Editing Propulsor

{{short description|Mechanical device to propel a vessel}}
A '''propulsor''' is a mechanical device that gives propulsion.  The word is commonly used in the marine vernacular, and implies a mechanical assembly that is more complicated than a [[propeller]]. The [[Kort nozzle]], [[pump-jet]] and [[rim-driven thruster]] are examples.

An example propulsor is shown in the accompanying picture.  It has a shroud which cuts down on blade-tip [[cavitation]] and radiated noise. It also has a rotor element and a [[Axial_compressor#_Description|stator]]. The stator concentrates the thrust in axial direction and reduces energy wasted in the tangential flow (therefore eliminating torque on the hull).  The number of blades in the rotor and stator will typically be two different prime numbers to avoid [[standing wave]]s. The blades in the rotor or the stator may be angled to further reduce noise.  The physical design and layout is very much similar to a single-stage [[axial-flow compressor]].

==Other propulsors==
===Voith Schneider===
[[Image:VSPreal.jpg|left|thumb|150px|Voith‐Schneider propeller]]

The [[Voith Schneider Propeller]], also known as a '''cycloidal drive''' is a specialized [[marine propulsion]] system. It is highly maneuverable, being able to change the direction of its [[thrust]] almost instantaneously. It is widely used on [[tug]]s and [[ferry|ferries]].

From a circular plate, rotating around a vertical axis, a circular array of vertical blades (in the shape of [[hydrofoil]]s) protrude out of the bottom of the ship. Each blade can rotate itself around a vertical axis. The internal gear changes the [[angle of attack]] of the blades in sync with the rotation of the plate, so that each blade can provide thrust in any direction, very similar to the ''[[collective pitch]] control'' and ''[[cyclic pitch|cyclic]]'' in a [[helicopter#Flight controls|helicopter]].

===Azimuth thruster===
[[Image:Siemens Schottel Propulsor.jpg|thumb|150px|right|[[Siemens AG|Siemens]] ''Schottel'' azimuth thrusters]]
An '''[[azimuth thruster]]''' is a configuration of [[ship]] propellers placed in pods that can be rotated on the horizontal plane, making a [[rudder]] unnecessary. These give ships better maneuverability than a fixed [[propeller]] and rudder system.

===Magnetohydrodynamic drive===
A '''[[magnetohydrodynamic drive]]''' or '''MHD propulsor''' is a method for propelling seagoing vessels using only electric and magnetic fields with no [[moving parts]], using [[magnetohydrodynamics]]. The working principle involves electrification of the propellant (gas or water) which can then be directed by a magnetic field, pushing the vehicle in the opposite direction. Although some working prototypes exist, MHD drives remain impractical and exist mostly in the world of science fiction. A magnetohydrodynamic drive was featured in the 1990 film [[The Hunt for Red October (film)|''The Hunt for Red October'']], differing from the pump jet propulsion system featured in the Tom Clancy novel ''[[The Hunt for Red October]]'' upon which the movie was based.

==See also==
* [[Z-drive]]
* [[L-drive]]
* [[Voith-Schneider]]
* [[Axial fan design]]
* [[Axial-flow compressor]]

==External links==
*[http://www.rolls-royce.com/marine/products/propulsion/default.jsp Rolls-Royce Marine]
*[https://web.archive.org/web/20040805122512/http://schottel.de/index_e.htm Schottel marine propulsion]
*[https://web.archive.org/web/20081029064858/http://www.flowserve.com/vgnfiles/Files/Literature/ProductLiterature/Pumps/pss-90-8.1-e.pdf Pleuger Propulsion]
*[http://www.voithturbo.de/vt_en_pua_marine_vspropeller.htm Voith Schneider propulsors]
*[https://web.archive.org/web/20040816085147/http://marinepropulsion.net/kort/nozzle.htm Kort nozzles]
*[http://www.fairplay-tugs.com/main/faq-all.php Tug boat FAQ]
*[http://www.ultradynamics.com UltraJet web site]
*[http://www.zf.com/marine ZF Marine]
<!-- Patents ES0293837, ES8300608, ES044150, ES8205166, ES8100010, ES0445822, ES0448660, by Astilleros Españoles (see Espacenet) -->

[[Category:Marine propulsion]]

[[de:Düsenringpropeller]]