Turboprop, turbofan, propfan
Hello everyone,
I'm doing some research at the moment of why faster aircraft use turbofans compared to slower aircraft using turboprops. I understand the theory that the fan in a turbofan accelerates a smaller mass of air much faster than the large mass of slow air in a turboprop.
What I don't understand is how the turbofan can accelerate the air faster?
I know propellers and hence fan blades in turbofan become inefficient when airflow over them becomes supersonic so this implies that prop and fan have tip speed limits.
How is a propfan faster than a turboprop when their aerofoils are both limited by tip speed?
How is one form of fan/prop able to accelerate air faster than the other assuming they are both limited by around mach 1 tip speed?