A Fluidyne engine is an alpha or gamma type

Stirling engine A Stirling engine is a heat engine that is operated by the cyclic expansion and contraction of air or other gas (the ''working fluid'') by exposing it to different temperatures, resulting in a net conversion of heat energy to mechanical Work (ph ...

with one or more liquid pistons. It contains a working

gas Gas is a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such as ...

(often

air An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

), and either two liquid pistons or one liquid piston and a displacer. The engine was invented in 1969. The engine was patented in 1973 by the

United Kingdom Atomic Energy Authority The United Kingdom Atomic Energy Authority is a UK government research organisation responsible for the development of fusion energy. It is an executive non-departmental public body of the Department for Energy Security and Net Zero (DESNZ). T ...

.GB1329567 (A) - STIRLING CYCLE HEAT ENGINES
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Engine operation

Working gas in the engine is heated, and this causes it to expand and push on the water column. This expansion cools the air which contracts, at the same time being pushed back by the weight of the displaced water column. The cycle then repeats. The U-tube version has no moving parts in the engine other than the water and air, although there are two check valves in the pump. This engine operates at a natural resonance cycle that is "tuned" by adjusting the geometry, generally with a "tuning tube" of water.

Engine as a pump

In the classic configuration, the work produced via the water pistons is integrated with a water pump. The simple pump is external to the engine, and consists of two

check valve A check valve, non-return valve, reflux valve, retention valve, foot valve, or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction. Check valves are two-port valves, meaning they have ...

s, one on the intake and one on the outlet. In the engine, the loop of oscillating liquid can be thought of as acting as a displacer piston. The liquid in the single tube extending to the pump acts as the power piston. Traditionally the pump is open to the atmosphere, and the hydraulic head is small, so that the absolute engine pressure is close to

atmospheric pressure Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1,013. ...

.
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Demonstration video

The videos show operation of a U-tube type model Fluidyne engine. Hot pipe is heated by a heat gun, and water column oscillation builds up to a

steady-state In systems theory, a system or a process is in a steady state if the variables (called state variables) which define the behavior of the system or the process are unchanging in time. In continuous time, this means that for those properties ''p'' ...

level. Second video shows a detail of the actual water displacement.

References

External links

Fluidyne Engines
(link broken - 2023-June-04)
Thermofluidics Engine

Article by Alejandro Romanelli
{{DEFAULTSORT:Fluidyne Engine Stirling engines Piston engines Pistons Articles containing video clips

Engine operation

Engine as a pump

Demonstration video

See also

References

Further reading

External links