water injection questions???

[Michael D. Porter]

tom sparks wrote:
> 
> If all a person wants to do is lower the heat of combustion and hence the
> speed of the flame front, then why not just fatten up the fuel curve at the
> point where detonation is expected?  Why add all the extra hardware and
> expense (and risk) of a water injection system?

It may be that enrichment might work for a very short while, but then, 
the mixture would have to go below that for maximum power, and there's 
fuel wasted, besides.  The other consideration (just speculating, here) 
is that richer mixtures may not prevent detonation--if the chamber is 
warm enough, and there are hot spots hot enough, the mixture may not be 
_homogenously_ rich enough, and detonation may begin anyway, unless the 
mixture is downright lumpy, sooty rich.    

The other thing I've not seen mentioned yet is that water, in a 
Brayton-cycle turbine, serves to add mass to the burning mixture, which 
translates to higher forces impinging on the turbine section.  Water 
injection may serve the same purpose in an IC engine, to some small 
degree, by applying slightly greater force to the pistons.
Cheers.