Both rotors turn in the same direction within the housing and are separated by a central section, inlaid in this central section are 12 vanes that can slide between one or the other rotor housing but do not turn with the engine's rotation.
Both rotors turn in the same direction within the housing and are separated by a central section, inlaid in this central section are 12 vanes. These 12 vanes can slide between one. These 12 vanes can slide between the other rotor housing. These 12 vanes do not turn with the engine's rotation.