Throttling means for geothermal streams

Claim 1

A helical screw expander for deriving energy from geothermally heated water, comprising: a block enclosing an expander chamber; a chamber wall having an axis and including an axially-extending portion and a pair of planar end faces, said portion and said end faces defining said expander chamber; a pair of mating helical rotors extending axially and side-by-side in said expander chamber, each helical rotor including a helical structure which moves in adjacency to the axially-extending portion, and further including a pair of end faces, each of which moves in adjacency to a respective end face of the chamber wall; an exhaust port opening into one end face of the expander chamber; an exhaust passage extending through the block and opening into the exhaust port; a throttle port in the other end face of the expander chamber; a supply passage extending through the block and opening into the throttle port; an adjustably movable throttle block forming together with the wall of the supply passage an adjustable nozzle which terminates at the respective end face of the expander chamber and is so proportioned and and arranged as to direct a stream of liquid from the supply passage to impinge onto a helical structure whereby to impart kinetic energy to said helical structure and assist in rotating it, the cross-section of the throttle, at the throttle port, being the least cross-section of the supply passage; and means to move the throttle block and thereby adjust the size of the nozzle.