Two questions concerning water injection.

Cameron Shepherd cshphrd at earthlink.net
Thu May 1 15:28:06 GMT 1997


John Bertram wrote:
> 
> First, if you add the water before the turbo, the water will obviously be
> well stirred up by the compressor wheel.  I have a large intercooler on my
> car.  My question is... Will the water have a tendency to condense and
> puddle in the bottom of the intercooler as the charge air is cooled?

Depends -- the more condensing area the intercooler offers, and the more humidified 
air is in it, the more likely you are to get water dropout, which is balanced 
against the heating of the air by the turbo and how much time it spends hanging 
around in the intercooler, which is to some degree a function of the cooler's 
design as much as of its size.  Unless you're running truly insane boost levels 
(very hot charge air), there will be non-trivial condensation and wetting of some 
intercooler surfaces, without doubt.  This is something you'd have to play with to 
see if you get an amount of puddling that is in excess of what the airflow can draw 
back.  I'd be very interested to know what results you get.

> Second, when the air/fuel/water mixture burns in the combustion chamber,
> does the water turn to steam?  If it does, the steam is obviously being
> created by some of the energy that would be lost as heat.  Since steam
> takes up a lot more space than water, wouldn't that create a lot more
> exhaust volume?  Would this extra volume of exhaust be useful in spooling
> up the turbo quicker?

This is an interesting idea...  you'd do a state change and an energy transform and 
lose a lot of units, so my feeling is that the gains would be of a pretty low 
order.  On the other hand, it would be fun to see if there's something here. 

Cameron



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