Aux 1 Unit 10 Q8

A transverse, water jet thruster is a type of propulsion device installed on a vessel that utilizes a pump and nozzle system to create a powerful jet of water, generating thrust perpendicular to the ship’s longitudinal axis. This lateral thrust enables the vessel to move sideways (port or starboard) or rotate in place, enhancing maneuverability, especially in confined spaces or during docking operations.  

1. Maneuvering thruster – Wikipedia

2. Wärtsilä Transverse Thrusters

Key Components and Operation:

1. Intake:
   • An opening in the hull allows seawater to enter the thruster.   1. Crabbing Motion Testing of Waterjet-Powered Ships Using Stern Thrusters – Journal of Ocean Engineering and Technology www.joet.org
   • Typically located below the waterline for efficient water intake.   1. Maneuvering thruster – Wikipedia en.wikipedia.org
2. Impeller Pump:
   • A powerful centrifugal pump, usually driven by an electric motor or hydraulic motor, draws in seawater from the intake.
   • The impeller accelerates the water, increasing its velocity and kinetic energy.   1. An Energy Conversion Machine – How a centrifugal pump actually works – KSB www.ksb.com
3. Nozzle:
   • The high-velocity water is directed through a specially designed nozzle that further accelerates the flow and shapes the jet.   1. Maneuvering thruster – Wikipedia en.wikipedia.org
   • The nozzle can be rotated or swivelled to direct the jet in the desired direction (port or starboard).   1. Trim tab for jet propulsion system – US6113443A – Google Patents patents.google.com
4. Thrust Generation:
   • As the high-velocity water jet is expelled from the nozzle, it creates a reaction force in the opposite direction, propelling the vessel sideways.   1. Transverse thruster – KSB www.ksb.com
   • The direction of thrust can be reversed by reversing the direction of the impeller or by swiveling the nozzle.

Advantages of Water Jet Thrusters:

• Enhanced Maneuverability: Provides excellent maneuverability in tight spaces, enabling precise control during docking, undocking, and close-quarters operations.
• No Protruding Parts: Unlike tunnel thrusters with exposed propellers, water jet thrusters have no external moving parts, reducing the risk of damage or entanglement with lines or debris.
• Shallow Water Operation: The compact design and absence of protruding parts allow for operation in shallow water without the risk of grounding the propeller.
• Reduced Noise and Vibration: Water jet thrusters are generally quieter and produce less vibration than tunnel thrusters.   1. Water Jet Thrusters – No Tunnel – No Noise – So-Pac Marine sopac.co.nz
• High Efficiency at Higher Speeds: Their efficiency tends to improve at higher speeds, making them suitable for vessels that operate at a range of speeds.   1. Maneuvering thruster – Wikipedia en.wikipedia.org

Disadvantages:

• Complexity and Cost: They are generally more complex and expensive than tunnel thrusters due to the sophisticated pump and nozzle system.
• Maintenance: The impeller pump and nozzle require regular maintenance to prevent clogging, corrosion, and wear.
• Efficiency at Low Speeds: Their efficiency can be lower at very low speeds compared to tunnel thrusters.

Applications:

• Superyachts: Often used on larger yachts to enhance maneuverability during docking and in marinas.
• Dynamic Positioning Vessels: Can be part of a dynamic positioning system for maintaining precise position and heading.
• Ferries and Cruise Ships: Improve maneuverability in harbors and during docking.
• Other Vessels: Used on various other vessels where precise control and shallow water operation are important.

In conclusion, transverse, water jet thrusters offer several advantages in maneuverability, safety, and efficiency. Their unique design and operational characteristics make them a valuable addition to vessels where precise control and the ability to operate in shallow water are crucial considerations.

let’s illustrate the typical arrangement of a transverse, water jet thruster on a vessel:

Location:

• Athwartships: The thruster is mounted transversely (sideways) through the hull, typically at the bow (forward) or stern (rear) of the vessel.   1. Maneuvering thruster – Wikipedia en.wikipedia.org
• Below Waterline: The intake and outlet openings are positioned below the waterline to ensure a constant supply of water for the pump.   1. How does a Jet Thruster Work www.jetthruster.com

Key Components and Arrangement:

1. Intake:

• Hull Penetration: A carefully shaped opening is cut into the hull, allowing seawater to enter the thruster.
• Grating or Grille: A grating or grille might be installed over the intake to prevent debris and larger objects from entering the system.

2. Impeller Pump:

• Internal Mounting: The pump is housed within the hull, usually in a dedicated compartment near the intake.
• Impeller: A centrifugal pump with an impeller draws water in from the intake.
• Drive System: The impeller is driven by either:
  • Electric Motor: Directly coupled or connected via a belt drive.
  • Hydraulic Motor: Connected to the vessel’s hydraulic system.

3. Ducting:

• Intake Duct: A duct connects the intake opening to the pump, ensuring smooth water flow and minimizing turbulence.
• Discharge Duct: A duct carries the high-velocity water from the pump to the nozzle.

4. Nozzle:

• Hull Penetration: The nozzle protrudes through the hull, typically near the waterline.
• Directional Control: The nozzle can be:
  • Fixed: For unidirectional thrust.
  • Rotatable: To direct the jet in different directions (port or starboard).

5. Control System:

• Bridge Control: The thruster is controlled from the bridge, often with a joystick or a dedicated control panel.
• Electrical or Hydraulic Controls: The control system sends signals to the motor or hydraulic valves to start/stop the pump, adjust its speed (if variable), and control the nozzle’s direction (if rotatable).

Additional Considerations:

• Size and Number: The size and number of thrusters depend on the vessel’s size, maneuverability requirements, and operating conditions. Larger vessels may have multiple thrusters at the bow and/or stern.   1. Maneuvering thruster – Wikipedia en.wikipedia.org
• Hull Shape and Integration: The thruster’s location and the design of the intake and nozzle need to be carefully integrated with the hull shape to minimize drag and optimize performance.
• Maintenance Access: Provisions should be made for accessing the thruster, pump, and other components for inspection and maintenance.

Benefits of this Arrangement:

• Compact Design: The internal mounting of the pump and ducting minimizes the thruster’s external profile, reducing drag and improving the vessel’s aesthetics.
• No Protruding Parts: There are no external propellers or other moving parts, minimizing the risk of damage or entanglement.
• Shallow Water Operation: The absence of protruding parts allows for operation in shallow water without the risk of grounding.

In summary, the arrangement of a transverse, water jet thruster is optimized for compactness, efficiency, and safety. The internal placement of the pump and ducting, along with the controllable nozzle, provides effective lateral thrust for maneuvering while minimizing drag and risk of damage.

Thrust in a water jet thruster is created by

the principle of Newton’s Third Law of Motion, which states that for every action, there is an equal and opposite reaction.In simpler terms, the thruster expels a high-velocity jet of water in one direction, and in response, the vessel experiences a force (thrust) in the opposite direction.

1. Science in Action: Newton’s Third Law of Motion – Space Center Houston

2. ts2.space

3. Water jet propulsion – Best propulsion for ship – YouTube

Here’s a breakdown of how thrust is generated:

1. Water Intake:

• Suction: Seawater is drawn into the thruster through an intake located below the waterline.   1. Water jet propulsion – Best propulsion for ship – YouTube www.youtube.com
• Impeller Pump: A powerful impeller pump, driven by an electric or hydraulic motor, accelerates the incoming water, increasing its velocity and kinetic energy.   1. Water jet propulsion – Best propulsion for ship – YouTube www.youtube.com

2. Acceleration and Pressure Increase:

• Impeller Action: The rotating impeller blades impart energy to the water, increasing its velocity significantly.   1. Water jet propulsion – Best propulsion for ship – YouTube www.youtube.com
• Ducting: The fast-moving water is then channeled through a specially designed duct or impeller housing.   1. Design and Construction of a Modular Pump-Jet Thruster for Autonomous Surface Vehicle Operations in Extremely Shallow Water – MDPI www.mdpi.com
• Pressure Build-up: As the water’s velocity increases within the confined space of the duct, its pressure also increases according to Bernoulli’s principle.

3. Nozzle:

• Further Acceleration: The high-pressure water is directed into a nozzle, which is designed to further accelerate the flow and shape it into a concentrated jet.   1. How to Design a Waterjet: Key Elements of Waterjets – DMS Marine Consultant www.dmsonline.us

4. Discharge and Thrust Generation:

• High-Velocity Jet: The water is expelled from the nozzle at a very high velocity, creating a powerful jet.   1. Design and Construction of a Modular Pump-Jet Thruster for Autonomous Surface Vehicle Operations in Extremely Shallow Water – MDPI www.mdpi.com
• Reaction Force (Thrust): As the water is expelled backward, the vessel experiences an equal and opposite reaction force in the forward direction, propelling it sideways.
• Directional Control: The direction of thrust can be controlled by either reversing the impeller’s rotation or by swiveling the nozzle to direct the jet in the desired direction (port or starboard).

Key Factors Affecting Thrust:

• Water Flow Rate: The volume of water pumped through the thruster per unit time. A higher flow rate generally results in more thrust.
• Jet Velocity: The speed at which the water is expelled from the nozzle. Higher jet velocity leads to greater thrust.
• Nozzle Design: The shape and size of the nozzle influence the jet’s velocity and shape, affecting thrust efficiency.

In Summary:

A water jet thruster creates thrust by drawing in seawater, accelerating it using an impeller pump, and then expelling it at high velocity through a nozzle. The reaction force from this expulsion of water propels the vessel in the opposite direction, enabling lateral movement and enhancing maneuverability.  

1. What is a Waterjet and How Does it Work – Marine Jet Power