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The use of the flow coefficient offers a standard method of comparing valve capacities and sizing valves for specific applications that is widely accepted by industry. The general definition of the flow coefficient can be expanded into equations modeling the flow of liquids, gases and steam using the discharge coefficient.
In the 20th century, slide valves were gradually superseded by piston valves, particularly in engines using superheated steam. There were two reasons for this: It is difficult to lubricate slide valves adequately in the presence of superheated steam; With piston valves, the steam passages can be made shorter.
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.
If the fluid is a liquid, a different type of limiting condition (also known as choked flow) occurs when the venturi effect acting on the liquid flow through the restriction causes a decrease of the liquid pressure beyond the restriction to below that of the liquid's vapor pressure at the prevailing liquid temperature.
The devices shown are on steam engines. Power is supplied to the governor from the engine's output shaft by a belt or chain connected to the lower belt wheel. The governor is connected to a throttle valve that regulates the flow of working fluid (steam) supplying the prime mover. As the speed of the prime mover increases, the central spindle of ...
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 marine engines. [1]
During the 1830s, the most popular valve drive for steam locomotives was known as gab motion in the United Kingdom and V-hook motion in the United States. [3] The gab motion incorporated two sets of eccentrics and rods for each cylinder; one eccentric was set to give forward and the other backwards motion to the engine and one or the other could accordingly engage with a pin driving the ...
Superheated steam was widely used in main line steam locomotives. Saturated steam has three main disadvantages in a steam engine: it contains small droplets of water which have to be periodically drained from the cylinders; being precisely at the boiling point of water for the boiler pressure in use, it inevitably condenses to some extent in the steam pipes and cylinders outside the boiler ...