--- Water injection VS Steam Injection ---

[Christ]

Water being homogenously mixed with air yields a smaller percentage of available O2 per unit.

Ideally, you'd want to limit the combustion chamber's floor and walls, keeping ("dry" water not included) mixture as close to the spark plug as possible, and in an oblong-ish football shape, which enhances the flame front to spread at the fastest rate possible. (This is evidenced by modern piston design, which limit access to the intake valve, concentrate fuel mixtures nearer the exhaust valve to take advantage of heat, and propagate an initial flame front in a sort of oval shape.)

To do this, a valve at the bottom of the piston's travel could be used, to ensure that any water/steam introduced would "pre-compress" any mixture in the cylinder. Keep in mind that this would also increase cylinder pressure, which technically would act sort of like boost, except it wouldn't really increase VE.

That's how I understand it, at least. The best thing I can tell you is to try it... the worst that happens is you have to replace some rings and bearings, right?

[hypermiler01]

Originally Posted by basslover911

^ Thing is, turbine engines actually use steam (from water being burnt into steam in the exhaust area, just like what I wanted to do), and it works perfectly fine.

Not just like you want to do. They boil the water in a pressurized container and the high pressure steam turns the turbine as it escapes. You are talking about injecting steam into the intake manifold, which is open to the atmosphere, and so will be at regular manifold pressure when it enters the combustion chamber.

If you put steam in the combustion chamber, it will just be taking up space. Again, by injecting water, rather than steam, you have a gas that is EXPANDING INSIDE THE COMBUSTION CHAMBER, which is a good thing.

[Frank Lee]

Non-oiled cylinder walls?

Then how do piston steam engines avoid self-destruction?

[tasdrouille]

Originally Posted by Christ

You can add propane to your gas engine relatively easily if you want to use less gasoline per combustion cycle, but in order to lower the actual size of your engine, you should just REALLY lower the size of the engine, instead of trying to add stuff to your mixture.

There's EGR. I would believe injecting steam is pretty much just like injecting an other inert gas.

[hypermiler01]

Originally Posted by Frank Lee

Non-oiled cylinder walls?

Then how do piston steam engines avoid self-destruction?

Firstly, they don't run at 3000 rpm.

[Frank Lee]

They can go 100 rpm; w/o oil they'll seize up... right?

[BrianAbington]

most water injection units have such a fine spray that its almost as fine as steam. However...the problem is that if you use steam it already has heat in it so thats less heat that the water will take away from the engine...compared to a water injection that pulls water or methanol from a tank that you can put ice in.

[Andyman]

I found a web site that has plans to make a steam injection system. They say that steam injection works better than water injection because the steam condenses into smaller droplets when it mixes with the air stream and the extra heat helps to vaporize the gasoline.

I don't consider their plan to be ideal. It uses vacuum to draw in the steam so it wouldn't work under full throttle. I think it would be best to have the system vary the water flow rate according to the fuel flow.

Here is the web site with the plan:
Better Gas Mileage with improved energy efficiency by water injection.

Here is one about water injection that includes some test results:
Water Injection By Robert Mann

Mother Earth News had an article about using an emission control air pump to power a water injection system.
WATER INJECTION WIZARDRY

Wikipedia has another article about water injection. It include links to some more web sites.
http://en.wikipedia.org/wiki/Water_injection_(engines)

[Azmio]

wow this thread is great. Here's what I did in my water injection research. I first compress the water to more than 100 bar. Next I subject it to intense heat sources like exhaust gas and coolant. Water when compressed has its specific heat capacity and boiling temperature increased. This means, it can absorb a lot of heat without boiling.

Once water is heated, I inject it into the combustion chamber right after ignition has started. The intense heat will be absorbed by the water and the water will turn into steam to expand. High gas constant R will ensure that the steam expands few times better than air.

Read more of these in my 2 papers; SAE 2009-01-2808 and SAE 2009-32-0047. You guys gonna love these 2 papers.

[dcb]

you have copies you can attach?