A reciprocating engine is an internal combustion machine fitted with cylinders in which the piston moves back and forth and transmits this mechanical power to a crankshaft. The crankshaft in turn transmits this power to the drive shaft, and this to the differential gear. Thus, this type of machine makes it possible the conversion of the chemical energy contained in the mixture fuel/hot air into mechanical rotatory energy that drives the vehicle or turns an AC generator.
According to the way the engine is started, there are two types of reciprocating engine; spark-ignition and compression-ignition engine, with the former being powered by gasoline and the latter by diesel. According to the types of operating cycle, there are the Otto cycle (four-stroke) and the two-stroke cycle engine. According to the layout, there are the V-shaped, in-line (in a row), radial engine, and opposed cylinder (with two cylinders opposing each other sharing the same crankshaft). In all of them, the piston is connected to the crankshaft by a crank gear, making it possible that the reciprocating movement of the piston is converted into the rotary motion of shaft.
All the reciprocating engine parts are set up in block, which is usually made of cast iron or aluminum alloy. It is characterized by cyclic reoccurrence and intermittence of operation. Because of this cyclic reoccurence of operation and the presence of a crank gear, it does not operates at speeds as high as those obtained by turbines in jet engines, which are rotodynamic machines.
Below, a typical reciprocating engine; a V-6 spark-ignition machine of a gasoline car.
