Abstract: A fluid displacement apparatus includes a housing defining a chamber therein having a first port and a second port. First and second helical rotors with opposing pitches are meshed within the chamber, in fluid communication with the first and second ports. A respective one of the first and second helical rotors includes a cylindrical body portion having a helical groove therein and a helical tooth portion extending radially from the cylindrical body portion adjacent the helical groove. The first and second helical rotors are arranged such that respective longitudinal axes of the first and second helical rotors are parallel to one another and a helical tooth portion of one of the first and second helical rotors engages a helical groove of another of the first and second helical rotors, such that the first and second helical rotors are operative to rotate within the chamber and provide fluid transport between the first and second ports parallel to the longitudinal axes.