Six Stroke - The answer to our addiction to oil.

[hurricanecentral]

I would like to have some opinions on this. I think it is a great idea.

http://en.wikipedia.org/wiki/Crower_six_stroke

[beef_bourito]

that looks like a very interesting concept. it would be interesting to see the cam tuning in something like this, you wouldn't really want to get rid of all the exhaust in the chamber and might actually want to close the exhaust valve BEFORE TDC to keep some extra hot gasses and allow more water to be turned into steam.

One definite problem i can see with this would be the fact that steam is passing through the exhaust. this could cause problems with mufflers and might force people to use straight through mufflers in order to reduce the water that gets stuck. also, i wonder how efective the cool down period would be at removing this water, because in cold climates you definitely don't want water freezing in your muffler.

another thing would be lubrication. does anyone know how this would affect lubrication?

it would be really cool to hear one of these go though, the sound would be completely different from any normal vehicle you see nowadays. i also wonder, if it was made and improved upon, what kind of revs it could achieve. i doubt it would be able to get very high revs, but it'd be interesting to see.

edit: one possible solution to the steam in the exhaust would be to use one valve for your regular exhaust and one valve for the steam exhaust and have two separate systems of disposal. this would make the system more complex and might hurt exhaust flow or make the heads strange or complicated but would solve the problem.

[Steel]

It would suck for all of us up north that depend on the inefficiency of the ICE to warm up our frozen toes!

[beef_bourito]

haha very true. these would probably need an electric heater for the winter.... or a gas heater like in the old bugs haha.

this is somewhat off topic but somewhat related. i was doing some searching and there's this guy who made an engine that he claims is a 6 stroke engine, i don't really think it would count as one. http://www.sixstroke.com/ it's an interesting design that looks as though it could be a valid technology. the concept looks good but the sight looks like very similar to a scam website and the only drawing or hint at what the hell his engine is is that little animated .gif (http://www.sixstroke.com/images/sixstroke.gif) on the side of the webpage.

i don't want to highjack this thread, but any thoughts about this?

[KiwiBacon]

They claim 40% improvement over a conventional engine. Baseline your current engine at 25% max, this one would make it to 35% efficient.

That's still leaving 65% of your fuel as waste heat and is only competitive with old diesel engines. Modern diesel engine efficiency is still higher, without the water injection sixth stroke.

[beef_bourito]

what if you made it out of a diesel engine? that's what i was thinking about. you've already got direct injection, all you need is either a second injector or a second line to the single injector for water, and of course different cams, and the top end it done.

[KiwiBacon]

Originally Posted by beef_bourito

what if you made it out of a diesel engine? that's what i was thinking about. you've already got direct injection, all you need is either a second injector or a second line to the single injector for water, and of course different cams, and the top end it done.

A six stroke diesel existed about 5 years ago, but the purpose of the 5th and 6th stroke were emission control. Essentially burning any excess soot. I don't know what happened to it.

A six stroke engine would have to demonstrate a large advantage to offset the loss of power (hence weight and size gain to get the required power) and extra complexity. I guess they're not there yet.

[hurricanecentral]

Originally Posted by beef_bourito

that looks like a very interesting concept. it would be interesting to see the cam tuning in something like this, you wouldn't really want to get rid of all the exhaust in the chamber and might actually want to close the exhaust valve BEFORE TDC to keep some extra hot gasses and allow more water to be turned into steam.

One definite problem i can see with this would be the fact that steam is passing through the exhaust. this could cause problems with mufflers and might force people to use straight through mufflers in order to reduce the water that gets stuck. also, i wonder how efective the cool down period would be at removing this water, because in cold climates you definitely don't want water freezing in your muffler.

another thing would be lubrication. does anyone know how this would affect lubrication?

it would be really cool to hear one of these go though, the sound would be completely different from any normal vehicle you see nowadays. i also wonder, if it was made and improved upon, what kind of revs it could achieve. i doubt it would be able to get very high revs, but it'd be interesting to see.

edit: one possible solution to the steam in the exhaust would be to use one valve for your regular exhaust and one valve for the steam exhaust and have two separate systems of disposal. this would make the system more complex and might hurt exhaust flow or make the heads strange or complicated but would solve the problem.

I like the idea of seperate exhaust systems. Maybe just go with the typical four valve configuration found on most of today's small four cylinder engines, but just have the two exhast valves opening on different strokes. Good thinking. I also like the idea of converting a diesel engine as opposed to a gasoline engine. Hotter temperatures = more efficience in this case I would guess.

[KiwiBacon]

The Beare design is basically moving the head to increase the expansion volume.

It's a little like the take on the atkinson cycle where the power stroke is longer than the compression stroke. I think it has some potential, but there are a lot of details to overcome.

[vgames33]

Sinch this thread is essentially about recovering energy wasted through exhaust heat, I suppose this post fits.

What about stirling engines? Perhaps they could be placed near the cooling or exhaust systems to recover heat energy? I know it would be complex, but it is possible.

[KiwiBacon]

Originally Posted by vgames33

Sinch this thread is essentially about recovering energy wasted through exhaust heat, I suppose this post fits.

What about stirling engines? Perhaps they could be placed near the cooling or exhaust systems to recover heat energy? I know it would be complex, but it is possible.

An excellent solution for large and stationary plants. But too bulky and heavy for transport solutions.

Check out http://www.whispergen.com
It's a New Zealand based company which started at the university I attended.

[GreyGoose006]

only problem with converting a diesel is that diesels typically run at lower temperatures than gas engines do.
in my experience at least

[kodackz]

Originally Posted by hurricanecentral

I would like to have some opinions on this. I think it is a great idea.

http://en.wikipedia.org/wiki/Crower_six_stroke

A few things.

Water does not easily flash to steam against a hot metal surface. What happens is that once the water comes in contact with the surface it immediately expands causing a buffer of hot steam to prevent the rest of the water from easily touching the heated surface. You can observe this by heating a pan to 400degrees and putting a few drops of water in it, they will dance across the surface, not immediatley turning to steam.

This same process is what can cause nuclear meltdowns as water is pushed away from the hot reactor core by steam, which causes the core to heat up even more. In systems like that the water must be injected in at very high pressure to prevent steam from forming too soon. This super heated water only flashes to steam once it is de-pressurized.

I don't see this as working well in an internal combustion engine. The water would need to be injected at tremendous force during the up cycle of the piston. Valves are normally closed when the piston is in it's compression phase for a good reason. You will ruin your valves if they have to fight the compression stroke.

The second problem is the water would have to be greatly pre-heated to just below flash temperature before it is injected.

The last problem is that water in any closed piston system can cause your engine to self destruct as water does not compress. Any failure to completely evacuate the water after each stroke could lead to engine failure.

One further thing, steam expansion inside of a piston is much slower than with a fuel/air combustion stroke. Think "steam engine". This would cause a power drain as this piston tries to move slower than the others burning fuel in their combustion cycles.

Modern steam installations use turbines to overcome this.



Now I do know that during WW2 they sometimes used water/steam injection on certain rotary aircraft engines to provide additional power for carrier take offs. I'm not sure how they made that work, but they only used it briefly and for all I know the water only added additional cooling for an ultra lean fuel air ratio.

[kodackz]

Originally Posted by vgames33

Sinch this thread is essentially about recovering energy wasted through exhaust heat, I suppose this post fits.

What about stirling engines? Perhaps they could be placed near the cooling or exhaust systems to recover heat energy? I know it would be complex, but it is possible.

Sterling engines don't like to change RPM and were found to be unsuitable in mobile applications. They require a stable motionles platform to do their work.

What might be interesting is if we found an efficient way to store the heat from our exhaust for re-use later.