2 - Background

2.1 - Basics

Two main types of machines are used to move fluids or create rotary movement:

- piston machines,

- machines that we generally call "turbines".

Piston machines work based on the principle of the volume contained inside a cylinder changing when a piston travels from one end to the other and back again. This movement compresses or expands a fluid, generally a gas.

Piston engines are equipped with mechanisms that transform a straight-line motion into a rotary motion and vice versa.
These generally complex mechanisms usually consist of connecting rod assemblies, but there are other systems such as camshafts, swash plates, and so on.
The pistons in these machines create friction as they rub against the cylinder wall.

In order to withstand the pressure that develops in these cylinders, they are equipped with compression rings.

In most cases, including in compressors and internal combustion engines, the piston-compression ring-cylinder assembly has to be cooled in order to preserve the quality of the lubrication oil and keep the friction created between the various components to a minimum.

Turbines consist of a rotor equipped with blades turning in a stator. Therefore, there is no need for a mechanical system that converts a straight-line movement into a rotary movement.

Turbines cannot operate at high pressures because they do not have a system capable of varying the volumes between the blades. That is to say, the turbine is not what we call "volumetric".

But they do have one major advantage: the blades do not rub against the stator to create friction.

The "Technology" section below explains how the advantages of the piston machines can be brought to the turbine, i.e. by creating a machine:

- without a straight-line to rotational conversion system, like a turbine,

- whose components do not cause friction, like a turbine,

- which can be used to generate volume and pressure variations, like a piston machine,

- in which the seal is created by controlled pressure losses.

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