Ducted propeller or tunnel 6 blade propeller
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- Brand name
- Ijin Marine
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- Negotiable / Negotiable
- Keyword
- propeller, ducted propeller, propeller blade, tunnel propeller
- Category
- Machinery Engines & Parts
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| Product name | Ducted propeller or tunnel 6 blade propeller | Certification | - |
|---|---|---|---|
| Category | Machinery Engines & Parts | Ingredients | - |
| Keyword | propeller , ducted propeller , propeller blade , tunnel propeller | Unit Size | - |
| Brand name | Ijin Marine | Unit Weigh | - |
| origin | Stock | - | |
| Supply type | - | HS code | - |
Product Information
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.
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 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.
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.
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.
The above material is from Wikipedia,edited by Ijin Marine.
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.
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 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.
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.
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.
The above material is from Wikipedia,edited by Ijin Marine.
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| Price (FOB) | Negotiable | transportation | - |
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- President
- Bill Jia
- Address
- 603,No2,Lane 138,Rushan Road,Shanghai,China
- Product Category
- Other Machinery Parts,Steel Wire,Valves
- Year Established
- 2010
- No. of Total Employees
- 1-50
- Company introduction
-
<p>Ijin Marine Limited, born in Hong Kong, is a hardware supplier and marine service agent in China. In around 90 sea ports and river ports of China, Ijin can directly deliver on board steel wire rope, anchor, anchor chain, pump, valve, lashing material, ship outfitting, and hardware, etc. In the past 2 years, Ijin has delivered 1,000.00 tons of wire rope, anchor chain, etc in 30 ports such as Xingang, Nantong, Lanshan, Zhanjiang, Bayuquan, Fangchenggang, etc. Thanks to our staffs’ hard work and kind cooperation of 300+ vendors, now Ijin has developed to be a reliable hardware supplier for commercial ship, tug boat, cruise vessel, naval vessel, etc. Not only supplying, Ijin also trades above hardware to other countries Malaysia, Germany, USA, UAE, India, etc.
As an agent, Ijin provides 50 kinds of marine service in 300+ ports, 80 countries. In our database, Ijin has more than 2500 suppliers, repairers, dockyards, etc in the world. So far, in at least 20 ports, Ijin has delivered service life saving inspection, fire fighting inspection, radio inspection, underwater hull cleaning, wire rope delivery, store, spare part and provision supplying etc, for more than 15 ship owners of China, India, Taiwan, UAE, etc. Ijin moves fast enough to follow your vessel schedules every 24 hours and 7 days. In Sudan, Sierra Leone, Togo, or any other port in the whole world, Ijin always stands with you.
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China
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