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

[P-hack]

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.

[arcosine]

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

[Christ]

Originally Posted by arcosine

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.

[RustyLugNut]

Originally Posted by P-hack

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.

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.

[RustyLugNut]

Originally Posted by P-hack

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.

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.

[RustyLugNut]

Originally Posted by t vago

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

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.

[P-hack]

Originally Posted by RustyLugNut

...
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.

[RustyLugNut]

Originally Posted by P-hack

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.

. . . 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.

[P-hack]

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.

[RustyLugNut]

Originally Posted by P-hack

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.

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.