The heat energy (kinetic) is being converted into entropic energy (liquid to gas transition--the heat of evaporation (heat needed to disassociate H2O molecules)).
Ideally at the moment the adiabatic heat is generated, it is absorbed by the water evaporation. Compression occurs with less heat imparted to the compressed air.
If liquid water traverses the impeller wheel without evaporating, we are no better off injecting before the turbo as after.
Now the water droplet will spend very little time traversing the impeller wheel. We what it to completely evaporate during its journey. Hence, the dialogue about droplet size. We can calculate this time frame with some precision, but the time to evaporate a droplet is a difficult one. Pressure, temperture, velocity, increasing surface to volume ratio, and methanol mixture, will make it a multivariable calculation, one best left to empircal determination.
Aquamist at 147 psi is our best bet for small droplet size. Smaller droplets can be made, but the pressure and nozzle sophistication to make them is untenable in automobiles with current technology. I know of no sensor that could easily be rigged to detect droplet exit from the compressor wheel (a spectrophotometer could work, but we are talking at least a $1000).
Hotrod has kindly displayed his turbo impeller after 7000 miles at 2.7% water to air mass. It shows some notable erosion at the edge (with extenuating circumstance). The erosion can be viewed as a cost of implementing the impeller injection, or we can wait for creation of a nozzle that expels smaller droplets. By injecting less water than hotrod, and only at high RPM and boost, I hope to reduce the erosion substantially (using a solenoid to inject only under the chosen parameters). None the less I expect some erosion to occur. If a new turbo is needed every 20,000 mi, that is a cost of running such a system. It remains to be seen if the benefit outweighs the cost. If a 10% increase in airflow can be achieved at high RPM, it would be worth about 40 hp; that is worth it to me.
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