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Cutoff (steam Engine)
In a steam engine, cutoff is the point in the piston stroke at which the inlet valve is closed. On a steam locomotive, the cutoff is controlled by the reversing gear. The point at which the inlet valve closes and stops the entry of steam into the cylinder from the boiler plays a crucial role in the control of a steam engine. Once the valve has closed, steam trapped in the cylinder expands adiabatically. The steam pressure drops as it expands. A late cutoff delivers full steam pressure to move the piston through its entire stroke, for maximum start-up forces. But, since there will still be unexploited pressure in the cylinder at the end of the stroke, this is achieved at the expense of engine efficiency. In this situation the steam will still have considerable pressure remaining when it is exhausted resulting in the characteristic “chuff chuff” sound of a steam engine. An early cutoff has greater thermodynamic efficiency but results in a lower mean effective pressure so les ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steam Engine
A steam engine is a heat engine that performs Work (physics), mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a Cylinder (locomotive), cylinder. This pushing force can be transformed by a connecting rod and Crank (mechanism), crank into rotational force for work. The term "steam engine" is most commonly applied to reciprocating engines as just described, although some authorities have also referred to the steam turbine and devices such as Hero's aeolipile as "steam engines". The essential feature of steam engines is that they are external combustion engines, where the working fluid is separated from the combustion products. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle. In general usage, the term ''steam engine'' can refer to either complete steam plants (including Boiler (power generation), boilers etc.), such as railway steam locomot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder (engine), cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and uncovering Porting (engine)#Two-stroke porting, ports in the cylinder. __TOC__ Piston engines Internal combustion engines An internal combustion piston engine, internal combustion engine is acted upon by the pressure of the expanding combustion gases in the combustion chamber space at the top of the cylinder. This force then acts dow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steam Locomotive
A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material (usually coal, Fuel oil, oil or, rarely, Wood fuel, wood) to heat water in the locomotive's Boiler (power generation), boiler to the point where it becomes gaseous and its volume increases 1,700 times. Functionally, it is a steam engine on wheels. In most locomotives, the steam is admitted alternately to each end of its Steam locomotive components, cylinders in which pistons are mechanically connected to the locomotive's main wheels. Fuel and water supplies are usually carried with the locomotive, either on the locomotive itself or in a Tender (rail), tender coupled to it. #Variations, Variations in this general design include electrically powered boilers, turbines in place of pistons, and using steam generated externally. Steam locomotives were first developed in the United Kingdom of Great Britain an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reversing Gear
Reversing gear is a mechanism used to both control the direction of travel of a steam locomotive and adjust its engine's steam cutoff. Reversing lever The most common form of reversing gear uses a lever to engage (known as a ''Johnson bar'' in the United States) mounted parallel to the direction of travel on the driver’s side of the cab. It is controlled by a handle and sprung trigger at the top, and pivots at the bottom to pass between two notched sector plates. The reversing rod, which connects to the valve gear, is attached to the lever either above or below the pivot in an alignment that gives good leverage. A square pin is arranged to engage with notches cut in the plates and holds the lever (and valve gear) in the desired position when the trigger is released. The advantages of this design are that change between forward and reverse gear can be made very quickly (as is needed in, for example, a shunting engine). Limitations and drawbacks The reversing lever has a cat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adiabatic Process
An adiabatic process (''adiabatic'' ) is a type of thermodynamic process that occurs without transferring heat between the thermodynamic system and its Environment (systems), environment. Unlike an isothermal process, an adiabatic process transfers energy to the surroundings only as Work (thermodynamics), work and/or mass flow.. A translation may be founhere. Also a mostly reliabltranslation is to be foundin As a key concept in thermodynamics, the adiabatic process supports the theory that explains the first law of thermodynamics. The opposite term to "adiabatic" is ''diabatic''. Some chemical and physical processes occur too rapidly for energy to enter or leave the system as heat, allowing a convenient "adiabatic approximation".Bailyn, M. (1994), pp. 52–53. For example, the adiabatic flame temperature uses this approximation to calculate the upper limit of fire, flame temperature by assuming combustion loses no heat to its surroundings. In meteorology, adiabatic expansion an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mean Effective Pressure
The mean effective pressure (MEP) is a quantity relating to the operation of a reciprocating engine and is a measure of an engine's capacity to do work that is independent of engine displacement. Despite having the dimension of pressure, MEP cannot be measured. When quoted as an ''indicated mean effective pressure'' (''IMEP''), it may be thought of as the average pressure acting on a piston during the different portions of its cycle. When friction losses are subtracted from the IMEP, the result is the brake mean effective pressure (BMEP). Derivation Let: :P = power output in watt; :p_\text = mean effective pressure in megapascal; :V_\text = displacement volume in cubic centimetre; :i = number of cycles per revolution (for a 4-stroke engine, i =0.5, for a 2-stroke engine, i =1);Wankel engines are four-stroke engines, so i =0.5; the displacement V_\text is derived from the chamber volume V_\text by multiplying it with the number of rotary pistons i and 2: V_\text = 2 V_\text i (see ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indicator Diagram Steam Admission
Indicator may refer to: Biology * Environmental indicator of environmental health (pressures, conditions and responses) * Ecological indicator of ecosystem health (ecological processes) * Health indicator, which is used to describe the health of a population * Honeyguides, also known as "indicator birds", a family of Old World tropical birds ** ''Indicator'' (genus), a genus of birds in the honeyguide family * Indicator species, a species that defines a characteristic of an environment * Indicator bacteria, bacteria used to detect and estimate the level of fecal contamination of water * Indicator organism, organisms used to measure such things as potential fecal contamination of environmental samples * Indicator plant, a plant that acts as a measure of environmental conditions * Indicator value, one of two terms in ecology referring to the classification of organisms * Iodine–starch test, a method to test for the presence of starch or iodine. Chemistry * Complexometric ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Valve Events
A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings, but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure. The word is derived from the Latin ''valva'', the moving part of a door, in turn from ''volvere'', to turn, roll. The simplest, and very ancient, valve is simply a freely hinged flap which swings down to obstruct fluid (gas or liquid) flow in one direction, but is pushed up by the flow itself when the flow is moving in the opposite direction. This is called a check valve, as it prevents or "checks" the flow in one direction. Modern control valves may regulate pressure or flow downstream and operate on sophisticated automation systems. Valves have many uses, including controlling water for irrigation, ind ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stationary Steam Engine
Stationary steam engines are fixed steam engines used for pumping or driving mills and factories, and for power generation. They are distinct from locomotive engines used on railways, traction engines for heavy steam haulage on roads, steam cars (and other motor vehicles), agricultural engines used for ploughing or threshing, marine engines, and the steam turbines used as the mechanism of power generation for most nuclear power plants. They were introduced during the 18th century and widely made for the whole of the 19th century and most of the first half of the 20th century, only declining as electricity supply and the internal combustion engine became more widespread. Types of stationary steam engine There are different patterns of stationary steam engines, distinguished by the layout of the cylinders and crankshaft: * Beam engines have a rocking beam providing the connection between the vertical cylinder and crankshaft. * Table engines have the crosshead above the v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Centrifugal Governor
A centrifugal governor is a specific type of governor with a feedback system that controls the speed of an engine by regulating the flow of fuel or working fluid, so as to maintain a near-constant speed. It uses the principle of proportional control. Centrifugal governors, also known as "centrifugal regulators" and "fly-ball governors", were invented by Christiaan Huygens and used to regulate the distance and pressure between millstones in windmills in the 17th century. In 1788, James Watt adapted one to control his steam engine where it regulates the admission of steam into the cylinder(s), a development that proved so important he is sometimes called the inventor. Centrifugal governors' widest use was on steam engines during the Steam Age in the 19th century. They are also found on stationary internal combustion engines and variously fueled turbines, and in some modern striking clocks. A simple governor does not maintain an exact speed but a speed range, since under increa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Expansion Valve (steam Engine)
An expansion valve is a device in steam engine valve gear that improves engine efficiency. It operates by closing off the supply of steam early, before the piston has travelled through its full stroke. This cut-off (steam engine), cut-off allows the steam to then expand within the cylinder. This simple expansion steam engine, expanding steam is still sufficient to drive the piston, even though its pressure decreases as it expands. As less steam is supplied in the shorter time for which the valve is open, use of the expansion valve reduces the steam consumed and thus the fuel required. The engine (on 1875 figures) may deliver two-thirds of the work, for only one-third of the steam. An expansion valve is a secondary valve within a steam engine. They represent an intermediate step between steam engines with non-expansive working and later valve gears that could provide for expansion by controlling the motion of a single valve. Expansion valves were used for stationary engines and mar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trip Valve
Trip valve mechanisms are a class of steam engine valve gear developed to improve efficiency. The trip mechanism allows the inlet valve to be closed rapidly, giving a short, sharp cut-off. The valve itself can be a drop valve or a Corliss valve. Trip valve gear was applied to larger stationary engines. It was not used in transport applications,An exception was the very early London Steam Carriage (1803) which had a form of trip gear. as it was not suitable for high speed. The trip point of the valve mechanism, and therefore the cut-off, would be adjusted either manually or automatically by the governor. The valve is opened by the mechanical valve gear mechanism, and when the trip gear trigger releases the mechanism the valve is snapped closed, usually by a spring acting against a dashpot A dashpot, also known as a damper, is a mechanical device that resists motion via viscous damping. The resulting force is proportional to the velocity, but acts in the opposite direction, sl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
