Hydrogen AND gas engines?

[DarkTirade]

Take a looksee at the wave of the future perhaps?
http://www.damninteresting.com/?p=195
I find that... dare I say it, damn interesting? :)

[skids]

1. It really has nothing to do with the "hydrogen economy" cult.

It's just being used as a fuel additive, in extremely small quantities. But heck since there seem to be a huge number of people all singing the hosanas of "holy hydrogen" if the HFI systems can utilize that insanity to get some free press coverage, more power to them.

[Dead_Parrot]

2. Going back a while...

Something along similar lines used to be messed around with as an engine tweak - adding a small amout of water to the carb mix, on the grounds that it would break down under compression - giving a bit of boost from the hydrogen, but mainly by getting extra oxygen in the mix. This is 70's era stuff, though. No idea if it acually worked...

[NNadir]

5. The admixture of water to fuels can indeed affect combustion processes.

This was the subject of a recent paper in the journal Energy and Fuels, although I cannot remember the exact reference.

In this case the water catalyzes combustion in a type of water gas reaction, wherein the water is reduced by the hydrocarbon. (This is the same reaction by which hydrogen is now made industrially - however the hydrocarbon in question is not diesel fuel but is instead natural gas, which is mostly methane.)

These types of reactions are mostly used for adjusting the pollutant profile, not so much to raise efficiency, although it is possible to imagine circumstances under which this occurs.

Probably small amounts of hydrogen are generated in most flames where water is present, since all fuels in this atmosphere are reducing agents. Water is of course, to some extent almost always present from the humidity of the air.

[One_Life_To_Give]

10. Water delayed engine knock

The only part that "worked' in the 70's. Was adding water to allow the engine to use lower octane fuel than would otherwise be required. The water cooled the burn (absorbed heat by turning to steam) thereby reducing the high temp and pressure which accelerates the "Knock" detonation. As a side benefit it also helps clean carbon deposits from the motor.

[Coastie for Truth]

3. You never get as much energy out of recombining

2H2 + O2 --> 2H2O as you put into decomposing 2 H2O --> 2H2 + O2.

Get out your Physical Chemistry Book (or your Chem E Thermo book). Look at "Overvoltage" and "Back Voltage" and "Tafel Curve" and "Debye Layer."

Also, electrolytes and electrode substrates are not super conductors -- so look up "Ohmic Resistance."

Some time ago an inventor in Michigan invented:

Using Fuel Cells To "Time Shift" Solar Energy



Generate electricity by photovoltaic cells when the sun is shining




\|/




Immediately, in real time, electrolyze water to get H2 and O2




\|/




Recombine the H2 and O2 in a fuel cell when you need the electricity -- "Time Shifting Solar Energy"

[Dead_Parrot]

4. Pesky Thermodynamics... :)

[DarkTirade]

6. It isn't about using hydrogen as a fuel

It's about getting more efficiancy out of the engines we already have, and apparently adding a tiny amount of hydrogen to the mix right before it goes boom does that.

[Coastie for Truth]

7. In situ generation is not pleasing.

I would tend to favor a flexi-fuel system, with methane injection (4 hydrogens per carbon) to supplement the gasoline (1.1 hydrogens per carbon). Get almost the same effect with less hardware.

And, less hardware means more "idiot proof."

[dcfirefighter]

8. Except you have to have a compressed gas tank

instead of a distilled water tank

[Coastie for Truth]

9. Good catch.

I remember some kind of a system from my teen age days - where some exhaust (rich in carbon monoxide and even unburned hydrocarbons) was recycled back into the intake manifold.

[dcfirefighter]

12. Shouldn't happen too much with O2 sensors and EFI

I do remember my VW had a crankcase rebreather. I've never bothered to figure out what my Honda does.

[phantom power]

11. I saw a program on the Bermuda Triangle (I swear this is relevant)

Where they were testing the theory that methane would stall an internal combustion engine. They found that an old plane engine would stall out at 1% methane. Was this just a consequence that the engine wasn't designed to use a methane supplement, or is it that a gasoline engine simply cannot burn methane as a supplement?

[dcfirefighter]

13. I think I saw this episode as well.

I don't remember the percentage, though I think that a modern automotive engine would be more forgiving than a 1945 high strung double wasp air-cooled 2000 shp radial engine flown at 5000'.

In general, if air flow wasn't increased and/or fuel flow decreased, it would richen the mixture, possibly to the point of choking out.

I have no idea about the special dynamics of adding hydrogen (as a gas or as CH4). It would change the stochiometry such that more H20 was produced, and relatively less C02 / C0. I don't know what the efficiency derives from, possibly differences in bond strength btw C&O and H&H&O.