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

[P-hack]

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.

[RustyLugNut]

Originally Posted by P-hack

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.

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

[P-hack]

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.

[mechman600]

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.

[serialk11r]

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

[RustyLugNut]

Originally Posted by serialk11r

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

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.

[maxc]

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.

[RustyLugNut]

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

[Daox]

Very interesting.

These two points basically sum up the technology:

- Running rich in the D-EGR cylinder produced reformate that improved the knock tolerance of the engine. Based on measurements of hydrogen in the D-EGR exhaust port, the engine was running with approximately 1% hydrogen by volume. 1% hydrogen was sufficient to stabilize combustion with 25% EGR at low engine loads.

- 25% D-EGR combustion allowed the engine BSFC to be reduced by at least 10%. The reduction was lowest at low speeds and high loads where the elevated compression ratio required spark retard and the supercharger was used. The maximum reduction was at high speeds and high loads where the elimination of enrichment improved the BSFC by over 30%.