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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 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 waves. 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 The Voith Schneider Propeller, also ... [...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 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] |
Rim-driven Thruster
The rim-driven thruster, also known as rim-driven propulsor/propeller (or RDP) is a novel type of electric propulsion unit for ships. The concept was proposed by Kort around 1940, but only became commercially practical in the early 21st century due to advances in DC motor controller technology. As of 2017, commercial models of between 500 kW and 3MW are available from manufacturers such as Rolls-Royce, Schottel, Brunvoll, Voith, Van der Velden, etc. Principle The rim-driven thruster is a marine propeller that does not use a central hub for transmission of the driving torque. Conventional hubcentric propellers typically use a shaft driven by a turbine, a diesel engine or an electric motor. The more recent podded drives consist of a propeller driven by a conventional electric motor into an azimuthable gondola under water, but they still incorporate a traditional hubcentric propeller. The blades of the rim-driven thruster, by contrast, are mounted on an outer ring rathe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Axial Fan Design
An axial fan is a type of fan that causes gas to flow through it in an axial direction, parallel to the shaft about which the blades rotate. The flow is axial at entry and exit. The fan is designed to produce a pressure difference, and hence force, to cause a flow through the fan. Factors which determine the performance of the fan include the number and shape of the blades. Fans have many applications including in wind tunnels and cooling towers. Design parameters include power, flow rate, pressure rise and efficiency. Axial fans generally comprise fewer blades (two to six) than ducted fans. Axial fans commonly have larger radius and lower speed (ω) than ducted fans (esp. at similar power. Stress proportional to r^2). Calculation of parameters Since the calculation cannot be done using the inlet and outlet velocity triangles, which is not the case in other turbomachines, calculation is done by considering a mean velocity triangle for flow only through an infinitesimal bla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
L-drive
An L-drive is a type of azimuth thruster where the electric motor is mounted vertically, removing the second bevel gear from the drivetrain. Azimuth thruster pods can be rotated through a full 360 degrees, allowing for rapid changes in thrust direction and eliminating the need for a conventional rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally air or water). On an aircraft the rudder is used primarily to counter adverse yaw a .... This form of power transmission is called a L-drive because the rotary motion has to make one right angle turn, thus looking a bit like the letter "L". This name is used to make clear the arrangement of drive is different from Z-drive. See also * * * * * Notes {{DEFAULTSORT:L-Drive Marine propulsion ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Z-drive
A Z-drive is a type of marine propulsion unit. Specifically, it is an azimuth thruster. The pod can rotate 360 degrees allowing for rapid changes in thrust direction and thus vessel direction. This eliminates the need for a conventional rudder. The Z-drive is so named because of the appearance (in cross section) of the mechanical driveshaft or transmission configuration used to connect the mechanically supplied driving energy to the ''Z-Drive'' azimuth thruster device. This form of power transmission is called a Z-drive because the rotary motion has to make two right angle turns, thus resembling the letter "Z". This name is used to differentiate the arrangement of drive to that of the L-drive. It does not refer to an electric motor in a rotating pod. The device is different from the Voith-Schneider marine propulsion system (also mechanically linked), which can also quickly change the direction of thrust, as the ''Z-drive'' uses a shrouded conventional screw A screw and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Azimuth Thruster
An azimuth thruster is a configuration of marine propellers placed in pods that can be rotated to any horizontal angle (azimuth), making a rudder unnecessary. These give ships better maneuverability than a fixed propeller and rudder system. Types of azimuth thrusters There are two major variants, based on the location of the motor: # Mechanical transmission, which connects a motor inside the ship to the outboard unit by gearing. The motor may be diesel or diesel-electric. Depending on the shaft arrangement, mechanical azimuth thrusters are divided into L-drive and Z-drive. An L-drive thruster has a vertical input shaft and a horizontal output shaft with one right-angle gear. A Z-drive thruster has a horizontal input shaft, a vertical shaft in the rotating column and a horizontal output shaft, with two right-angle gears. # Electrical transmission, more commonly called pods, where an electric motor is fitted in the pod itself, connected directly to the propeller witho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft and many forms of STOL (Short TakeOff and Landing) or STOVL (Short TakeOff and Vertical Landing) aircraft cannot perform without a runway. In 1942, the Sikorsky R-4 became the first helicopter to reach full-scale production.Munson 1968.Hirschberg, Michael J. and David K. Dailey"Sikorsky". ''US and Russian Helicopter Development in the 20th Century'', American Helicopter Society, International. 7 July 2000. Although most earlier designs used more than one main rotor, the configuration of a single main rotor accompanied by a vertical anti-torque tail rotor (i.e. unicopter, not to be confused with the single-blade monocopter) has become the most ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voith-Schneider
A cyclorotor, cycloidal rotor, cycloidal propeller or cyclogiro, is a fluid propulsion device that converts shaft power into the acceleration of a fluid using a rotating axis perpendicular to the direction of fluid motion. It uses several blades with a spanwise axis parallel to the axis of rotation and perpendicular to the direction of fluid motion. These blades are cyclically pitched twice per revolution to produce force (thrust or lift) in any direction normal to the axis of rotation. Cyclorotors are used for propulsion, lift, and control on air and water vehicles. An aircraft using cyclorotors as the primary source of lift, propulsion, and control is known as a cyclogyro or cyclocopter. A unique aspect is that it can change the magnitude and direction of thrust without the need of tilting any aircraft structures. The patented application, used on ships with particular actuation mechanisms both mechanical or hydraulic, is named after German company Voith Turbo. Operating princi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Hunt For Red October
''The Hunt for Red October'' is the debut novel by American author Tom Clancy, first published on October 1, 1984, by the Naval Institute Press. It depicts Soviet submarine captain Marko Ramius as he seemingly goes rogue with his country's cutting-edge ballistic missile submarine ''Red October'', and marks the first appearance of Clancy's most popular fictional character, Jack Ryan, an analyst working for the Central Intelligence Agency, as he must prove his theory that Ramius had intended to defect to the United States. ''The Hunt for Red October'' launched Clancy's successful career as a novelist, especially after then-U.S. President Ronald Reagan remarked that he had enjoyed reading the book. A film adaptation was released on March 2, 1990, and several computer and video games based on the book have been developed. The book was instrumental in bringing the book genre of techno-thriller into the mainstream. Plot summary During the Cold War, Marko Ramius, a Soviet Navy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Hunt For Red October (film)
''The Hunt for Red October'' is a 1990 American submarine spy thriller film directed by John McTiernan, produced by Mace Neufeld, and starring Sean Connery, Alec Baldwin, Scott Glenn, James Earl Jones, and Sam Neill. The film is an adaptation of Tom Clancy's 1984 bestselling novel of the same name. It is the first installment of the film series with the protagonist Jack Ryan. The story is set during the late Cold War era and involves a rogue Soviet naval captain who wishes to defect to the United States with his officers and the Soviet Navy's newest and most advanced ballistic missile submarine, a fictional improvement on the Soviet Typhoon-class submarine. A CIA analyst correctly deduces his motive and must prove his theory to the U.S. Navy before a violent confrontation between the Soviet and the American navies spirals out of control. The film was a co-production between the motion picture studios Paramount Pictures, Mace Neufeld Productions, and Nina Saxon Film Design. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetohydrodynamics
Magnetohydrodynamics (MHD; also called magneto-fluid dynamics or hydromagnetics) is the study of the magnetic properties and behaviour of electrically conducting fluids. Examples of such magnetofluids include plasmas, liquid metals, salt water, and electrolytes. The word ''magnetohydrodynamics'' is derived from ' meaning magnetic field, ' meaning water, and ' meaning movement. The field of MHD was initiated by Hannes Alfvén, for which he received the Nobel Prize in Physics in 1970. The fundamental concept behind MHD is that magnetic fields can induce currents in a moving conductive fluid, which in turn polarizes the fluid and reciprocally changes the magnetic field itself. The set of equations that describe MHD are a combination of the Navier–Stokes equations of fluid dynamics and Maxwell’s equations of electromagnetism. These differential equations must be solved simultaneously, either analytically or numerically. History The first r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moving Parts
Machines include both fixed and moving parts. The moving parts have controlled and constrained motions. Moving parts are machine components excluding any moving fluids, such as fuel, coolant or hydraulic fluid. Moving parts also do not include any mechanical locks, switches, nuts and bolts, screw caps for bottles etc. A system with no moving parts is described as "solid state". Mechanical efficiency and wear The amount of moving parts in a machine is a factor in its mechanical efficiency. The greater the number of moving parts, the greater the amount of energy lost to heat by friction between those parts. For example, in a modern automobile engine, roughly 7% of the total power obtained from burning the engine's fuel is lost to friction between the engine's moving parts. Conversely, the fewer the number of moving parts, the greater the efficiency. Machines with no moving parts at all can be very efficient. An electrical transformer, for example, has no moving parts, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
