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Author Topic: Does hydrogen and oxygen fed to a petrol engine improve performance?  (Read 14274 times)

Online chiralSPO

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Some people claim they can get increased gas mileage on their cars by employing an electrolyzer to generate hydrogen and oxygen gas (HHO) which is fed into the combustion engine. Since the energy used for the electrolysis comes from said combustion engine, I don't see how there can be any real increase in efficiency unless this energy would otherwise be wasted (or if the energy comes from application of the breaks, as in a hybrid vehicle). Even with optimal conditions, the electrolyzer will probably waste about 20% of the energy (output = 80% of input).

Is there something I'm missing here? Is there substantial improvement of combustion having some H2 and a little extra O2 in the mix?
« Last Edit: 09/10/2013 09:32:41 by chris »


 

Offline peppercorn

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Re: thermodynamics and automotive HHO
« Reply #1 on: 07/10/2013 21:10:05 »
No, there is nothing you are missing. 'HHO', as you show by simple deduction, is - at best a naive myth - at worst a scam.
 

Offline alancalverd

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Re: thermodynamics and automotive HHO
« Reply #2 on: 09/10/2013 00:58:22 »
"Brown's gas", a 2:1 mixture of hydrogen and oxygen, is a useful fuel but not a magic one.
 

Offline peppercorn

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"Brown's gas", a 2:1 mixture of hydrogen and oxygen, is a useful fuel but not a magic one.
Calling it a 'useful fuel' implies it's out there hanging around in the world, ready to be exploited.  But unlike proper fuels (petroleum, methane, wood, etc) it isn't.
So it's useful in the sense that if you already have some way of freely generating it - it will burn  But the only practical everyday means to produce it is with an electrolyser and that's a far less efficient use for electricity than running an electric motor.
« Last Edit: 09/10/2013 13:40:38 by peppercorn »
 

Online chiralSPO

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I don't think calling it a fuel implies that it is out in the world. A fuel is just a substance that stores energy. All fuel has to be made somehow, and that takes energy (all that petroleum and natural gas is just fuel that was made a long time ago.)

But thanks for confirming my skepticism.
 

Offline alancalverd

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It's an interesting fuel because it burns without additional oxygen and produces only drinking water, so is ideal for generating a flame in a confined space - like a house!

You the taxpayer are subsidising windmills, either to destabilise the grid by producing electricity when the wind blows (so you have to shut down conventional and nuclear stations, which work best when run continuously), or not to generate electricity at all when it is not required. Far better to use all this opportunistic electricity to generate HHO that can be stored and fed into the existing, reliable, gas grid, instead of foreign, fossil methane that produces CO and CO2 when you burn it.
 

Offline peppercorn

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It's an interesting fuel because it burns without additional oxygen and produces only drinking water, so is ideal for generating a flame in a confined space - like a house!

A flame? In a house? ... Are you suggesting generating it using, what, Economy 7 electric? And then storing it until you want to cook or have a shower in the daytime? Something like that?
I did have to grin at the thought of this 'fuel' in a 'confined space' - a large tank of low pressure hydrogen and oxygen somewhere in your house ... it sounds like an excellent way to demolish a house to me!

If you are, on the other hand, using it as fast as you make it, what's the point?
Why not turn electricity directly into heat and save all the complexity and waste power?

And in terms of what burning it produces, that 'natural gas' stuff looks promising! Less water vapour and harmless CO2 through a simple jet on your cooker or boiler.

Far better to use all this opportunistic electricity to generate HHO that can be stored and fed into the existing, reliable, gas grid, instead of foreign, fossil methane that produces CO and CO2 when you burn it.

As an alternative to pumped storage and other grid balancing strategies, again why do it?  It will be more lossy than pumping water uphill, and probably cost nearly as much as a battery bank does.  Alternatively one could maybe just seperate the gases, and then recombine them in an enormous fuel cell... which ever way you suggest using it I don't reckon any power companies (or off-grid enthusiasts, for that matter) will be bothering.

On a note of foreign gas imports, part of the privatisation of the CEGB (following on from British Gas/our North Sea reserves) was to remove the limits on gas-firing power stations. Then we had the inevitable 'dash for gas', and now unsurprisingly our reserves are all but gone.
 

Offline peppercorn

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I quite like the idea of welding with it though!  :)
 

Offline CliffordK

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Electrolysis of water can be used to either make mixed gas, or pure Hydrogen & Oxygen.  If you were delivering it to houses to replace natural gas (or perhaps mixed with the natural gas), then it would be best to just release the oxygen, or use the Oxygen for other uses, and only deliver the hydrogen. 

It isn't a bad idea to generate hydrogen during off-peak electricity generation from renewable resources (solar, wind, hydroelectricity). 

You can buy small jewelry welders that use mixed gas (hydrogen/oxygen), generally also using some acetone to dry the mix a bit.
 

Offline CliffordK

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As far as using "HHO" in automobiles.  It certainly is a controversial subject.  Certainly one can't expect it to provide 100% of the power for the vehicle in a self generating fashion. 

One of the fallacies that people often fall into is that an alternator may seem to turn freely at low RPM, and no load.  However, under load, it takes more energy, and one can often hear the difference in engine performance when doing something like jump starting another car.

Some people have used water injection systems (without electrolysis) which can cool the engine slightly, provide more "gas" for expansion, and better engine cleaning.  And, of course, is an extremely simple system.

As far as the electrolysis based HHO systems, theoretically it should be inefficient due to energy losses in the generation/fuel process.  However, some people have suggested that it does in fact work because it improves the fuel combustion in the vehicles.  One of the reasons for the catalytic converter is to reduce the unburnt hydrocarbons.

However, this may also be dependent on the target vehicle.  Using a 20 or 30 year old vehicle with a carburetor and no catalytic converter may well be different than some of the newer fuel injected vehicles.

Anyway, I've decided to order one of the HHO systems off of E-Bay so I can try it out myself...  paying a little less than "retail" price.  Unfortunately I don't drive a lot, but perhaps I'll have a chance to use it on a longer trip that I have planned, or fix up a system to do more accurate calculations on smaller amounts of fuel than a full tank.
 

Offline peppercorn

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It isn't a bad idea to generate hydrogen during off-peak electricity generation from renewable resources (solar, wind, hydroelectricity).

This may well make more sense when the 'always just around the corner' hydrogen economy finally arrives (for what it'll be worth if it ever does). But, as you point out, just making straight hydrogen (and liquefying it) is the only method which looks halfway sensible (the huge static FC suggestion was rather tongue in cheek).

I have seen video of a guy welding a car with HHO/Brown's gas but I figure he had constructed himself a pretty serious bank of cells to get the gas throughput.
 

Offline peppercorn

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Water injection is shown to have fairly good results on many direct-injection diesels - mainly because most DI diesels are much happier running on cool air.  As more petrol/gas cars adopt DI as well it may follow that similar economy advantages can be seen.  Water/methanol is a common additive for highly boosted petrol engines to keep the charge cool and prevent pinking/detonation - the mixture has shown further fuel saving over straight distilled water on diesels too, though I'm not 100% sure why the methanol helps in this case.

All properly controlled HHO tests run on well tuned fuel injected vehicles have shown negative results on fuel saving. The idea that Catalytic converter will have less 'cleaning up' to do is a bit of a misnomer as a 3-way cat actually requires incompletely oxidised fuel (COs and HCs) to remain in trace amounts in the exhaust to keep the cat' lit and drive the reduction of oxides of nitrogen.
 

Offline alancalverd

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Quote
A flame? In a house? ... Are you suggesting generating it using, what, Economy 7 electric? And then storing it until you want to cook or have a shower in the daytime? Something like that?
I did have to grin at the thought of this 'fuel' in a 'confined space' - a large tank of low pressure hydrogen and oxygen somewhere in your house ... it sounds like an excellent way to demolish a house to me!

Have you never lived in a city, or been to a restaurant? Cooking, and heating water with gas, has been going on for a couple of centuries, using a low-pressure grid to distribute the stuff.

The joy of supplying HHO rather than pure hydrogen is that it arrives in the optimum mix for controlled combustion and, unlike town gas, LPG or any other gaseous fuel, you don't need additional ventilation to burn it safely.   

And as I said earlier, the sensible use of windmills is to generate gas whenever the wind is available, and store the energy as gas until you need it. There being no shortage of water, and no objection to returing it to the atmopsphere when you have finished with it, what cleaner and more sustainable form of controlled power could here be?

Quote
As an alternative to pumped storage and other grid balancing strategies, again why do it?  It will be more lossy than pumping water uphill, and probably cost nearly as much as a battery bank does.

Loss doesn't matter much if the source is free, which wind-generated electricity would be if we could use it whenever it was available. Pumped storage requires an enormous capital investment and actually stores only a tiny amount of energy in a vast tract of land: it's not used for grid balancing but for plugging acute gaps while conventional  stations are ramped up to meet peak demand. Dinorwig could operate the UK railway system for about 20 minutes: its real importance is that it can run up to full power in 12 seconds.

There's no significant cost involved in my proposal, since the gas grid already exists, with both high and low pressure storage and distribution systems installed. Town gas was about 50% hydrogen until the 1960s - the technology is already fullly installed in homes and businesses!
 

Offline CliffordK

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The joy of supplying HHO rather than pure hydrogen is that it arrives in the optimum mix for controlled combustion and, unlike town gas, LPG or any other gaseous fuel, you don't need additional ventilation to burn it safely.   
And, without proper flashback arresting, you could loose your entire grid, and perhaps the entire city in a matter of seconds.

It would also be a tempting target for terrorists.

When you use just the reducing component of the fuel, then an explosion is generally limited to where the fuel exits the pipeline, and gets access to oxygen, and can generally be extinguished by removing the oxidizing agent. 

A mixed gas fire would be much more difficult to fight, and the explosion would have a greater propensity to travel up the pipes.

A jeweler's welder is reasonably safe because it generates a very small quantity of mixed gas at the point of use.  Firing up your gas furnace requires a much larger pipeline and greater overall supply.

One would also note that the current municipal grids are designed for a reducing only fuel.  A mixed fuel would likely require larger pipelines, greater pressure, and new appliances.

You could use distributed generation, but for peak hours, it is cheapest to just use direct electricity for the heat.  There may be a slight advantage of distributed storage of gas generated with off-peak electricity, but again, it would be much safer to just store the hydrogen.

Consider this.  A good high pressure hydrogen cylinder may be able to survive a house fire.  Undoubtedly, even at relatively low pressures, a mixed gas cylinder could self-ignite with heat alone, and explode.
 

Offline peppercorn

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Cooking, and heating water with gas, has been going on for a couple of centuries, using a low-pressure grid to distribute the stuff.
That was kinda my point.

Hydrogen though will leak out all over the place when transferred in gas-tight (N.G. being the gas) pipelines.
Hydrogen is small. It also embrittles metal.

You don't need additional ventilation to burn it safely.
Unless you don't want a room full of damp air of course.

generate Brown's gas whenever the wind is available, and store the energy until you need it. ... what more sustainable form of controlled power could here be?
A more efficient one - like pumped storage. What volume of HHO is needed to match the reservoir half way up the side of Snowden for instance?
If hydrogen cars ever become practical then making -just- H2 would probably look worthwhile, but I won't be holding my breath for that one.

I forgot to mention that the mixed gas if stored will tend to recombine over time (due to some chemistry I don't properly remember).

Loss doesn't matter much if the source is free, which wind-generated electricity would be if we could use it whenever it was available. Pumped storage requires an enormous capital investment and actually stores only a tiny amount of energy in a vast tract of land
I suggest we need some like-for-like figures here. The idea of 'free' electricity from renewables (as I think you have alluded to several times yourself) is a bit misleading. The fuel source might be free but everything else isn't (I realise I'm stating the obvious here) ... What it means it that whether or the government or whoever is offsetting generation is some way or other, the national grid or leccy companies will still pick the tech that offers them the best return on investment. - So I can't quite see how this tech is going to compete.

A mixed fuel would likely require larger pipelines, greater pressure, and new appliances.
Yes. A lot larger I think. Al those O2s swimming about in the pipe (with their much larger molar mass) will take a lot of energy (plus the pipe drag) to pump around.
 

Online chiralSPO

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I would not want to store or transport a mixture of H2 and O2. Just a matter of time before.....KABOOM! Static discharge, cosmic ray, contact with an impurity that catalyzes recombination (like Ni, Co, Pd or Pt), any of these would cause real problems.

As mentioned above, H2 leaks out of plastic and metal pipes (it actually dissolves in steel, so it goes right through and changes the physical properties of the metal for the worse...)

However, I think that an electrolyzer/fuel cell couple could be a very good way of smoothing energy output from sources like wind and solar capture devices. You only have to store a relatively small amount of hydrogen for a short period (likely no longer than 24 for solar).

Splitting one liter of water can store about 16 MJ of energy (1300 L of H2 at stp or 13 L at 100 atm [470 psi]). Using the gravity method, you would need to elevate that liter of water into orbit to store the same amount of energy (or lift 1600 L of water one km)
 

Offline alancalverd

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This is a most interesting forum. I have just learned that the entire gas grid, established by our Victorian forbears and still in use, cannot work and will explode if anyone sneezes. Either that, or town gas never contained any hydrogen and all the textbooks, O-level examinations, gas fitters' certificates and my childhood recollections, were wrong. The films of hydrogen burning quietly after London gasholders were strafed by the Luftwaffe are fakes. Please don't tell the energy companies, or the millions of homes and businesses that use their product, or the economy will collapse.
 

Offline peppercorn

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This is a most interesting forum. I have just learned that ...

What's 'interesting' is the things you have 'learned' are completely at odds with what other contributors have done their best to explain above.  The problems/risks are those of oxygen being transported/stored with the fuel (H2) and the leakiness/reactivity (with metals esp.) of -Elemental- hydrogen.
 

Offline peppercorn

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Splitting one liter of water can store about 16 MJ of energy (1300 L of H2 at stp or 13 L at 100 atm [470 psi]). Using the gravity method, you would need to elevate that liter of water into orbit to store the same amount of energy (or lift 1600 L of water one km)

It still leaves the, uhum, burning question of round-trip efficiency in the storage process. I believe it will still be somewhat worse than pumped storage is. ... If you want the H2 to power a fuel cell vehicle on the other hand that might not be such a bad solution (when their day comes).
 

Offline alancalverd

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Right now, a considerable proportion of the actual and potential output of windmills is wasted. You, the taxpayer, hand out subsidies to the owners when the wind is blowing but there is no demand for electricity, and at other times you pay over the odds for windmill watts because "they" have shut  down a cheaper, reliable source to allow the windfarmers to take your money, and when the wind is not blowing, you pay a subsidy to the greedy speculator to offset his capital depreciation.

Since the product is inherently free of revenue costs, it makes more sense to run the windmills whenever wind is available and store the energy in any useful form, regardless of the efficiency of that process - any number larger than zero will do, and if it makes use of an existing infrastructure, so much the better. Then maybe we can get rid of subsidies and make windfarming into a viable business rather than a burden on the poor.
 

Offline CliffordK

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Yes, off-peak power generation may be a problem, especially variable output off-peak power generation.  So, one may choose to use some of it to generate hydrogen.  I have mentioned in the past that hydroelectric facilities should be designed to reduce flow at night during offpeak demand levels, and they may be able to compensate somewhat for variable winds.

Mixing some pure Hydrogen gas with the Methane/Ethane natural gas is probably safe enough.

Mixing just a little pure oxygen into the mix may be ok (the equivalent of being below the LEL), but if one got anywhere close to 33% oxygen, 66% hydrogen (by volume), and it would be extremely dangerous to send through your pipeline network (for reasons mentioned above).

Assuming your natural gas is mostly methane, with a fairly fixed methane/ethane/Other mix:

CH4 + 2O2 --> 2H2O + CO2

2H2 + O2 --> 2H2O

In the first equation, one uses a 1:2 mix of methane:oxygen.
In the second equation, one has a 2:1 mix of hydrogen:oxygen. 

Thus, if you add a lot of hydrogen, the appliances would be designed to add too much oxygen, and it would not burn well.

So, even if you could reasonably safely add a few percent of hydrogen gas, and one or two percent of oxygen gas, your problem is that the stock appliances already would be adding too much oxygen to the mix.  Adding more oxygen would be more of a problem than a help.

Moisture in the air would be little different between burning hydrogen and methane, although, of course, the risk of carbon monoxide from an appliance would be eliminated by using hydrogen as a fuel (carbon monoxide risk still comes from smoldering fires as part of house fires.
 

Offline CliffordK

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Thinking a bit more about the HHO and automobiles.

I've seen descriptions of the system generating a lot of gas. 

To put it in perspective.  Say the system generates 1 gallon per minute of low pressure mixed hydrogen/oxygen gas.

A basic 2L, four stroke auto engine, running at 2000 RPM, one uses about 1L air per crank revolution.  That means that the auto engine is using about 500 Gallons of air a minute.  Thus, at about 1 GPM, the hydrogen generator is supplying only about 0.2 % of the fuel supply of the vehicle.

(oops, I wrote down the wrong numbers).
« Last Edit: 11/10/2013 21:38:23 by CliffordK »
 

Offline peppercorn

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Thus, at about 1 GPM, the hydrogen generator is supplying only about 0.02 % of the fuel supply of the vehicle.

Hmm. 0.02% eh? - Almost sounds like homoeopathy for cars! ;)
 

Offline syhprum

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If I see any more correspondence on using Water/Hydrogen in IC engines I will scream, water injection was popular in the early 1900's when the petrol octane rating was only sufficient to allow expansion ratios of 5 to 1 but now modern fuels and computer control of timing etc allows up to 11 to 1 so the complexity of water injection is no longer justified.
When I drive thru France where at least 80% of the power comes from nuclear stations and see all the wind mills I often wonder if they are used as fans to dissipate some of the power when they have shovelled in too many atoms ?
« Last Edit: 11/10/2013 20:00:49 by syhprum »
 

Offline CliffordK

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Oops, I meant 0.2% rather than 0.02%.  Still, the hydrogen is a very small portion of the overall fuel.  Perhaps not enough to either detect a significant battery drain, nor give a significant boost from the hydrogen alone. 

Could it aid combustion? 

Not everyone drives the latest model of car. 

However, when I was considering a CAT for my Fiat 500, it required also adding a complex O2 sensor/air injection feedback system to reduce the hydrocarbons to a level manageable by the CAT.  So, you are right that modern cars should have many of the controls required for a clean burning, and presumably efficient engine.

Nothing substitutes for empirical testing.  I'm still waiting for my HHO system to arrive.  I think it was supposed to be a $1000 system, but I managed to snag it off of e-bay for a mere 99 cents (plus shipping).
 

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