A double-acting cylinder in a reciprocating engine

Reciprocating engine

A reciprocating engine, also often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert pressure into a rotating motion. This article describes the common features of all types...

 is a cylinder

Cylinder (engine)

A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or cast iron before receiving precision machine work...

 in which the working fluid

Working fluid

A working fluid is a pressurized gas or liquid that actuates a machine. Examples include steam in a steam engine, air in a hot air engine and hydraulic fluid in a hydraulic motor or hydraulic cylinder...

 acts alternately on both sides of the piston

Piston

A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...

. This is in contrast to a single-acting cylinder

Single-acting cylinder

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

, in which the working fluid acts in one direction only.

Double-acting cylinders are common in steam engine

Steam engine

A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

s but unusual in internal combustion engine

Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

s. 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

Fuel injection

Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive petrol engines, having almost completely replaced carburetors in the late 1980s....

 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

Gland (engineering)

A gland is a general type of stuffing box, used to seal a rotating or reciprocating shaft against a fluid. The most common example is in the head of a tap where the gland is usually packed with string which has been soaked in tallow or similar grease...

 to prevent escape of the working fluid.

Double-acting cylinders are also found in hydraulic cylinder

Hydraulic cylinder

A Hydraulic cylinder is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in engineering vehicles.- Operation :...

s (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).

External Links

• "Amazing Airplane Motor Doubles The Power", September 1932, Popular Mechanics cutaway drawing of double action aircraft engine