Hydrogen Generator

The claim is not that the burning of the H2 itself yields energy. It is that the addition of H2 increases the combustion efficiency. Not all of the gasoline in the cylinder burns. Supposedly the H2 acts as a catalyst to make more of the gasoline burn and that additional gasoline being burnt then yields more energy than it took to electrolize the hydrogen.

Even if it worked in a regular car, it would not work in a Prius. The Prius uses electric motors at low speeds, where the H2 (HHO, Brown's gas, whatever, who cares...) would have the most effect in an ICE due to the lower air to H2 ratio.

 

H2 is not a catalyst either, unless you're saying it makes it out the tailpipe unburnt, as a catalyst is not consumed in a chemical reaction. The general formula for burning hydrocarbons is

Code:

C(n)H(2n+2)    +  [(3n+1)/2] O2  ------->  (n) CO2  + (n+1) H2O

n is the number carbon atoms, for example octane has n=8. Where does the extra H2 go in this formula?
I think it actually goes here:

Code:

2H2 + O2 = 2H2O

Unfortunately, this gives you less energy than creating the H2.

 

I don't want to get hung up on terminology and chemical equations, so let me re-state that: H2 is supposed to enhance the burn of of the fuel/air mixture, supposedly making it more efficient. I'm just stating what the Hydrogen injection proponents are claiming.

According to a DOE EERE article on MIT's Plasmatron Hydrogen generation device, http://www.eere.energy.gov/vehiclesandfuels/pdfs/success/plasmatron-ld-dec01.pdf, "Engineers have long known that adding hydrogen to gasoline makes an engine run cleaner and more efficiently... The hydrogen-rich gas ... is fed into the vehicle's gasoline engine where it promotes more efficient combustion." Scientists at MIT are claiming that the process works, according to their research which was funded by the DOE. Who am I to argue with them?

The HHO people are trying to utilize this mechanism, generating hydrogen by electrolysis (which is inherently inefficient) instead of using a "Plasmatron" device. I have not personally done any actual experimentation on a vehicle to see if it works, though I have done some experimentation with it. What I do know from my own personal experience is that HHO generators (by electrolysis) do not generate much gas, the apparatus is messy and expensive to build, and that you stand an excellent chance of messing up your car if you implement it. I also know that there is a lot of people out there on the web building this stuff, and once they get it built and installed, they go quiet. That does not indicate that they are having success. I started down the road of building one for my truck without doing my homework (acting more on impulse), had a lot of fun, read a lot of material, learned a lot about cars and electrolysis, built some stuff and decided it wasn't worth the trouble or the risk.

The original poster asked if anyone had any experience with HHO. I was just relating my experience to them. I suggest that they do not waste their time if gas mileage is their goal. I also suggest that it would be an even bigger waste of time on a Prius even if it worked on a standard ICE vehicle (per my previous postings). It makes a great science experiment if you want to learn and teach your kids about electrolysis & cars, which I did.

 

Note that there is no mention of the cost of producing the hydrogen. Burning hydrogen is about as clean and efficient as you can get: all you get are heat and water. It's even cleaner to just burn hydrogen than to add it to gas. The problem is the cost, and that is the central issue. Any closed loop chemical cycle comes out in the hole, and making hydrogen from water to burn to turn back into water is no exception.

I take exception to your comment: "Scientists at MIT are claiming that the process works...". They make no such claim. Scientists at MIT claim to have developed a more efficient method of splitting water into hydrogen and oxygen. I have no reason not to believe that claim. They also claim that hydrogen helps the combustion process. That's not much of a stretch either. What they don't claim is making energy in the process. Their process is a net consumer of energy, not a producer. It appears to be an attractive process if you have a source of cheap or excess energy, which can then be converted into hydrogen at some loss. It doesn't make energy, it stores energy. Let's not confuse the MIT claims with those of the tinfoil hat water-for-gas crowd.

Tom

 

The idea behind the plasmatron is to divert around 25% of the gasoline being consumed into hydrogen production. The increase in efficiency is not the hydrogen per se, but that it allows a high compression, lean burn engine. They estimate this could increase vehicle efficency about 25% (engine efficiency by 30%). The plasmatron isn't electrolysis, but instead creates hydrogen directly from gasoline.

This isn't something you can accomplish by bolting on a hydrogen source to an existing car, and it's not the trivial amount of hydrogen produced by the so-called "HHO" devices. See this presentation, starting about page 24.

 

Okay, now this makes sense. There is nothing about this idea that defies basic laws of physics.

Tom

 

You get twice as much H2 as O2, since there are 2 H atoms per O atom in the water molecule.

 

qbee42: Now don't go putting words in my mouth... I never said anything about this being a "net producer of energy". What I said was that the claim is that the increase in combustion efficiency due to the presence of H2 in the mixture yields more energy (from the combustion of additional gasoline that is not wasted) than it took to generate the H2 by electrolysis. There is no net production of energy in that statement. Simply a net improvement in gasoline utilization efficiency.

The "tinfoil hat" crowd has been saying "hydrogen helps the combustion process". The MIT research now says "hydrogen helps the combustion process". I'm not sure what came first here - the chicken or the egg.

The addition of H2 to the mixture makes the combustion process more efficient (burns more of the existing fuel in the cylinder), so to get the same amount of energy you can burn less fuel (lean out your mixture) and use less gasoline. I think that this is what I've been trying to explain all along (in the first few lines of posts #55 and 61).

And yes, it is something you can accomplish by bolting on an efficient hydrogen source (e.g. Plasmatron, tank of H2, maybe even a really good electrolysis machine) to an existing car. But for an existing car, you have to add an EFIE device to offset your O2 sensor output so that you can lean out your mixture, otherwise the car computer will detect less O2 in the exhaust and richen the mixture. You cannot run too lean with a standard gasoline engine because they are not built to handle hot (lean) combustion.

The process is known to work far better on diesel engines because they are built to run lean and hot, which is why the idea was sold to Arvin-Mentor who is (or was) going to build bolt-on Plasmatrons for diesel engines. I don't know if they are still going to do so.

 

No, this won't work. You need a different engine design to get the benefits of the MIT claim. Adding an EFIE device only makes for an overly lean conventional engine, which will result in better mileage at the expense of engine damage, which is what you point out at the end of your paragraph. You seem to be arguing both sides of the point.

Tom

 

10 A won't make much hydrogen: only about 75 mL/min in a single cell. You could perhaps run up to 3 cells in series on 12 V depending on the overvoltage at your electrodes, but that's still only 225 mL/min of H2. Hydrogen production will be proportional to current, but even at 100 A you're not generating a whole lot of hydrogen- 2250 mL/min at most.

In energy efficiency terms, the energy content of that hydrogen will be small relative to the energy it took to make it. By the time it's through your IC engine, the WORK you get back out of that chemical energy will be even less. Electrolysis is at best 60% efficient, and the IC engine is what, 15-30% efficient at converting chemical energy to work- do the math.

Compare that hydrogen flow to the 1.5 L IC engine's draw of about 1500 L/min of air at 2000 rpm. That's 50 to 150 ppm(V) of hydrogen in the feed air. Not enough for the engine to notice in any way that's going to affect fuel economy. LOTS of components of gasoline vary by tens to hundreds of times this amount from source to source.

Comparing this tiny hydrogen addition to the SIGNIFICANT quantiities of hydrogen made by a Plasmatron FROM THE FUEL ITSELF is plain silly. The Plasmatron is a fuel reformer which completely alters the fuel chemistry.

You don't get power from the alternator for free: it represents fuel-sapping drag on the IC engine which is proportional to the current draw. And if you divert energy from the traction battery, that's energy that you could have used (part of) later to move your vehicle. You get no free lunch here.

As to the notion that hydrogen makes the fuel burn more efficiently: that implies that there's unburned hydrocarbon and CO in the exhaust in sufficient quantity to get the desired energy from, and there isn't. The (ppm) quantities of HC and CO that are there in Prius exhaust are there deliberately to reduce NOx in the catalytic converter.

As to the theory that the hydrogen affects the ignition or propagation of the burn: lovely theory, but I fail to see how it could work at these tiny concentrations. Get the hydrogen concentration up to a couple percent (ie. 10,000 ppm(V) or more) and perhaps you have a shot. In a diesel- even more chance because it could actually affect burn efficiency rather than just timing. But there's precious little soot being generated by a properly tuned diesel either.

Those who think hydrogen is a magical substance will not be convinced, so why did I bother to comment?

 

You're right, I do seem to be contradicting myself, but let me qualify that. I had thought about this quite a bit when I was doing it. There is a way not to wreck your engine, but it adds to the complication level - which is why I went the Prius route. To understand just how great the Prius really is, you almost have to try to solve the problem of getting better cas mileage yourself...

As an engineer, this has been a very technically satisfying excercise for me .

The ICE is most inefficient when it is idling and driving slow in traffic, so you get your worst mpg there. The EGT (exhaust gas temperature) and hence the burn temperature is also the lowest in that speed range. When you are driving at high speeds, uphill or pulling a heavy load, that's when your EGT goes up to it's maximum levels and your valves etc can get burnt. But at higher speeds (55-65 mph, normal load), the ICE is also in it's most efficient range (best mpg). So what I was thinking at the time was I would only have enabled the hydrogen injection/lean mixture while driving slow in traffic (and believe me, I sit in plenty of that). I would have installed an EGT gauge and monitored it to make sure that I didn't screw up my engine. Actually implementing all of that so it works automatically becomes very complicated. There are many engineering problems that have to be solved. It's not for the average backyard mechanic who just wants to slap something together and save gas.

 

But what if I really, really want it to work? Will it work then? :madgrin:

 

Exactly, but these hydrogen gizmos are just that -- something slapped together. Significant fuel savings are only going to come from a significant reengineering of the car and its engine, as was done with the Prius. You can't just bolt on one thing.

 

I'd say your time and money would be much better spent learning how to drive your Prius properly. There are plenty of people on here who get 60mpg without any major mods.

I have to go along with the majority of the folks here and agree that its pretty much as simple as no free lunch (ie first law of thermo always applies). Electrolysis is a fairly inefficient process, as is burning Hydrogen in an ICE. Put them together and you get much less mechanical energy out than the added mechanical load the alternator puts on the ICE. Adding Hydrogen to gasoline may make it burn better. But using gasoline to make electricity, and then using electricity to make hydrogen, and then using the Hydrogen to make the gasoline burn more efficiently is heading for perpetual motion territory. Given how inefficient an ICE is in certain operating regions, there may very well be conditions under which efficiency could be improved. My guess is that the vast majority of the time you would be at a net loss and at least canceling out any gains. You could of course design a fairly sophisticated control system that would load the engine to improve efficiency in low efficiency conditions, storing the excess energy as Hydrogen and then burning it off at the times when it can be used to improve combustion efficiency. Now you are talking about designing something almost as complicated as the Prius' control systems. I kind of doubt that can be accomplished in anyones spare time for a few 100 dollars in parts from the HW store. On top of that, the Toyota has pretty much already played that card. Since the hybrid system already works to optimize efficiency under most of the classic low efficiency operating regions of the ICE, there will probably be very little benefit to further optimization.

If you like to tinker and want to reduce your fuel usage a plug-in conversion would be way more effective.

Rob

 

I would have to say that if the OP is getting 44mpg with his Prius then he is robbing himself of decent mpg buy using that junk that he is selling but saying he isnt.

I get 50 just by driving with only what Toyota and ScanGauge envisioned.

 

Screw this H2 Generator crap, just run down to to your local Airgas, BP gas, or other industrial gas house and buy a 60 lb. tank of h2 and strap it in the back of the car. Plumb some tubing, hook up a regulator, and directly inject into the ICE!!! Your good to go!!!

WARP SPEED de Pat KK6PD

PS NO SMOKING IN DA CAR!!!

 

This topic has been kicked around before. Some of the previous proponents were charter members of the tinfoil hat group, and had some very goofy ideas. You hit a nerve, which doesn't excuse the attacks, but does help explain them.

Tom

 

Well, before just assuming it's all crap, it could be informative to read through some of the research that has already been done on hydrogen. None of this is new; here's an excerpt:


"A study by the California Institute of Technology, at its Jet Propulsion Lab Pasadena, in 1974 concluded:

• The J.P.L. concept has unquestionably demonstrated that the addition of small quantities of gaseous hydrogen to the primary gasoline significantly reduces CO and NOx exhaust emissions while improving engine thermal efficiency"

For those interested, here's the address

hydrofuelsolutions.com/Goverment_press_releases.html

-Cheers

 

hydrogen != prius

If you wanted to discuss methane, ethanol or manufactured gas as part of your on-going experiment with some data, no problem. But the world is full of folks who will express and opinion without doing the 'heavy lifting' and doing the experiment.

Bring back your experimental results, and I'm interested. Bring up "I wonder if ..." without evidence of having done the experiment in a controlled fashion and I would recommend "Fred's House of Pancakes."

There is nothing 'hybrid' about 'hydrogen' except they share the first two letters.

Bob Wilson