Abstract: Disclosed are apparatuses for controlling the flow of fluids which comprise a plurality of identical nozzle means arranged in an axially symmetrical configuration on a stator means and defining a plurality of identical flow channels or passageways. Each nozzle means comprises a fixed-spacer member and an adjustable-segment member. The fixed-spacer members are sealably fixed to the stator and mandate that the fluid flows through the flow channels. The adjustable-segment members are slideably connected to the fixed-spacer members in an essentially sealing relationship. Adjustable-segment members are operable to move only in straight-line direction and are not permitted to move pivotally. Jar-free movement of the adjustable members is possible regardless of flow or pressure of fluid. An essentially constant angle of discharge is possible for all adjustable positions of the nozzle means thereby enabling a high operating efficiency of the apparatus over a wide range of operating conditions.

Abstract: Disclosed are apparatus and methods for controlling parameters of fluid-driven systems. A control unit of the invention compares an input control signal to a tachometer signal from a fluid-driven turbine to produce a flow signal for controlling the turbine speed. The speeds of turbines in series are linked by the tachometer signal of the first turbine acting as the control signal for the following turbines. A critical speed interval is identified in relation to a range of values of the control signal. As the speed of a turbine is increased or decreased, its control unit holds the turbine speed at the limit of the critical speed interval, then rapidly accelerates the turbine through the interval to avoid prolonged operation at the turbine's critical speed. The individual critical speeds of separate turbines in series may be accommodated by critical speed intervals defined in separate control units for each of the turbines.