Water Injection
I have a couple of questions that I hope someone will be able to answer regarding water injection systems as used on Engines such as the Rolls Royce Spey and P+W JT3
I understand this is in order to increase thrust for take off and is achieved by injecting water into the compressor inlet.
I am curious as to how much water is required to produce a significant increase in thrust. For example, is an increase in thrust noticeable simply when flying through cloud which presumably would have a similar effect.
Secondly is this technique still used? and finally is it necessary to take any precautions to prevent the water in the injection system from freezing?