HHO: Good, bad, or ugly?

[euromodder]

Originally Posted by ngrimm

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?

That's what the study proved, improving from 22 to 28% of bhp vs injected fuel HP by injecting H2.

mort quoted it before :

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)

So rather than making 22% of the possible HP contained in the fuel, it made 28% of the HP contained in both fuels.

It's the same kind of efficiency benefit you get when adding LPG or CNG/LNG to diesel - the diesel burns better, so it makes more HP, so you need less of it. Even when compensating for the gas, you're still using less fuels.

[ngrimm]

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.

[IamIan]

Originally Posted by Blacktree

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

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

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)
-m

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

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

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?

[niky]

The weight of the water and a water injection system is a minor thing. Biggest tanks I've seen are five gallons... maybe forty pounds. Not much compared to the other useless stuff on modern cars.

But yeah, on a modern, non-turbocharged ultra-lean burn engine, not really worth it. On a turbocharged engine, helps longevity, (which is why GM used it for a while) but as OEM, it's difficult to get people to refill the darn tank, which is why it was dropped.

[ngrimm]

Originally Posted by IamIan

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How is it different from the one already used for ~12 years in the MT Gen-1 Honda Insight?

From what I have read, the Incite didn't appear to have a deNOx catalyst. It apparently uses a purge mode requiring it to leave lean burn mode.

Possible Solution for NOx Purges - Insight Central: Honda Insight Forum

[rmay635703]

I really can't understand why no one wants to sell a lean burn gasoline motor.

Given the fact we can remove all the Nox from diesel applications I see no reason why the same tech could not be moved over to gasser applications.

Urinate in a bottle and mist that into your exhaust and no more nox, couldn't be simpler.

[niky]

They do. Direct injection on Audis allows for stratified direct injection (ultra-lean) in Europe... it's only in the US and other markets with piss-poor gas or strong NOx regulations where they can't do it. Most modern engines are already very lean-burn at part throttle. Most DI engines are ultra-lean. And many upcoming engines promise to run even leaner... can't wait to try out Mazda's SkyActiv.

[ngrimm]

Actually I believe the advent of continuously variable valve timing is also taking care of NOx. From Fine Tuning Engine Performance with Variable Valve Timing - TechConnect Online News Blog

"The use of an EGR valve was an early method for reducing the formation of NOx. Exhaust gas is reintroduced into the intake manifold through a valve, diluting the intake charge and effectively reducing combustion chamber temperatures and the formation of NOx. A side effect of introducing external EGR to reduce NOx is that it causes the hydrocarbon (HC) levels to increase.

Internal EGR

A more effective method of controlling emissions is to increase intake and exhaust valve overlap, a version of internal EGR. Valve overlap refers to the amount of time in the four-cycle engine event when both the intake and exhaust valves are open. A reversion occurs in the cylinder as the piston is moving down while both valves are open. Exhaust gas is drawn back into the cylinder, simulating an EGR function. Being able to control the length of this event can substantially lower NOx. HC levels are also reduced by re-burning the tail of the exhaust event that is rich in hydrocarbons. However, placing the camshafts in a permanently increased overlap position would affect idle and low rpm performance. The greater the overlap, the lower the intake manifold vacuum levels.

Fixed camshafts compromise between smooth idle, good low-rpm torque and high-rpm power. But variable camshaft timing accommodates the sometimes divergent needs for power, drivability, economy and emission control.

Variable valve timing uses a cam phaser to dynamically change valve timing events relative to piston timing by controlling the camshaft. This allows the position of the camshaft to be changed, dependent on need. At idle and low engine load, overlap is minimum, improving idle quality. At higher engine speed and load, overlap is increased, allowing emissions to decrease.

The cam phaser allows the PCM to change the relationship of the camshaft relative to the crankshaft, permitting better control over emissions and performance. "

[IamIan]

Originally Posted by ngrimm

From what I have read, the Incite didn't appear to have a deNOx catalyst. It apparently uses a purge mode requiring it to leave lean burn mode.

Possible Solution for NOx Purges - Insight Central: Honda Insight Forum

Yes that is how the Gen-1 Insight NOx system works ... store it during lean burn and then catalyze it into 'Harmless' Other things with the addition of a little bit of unburned hydrocarbons of fuel and heat experienced during the 'purge' part of the cycle, where you leave Lean Burn.

What I don't yet see is how this is a different catalyzing method than the 'new' one...

I thought you were refering to the same one as discussed here, From the EERE

They say,

The high conversion rate of the Argonne catalyst results from its effective interaction with hydrocarbons in diesel fuel

Which means it still needs those diesel fuel hydrocarbons in the exhaust after the combustion chamber ... which to me reads like the same kind of system the Gen-1 Insight already had ... This 'new' catalyst still needs heat and unburned hydrocarbons from bits of unburned fuel in the exhaust from a 'purge' engine operation... sure you could just run your engine in a 'purge' like state all the time to keep very low NOx emissions ... but you would also be wasting lots of unburned hydrocarbon fuel at the same time.

If you are thinking of something else ... please give me a link ... I'd like to read about it, if it is something different than this.

[ngrimm]

Looking at this pdf
http://www.google.com/url?sa=t&rct=j...hh97-NKC-E4KMA
The diagram shows fuel being fed directly into the catalyst so the engine is able to remain in lean burn mode. Hence the reason for the catalyst in the first place.