Harvested crop processing unit with number of circulation circuits depending on throughput

A harvested crop processing unit with a rotor and a rotor housing enclosing the rotor, that includes a cover element under which a first group of helically shaped guide rails and a second group of helically shaped guide rails are attached, where the guide rails of the two groups follow each other alternately and are provided with a leading end and a trailing end in the direction of rotation of the rotor and the guide rails of the first group are arranged offset to the rear of the guide rails of the second group in the direction of rotation of the rotor. The trailing ends of the guide rail of the first group are directed at the leading end of the guide rails of the second group following in the axial direction of the rotor housing.