Hi QJB,
Why do turbine engines require a compressor section
Good question. In an internal combustion engine, the direction of rotation is controlled by the ignition timing (you can get a two stroke to run backwards if the timing is too far advanced) and the gas flow direction is controlled by valves.
Since there is no ignition timing or valves as such in a turbine engine, in order to prevent the combustion gases from travelling forwards, it's necessary to "compress" the air flow by increasing its KE towards the rear. It can then enter the combustion chamber through a much smaller area. After combustion the gas finds an easier exit route rearwards, expanding across the turbine.