VOLVO B5254T Piston 3D print model

Piston from a 2.5l Volvo B5254T engine, this engine can be found on a number of popular models of the group, such as the S70 and V70.

A piston is a moving disk enclosed in a cylinder that is made gas-tight by piston rings. The disk moves inside the cylinder as a liquid or gas inside the cylinder expands and contracts. A piston aids in the transformation of heat energy into mechanical work and vice versa. Because of this, pistons are a key component of heat engines. Pistons work by transferring the force output of an expanding gas in the cylinder to a crankshaft, which provides rotational momentum to a flywheel. Such a system is known as a reciprocating engine.

A piston must follow a cyclical process in order for it to continuously convert heat energy to work, and there are many ways to complete this cycle. For example:

By inputting heat to the gas inside the cylinder, the gas will expand increasing the volume in the cylinder and provide useful work. By removing heat from the cylinder, the gas's pressure will decrease, allowing it to be compressed more easily. By inputting work to the piston, the piston will compress back to its initial state, ready to perform the cycle once again.