Engines running on hydrogen...?

[rtbcomp]

There are plenty of videos on YouTube showing sperk-ignition engines running on wood gas without a complicated mixer, just a pipe blowing the gas into the inlet manifold. with a tap on the gas pipe to control the mixture.

My LPG conversion started on gas from cold or hot with no problems, there was a solenoid which just enriched the mixture slightly.

The injector was a simple ring of holes between the air filter and the carb. The only complicated bit was an evaporator and regulator unit.

 

[Cris B]

Very interesting topic. I had a search on our academic databases on the university library and I'd recommend you look at some articles in the International Journal of Hydrogen Energy. Quite a few things written on this by the experts in this field.

 

[Cris B]

Highlights from IC Engine section in issue 7 volume 36

► Hydrogen engines may be designed to run stoichiometric using direct injection of hydrogen fuel and port injection of water. ►*This simple but reliable design avoids the three regimes of hydrogen abnormal combustion, knock, pre-ignition and backfire. ►*The water injection also keeps the temperature of gases to turbine below the manufacturer's recommendation. ► The stoichiometric*turbocharged hydrogen engine has very high power and torque densities permitting amazing downsizing. ► The sample engine delivers more than 40 bar of brake mean effective pressure with fuel conversion efficiencies above 40%.

 

[Gas mark 5]

Thanks for all the responses! The International Journal of Hydrogen Energy looks great, I'm trying to see if the school will pay for anything though

I thought this thread was in need of a couple of pictures, so I dug out the engines I have in mind to check what condition they're in.

I thought there were three engines in that box, there were nine! They're breeding!

Here's the first one, just about fine to run off petrol at the moment. I think I may have nicked a bit of the carb, and the pull start is dead, but otherwise it's working all right.

And here's the other one, it had been sat outside for years before I got it, I haven't investigated it much at all yet. It turns over, and has compression, and a nice big spark, which is a start. Peering in through the plug hole it looks clean (No water / rust or anything).

Should be a laugh at any rate, I'm not too fussed if it works in the end or not, I'm young and foolish and just want to have fun. I might see if I can get hold of some stainless (Unless anyone's got some cheap platinum lying around? ) and have a go making a better electrolyser. Then I can have some reasonable quantities of hydrogen to play around with.

I'll let you know how it goes

 

[rtbcomp]

Carbon might work as an electrode, I suspect stainless won't last all that long.

 

[jimzzr]

A few points:.

1) It would be better to get a gas cylinder and then you can just regulate the flow to premix (assuming you also have a compressed air supply) whatever air fuel ratio you wish to use. I think with your electrolysis idea you'll end up with a stoichiometric (all the fuel reacts with all the oxidant) H2/O2 mix (i.e. 66% H2 and 33% O2 by volume mix) unless the anode and cathode are positioned so that gases can be collected separately. Stoichiometric hydrogen in air is 29.5% by volume.

2) combustion is a lot more complicated that schoolboy chemistry suggests. H2/air combustion actually proceeds by free radical chain branching reactions with some 60 different reactions being required to fully describe the reaction kinetics.

3)For explosion of stoichiometric hydrogen initially at RTP (i.e. 1 bar absolute) in an enclosed volume you'd get a theoretical peak overpressure (no heat losses) of 7 barg (10 bar for hydrogen oxygen). If the initial pressure is doubled the overpressure is also doubled. For lengths of pipe detonation (Delagration Detonation Transition) with higher overpressures could be an issue. There is a free thermochemical equilibrium solver called GASEQ which is useful for predicting such things. The overpressure is similar to that for hydrocarbons but hydrogen is much faster burning (5 times 300cm/s vs around 60cm/s for propane - presumably why pre-ignition is a problem) and much more easily ignited. Small premixed hydrogen explosions can be very loud. Trying to store significant quanties of premixed H2/O2 or air could be risky.

 

[Gas mark 5]

Hello, thank you for that.

I've lit balloons of stoichiometric ratios of hydrogen + oxygen before, I'm in no hurry to store large quantities of the mixture!

I'm not sure if you're suggesting I should be compressing the hydrogen in a gas cylinder (Where does the compressed air supply come in?). I see what you mean about being able to regulate the flow easily though. I'm planning on collecting the gasses separately, however I believe the hydrogen needs to be 97% purity (Or rather, no more than 3% Oxygen) to ensure it isn't flammable, and I don't trust myself to get that sort of purity when it comes to compressing / storing it. The idea of flying gas cylinder shrapnel doesn't appeal! So I was wondering about temporary uncompressed storage, in plastic bottles or something. Enough to run an engine for a few seconds, but that if it did go pop it wouldn't be as lethal. I wonder if that means I get to blow up drinks bottles by way of my risk assessment?

Points 2 and 3, as you mention I'm still at schoolboy level. I understand mostly what you're saying but wouldn't know how to do calculations based on it. I've had a look at the GASEQ program, it looks potentially very useful, but I don't know how to use it yet. Are there any in depth books on these sorts of subjects, or will I just have to wait for uni to understand more theory behind this?

Otherwise I'll just use what I know all ready and experiment and see if anything works. I'm usually quite good at that, but it's nice to really understand the underlying principals.

 

[Rich H]

The cam is in the block and driven by a gear, so you could advance or retard it a tooth at a time but it'll be a pain to do and quite a coarse adjustment.

If detonation is a problem then whip the head off the engine you are going to use and clean everything up, they soot up like mad inside and this will give hotspots that may upset your hydrogen mix.

Have a look at the woodgas engines and how they meter the fuel air mix.

If you can work out how to adjust the ignition timing I don't think it'll be that hard to get it to run a bit.

How about using a electrolysis cell to generate your hydrogen (Vent the O2) for immediate use. Storing any quantity would be hazardous and bottles of H2 would be expensive and similary dangerous.
Either way good luck and keep us posted!