Ballpark Intake Temperatures?

[Begle1]

Could anybody who's ever used intake temperature gauges tell me the approximate temperatures you saw at given boost pressures?

[c12h26]

At 35 psi our charge air temp was 589*. so we put a water to air intercooler and got the temp to 120*and the boost went down to 29psi

[Begle1]

At 35 psi our charge air temp was 589*. so we put a water to air intercooler and got the temp to 120*and the boost went down to 29psi

The reason why I ask...

At 35 PSI, water is supposed to boil at 289 degrees (plus some due to barometric pressure). When you fumigate liquid water, it absorbs heat as it turns into steam; that lowers the temperature and pressure.

So theoretically, any water fumigated when the temperature is below boiling will remain a liquid and will not affect the charge air temperature.

And yet I hear stories of water fumigation reducing the intake temperature below the boiling point of water.

So are those stories mistaken, or am I missing an additional affect of the water beyond the evaporation?

[dpuckett]

I'm not sure of the physics and exact numbers involved, but one must also consider the pressure of the air and water mixture. I'd think that would raise the boiling point of the water.

Daniel

[c12h26]

the 35 psi is boost [charge air] to the intake for combustion, it seems you are compairing 35 psi of "boost "to "35 psi" in a sealed coolant system that will increase the boiling point.

[Begle1]

I'm putting liquid water into a system that's 500 degrees and 30 PSI. What's the difference between that and a sealed system?

The system is "sealed" for the time frame that I'm looking at it, no?

[c12h26]

I don't understand what your sealed system is?? our ice water to air intercooler is nothing more than a "heat exchanger" using icewater to remove heat from the charge air, the" water" never enters the "air "system. are you thinking of a "water/meth" system that actually injects "atomized liquid" into the combustion air ??

[Begle1]

Yeah, I'm talking about a system that would be spraying water into the intake; I'm trying to figure out why those systems reduce temperatures below the boiling point of water.

I kind of just took your "539 degree at 35 PSI" number and ran with it while ignoring the rest of your anecdote.

Although I do find that kind of drop pretty impressive.

[wannadiesel]

Liquids can and do vaporize below their boiling point. When they vaporize they absorb heat.

[Begle1]

Well, they can turn into water droplets... But it's still liquid water and not a gas. I have a hunch that it actually stays as liquid until the fuel is injected...

I guess that since the water droplets are cooler than the hot air, they do act to "average" the temperatures between the water temperature and chage temperature. Just conduction between the drops and the air.


The deal is that I'm trying to figure out an equation that I can use to determine the optimal rate of water fumigation to feed into the engine.

If I know the boost pressure and intake temperature, then I can ensure that the water is always a gas and never a liquid going into the cylinder; but I think it's clear that water injection works even when the water is a liquid.

So I'm pretty stumped as to an equation I can use... If I can find an equation it would be no more difficult to implement it then it would be to use even a direct ratio between boost and water rate, but I'm tired of thinking about it today...

[wannadiesel]

Looks like somebody slept through science class. Re-read my last post.

[Begle1]

Yeah?

By "vaporize" you mean "actually turning into a gas" and not "turning into small drops of liquid"?

[CAJUN 93]

dude, set your garden hose nozzle to fine spray and walk through it. its a lot cooler than the temp of the water in the hose and the surrounding air. the higher the pressure on the hose the cooler the mist will get.

you dont have to have an actual change in physical state (solid to liquid, liquid to gas) to decrease the temps. the increase in surface area gives more opportunity for heat exchange.

think of a large lake on a cold day. if the wind is still, it takes a long time for lake temps to drop due to limited surface area. let the wind blow and make waves and the lake temps will drop faster due to a larger surface area to interact with the cold air. take into effect the stirring action of the waves and temps drop even faster. none of this changes the physical state of the lake. it's still liquid.

hope that make sense. i'm not real good at conveying what's in my mind onto print.

daryl

[Begle1]

So I should be looking for an equation that will tell me how much water can evaporate into an air stream of given humidity, temperature and pressure?

[wannadiesel]

That would be more accurate if you are trying to model what is happening.