A pump-jet or water jet is a marine system that creates a jet of water for propulsion. A personal water craft ( PWC) is a Recreational Watercraft that the rider sits or stands on rather than inside An ocean (from Greek, ''Okeanos'' (Oceanus) is a major body of saline water, and a principal component of the Hydrosphere. Water is a common Chemical substance that is essential for the survival of all known forms of Life. Marine propulsion is the act of moving a floating object over or through water The mechanical arrangement may be a ducted propeller with nozzle, or a centrifugal pump and nozzle. A propeller is essentially a type of fan which transmits power by converting Rotational motion into Thrust for propulsion of a vehicle such as an A nozzle is a mechanical device or Orifice designed to control the characteristics of a Fluid flow as it exits (or enters an enclosed chamber or Pipe. As the name suggests a turbopump comprises basically two main components a rotodynamic Pump and a driving Turbine, both mounted on the same shaft The first functioning pump-jet engine was created by New Zealand inventor, Sir William Hamilton in 1954. New Zealand is an Island country in the south-western Pacific Ocean comprising two main landmasses (the North Island and the South Island An inventor is a person who creates or discovers a new method form device or other useful means William Hamilton (and shortened forms may refer to Europeans William Hamilton (Lord Chancellor, (d Year 1954 ( MCMLIV) was a Common year starting on Friday (link will display full 1954 Gregorian calendar)
Advantages
Pump jets have some advantages over bare propellers for certain applications, usually related to requirements for high-speed or shallow-draft operations. The draft (or draught) of a ship's hull is the vertical distance between the Waterline and the bottom of the hull ( Keel) with the thickness These include:
- Increasing the speed before the onset of cavitation, due to the raised internal dynamic pressure
- High power density (with respect to volume) of both the propulsor and the prime mover (since a smaller, higher-speed unit can be used)
- Protection of the rotating element and making operation safer around swimmers and aquatic life
- Improved shallow-water operations, since only the inlet needs to be submerged
- Increased maneuverability, by adding a steerable nozzle to create vectored thrust
- Ultra-quiet designs for submarines; for example the Royal Navy Trafalgar-class, the US Navy Seawolf-class, the French Navy Le Triomphant class, and the Russian Navy Borei class. Cavitation is defined as the phenomenon of formation of vapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapour pressure In Fluid dynamics dynamic pressure (indicated with q, or Q, and sometimes called velocity pressure) is the quantity defined by Thrust vectoring is the ability of an Aircraft or other vehicle to direct the Thrust from its main Engine (s in a direction other than parallel to A submarine is a Watercraft that can operate independently below water as distinct from a Submersible that has only limited underwater capability The Royal Navy of the United Kingdom is the oldest of the British armed services (and is therefore known as the Senior Service) Description The Trafalgar is a refinement of the ''Swiftsure'' class and designed six years later than its predecessor Boats ''Seawolf'' (SSN-21, commissioned and in service ''Connecticut'' (SSN-22, commissioned and in service ''Jimmy The French Navy, officially the Marine nationale ( National Navy) and often called La Royale ( The Royal Navy) is the maritime arm See also France and weapons of mass destruction FOST The Russian Navy or VMF ( Russian: Военно-Морской Флот (ВМФ России- Voyenno-Morskoy Flot Rossii (VMF or literally Military Maritime History and description Work on the first unit of the Borey class (officially designated Project 935) started in 1996 A pumpjet also formed a central plot element in Tom Clancy's novel The Hunt for Red October, although it was changed to a more advanced version, a magnetohydrodynamic drive (called a caterpiller drive) in the film. Thomas Leo Clancy Jr (born April 12 1947) is an American author best known for his technically detailed espionage and Military science storylines The Hunt for Red October is a Novel by Tom Clancy. The story follows the intertwined adventures of Soviet Submarine captain Marko A magnetohydrodynamic drive or MHD Propulsor, is a method for propelling seagoing vessels using only electric and magnetic fields with no Moving parts,
- Some Torpedoes such as the Spearfish and Mk 48 weapons. The modern torpedo (historically called an automotive automobile locomotive or fish torpedo is a self-propelled explosive Projectile weapon launched above or below The Spearfish torpedo (formally Naval Staff Target 7525 is the heavy Acoustic homing Torpedo used by the Submarines of the Royal Navy. The Mark 48 and its improved ADCAP ( Ad vanced Cap ability variant are heavyweight submarine-launched torpedoes
In these situations, the benefits outweigh the somewhat reduced efficiency (especially marked at low forward speeds) caused by the increased wetted surface and higher rotational speeds than an open propeller. One disadvantage is that pump jets (especially when fitted to outboard engines) are prone to becoming clogged with debris such as seaweed. The operator must clear the impeller by stopping the craft and briefly revving the engine in reverse.
See also
External links
- Personal Watercraft Industry Association
- American Watercraft Association
- U.S. Coast Guard Boating Safety
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic