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Old 01-19-2012, 07:18 PM   #63 (permalink)
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Originally Posted by Blacktree View Post
Also of note is that if you inject water into the engine directly (i.e. without electrolysis),

The big question is whether or not it'll be worth the effort.
The more efficient method of doing that is the 6 cycle engine that uses the injected water as a form of waste heat recovery ... effectively boosting the ICE energy efficiency and converting a larger % of the energy content of the fuel into mechanical power.

Unfortunately so far there have been significantly negative longevity issues that prevent this method from wide spread adoption.

Also ... any form of water injection requires you to carry that water around with you ... which means you are carrying weight that does not itself contain energy ... it would have to increase your efficiency by at least as much as it reduces it just to break even.

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Originally Posted by ngrimm View Post
All very good points. A question though. Is it possible that hydrogen injected in a sufficient quantity could serve as a catalyst and thereby contribute to the combustion efficiency? And if so is it possible that it could add more than enough power to compensate for say 20 amps or .24 kw or so required to produce it? Just playing devils advocate.
Although as others have said ... Hydrogen is not a catalyst ... it's higher flame speed does allow an engine not designed for it to sustain lean burn operating conditions ... which are more efficient.

To the 2nd part ... short version no... it takes more than it gives.

Long version As posted before:
Originally Posted by mort View Post
If the paper is to be believed, the addition of 1.5 lb/hr of hydrogen improved efficiency from 21.95% to 22.78% (bhp/fuel hp)
21.95% to 22.78% is a ~3.6% increase ... but is only 0.83% more mechanical energy for a given amount of fuel put in.

Now for the bombs...
1.5lbs of hydrogen = ~0.68kg = ~26.8kwh of chemical energy.
They tested at constant ~26.9kw mechanical drive shaft ... see it?
0.83% of ~26.9kw = ~223w of additional power per unit of fuel.
They consumed ~26,800wh of hydrogen chemical energy to save ~223wh of gasoline energy.

And that was hydrogen from a bottle ... less than 100% efficient alternator means you consume more mechanical power than you produce electrical power to feed your electrolysis.

Plus the additional vehicle weight of the equipment and the water.

Further ... Honda's Lean Burn Engines without Hydrogen have been tested to get a ~20% efficiency improvement ... which is itself better than the hydrogen ... and it also does not require the additional weight of the hydrogen system or water or any of the additional energy losses of creating the hydrogen... so even if it did work ... it is still inferior.

Originally Posted by ngrimm View Post
Seems logical. A couple more questions if you don't mind. Since the timing of the ignition event is so critical in a combustion engine, is it possible that the addition of hydrogen accelerates the process and improves efficiency of the gasoline burn in that way? Possibly similar to the use of higher octane fuel (as I understand it contains less energy than lower octane fuel) in a high compression or boosted engine allowing one to advance the ignition timing and thereby increasing power output?
yes adding hydrogen will increase the flame speed of the combustion event ... and could support different ignition timing ... which they also already did in the paper previously linked to and which only got very small % benefit with free hydrogen.

Additionally ... you don't need hydrogen itself or any of the energy spent to produce it to get those benefits ... many modern engines automatically adjust the ignition timing already.

Originally Posted by ngrimm View Post
It seems there is a solution to the increased NOx emissions mentioned earlier. Argonne National Labs which is operated by the US Department of Energy has engineered an exhaust DeNOx catalyst.
How is it different from the one already used for ~12 years in the MT Gen-1 Honda Insight?
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