I remember the KC-135's when I was in the Air Force used water injection. They injected about 750 gallons into their four engines for a dramatic increase in thrust that lasted about 120 seconds. I don't think that they injected them into the compressors stages or the combustion chamber, but rather into the exhuast section. Also, if memory serves me correctly-the fuel flow from each engine jumped from about 7,000 pounds per hour of fuel to about 12,000 pounds per hour. Since water turns to steam when vaporized and expands greatly I would be concened about injecting into the compressor area. Seems as if you could blow up the engine that way. But if it vaporized when injected in the exhuast area the sudden expansion of the vapor would be pushed out the back resulting in an increase of the thrust. On full scale aircraft they also used deionized water to prevent mineral deposits in the engine-I think distilled water would serve the same purpose.

Perhaps someone on the forum was, or knows an old engine mechanic from the military that that could give them more factual advice on how this concept works.