Streamline control for variable pitch marine screw - has ring duct with smaller diameter than screw to reduce flow rate around hub and increase flow rate through propeller blades

摘要

The ring duct (4) is mounted around the propeller shaft support, in front of the screw (1) and acts as a diffusor for the water flow to the screw. The ring diameter is less than 65 percent of the screw diameter and can be oval to optimise the flow around the hub. The ring duct is mounted on the propeller shaft housing by wing shaped struts (7) whose pitch enhances the diffusor effect. The effective flow centre of the ring is offset from that of the screw. USE/ADVANTAGE - Marine screws with thick hubs e.g. variable pitch screws. Improved thrust efficiency, improved water flow pattern.