How do I design a cylinder head?

[Machbuild]

I am currently working on my own hydrogen engine and I need a special cylinder head for my gx390. How do i go about designing by own rebust cylinder head for my engine. Thank you!

 

[Nerd1000]

That's a question one could write entire books on. Hydrogen is likely to be especially hard to work with because it is easily ignited by even the tiniest spark or friction source, such as your piston rings... for this reason most serious investigation into hydrogen engines has looked at direct injected designs.

Your starting point would be the way the rest of the engine is designed. E.g. the GX390 uses pushrods and rockers so you are stuck with head designs that work with that layout. Then you'd choose chamber shape, spark plug location and volume for your design goals (compression ratio, flow, etc). Finally you need to figure out everything else: valves, ports, valve train, bolt locations, finning for cooling.

I'm unsure why you'd want to design a whole new head though. Why not look at modifying the existing one for your needs?

 

[Lloyd-ss]

I guess you have already been doing a lot of reading on the subject, correct?
I am thinking about gasoline to propane conversions which are pretty run-of-the-mill these days. Gasoline vapor and propane in its gaseous state have characteristics that are similar enough that they can be run in the same engine with just a carburetor change.

But hydrogen is quite different.
Gasoline has a stoichiometric ratio with air by weight of 1 gasoline to 14.7 air.
Propane has a stoichiometric ratio with air by weight of 1 propane to 15.5 air. Or about 1 to 24 by volume.
Volume-wise, gasoline vapor and propane in stoichiometric ratios aren't too different, so there is reasonable engine compatibility without serious changes.

Hydrogen, on the other hand, has a stoichiometric ratio with air by weight of 1 hydrogen to 34.3 air. But volume-wise it is about 1 to 2.4 (yes, 2 point 4).
So wouldn't that require some serious changes in the head? I don't really know, but it sounds like a real challenge to me.

Do you have drawings of any hydrogen engines to use as a starting point?
Good luck to you, and keep us informed!

 

[Machbuild]

That's a question one could write entire books on. Hydrogen is likely to be especially hard to work with because it is easily ignited by even the tiniest spark or friction source, such as your piston rings... for this reason most serious investigation into hydrogen engines has looked at direct injected designs.

Your starting point would be the way the rest of the engine is designed. E.g. the GX390 uses pushrods and rockers so you are stuck with head designs that work with that layout. Then you'd choose chamber shape, spark plug location and volume for your design goals (compression ratio, flow, etc). Finally you need to figure out everything else: valves, ports, valve train, bolt locations, finning for cooling.

I'm unsure why you'd want to design a whole new head though. Why not look at modifying the existing one for your needs?

Hi thank you for your response. The biggest reason why I was planning on having to redesign the cylinder was because i remember reading somewhere that one of the best options for hydrogen in ICE is injecting the hydrogen during the compression stroke. It is possible for me to be able to use the original cylinder and just add a couple of sensors that know when hydrogen should be released into the engine and tap in another screw that would be used for the hydrogen injector. Do you think that tapping a screw into the engine would be structurally sound. I understand that the sparkplug makes a big hole in the cylinder head but I dont know if adding another one would screw it up or not. Also would using the stock cylinders work. Because i personally dont know how much of a seal the valves have with small particles such as hydrogen.

 

[Machbuild]

I guess you have already been doing a lot of reading on the subject, correct?
I am thinking about gasoline to propane conversions which are pretty run-of-the-mill these days. Gasoline vapor and propane in its gaseous state have characteristics that are similar enough that they can be run in the same engine with just a carburetor change.

But hydrogen is quite different.
Gasoline has a stoichiometric ratio with air by weight of 1 gasoline to 14.7 air.
Propane has a stoichiometric ratio with air by weight of 1 propane to 15.5 air. Or about 1 to 24 by volume.
Volume-wise, gasoline vapor and propane in stoichiometric ratios aren't too different, so there is reasonable engine compatibility without serious changes.

Hydrogen, on the other hand, has a stoichiometric ratio with air by weight of 1 hydrogen to 34.3 air. But volume-wise it is about 1 to 2.4 (yes, 2 point 4).
So wouldn't that require some serious changes in the head? I don't really know, but it sounds like a real challenge to me.

Do you have drawings of any hydrogen engines to use as a starting point?
Good luck to you, and keep us informed!

Hi thank you for your reply. I have been doing a good amount of research lol. I was planning on using pure oxygen instead of air. The largest reason for this is due to another pollutant that isnt the best for people and the environment NOx. This engine will be connected to an electrolysis machine. With this change the stoichiometric ratio being 1 to 2. This is also why I am also curious about if oxygen will do well behind a valve in a storage tank. Do you think I should change the intake valve to another fuel jet? Let me know.

 

[Lloyd-ss]

Hydrogen has more of a tendency to leak than oxygen.
I am sure you already know how dangerous either of these gasses can be if improperly handled, but I felt like I should say that since I am commenting on your project. Certainly no offense meant.

Seriously though, if you can find information on a successful hydrogen ICE, or do a patent search to see what pops up, that would be helpful.

 

[Nerd1000]

Hi thank you for your response. The biggest reason why I was planning on having to redesign the cylinder was because i remember reading somewhere that one of the best options for hydrogen in ICE is injecting the hydrogen during the compression stroke. It is possible for me to be able to use the original cylinder and just add a couple of sensors that know when hydrogen should be released into the engine and tap in another screw that would be used for the hydrogen injector. Do you think that tapping a screw into the engine would be structurally sound. I understand that the sparkplug makes a big hole in the cylinder head but I dont know if adding another one would screw it up or not. Also would using the stock cylinders work. Because i personally dont know how much of a seal the valves have with small particles such as hydrogen.

Ahh so you were thinking of direct injection. I don't know if you could just put another hole in the head to accommodate an injector, if you had a spare head maybe you could cut it up and see how much thickness is available.

That being said, I think building a gaseous hydrogen direct injection system is not a trivial matter.

 

[Machbuild]

Hydrogen has more of a tendency to leak than oxygen.
I am sure you already know how dangerous either of these gasses can be if improperly handled, but I felt like I should say that since I am commenting on your project. Certainly no offense meant.

Seriously though, if you can find information on a successful hydrogen ICE, or do a patent search to see what pops up, that would be helpful.

No offense taken. I defenitly know the dangers and I think thats why I am going to maybe use two fuel injectors.

 

[colby15642]

The Coolspring Power Museum operates some of its early Otto Cycle and Lenoir Cycle IC stationary engines on bottled hydrogen. The hydrogen mixes with the combustion air outside of the combustion chamber during the intake stroke. As expected, the combustion event is noticeably rapid but the amount of energy released during combustion is relatively low. By compression pressure measurement, most of these Otto Cycle engines have about a 2:1 compression ratio. Ignition is by traveling pilot flame. During starting, the occasional back-fire into the intake pathway can be disturbingly sharp and loud.

A mixture of 15% propane and 85% hydrogen makes a more powerful and controllable gaseous fuel. Making that blend in an empty propane tank is surprisingly easy.

Unburned hydrogen can quickly rise and accumulate at the ceiling or peak of you shop The limits of combustibility of hydrogen in air are reported to be 4% to 74% and in oxygen 4% to 94%. Among conclusions you can draw from that are 1) that precise stoichiometric proportioning needn't be a primary goal and 2) that you can instantly turn your shop into a smoldering pile of pine splinters and a cloud of drywall dust with relative ease. Piping the exhaust from your engine outside is highly recommended.

The amount of NOx that your model engine will generate will be virtually undetectable compared to the smoke resulting from combusting trace amounts of lube oil.

 

[Steamchick]

Your question "how to design a Cylinder head?"....
Based on a "one-day-snapshot" bit of training - 30-odd years ago at Engine Design in a Motor Car Manufacturer ... (If I remember much of that!).
Some steps to follow:

• Consider cylinder spacing (multi-cylinder engines) to determine how close the next cylinder is on each side, which restricts the "metal space" for valve gear and stuff. Also other considerations like stuff that hangs off the ends of the cylinder head. drive chains for cams, variable valve timing gear, oil feeds, ignition kit, etc.).
• When you know what space you have outside, consider the space inside: - the combustion chamber bit. - Flat pistons, domed pistons, cut-aways for valves, pockets for diesel pre-combustion, etc. are all considerations that have to be decided and integrated with the piston design. STICK TO a flat piston and head configuration.
• Think of as cylinder head not as a lump of metal with some holes in it, but a series of passages and chambers that all have to fit above the end of the cylinder. Easier to make some Solid tubes for intake and exhaust from Plasticine (Modelling clay) and stick them on a circle equivalent to the face of the end of the cylinder. The MOST important thing for MOST engineers is maximising gas flow flow into and out-of the cylinder. So start with those:
• WHEN you have a clear understanding of the passages you need, consider how you'll fit the valves and operating gear above the gas passages, to get the poppet valves (or whatever) at the ends of the gas passages. (One guy developed "swing valves" for his racing engines, that gave better gas flowed passages than straight acting valves - which are cheap and simple.).
• Only then can you consider where the spark-plug can fit, and anything like fuel injectors, etc.
• Now add the cooling water passages in the gaps, separated from all the other parts by solid metal...
• Finally, look at all the metal - a very complex shape - and consider how strong it is - and add more metal where it breaks on test! Large Motor manufacturers take a few years designing, doing finite element and stress models for temperature, gas flow, strength, durability and manufacture before getting close to casting early prototypes... then a couple of years more before getting to a production version. - I picked up on the last 12~18 months of the production development.... and found some early stuff was from 5 years earlier...
• After 5 years or so - with a team of half a dozen skilled engineers in various roles - you may get close to something Mr Honda has developed.....

There are guys who make racing heads for engines, and spend a lifetime perfecting their art. So be prepared for a long and interesting career... (Some actually do a lot of Design , and some just bodge around and develop-out the things that go wrong).
ENJOY!
K2

 

[iamthepokemonmaster69@yah]

No offense taken. I defenitly know the dangers and I think thats why I am going to maybe use two fuel injectors.

i made a go kart run on hho from a electrolysis cell in 2008 first thing id do is buy a total seal piston ring without liquid in the cylinder to help seal the rings you lose a lot of gas from blow by also without liquid in cylinder you need to raise the compression up way higher i went to 13 to1.

 

[HMEL]

I am currently working on my own hydrogen engine and I need a special cylinder head for my gx390. How do i go about designing by own rebust cylinder head for my engine. Thank you!

There are a number of good recommendations in the posts. You should know that a lot of work has already been done on developing engines that use hydrogen fuel. The Japanese have done considerable work on this topic. So has Ford and maybe GM. The heads are no different than an gasoline type engine. But however you do the calculations be sure to include the thermal expansion and the stress developed on the studs and bolts. Using gaseous fuels has been done for some time and there are a number of ways to handle them including hydrogen. For example when I was younger I operated a tractor that started on gas, was switched to tractor fuel and then to propane. It did take some care to keep it fueled but I dont ever remember running out of fuel. I also have had contact with people who design the carbon fiber tanks for utilizing hydrogen and the technology for doing this is pretty far advanced. I think about any compression ratio would do except in the diesel range of 12 to 1. or higher. The head space and your gasket will be a part of that calculation. I only say this because I do not have the information to share with you on the detonation point of hydrogen oxygen mixture on pressure.
Good Luck