Movable ramp inlet for water jet propelled ships

摘要

A movable ramp, forming part of the inlet flow channel of a water jet propulsion system, is adjustable to provide variable inlet area for various speed and propulsion requirements. In this flush or semi-flush type inlet, the lower lip is stationary and an upper ramp, forming an extension of the base-line shell, directs the flow into the inlet. If the baseline shell is not suited to the inlet installation, (for example, if a high deadrise angle exists) a forebody fairing is provided to make the baseline shell geometry suitable. The ramp is flexible, has a smooth surface, and is backed up by bell cranks and pusher bars that can move the ramp position to change the inlet area. The ramp position or inlet area may be adjusted manually or automatically to meet the requirements of speed and propulsion. If the centerline of the lip leading edge radius falls below the normal baseline (semi-flush inlet) suitably shaped "sideplates" are provided to avoid inlet cavitation or ventilation at yawed conditions. A "pressure alleviation" system may be provided to reduce the static pressure differential across the ramp to alleviate the structural design loading and reduce the total force required of an actuator to move the ramp.