Double-acting cylinder

Double-acting cylinder

A double-acting cylinder in a reciprocating engine is a cylinder in which the working fluid acts alternately on both sides of the piston. This is in contrast to a single-acting cylinder, in which the working fluid acts in one direction only.

Double-acting cylinders are common in steam engines but unusual in internal combustion engines. In both types of engine, inlet and exhaust valves are required at each end. In an internal combustion engine, an ignition device and/or fuel injection device is also required at each end.

In order to connect the piston to an external mechanism, such as a crank shaft, a hole must be provided in one end fitted with a gland to prevent escape of the working fluid.

Double-acting cylinders are also found in hydraulic cylinders (in which the hydraulic fluid can actively force the piston in either direction) and also in pumps (where the pumped fluid enters and exits the cylinder on both sides of the piston).

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