Free-piston engine

A free-piston engine is a linear, 'crankless' <a href="/facts/Internal_combustion_engine/Ju4BXzj0">internal combustion engine</a>, in which the piston motion is not controlled by a <a href="/facts/Crankshaft/oYCe9nB3">crankshaft</a> but determined by the interaction of forces from the <a href="/facts/Combustion_chamber/FNqjDrN8">combustion chamber</a> gases, a rebound device (e.g., a piston in a closed cylinder) and a load device (e.g. a <a href="/facts/Gas_compressor/I0vV0Tx2">gas compressor</a> or a <a href="/facts/Linear_alternator/kJW7MfSY">linear alternator</a>).
The purpose of all such piston engines is to generate power. In the free-piston engine, this power is not delivered to a crankshaft but is instead extracted through either <a href="/facts/Exhaust_gas/kLpq1eUX">exhaust gas</a> pressure driving a turbine, through driving a linear load such as an air compressor for <a href="/facts/Pneumatic/QzkvCCpk">pneumatic</a> power, or by incorporating a linear <a href="/facts/Alternator/r9KEPP9d">alternator</a> directly into the pistons to produce electrical power.
The basic configuration of free-piston engines is commonly known as single piston, dual piston or <a href="/facts/Opposed_piston/eEmgTJBn">opposed pistons</a>, referring to the number of combustion cylinders. The free-piston engine is usually restricted to the <a href="/facts/Two-stroke/Al4uUeo9">two-stroke</a> operating principle, since a power stroke is required every fore-and-aft cycle. However, a <a href="/facts/Split_cycle/P45RcPUx">split cycle</a> <a href="/facts/Four-stroke/70vDIDvJ">four-stroke</a> version has been patented, GB2480461 (A) published 2011-11-23.

Free-piston engine open-in-new

Free-piston engine