produces H2 and CO, which gets fed back into the intake.

Yup, more info on rich combustion to make a bit of hydrogen here:
http://www-diva.eng.cam.ac.uk/theses...n-mphil-thesis

But HCCI (speaking of gobs of egr)/DICI solutions still well ahead in efficiency.

I think we are all sort of waiting for a viable "not cam driven" valve train so we can have stroke by stroke control of the effective compression and expansion ratios, then you crank up the mechanical compression and detune from there, which would allow pretty much all the control you need for HCCI.

If i ran my 4 cylinder on 3 cylinders it would be 10% more efficient too.

If you ran it on two and modified the cam so that the two inactive cylinders acted like compressors on a 2 stroke cycle it'd be capable of essentially the same as OE power output and potentially 30% more efficient.

Homogeneous charge compression ignition is a very sensitive situation.
 

Complete control of compression would go a long way to expanding the running capabilities of HCCI, but there are far more variables to reign in before you could apply it broadly.

This is actually one of the most elegant applications of a POx reactor to date.
 

Partial Oxidation (POx) reactors external to an engine are cumbersome and wasteful. They waste the heat and pressure the reactor produces during operation. This design uses the heat and pressure from the reaction cylinder to produce mechanical work. The output of the reaction cylinder will be limited by its cyclic nature, but it should easily meet and exceed the 4% by volume hydrogen gas needed to take advantage of classic research mechanisms.

The engine used in this test car is one that already had a turbocharger and an EGR system so the only real addition is the routing and retuning. I would expect it to be robust and comparable in cost to the originally configured engine.

It is a standard turbocharged engine.
 

The 10% gain is in comparison to the engine in stock form. And, the volume of hydrogen they can produce is large enough to place them squarely within classic research. This is no gimmick.

Turning the hydrogen on and off is a simple matter of tuning of the reactor cylinder.

That cylinder is the bulk of the EGR source and provides torque as well (plus camless is good at cylinder deactivation, not "simple"). Given the number of variables to control hcci, this reactor is going to add a whole bunch more.

I was responding to your previous post . . .
 

. . . that implied a cam-less engine would be all one needed to implement HCCI. Now I am not sure what you are getting at with this statement. Seeding the fuel with a mix of CO and hydrogen allows a broader range of operation with HCCI along with the controlled variables of heat, pressure and turbulence.

But you are implying that it reduces the number of variables, when you have a reactor to control now, with varying amounts of hydrogen/etc generated per stroke.

I'm not sure if HCCI v DI v ? is the ultimate arrangement, but, like fuel injection (vs feedback carbs), we need to get precise control of the air charge and take it from there.

Ok, now I understand your train of thought.
 

And you are correct in that it would be another layer of complexity having a POx generator feeding an HCCI capable engine. And, it is not as "precise" in it's production as we would like. Intake air heating and intake boosting are also "imprecise" to the needs for the very narrow value of variables to induce the combustion event. This is why some researchers simply track the airflow temperature and pressure and inject a varying mix of gasoline and diesel since those can be precise in delivery. Using Direct injection is an advantage adding that much more precision in comparison to port injection and I am certain that it will be tried with HCCI, if not now, soon.

However, the original post and links was for a device that simply feeds a common engine with a reactive diluent. The device is more than precise enough, and rapid enough to provide the needs of an engine this way. It looks like it is capable of using the EGR from off idle on up to full power reducing engine out emissions considerably and saving on cost and complexity in that sense. They claim a peak thermal efficiency of 42% - right in the ballpark of current diesel tech. However, the emissions advantage of the D-EGR engine means only a TWC ( three way catalyst ) is needed unlike a "clean" diesel's need for a DOC ( direct oxidation catalyst ), diesel particulate filter (DPF) and NOx trap with urea dosing.

A friend of mine bought a Chevy Volt and likes all aspects of it except for it's pedestrian mileage return on the freeway. HCCI would be ideal in this application since the engine dynamics would be near constant. But, a solution such as the D-EGR engine, could, for the time being, help narrow the efficiency gap between gasoline SI engines and modern diesels without the cost and complexity of the diesel. This will allow serial hybrids to improve on the highway portion of their use.

the complexity of the reactant (1/4 of the engine plus a whole new controller/sensor algorithm to reign in + various plumbing, might even need separate wide-band on the reactor cylinder plus a lot of fudge) for %10 doesn't seem like it is worth it. There is a lot of complexity there, not simplifying, nor cost saving, like the video goes on about.

And if you are talking fixed speed/load, as in series hybrid, then hcci w/a cam just got a lot easier too.

You do realize many cars already exceed this complexity.
 

Electronics and software is cheap once in production. An extra injector is mentioned for the reaction cylinder (RxC). Port injectors cost about 10 USD wholesale. The reaction cylinder is of the same design and construction as the others. No cost there. There is the need for a wide-band O2 sensor to monitor the RxC output. That does incur a considerable cost penalty but doesn't break the bank at about 80-100 wholesale. It was implied the turbo was upgraded to a "two stage compressor" though more likely a variable vane turbo will be used in production. Many cars already come equipped with VVTs as standard fare. No real cost and complexity disadvantage there. The mixer and D-EGR piping would cost a few dollars and have a simple robust construction. They have already completed the FTP 75 test and PSA Peugeot Citroen, who partially funded the research, has committed to production by 2018 if not before. I do not think they share your concerns.

An engine such as this would see early introduction into higher end cars and trucks to market to people who are ready and willing to absorb the slightly higher costs. If PSA holds to it's announcements, they will have this tech applied across their entire model range by 2018.

HCCI is soon to follow but will be limited greatly in it's applications. HCCI, as well as the D-EGR system are just tools to reach the required mileage and emissions standards which become much more stringent as we move towards 2025.

Here is the link to the SAE Abstract.

A Demonstration of Dedicated EGR on a 2.0 L GDI Engine

I think camless is where the engineering should focus. EGR becomes a matter of valve timing, you "miller" by leaving the exhaust valve open on the intake instead of pushing fuel/air out the intake valve. you can create ideal auto-ignition conditions (which the reformation here is a band aid for), deactivate cylinders, act like a compressor.

It too is "cheap and simple", a solenoid on a poppet being a glorified injector.

The reformation is interesting, as using the heat/expansion to help create torque is very co-generation like. But so many more variables and control complexity to compensate for having a camshaft. Sure some may pay more for it initially, not really sure what that has to do with engineering.

Camless is not as simple as it sounds. The issue with camless is that it robs a lot of power.
A conventional camshaft does not take all that much power to rotate, because after the valves are forced open against their springs by the front side of the lobe, the spring actually helps the cam rotate, pushing it along as the valve retracts against the backside of the lobe. Power required nets very little.
When using hydraulics/electronics it is very difficult to recapture the energy released by the closing valve back into the rotation of the engine. Many manufacturers have been trying hard for years but there are on success stories yet.

I don't really get why this dedicated EGR loop is better than normal external EGR, they don't really say anything about it.

It has to do with the production of hydrogen gas.
 

If you Google Partial Oxidation Reactor (POx reactor) you will get a bunch of sciencey stuff and a few useful links to how one works. Basically, the reactor combusts the gasoline as a rich mixture resulting in the production of the usual CO2 and H2O along with smaller quantities of CO and H2. The carbon monoxide just adds to the combustible fuel mix and so does the hydrogen, but the hydrogen does more. It accelerates the flame speed and the reaction rate resulting in more possible power production for the same amount of fuel used as well as a greater reduction of emissions.

This compares to standard exhaust gas which has only Nitrogen, CO2 and water as it's main constituents and can provide only a flame quenching effect.

Problem is the very fast burning h2 and the very slow burning co may nullify each other.
HCCI problem is a tuning compromise because of all the different ignition temps of the over 200 chemical components of pump gas.

More information on this technology.

Green Car Congress: SwRI D-EGR gasoline demo vehicle delivers diesel efficiency at lower cost; potential for LEV III/Tier 3 emissions

Very interesting.

These two points basically sum up the technology: