Quote Originally Posted by mmarien View Post
On the other hand there are modern turbine engines that are mostly pushing air that bypasses the jet engine. The turbines have multiple vanes turning at ~30,000 RPM.
I think you're confusing two parts of a jet engine: the fan that pushes bypass air and the turbine that drives it. Rotational speed varies somewhat from model to model, but roughly speaking the N1 fan on a typical airliner engine spins at somewhere between 2,200 and 3,000 RPM. The N2 compressor spool spins in the neighborhood of 10,000 RPM and the turbine spool at ~25,000 RPM. The fundamental difference is that the N1 fan is pushing air -- that is, functioning like a propeller -- while the turbine is being driven by hot gasses.