--- Water injection VS Steam Injection ---
 

I know that water injection supresses detonation, and you can increase timing on the engine (all because the water vaporizes in the combusion chamber and cools etc etc).

But what if you injected the water as a vapor already? Heat the water to around 300 degrees and inject it... what would happen? Would it heat the engine up to much? Could you still advance timing?

Wouldn't have the same cooling effect. Remember heat of vaporization: it takes a whole bunch of energy to turn water at 212 F to steam at the same temperature.

The benefit of water injection is that you can get cheap fuel(meth) in the form of winter windshield wiper fluid, and lean out your top end, or any end that the WMI is spraying at. Water as a vapor may help, but it's the phase change that sucks out the heat, and allows more timing/boost/whatever. I don't know if the steam would do much as far as absorbing heat, but I know it would absorb space.

It'd probably make the innards nice n clean.

Well if it "absorbs" space then that is good when cruising because it means less fuel and more throttle (opening more, reduce pumping losses).

I dont know if I am right, but doesn't steam have more surface area than drops of water? What i am trying to get to is if this would make up for the hotter temp of steam vs water and have the same cooling effect...

Surface area is a meaningless concept for steam: it's a gas, which by definition doesn't have a surface.

What would happen is you would just pump the crankcase full of water.

That would be a BAD thing, because the cylinder walls need to be oily.

Not only does water injection absorb heat and cool the engine, but while it is absorbing the heat, it converts to steam and expands, assisting the other combustion gasses in pushing the piston downward. This effect would be completely lost if it was steam already.

As far as taking up space in the combustion chamber, this was discussed in another thread using gaseous CO2... the end effect could cause a problem, unless the influx of steam/water/whatever was specifically controlled to allow the air/fuel mixture to remain as close to the spark plug as possible. What you wouldn't want is a cloud of steam shrouding the spark plug, because you would then have a net loss of power, a bunch of wasted fuel for each spark event, and a net loss of MPG.

Oh, and non-oiled cylinder walls as well.

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.

^ 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. Its actually called "energy recovery".

As far as being mixed in with the fuel, it will be a homogenious charge since it will be injected FAR behind the throttle plate and it will thoroughly mix with the air....

Who knows, I am just theorizing here

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?

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.

Non-oiled cylinder walls?

Then how do piston steam engines avoid self-destruction?

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

Firstly, they don't run at 3000 rpm.

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

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.

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)

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.

you have copies you can attach?

dude, you have to purchase it online for 12 bucks. It's protected by SAE copyright. otherwise i would have given you for free.

Buy the first paper and if you like it you can purchase the second one. The second one discusses on the theoretical performance of the engine.

I don't charge for what I know on an open forum. sorry, cant relate.

Even if SAE gets millions from selling my paper, I wont get a single cent. In this context, I also dont charge anything for sharing my knowledge.

However, if you want to ask me anything with regard to the content of the papers, i wont mind spending days answering your questions in this thread free of charge.

Gimmie $14 dollars and I will respond to that post :)

sorry dude, i dont pay others to share my expertise in this forum

I can't see paying anything just to see if random guy has a clue for that matter. I did see you posting your sae numbers all over the net though.

Why not cut the SAE stupidity and say something useful?

what's wrong with asking comments from others? any problems pointed out can be used to evolve the concept further. I welcome criticisms even in international conference.

you are asking people to give money to SAE, constantly, all over the net. This forum is for sharing info, not solicitations, that borders on spam.

Honestly, like I said, I can't relate to the agenda where someone would hide their hard work in the SAE so it isn't freely available. How many $15 papers is the rest of the world suppost to buy that result in crap conclusions or assumptions? If I had something to share, I would share it, what is in it for you to lock it up in SAE and try to persuade everyone else it is worth paying for? What is your agenda?

so what do you want me to share since you havent asked any technical question yet about the water injection?

I would be happy to know what was the net efficiency gain was for starters :)

calculated to be roughly above 70%. The thing is, many of the engine parts and simulation codes that I need are not available anywhere.

The trick is simple, minimize heat from going to coolant and exhaust gas. even if some escapes, absorb it using heat exchangers and inject the heated water back into the combustion chamber

you can even heat up the water to be injected using heat from your brake caliper. any increase even by 5 degree C will simply mean that the water require 5 degree C less to evaporate in the combustion chamber

Yup, it is interesting. Direct hot water injection. Hopefully nobody here still uses gasoline to heat up their brake calipers much ;) , but I get your meaning.

I'm trying to envision it as integral to the cooling system, I don't think my engine's cooling jackets are ready for 1500 PSI though, but I suppose it doesn't HAVE to be pre-pressurized before the engine. The water could flow through the engine (and circulate as needed), then the pump then coil around the exhaust.

Course you might not have tested all these but anyway:


What operating range saw the most efficiency increase? high load/low/mid load, high/low/mid rpm?

What operating ranges was it impractical in? i.e. where it reduced power significantly or increased emissions too much?

Was this a diesel or gasoline setup or did you try both?

Lastly, is it bigger than a breadbox? ;)

since water is a good energy carrier, we just need to direct a small coolant hose to the brake caliper. This should be good for the future F1 cars.

You can have low pressure circuit for low temperature heat exchanger, but the moment it goes to the exhaust gas heat exchanger, it needs to be pressurized or else it will turn into steam. Pumping steam requires 10 times more power than pumping liquid water.

Considering that i draw oxygen from the pressurized oxygen tank, the peak efficiency is constant across engine load/rpm. it works very differently from regular car where the volumetric efficiency depends on engine speed, throttle opening, tuning, turbo, etc.

The vehicle needs to run with methanol or else the range is below the requirement. Assuming that we use the same composite tank for NGV, oxygen having almost twice the density of methane ensures plenty of oxygen to be available for every refilling. Other than that, high engine efficiency is a must or else the car wont be travelling far.

I used to work as a engine design engineer for a japanese oem and an F1 team. I have to say that once I develop compression ignition engine and understand its efficiency, i am a true convert of CI engine. Furthermore, i need the center of the combustion chamber for fuel injector, there is no place for a spark plug.

It's not as small as breadbox, but considering that the engine makes power in every revolution at constant peak torque even at low rev. I would say the displacement is really small.

so to get a %70 improvement you would have to absorb a lot of "waste" heat, which means you have to pump in a lot of water (without putting out the flame). What is the ratio of water/fuel approximately?

not really, the trick is to absorb as much combustion heat as possible using the best cooling agent around because this will minimize waste heat going to the coolant and exhaust gas. The more heat is absorbed by water in the combustion chamber, the more it will expand to push the piston down.

Understanding that it's almost impossible to have 0 waste heat, the escaping waste heat can be recovered and injected back into the combustion chamber. You will also notice that I dont use a smaller steam turbine to capitalize on the recovered waste heat. My research made me believe that using a single engine but getting the most from every stroke is the way to go.

It is the first I've heard of it (not saying much there), but it makes sense. You give the fuel a chance to light, then add water.

Did your 70% net gain include brake calipers? Just curious because we don't encourage braking like a normal yahoo here. What would be the gain without that heat source?

my calculation does not include any thermal energy from the caliper. That 70% comes only from "energy within the system".

For stationary engine, you can pack in lots of thermal energy from sun, geothermal, industrial waste heat, you name it. Anything that increases the water temperature counts. For normal steam engine, Water at 80C or 90C carries lots of energy but the enthalpy is low so you cannot do any work. Not anymore with this engine, just pack in whatever thermal energy that the water can carry and shoot it into the combustion chamber. Within milisecond the enthalpy of the water will increase by 20 times.

oh by the way, most of other engines with water injection system inject water before ignition. To me, this is a real waste.

Instead, i have my exhaust valve timing strategy to control the effective compression ratio and the amount of exhaust heat to be trapped. At low or high load, i always have the optimum temperature for fuel autoignition.

Another thing, injecting water before auto ignition will disrupt the flame development. It's better that we wait until the chamber is optimally hot before we inject the water.

the optimum water to fuel ratio for best efficiency, i need around 9.5:1 at 320C. Much of the water injected will be recovered once it is condensed.

9.5:1 at 320 C is difficult to achieve unless the vehicle is braking. For stationary engine with solar thermal, it's not difficult to get this.

try this link and it's free

http://www.engine-expo.com/forum_200...azmi_osman.pdf