1
Project Elise- Ducted propeller test
Project Elise- Ducted propeller test
DATE: 2008/07/10::
2
Ducted propeller project by Sławek Maiden Flight
Ducted propeller project by Sławek Maiden Flight
DATE: 2014/01/05::
3
AUTOGRID DUCTED PROPELLER GRID
AUTOGRID DUCTED PROPELLER GRID
DATE: 2014/03/01::
4
Project Elise- Ducted propeller test #2
Project Elise- Ducted propeller test #2
DATE: 2008/07/22::
5
AUTOGRID DUCTED PROPELLER GRID 2
AUTOGRID DUCTED PROPELLER GRID 2
DATE: 2014/03/01::
6
Flying on the Ground
Flying on the Ground
DATE: 2012/09/21::
7
Carbon made Small Unmanned Aerial System (SUAS); named NEO
Carbon made Small Unmanned Aerial System (SUAS); named NEO
DATE: 2014/03/19::
8
Deformación tobera - Ducted propeller deformation
Deformación tobera - Ducted propeller deformation
DATE: 2009/10/19::
9
WINGLET (Propfan) propellers for multi-copters (Ducted)(EDF)
WINGLET (Propfan) propellers for multi-copters (Ducted)(EDF)
DATE: 2014/02/01::
10
Ducted Fan Bixler
Ducted Fan Bixler
DATE: 2013/01/26::
11
UH-8FS Personal or Racing Hovercraft
UH-8FS Personal or Racing Hovercraft
DATE: 2012/05/15::
12
Coupled fluid-structure analysis (FSI) of a ducted propeller
Coupled fluid-structure analysis (FSI) of a ducted propeller
DATE: 2009/12/21::
13
SUPER FAST Piasecki X-49A Helicopter for US Military
SUPER FAST Piasecki X-49A Helicopter for US Military
DATE: 2014/11/12::
14
The Case For Ducted Fan VTOL
The Case For Ducted Fan VTOL
DATE: 2011/10/07::
15
SUPER FAST Piasecki X 49A Helicopter for US Military
SUPER FAST Piasecki X 49A Helicopter for US Military
DATE: 2014/02/04::
16
SUPER FAST X 49A Helicopter for US military
SUPER FAST X 49A Helicopter for US military
DATE: 2014/06/20::
17
Piasecki X-49A Speedhawk flight tests
Piasecki X-49A Speedhawk flight tests
DATE: 2007/10/18::
18
Piasecki Aircraft VTDP Compound Helicopter Technology
Piasecki Aircraft VTDP Compound Helicopter Technology
DATE: 2013/08/28::
19
SUPER FAST Piasecki X 49A military transport helicopter for US military
SUPER FAST Piasecki X 49A military transport helicopter for US military
DATE: 2014/03/10::
20
Raven EPP rc Flying wing with ducted fan
Raven EPP rc Flying wing with ducted fan
DATE: 2009/12/11::
21
ducted fan
ducted fan
DATE: 2015/01/09::
22
Piasecki Aircraft VTDP Compound Helicopter Technology
Piasecki Aircraft VTDP Compound Helicopter Technology
DATE: 2014/11/01::
23
Launch M.V. "Vlieborg", Ferus Smit, Westerbroek, The Netherlands
Launch M.V. "Vlieborg", Ferus Smit, Westerbroek, The Netherlands
DATE: 2012/08/29::
24
Universal Hovercraft - UH-10F Entry Level Hovercraft Racing- Plans & Kits available
Universal Hovercraft - UH-10F Entry Level Hovercraft Racing- Plans & Kits available
DATE: 2010/01/25::
25
A flying ship using the Coanda effect to generate horizontal power
A flying ship using the Coanda effect to generate horizontal power
DATE: 2013/07/06::
26
ROV Thrusters - Part 3 - Testing Props
ROV Thrusters - Part 3 - Testing Props
DATE: 2014/03/18::
27
LOW ENERGY WATERCRAFT AND AIRCRAFT USING COANDA EFFECT FOR PROPULSION
LOW ENERGY WATERCRAFT AND AIRCRAFT USING COANDA EFFECT FOR PROPULSION
DATE: 2014/07/08::
28
Imperator S100 surface fast running - RC Submarine Model
Imperator S100 surface fast running - RC Submarine Model
DATE: 2014/03/20::
29
Multiplex Xeno with Electrical Ducted Fan makes much fun
Multiplex Xeno with Electrical Ducted Fan makes much fun
DATE: 2010/05/30::
30
US Naval Research First Flying Platform 1955  (2X4 Cyl & counter rotating propellers)
US Naval Research First Flying Platform 1955 (2X4 Cyl & counter rotating propellers)
DATE: 2011/06/29::
31
Electric ducted fan test (64mm EDF, brushless motor, 30A ESC)
Electric ducted fan test (64mm EDF, brushless motor, 30A ESC)
DATE: 2010/05/10::
32
U.S. Army 160th SOAR: Helicopters Must Fly FASTER & FARTHER
U.S. Army 160th SOAR: Helicopters Must Fly FASTER & FARTHER
DATE: 2010/01/20::
33
Stipa-Caproni Flying Barrel (take-off footage only)
Stipa-Caproni Flying Barrel (take-off footage only)
DATE: 2007/09/30::
34
R/C Sub, Scratch-built From Sewer Pipe
R/C Sub, Scratch-built From Sewer Pipe
DATE: 2011/11/27::
35
Newly invented combination of terrestrial and water craft
Newly invented combination of terrestrial and water craft
DATE: 2013/07/06::
36
1933 Stipa-Caproni Aircraft
1933 Stipa-Caproni Aircraft
DATE: 2014/06/27::
37
R/C Sub USS Virginia: Assorted Clips
R/C Sub USS Virginia: Assorted Clips
DATE: 2011/11/27::
38
Scratch Built YC-14 Twin Prop RC Cargo plane
Scratch Built YC-14 Twin Prop RC Cargo plane
DATE: 2011/01/09::
39
RC Model Rescue Boat.wmv
RC Model Rescue Boat.wmv
DATE: 2012/02/06::
40
Doak VZ-4 VTOL Aircraft "Army R and D Progress Report 1" 1960 US Army
Doak VZ-4 VTOL Aircraft "Army R and D Progress Report 1" 1960 US Army
DATE: 2012/02/06::
41
Marlin Jet boat.mp4
Marlin Jet boat.mp4
DATE: 2013/02/24::
42
Stipa-Caproni
Stipa-Caproni
DATE: 2010/06/28::
43
Our Top Secret UFO
Our Top Secret UFO
DATE: 2010/10/01::
44
X-UAV Bobcat Rc airplane trainner EPO plane model with 70 ducted motor
X-UAV Bobcat Rc airplane trainner EPO plane model with 70 ducted motor
DATE: 2013/06/06::
45
Renewable Energy   M3 HYBRID   Pivotal Aero Turbines
Renewable Energy M3 HYBRID Pivotal Aero Turbines
DATE: 2014/01/27::
46
HorizonRC.com Preview: E-flite F-16 400
HorizonRC.com Preview: E-flite F-16 400
DATE: 2008/10/02::
47
ROV Thruster Testing
ROV Thruster Testing
DATE: 2011/01/03::
48
Investigative 1/4 build of full scale quadcopter part 2 DIY propeller
Investigative 1/4 build of full scale quadcopter part 2 DIY propeller
DATE: 2014/10/29::
49
Back to Propellers
Back to Propellers
DATE: 2012/06/27::
50
Terrafugia TF-X - hybrid-electric stop/fold tiltprop VTOL flying car
Terrafugia TF-X - hybrid-electric stop/fold tiltprop VTOL flying car
DATE: 2013/05/06::
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RESULTS [51 .. 101]
From Wikipedia, the free encyclopedia
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Not to be confused with Ducted fan.
The towboat Dolphin I in a floating drydock on the Mississippi River in Algiers, Louisiana.

A ducted propeller, also known as a Kort nozzle, is a propeller fitted with a non-rotating nozzle. It is used to improve the efficiency of the propeller and is especially used on heavily loaded propellers or propellers with limited diameter. It was developed by Luigi Stipa (1931) and Ludwig Kort (1934). The Kort nozzle is a shrouded propeller assembly for marine propulsion. The hydrodynamic design of the shroud, which is shaped like a foil, offers advantages for certain conditions over bare propellers.

Advantages are increased efficiency at lower speeds (<10 knots), better course stability and less vulnerability to debris. Downsides are reduced efficiency at higher speeds (>10 knots), course stability when sailing astern, and increase of cavitation. Ducted propellers are also used to replace rudders.

History[edit]

Luigi Stipa[1] and later Ludwig Kort (1934)[2] demonstrated that an increase in propulsive efficiency could be achieved by surrounding the propeller with a foil-shaped shroud in the case of heavily loaded propellers. A "Kort Nozzle" is referred to as an accelerating nozzle and is generally a MARIN 19A profile[clarification needed] or a MARIN 37 profile.

Advantages and disadvantages[edit]

Kort nozzles or ducted propellers can be significantly more efficient than unducted propellers at low speeds, producing greater thrust in a smaller package. Tugboats and fishing trawlers are the most common application for Kort nozzles as highly loaded propellers on slow moving vessels benefit the most. Nozzles have the additional benefits of reducing paddlewheel-effect (e.g. the tendency of a right-hand wheel to back to the left) and reduce bottom suction while operating in shallow water.

The additional shrouding adds drag, however, and Kort nozzles lose their advantage over propellers at about ten knots (18.5 km/h).

Kort nozzles may be fixed, with directional control coming from a rudder set in the water flow, or pivoting, where their flow controls the vessel's steering.

Shrouding of this type is also beneficial to navigation in ice fields since it protects the propeller tips to some extent. However, ice or any other floating object can become jammed between the wheel and nozzle, locking up the wheel. Fouled wheels in Kort nozzles are much more difficult to clear than open wheels.

A research paper by Bexton et al. (2012)[3] concluded that ducted propellers were the likely cause of fatal injuries of seals in the northeastern Atlantic. The authors hypothesized that the seals were drawn through the nozzle and past the rotating propeller blades, incurring curvilinear lacerations to skin and muscle tissue. This type of injury has come to be known as a "corkscrew" injury. The authors also comment that other animals, including harbour porpoises, have been seen to exhibit similar injuries.

Types[edit]

There are two types of ducts; accelerating and decelerating. With accelerating ducts, the inflow velocity and efficiency of the propeller is increased. This is the type that is used on heavily loaded propellers or propellers with limited diameter. As Ludwig Kort performed extensive research on this type, it is often called a "Kort nozzle".

With the second type, the inflow velocity is reduced, whereby pressure is increased, reducing cavitation. This is called a pump-jet, especially in combination with fixed blades or stators.

NACA 4415.

MARIN has done extensive research on ducted propellers. Many of the used profiles are based on the NACA airfoils of which the NACA 4415 has very good characteristics. Most commonly used are nozzle 19A and 37 of the MARIN series. These have a rounded trailing edge to ease fabrication and increase efficiency sailing astern. Initially, the propellers of the Wageningen B-series were used, later the Kaplan-type with a wider blade tip.

Physics[edit]

Circulation around accelerating and decelerating nozzle
Circulation around nozzles.svg

dT = Thrust
dL = Lift

pu: Negative pressure
po: Positive pressure

In a Kort nozzle, the inflow velocity is increased, reducing pressure. This lowers thrust and torque of the propeller. At the same time, a circulation occurs, resulting in an inward aimed force, that has a forward component. The duct therefore has a positive thrust. This is normally larger than the thrust reduction of the propeller. The small clearance between the propeller and duct reduces tip vortex, increasing efficiency.

As drag increases with increasing speed, eventually this will become larger than the added thrust. Vessels that normally operate above this speed are therefore normally not fitted with ducts. When towing, tugboats sail with low speed and heavily loaded propellers, and are often fitted with ducts. Bollard pull can increase up to 30% with ducts.

With decelerating ducts, the circulation opposite of the Kort nozzle, resulting in a negative thrust of the duct. This type is used for high speed vessels with increased exposure to cavitation and vessels that want to reduce noise levels, such as warships.

See also[edit]

References[edit]

Bibliography[edit]

External links[edit]

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