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Variable-pitch
In marine propulsion, a variable-pitch propeller is a type of propeller with blades that can be rotated around their long axis to change the blade pitch. Reversible propellers—those where the pitch can be set to negative values—can also create reverse thrust for braking or going backwards without the need to change the direction of shaft revolution. A controllable pitch propeller (CPP) can be efficient for the full range of rotational speeds and load conditions, since its pitch will be varied to absorb the maximum power that the engine is capable of producing. When fully loaded, a vessel will need more propulsion power than when empty. By varying the propeller blades to the optimal pitch, higher efficiency can be obtained, thus saving fuel. A vessel with a VPP can accelerate faster from a standstill and can decelerate much more effectively, making stopping quicker and safer. A CPP can also improve vessel maneuverability by directing a stronger flow of water onto the ru ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Propellers
A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working fluid such as water or air. Propellers are used to pump fluid through a pipe or duct, or to create thrust to propel a boat through water or an aircraft through air. The blades are specially shaped so that their rotational motion through the fluid causes a pressure difference between the two surfaces of the blade by Bernoulli's principle which exerts force on the fluid. Most marine propellers are screw propellers with helical blades rotating on a propeller shaft with an approximately horizontal axis. History Early developments The principle employed in using a screw propeller is derived from sculling. In sculling, a single blade is moved through an arc, from side to side taking care to keep presenting the blade to the water at t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Propeller
A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working fluid such as water or air. Propellers are used to pump fluid through a pipe or duct, or to create thrust to propel a boat through water or an aircraft through air. The blades are specially shaped so that their rotational motion through the fluid causes a pressure difference between the two surfaces of the blade by Bernoulli's principle which exerts force on the fluid. Most marine propellers are screw propellers with helical blades rotating on a propeller shaft (ship), propeller shaft with an approximately horizontal axis. History Early developments The principle employed in using a screw propeller is derived from sculling. In sculling, a single blade is moved through an arc, from side to side taking care to keep presenting the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blade Pitch
Blade pitch or simply pitch refers to the angle of a blade in a fluid. The term has applications in aeronautics, shipping, and other fields. Aeronautics In aeronautics, blade pitch refers to the angle of the blades of an aircraft propeller or helicopter rotor. Blade pitch is measured relative to the aircraft body. It is usually described as "fine" or "low" for a more vertical blade angle, and ,# "coarse" or "high" for a more horizontal blade angle. * i n Blade pitch is normally described as a ratio of forward distance per rotation assuming no slip. Blade pitch acts much like the gearing of the final drive of a car. Low pitch yields good low speed acceleration (and climb rate in an aircraft) while high pitch optimizes high speed performance and fuel economy. It is quite common for an aircraft to be designed with a variable-pitch * propeller, to give maximum thrust over a larger speed range. A fine pitch would be used during take-off and landing, whereas a coarser pitch is u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motorsailer
A motorsailer is a type of motor-powered sailing vessel, typically a yacht, that can derive power from its sails or engine, independently from each other during moderate seas or winds. A motorsailer may have a sail-to-engine power ratio in the range 30/70 to 70/30 (percent sail power/percent engine power). Characteristics Most motorsailers are yachts, with motors that can drive them at near hull speed in moderate seas, and sails that can provide power in moderate breezes without needing to use the engine. They normally have a sheltered steering station, which is likely to be a pilot house. The emphasis of such craft is typically comfort at sea and the ability to cruise long distances. The comparative capabilities of the engine and sails are often described as a ratio of sail-to-engine capabilities: * 30/70 has a relatively small sail plan and a large engine; * 50/50 derives equal power capability from sails and engine for a seaworthy, passage-making yacht; * 70/30 has an under ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Variable-pitch Propeller (aeronautics)
In aeronautics, a variable-pitch propeller is a type of propeller (airscrew) with blades that can be rotated around their long axis to change the blade pitch. A controllable-pitch propeller is one where the pitch is controlled manually by the pilot. Alternatively, a constant-speed propeller is one where the pilot sets the desired engine speed (RPM), and the blade pitch is controlled automatically without the pilot's intervention so that the rotational speed remains constant. The device which controls the propeller pitch and thus speed is called a propeller governor or constant speed unit. Reversible propellers are those where the pitch can be set to negative values. This creates reverse thrust for braking or going backwards without the need to change the direction of shaft revolution. Some aircraft have ground-adjustable propellers, however these are not considered variable-pitch. These are typically found only on light aircraft and microlights. Purpose When an aircraft is st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marine Propulsion
Marine propulsion is the mechanism or system used to generate thrust to move a watercraft through water. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting of an electric motor or internal combustion engine driving a propeller, or less frequently, in pump-jets, an impeller. Marine engineering is the discipline concerned with the engineering design process of marine propulsion systems. Human-powered paddles and oars, and later, sails were the first forms of marine propulsion. Rowed galleys, some equipped with sail, played an important early role in early human seafaring and warfares. The first advanced mechanical means of marine propulsion was the marine steam engine, introduced in the early 19th century. During the 20th century it was replaced by two-stroke or four-stroke diesel engines, outboard motors, and gas turbine engines on faster ships. Marine nuclear reactors, which appeared in the 1950s, pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crude Oil Tanker
An oil tanker, also known as a petroleum tanker, is a ship designed for the bulk transport of oil or its products. There are two basic types of oil tankers: crude tankers and product tankers. Crude tankers move large quantities of unrefined crude oil from its point of extraction to refineries. Product tankers, generally much smaller, are designed to move refined products from refineries to points near consuming markets. Oil tankers are often classified by their size as well as their occupation. The size classes range from inland or coastal tankers of a few thousand metric tons of deadweight (DWT) to the mammoth ultra large crude carriers (ULCCs) of . Tankers move approximately of oil every year.UNCTAD 2006, p. 4. Second only to pipelines in terms of efficiency,Huber, 2001: 211. the average cost of transport of crude oil by tanker amounts to only US. Some specialized types of oil tankers have evolved. One of these is the naval replenishment oiler, a tanker which can fuel a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Container Ships
A container ship (also called boxship or spelled containership) is a cargo ship that carries all of its load in truck-size intermodal containers, in a technique called containerization. Container ships are a common means of commercial intermodal freight transport and now carry most seagoing non-bulk cargo. Container ship capacity is measured in twenty-foot equivalent units (TEU). Typical loads are a mix of 20-foot (1-TEU) and 40-foot (2-TEU) ISO-standard containers, with the latter predominant. Today, about 90% of non-bulk cargo worldwide is transported by container ships, and the largest modern container ships can carry up to 24,000 TEU (e.g., '' Ever Ace''). Container ships now rival crude oil tankers and bulk carriers as the largest commercial seaborne vessels. History There are two main types of dry cargo: bulk cargo and break bulk cargo. Bulk cargoes, like grain or coal, are transported unpackaged in the hull of the ship, generally in large volume. Break-bulk car ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Narrowboat
A narrowboat is a particular type of canal boat, built to fit the narrow locks of the United Kingdom. The UK's canal system provided a nationwide transport network during the Industrial Revolution, but with the advent of the railways, commercial canal traffic gradually diminished and the last regular long-distance transportation of goods by canal had virtually disappeared by 1970. However, some commercial traffic continued. From the 1970s onward narrowboats were gradually being converted into permanent residences or as holiday lettings. Currently, about 8580 narrowboats are registered as 'permanent homes' on Britain's waterway system and represent a growing alternative community living on semi-permanent moorings or continuously cruising. For any boat to enter a narrow lock, it must be under wide, so most narrowboats are nominally wide. A narrowboat's maximum length is generally , as anything longer will be unable to navigate much of the British canal network, because the n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VLCC
An oil tanker, also known as a petroleum tanker, is a ship designed for the bulk transport of oil or its products. There are two basic types of oil tankers: crude tankers and product tankers. Crude tankers move large quantities of unrefined crude oil from its point of extraction to refineries. Product tankers, generally much smaller, are designed to move refined products from refineries to points near consuming markets. Oil tankers are often classified by their size as well as their occupation. The size classes range from inland or coastal tankers of a few thousand metric tons of deadweight (DWT) to the mammoth ultra large crude carriers (ULCCs) of . Tankers move approximately of oil every year.UNCTAD 2006, p. 4. Second only to pipelines in terms of efficiency,Huber, 2001: 211. the average cost of transport of crude oil by tanker amounts to only US. Some specialized types of oil tankers have evolved. One of these is the naval replenishment oiler, a tanker which can fuel a mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dredger
Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing dams, dikes, and other controls for streams and shorelines; and recovering valuable mineral deposits or marine life having commercial value. In all but a few situations the excavation is undertaken by a specialist floating plant, known as a dredger. Dredging is carried out in many different locations and for many different purposes, but the main objectives are usually to recover material of value or use, or to create a greater depth of water. Dredges have been classified as suction or mechanical. Dredging has significant environmental impacts: it can disturb marine sediments, leading to both short- and long-term water pollution, destroy important seabed ecosystems, and can release human-sourced toxins captured in the sediment. Descriptio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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