In my setting, magical civilizations have physical aversion to metals and moving metals have nasty distruptive effect to magic, so these civilizations development went completely different way from ours.
Eventually, after centuries of primitive protomagic, they discovered process to transform magic crystals(magic fuel, non-quark based matter) to magic cores, which could be endowed with spells/concepts(that still require magic crystals to run).
One of these are concepts of repelling or attracting something. This became a massive game changer, as it allowed to build them hovering ships, ships capable of flight up to hundreds of metres above water or ground (repelling solids and liquids). These ships are built similarly to normal ship (because they consume fuel to fly, they are usually in water for docking and can be sent by waterway to go cheap on fuel).
At first, they used side sails, sails to extend from sides of the ship, but later, they came up with idea of using air attraction core to propel the ship. My question is, how should such engine work? I myself came up with a rather simple but a crude design, but I feel that this design leaves a lot to be desired. I am not an engineer, and my few experiences are not even enough for me to call myself a dabbler.
So my question is: How would an engine that would be designed with use of magic of attraction (or repulsion) work? And is this kind of engine even worth it?
To set the technical restrictions: The cores require at least 0.25 second to turn on and off, so they can't use really short cycles of intake and expulsion. However, strength of their output can be controlled. The best the attractor core can reach is about 10 atmospheres stable pressure, the best the repellant core can do is 0.1 atmosphere.
My own idea was to use attraction cores to attract air - increase pressure in a wooden chamber, then block intake and turn the attractor core off, which pushes air into the only possible route of escape - thruster. However, with such technical constraints, I feel that my idea might produce only laughable thrust.