machine de Robertson

CONT: The Robertson engine. This device was not specifically designed with geothermal application in view: it was intended to operate on a variety of working fluids, but the inventor considers that it should also be suitable for extracting energy from geothermal fluids - water and/or steam .... It has a tapered rotor revolving within a tapered stator. The rotor has a ""single-start"" helix, while the stator has a ""double start"" helix of exactly twice the rotor pitch. The rotor is mounted on a crank, and its rotation on the crank-pin is governed by gears so that each cross-section of the rotor oscillates within the stator as it revolves. This arrangement gives rise to a series of trapped volumes which expand progressively from one end of the machine to the other as the rotor rotates.