Abstract: An apparatus and method for centrifugally separating the component species of a mixture, at least one of which species is a fluid, when the mixture includes at least one or more species of specific weight different from that of the fluid. The mixture is fed tangentially into the inlet end of a converging nozzle, at high speed, to establish an axial helical flow path of the mixture. As the mixture moves along the converging nozzle, generally the lighter species collect in the center and the heavier ones collect at the outside wall. A throat of constant diameter or slightly converging angle may follow the nozzle. As the mixture moves through the throat, the radial separation is maintained similarly as in the nozzle. A diverging diffuser is located downstream of the throat and a throttle valve element is located at least partially within the diverging diffuser. The throttle valve element controls the size of the diffuser gap between the throttle valve element and the diffuser.