Thanks a lot. I should slap myself for not coming across this paper in my younger days.
Anyway, I am trying to get any technical publication with regard to the WW2 Japanese long lance torpedo. The engine is rumored to work on oxygen and water. It travels faster and further than any other known torpedoes in its era including its ally the Nazi german.
Now I know why my simple steam injection did increase power. It helps speed combustion.
As for the Japanese torpedo engines. It would be easy too backfeed the steam exhaust too make that engine perform and even last.
NACA's extensive studies of water injection in aircraft piston engines always involved supercharging and were mainly focused on allowing higher boost and power while avoiding detonation (knock) and overheating. NACA's findings were in close agreement with Ricardo's earlier studies. There is a repro of Ricardo's results in a graph in Hugh MacInnis' books on turbocharging (Turbocharges (HP49) HP books). Ricardo's own book is rather expensive. Ricardo showed that water injection greatly decreased peak cylinder pressures, something that has implications on durability of parts. NACA's studies also focused on the cooling power of injected water such that they made a determination of how much water is need for total cooling.
There have been many studies of water injection in normally aspirated SI engines and studies of water in diesel engines.
azmios, Several torpedoe designs used IC engines that ran on hydrogen peroxide and a hydrocarbon. The same combination is also good rocket propellant. Hydrogen peroxide is NOT a cheap source of oxygen.
If you notice, people like me and Slim3 always believe that there must be some other unexplained phenomena that increases the horsepower more than what is achievable by just extending the knock limit. So far, no researchers have investigated the effect of water itself in the combustion chamber.
I am also aware of Ricardo's report about the decreased in peak pressure. However, up until now, nobody that I am aware of has investigated whether the decrease in peak pressure is contributed by the present of water in the combustion chamber that might have caused slowed down the flame propagation and to cause the unburned fuel to occur.
Somehow, I still think that oxygen using PSA is the way to go as it can be produced only when it is needed. I read about how the WW2 Japanese submarines produce the required oxygen for the torpedoes in the middle of ocean using an oxygen generator. I am very much interested to learn how they control the extreme temperature increase inside the combustion chamber. That's why, both high residual gas and water injection are part and parcel for oxygen combustion.
azmios. They used H2O2, hydrogen peroxide, in the torpedos. No "oxygen generator" necessary. Concentrated H2O2 is hypergolic with any fuel. The combination bursts into flame upon mixing. H2O2 can even cause metals to burst into flame. It's nasty.
You appear to believe that the world is oblivious to explanations and possibilities. "So far, no researchers have investigated the effect of water itself in the combustion chamber" On the contrary, brilliant minds have studied and are studying these issues constantly. The effects of excess water in the combustion process has been the focus of intense study for SI and CI engines. These inquiries began in the first decades of the 20th century. If you do enough research you will find recent studies by labs all over the world including some of the nuclear plasma labs that have the supercomputers to model burn processes.
I can't find the paper, but the nearest I saw to an explanation tried to explain that water dissociating into H+ and OH- interacted in the oxidation of hydrocarbons and controlled the speed the process. It was to long ago for me to remember the details. It had some enthalpy calculations I think, but was far from conclusive.
Bottom line is you cannot change the total energy released without resorting to over unity. You can only change when, how fast, in what form and where it is released. This can allow you to extract more work with less waste from it.
Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
I have my own reason for not using hydrogen peroxide. It needs to be reacted with enough activation energy before we can use it. Oxygen is much simpler to use and control.
When I made my comment, you have to look into the context of why injecting water makes more power even when there is no change in energy content of the fuel injected. i also do research in water so what you're alleging is more of myself contradicting of what I am doing for living.
All the papers that I have, mentioned about the power increase but none made convincing scientific explanations on why the power increases even if the ignition timing, boost, energy content remain the same. If you reckon that many have done so, proof me to be wrong by showing the link to the technical papers, I will be more than happy to buy the papers.
azmios, do you know what hypergolic means? If you did you would know that this "It needs to be reacted with enough activation energy before we can use it", doesn't make any sense at all. We are talking about concentrated hydrogen peroxide. There is nothing that needs to be done "before we can use it".
If you have done your own research on water injection and come up with some of the conclusions you have expressed, you need to go back and try again. If you know what you are doing you should be able to provide some "convincing scientific explanations on why the power increases" or doesn't increase. Other people have provided explanations.
Which paper claims "the power increases even if the ignition timing, boost, energy content remain the same." ??
Sometimes the note about ignition timing being adjusted for best torque or knock limited power during testing does not appear under each Figure or Table. For no ignition timing adjustment to be required I'd expect the initial, pre-water setting to have been creating angry unstable combustion, or for the testing to have required maintaining less than full throttle.
Are you saying that H2O2 can be reacted with fuel at ambient temperature? The keyword like fuel autoignition temperature is actually the activation energy required before fuel auto ignition can occur. Feel free to disagree with me.
There you go again, why do you have to resort into personal attack?
There is another debate going on in water+methanol by Slim3. Slim3 reported that there is no change in parameter other than injecting the water+methanol.
This figure is from NACA research memorandum E6106, which investigated methods of limiting peak cylinder head temperature in cylinder 10 of a Wright R-2800, where this cylinder would otherwise exceed the manufacturer's recommended temperature limit at military power, as installed in a P47G aircraft. One method investigated was water/ethanol injection into the intake pipe of cylinder 10. At the top of the figure above, the effect of coolant injection rate (x-axis) on net BHP is shown. The BHP indicated is for the entire engine, so the changes in BHP are due to changes in cylinder 10 only, since that is the only cylinder in which operating conditions were altered. It can be seen that, as coolant flow increased from 0 to 40lb/hr, cylinder 10 power decreased by 30 BHP. Assuming that cylinder 10 was contributing an equal share of the total engine power initially, this is a reduction of approximately 35%.
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
Correct me if I'm wrong at ambient humidity levels below 35% an engine will generally put out less power. Now the same engine and conditions with the ambient humidity 45% or higher the engine will put out less power. It the middle levels the engine will put out little more power. We all know about ignition delay. I think water cuts back on ignition delay too a point.
maxc, what do you mean by ignition delay? The ignition timing would not be effected by humidity unless the computer is adjusting to avoid marginal ping. Or do you mean the burn speed and the point in crank degrees of peak pressure?
Apologies to all, I meant to post the figure from NACA RM E6106 in the other thread, and when I didn't see it there I posted it a second time there not realizing it ended up here the first time I tried.
Anyway, maxc, my direct experience in compensating a spark ignited natural gas engine for ambient humidity is that, for excellent physical reasons, when no compensation is made for atmospheric humidity, power monotonically decreases with increasing specific humidity, from 0 on up as high as you like. There are two direct effects. One is, water vapour displaces other molecules in the atmosphere, in accordance with its concentration, which means less oxygen is available, by partial pressure, in proportion to water vapor that is present. The SAE net power correction formula takes this into account, so that power is corrected to the observed dry barometric pressure, i.e. the partial pressure of water vapour is subtracted out in the denominator of the correction factor, since the numerator assumes dry air (zero humidity). The above explanation pertains to an engine running at or rich of stoichiometry. The effect of humidity on an engine running lean of stoichiometry is more complicated and application specific, since since the effect of humidity is not the same for all methods that are used to control air/fuel ratio.
The second effect is a little more subtle, but also easy to understand. Water vapour in the charge acts as an inert diluent, effectively slowing the combustion rate and reducing peak temperature. This is exactly the same effect as EGR, for the same reason. With no change in operating conditions to compensate, slowing the combustion means it will be phased later in the cycle. Peak pressure, rate of pressure rise, heat release rate and effective expansion ratio will be reduced accordingly. The net energy release will be the same, but the energy is converted less efficently to pressure pushing down the piston; as a result, power correlates inversely with ambient humidity, assuming all control parameters are held constant.
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
