In old days reciprocating steam engines are used to convert heat energy into mechanical energy. Now a day’s steam turbine or internal combustion engines are used for the same work. But steam engine has many specialized applications. These steam engines can be classified according to its construction and operating features. Detail classification is covered as below.
A) Position of Cylinder: - According to the position of the cylinders steam engines can be classified as,
01) Vertical Engine
02) Horizontal Engine
03) Inclined Engine
B) Working Stroke: - Steam Engine is classified according to number of working strokes per revolution as,
01) Single Acting
02) Double Acting
In single acting engine there is only one stroke per revolution of the crankshaft as steam acts on one side of the piston. But in double acting engine two working stroke per revolution are obtained as steam acts on both sides of the piston.
C) Speed of Engine: - According to the running speed of the engine it can be classified as,
01) Low Speed Engine, Where engine runs at 100 or less revolution per minute.
02) Medium Speed Engine, Where engine runs at 110 to 200 revolutions per minute.
03) High Speed Engine, Where engine runs above 200 or more revolution per minute.
D) Field of Application: - Steam engines are classified according to its applications as,
01) Locomotive or Portable Engines
02) Stationary Engines
03) Marine Engines
E) Exhaust of Steam: - Steam engines are classified by exhaust of steam as,
01) Condensing Engines, Where exhaust steam passes into a condenser at lower pressure than atmosphere.
02) Non Condensing Engines, where exhaust steam passes directly to the atmosphere.
F) Governing Methods: - A classification is frequently made according to the governing method employed as,
01) Throttle Governing, in this method the speed of engine is controlled by means of valve in the steam pipe which regulates the pressure of the steam entering the engine.
02) Automatic Cut-Off Governing, in this method governor controls the quantity of steam admitted to the cylinder while the pressure of entering steam is remain constant.
G) Expansion of Steam: - Steam engines are classified according to expansion of steam in number of stages as,
01) Simple Steam Engine, where conversion of heat energy of steam into mechanical work in one stage only with one cylinder and piston.
02) Compound Steam Engine, where the conversion of heat energy of steam into mechanical work occurs in two stages with high pressure and low pressure cylinder.
03) Triple Expansion Steam Engine, where the steam expands successively in three cylinders.
04) Quadruple Expansion Steam Engine, where four cylinders and pistons are used for expansion of steam.
Besides above classification, steam engine can also be classified according its length of working stroke i.e. short stroke or long stroke engines and position of crank i.e. side crank or centre crank engines.
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