Waterjet Propulsion Systems for Marine Vessels

Most boats rely on an outboard engine connected to a propeller to provide propulsion for the vessel. Alternate designs do exist, however, with one of the most popular being the waterjet propulsion.

Waterjet systems feature an intake, usually located on the bottom of the hull, which guides water into a pump powered by an engine. The rotating part of the pump is referred to as an impeller. Unlike a propeller placed freely in the water, and impeller is enclosed in the pump chamber. Water rotating inside the pump needs to be aligned before leaving the pump system, which is accomplished by a stator with guide vanes designed to direct the water beam in the correct direction. The water beam passes through an outlet nozzle at the stern of the boat, and the difference between the water flow at the inlet versus that of the water at the outlet creates a reaction force, or thrust, which pushes the boat forward.

There are two main types of pumps used in waterjet propulsion systems: axial flow pumps, and mixed flow pumps. An axial flow pump increases pressure by diffusing the flow as it passes through the impeller blades and stator vanes. The pump nozzle then converts the pressure energy into velocity, which produces thrust. Axial-flow pumps produce large flows at lower velocity, making it ideal for low to medium speed boats. Mixed flow pumps, on the other hand, incorporate aspects of both axial flow and centrifugal flow pumps. As a centrifugal flow pump creates water pressure by using radial flow, the pressure from mixed flow pump is developed by both diffusion and radial outflow. This ends up producing lower flows of water at higher velocity, making them ideal for high-speed boats.

Waterjets are suitable for both small recreational craft like jet skis and larger boats. A major advantage of waterjets is that nothing is protruding beneath the bottom of the boat, meaning less hydrodynamic resistance and safer operations in shallow waters. This is particularly useful for military and ambulance boats that must be functional in all situations and marine environments. Waterjets also do not create many vibrations, making it comfortable for passengers.

One of the challenges with waterjets is keeping a straight course. Waterjet boats do not have propellers or rudders, which are typically used to keep course, so other design measures must be used. A boat powered by waterjets is sensitive to load and has poor efficiency at low speeds as well, which needs to be taken into consideration.

At Purchasing3Sixty, owned and operated by ASAP Semiconductor, we can help you find all the waterjet propulsion systems and parts for the aerospace, civil aviation, and defense industries. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, email us at sales@purchasing3sixty.com or call us at 1-434-321-4470.


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