Water injection for more hp AND mpg?

[Mookow]

Originally posted by: Roger

How does the cylinder head material affect combustion? I'm not doubting you, I just want to know how/why

Cast iron has a slower heat transfer rate than aluminum, therefor the combustion chamber sees higher temperatures, this has the effect of faster flame fronts than a similarly equipped aluminum head engine.
This is precisely why almost every automobile manufacturer has switched to aluminum heads, it reduces preignition, slows down the flame front and more precisely controls combustion temperatures.

Thanks

 

 

[Eli]

Originally posted by: Roger

How does the cylinder head material affect combustion? I'm not doubting you, I just want to know how/why

Cast iron has a slower heat transfer rate than aluminum, therefor the combustion chamber sees higher temperatures, this has the effect of faster flame fronts than a similarly equipped aluminum head engine.
This is precisely why almost every automobile manufacturer has switched to aluminum heads, it reduces preignition, slows down the flame front and more precisely controls combustion temperatures.

I was wondering the same thing. I suppose that's true, but I don't think it's the main reason they use aluminum..... they use aluminum because it's light weight and cheap, lol... i'm sure the added heat transfer is just a bonus.

I'm kinda having a hard time picturing this, though. I don't really understand how better or worse heat transfer is going to effect the flame front speed...

Just because the temperature in the combustion chamber is higher, so the air/fuel charge is heated up more before it's ignited?

 

[brtspears2]

My friend went to Mexico and said they put water in the engines while running to steam clean them. aka Mexican Tune-up. :disgust:

 

[Evadman]

Originally posted by: brtspears2
My friend went to Mexico and said they put water in the engines while running to steam clean them. aka Mexican Tune-up. :disgust:

I have been told by a reliable source that doing that will remove buildups of carbon. It tends to blow the chunks out and can stick a valve, but I have heard of it being done.

 

[Eli]

Originally posted by: Evadman

Originally posted by: brtspears2
My friend went to Mexico and said they put water in the engines while running to steam clean them. aka Mexican Tune-up. :disgust:

I have been told by a reliable source that doing that will remove buildups of carbon. It tends to blow the chunks out and can stick a valve, but I have heard of it being done.

Yeah, I've heard of that too. But not like putting it into the tank, that wouldn't work.. just dripping some from a cup into the intake while revving a bit.

 

[Evadman]

Originally posted by: Eli

Originally posted by: Evadman

Originally posted by: brtspears2
My friend went to Mexico and said they put water in the engines while running to steam clean them. aka Mexican Tune-up. :disgust:

I have been told by a reliable source that doing that will remove buildups of carbon. It tends to blow the chunks out and can stick a valve, but I have heard of it being done.

Yeah, I've heard of that too. But not like putting it into the tank, that wouldn't work.. just dripping some from a cup into the intake while revving a bit.

Right. I have never tried it, and probably never will, but have heard of it being done with good results. *shrug*

 

[GoSharks]

Originally posted by: FenrisUlf
Water is H2O, atomic weight 10. Gaseous Nitrogen (N2), the most common element in the atmosphere, has an atomic weight of 14. Therefore, when a water molecule replaces a nitrogen molecule, you get a net reduction in density.

uh no.

H = 1.0079
H = 1.0079
O = 15.999
-----------
18.0148

 

I was wondering the same thing. I suppose that's true, but I don't think it's the main reason they use aluminum..... they use aluminum because it's light weight and cheap, lol... i'm sure the added heat transfer is just a bonus.

I'm kinda having a hard time picturing this, though. I don't really understand how better or worse heat transfer is going to effect the flame front speed...

Just because the temperature in the combustion chamber is higher, so the air/fuel charge is heated up more before it's ignited?

Cast iron is cheaper than aluminum

Listen carefully, the thermodynamic properties of a compressed air/fuel charge is directly affected by the surrounding temperature, notice that a cold engine requires a much richer mixture to fire, while a warm engine requires a leaner mixture (Stoichiometric, 14.7 to 1), this is because fuel atomization is morte easily produced with the excitation of the fuel atoms (heat).

Picture the air/fuel charge not as one unit, but many thousands of gas droplets mixed in a small compressed atmosphere of oxygen/nitrogen, when the spark plug fires, the first micro fuel droplet ignites causing it's neighbor droplets to ignite and so on and so on, this is the flame front, now when temps rise in the combustion chamber, the fuel atoms are really jumping around, this causes the fuel to burn more rapidly, the flame front now spreads across the combustion chamber much quicker, ofcourse this is an over simplification of the events

You must also understand that as the combustion chamber grows hotter, the fuel atomization increases because the micro droplets are more easily broken up as the temperatures rise, as the drops get smaller, the fuel burns more readily causing yet another increase in flame front speed.


Got that ?
Good, now ever notice that an overheated engine pings ? (Detonation)
Apply what I just stated, as temps go up, the fuel becomes easier to burn, once it reaches the flash point it will self ignite with an extremely fast flame front causing an explosion inside the combustion chamber, this explosion rings the metal parts inside the engine causing the peculiar "ping" sound, this also happens when cheap gas is used because the resistance to ignition of the cheaper fuels have a direct relationship with flame front speed (low octane fuel burns much more rapidly than high octane fuel).

 

[Eli]

Originally posted by: Roger

I was wondering the same thing. I suppose that's true, but I don't think it's the main reason they use aluminum..... they use aluminum because it's light weight and cheap, lol... i'm sure the added heat transfer is just a bonus.

I'm kinda having a hard time picturing this, though. I don't really understand how better or worse heat transfer is going to effect the flame front speed...

Just because the temperature in the combustion chamber is higher, so the air/fuel charge is heated up more before it's ignited?

Cast iron is cheaper than aluminum

Listen carefully, the thermodynamic properties of a compressed air/fuel charge is directly affected by the surrounding temperature, notice that a cold engine requires a much richer mixture to fire, while a warm engine requires a leaner mixture (Stoichiometric, 14.7 to 1), this is because fuel atomization is morte easily produced with the excitation of the fuel atoms (heat).

Picture the air/fuel charge not as one unit, but many thousands of gas droplets mixed in a small compressed atmosphere of oxygen/nitrogen, when the spark plug fires, the first micro fuel droplet ignites causing it's neighbor droplets to ignite and so on and so on, this is the flame front, now when temps rise in the combustion chamber, the fuel atoms are really jumping around, this causes the fuel to burn more rapidly, the flame front now spreads across the combustion chamber much quicker, ofcourse this is an over simplification of the events

You must also understand that as the combustion chamber grows hotter, the fuel atomization increases because the micro droplets are more easily broken up as the temperatures rise, as the drops get smaller, the fuel burns more readily causing yet another increase in flame front speed.


Got that ?
Good, now ever notice that an overheated engine pings ? (Detonation)
Apply what I just stated, as temps go up, the fuel becomes easier to burn, once it reaches the flash point it will self ignite with an extremely fast flame front causing an explosion inside the combustion chamber, this explosion rings the metal parts inside the engine causing the peculiar "ping" sound, this also happens when cheap gas is used because the resistance to ignition of the cheaper fuels have a direct relationship with flame front speed (low octane fuel burns much more rapidly than high octane fuel).

lol.. Yes, I understand all that.. and that's basically what I asked in my post. Perhaps I should have worded it better, lol..

I just never thought about the cylinder head material when thinking about detonation and the like. It's interesting.

 

You made me type all that out when you already knew it !!!!!!!!!!!!

"GrumbleGrumbleGrumbleGrumble"

 

[KMurphy]

It absolutely does work. We have several large GE gas turbine generators (160MW) that have steam injection into the turbine combustion chamber. It help efficiency, boosts MVAR output (more power) and gives us environmental credits. Have you ever wondered why cars seem to run better with very high humidity; typically at lower altitudes? I don't know the physics, but I know it is widely used on an industrial scale. The benefits probably wouldn't be so great on a smaller scale like an automotive engine which is why you don't see or hear about it.

 

[Howard]

I think Roger burnt his fingers by touching a hot head. Maybe that's why he's so incensed (it's not a pun!).

 

[KMurphy]

http://europa.eu.int/comm/energy_transport/atlas/htmlu/combdintro.html

http://www.nfcrc.uci.edu/EnergyTutorial/gasturbine.html

It bascially lowers combustion temperature.

 

Turbines and Otto cycle engines are two completely different beasts, you cannot assume that because it works on jet turbines that it will work equally well on internal combustion piston engines.

To achieve maximum efficiency you have to keep the gasses as hot as possible (To maximize pressure on the piston) but also keep the metal parts (combustion chamber/ piston/cylinder walls) as cool as possible to prevent preignition.
Injecting water will reduce the air fuel charge as well as reducing the gas temps causing less pressure on the piston which results in less power produced.

 

[Ultima]

so, any hard numbers on whether it works or not in gas engines?

 

[Eli]

Originally posted by: Ultima
so, any hard numbers on whether it works or not in gas engines?

I don't think it's really practical.

While the net energy loss isn't going to be a net of the reduction in gas temperatures(because you have to take the energy from the expanding steam into account), you obviously aren't going to end up ahead.. It just depends on if the pros outweigh the cons in your particular application.