No, Water as I said it is commonly used in household well pumps does not need air to work. that is just one of the forms it is used in. In fact it is based on Bernoulli's Theorem. In the classical example a contricting water pipe is used with other pipes leading off vertically and filled with water. As the pipe consticts with water flowing through it, the pipes on the down stream side have lower fluid levels indicating lower pressure.
Probably most ejectors in use are most likely used with liquids of some kind I just happen to be more into airflow and am not aware of all the forms it take.
Ejectors are seperate from nozzles but can be used with them.
If you want to know about nozzle's check out DeLaval
nozzle, Might be good to machine into your blocks***JUST NEED A LITTLE SUPERSONIC ACTION
http://lifesci3.arc.nasa.gov/SpaceSe...et/rocket.html
Air, No I was just thinking air alone in blocks as a seperate matter