Method and apparatus for extending flow range of a downhole turbine

A turbine useful for power generation downhole, comprising:

• a stator having a fluid flow path sufficient to impart tangential and axial vector flow components on a fluid flowing past the stator;
• a rotor hydraulically communicating with the stator, impelled by the vectored fluid flow;
• a shaft coupled to the rotor;
• one or more restriction assemblies connected to the stator to selectively control a flow velocity of a fluid past the stator such that at high flow, the one or more restriction assemblies retract progressively to reduce the flow velocity and, thereby, relatively extend the effective flow rate of the turbine at higher flow rates, and at low flow, the one or more restriction assemblies extend to block off portions of the fluid flow path to thereby increase the flow velocity to relatively extend the effective flow rate of the turbine at lower flow rates;
• and,
• one or more braking vanes connected to the rotor, imparting an increasing drag force on the rotor as the rotor and braking vanes rotate to reduce a rate of increase in speed such that rotations per minute is lowered compared to not having the one or more braking vanes and, in turn, to relatively increase the flow range at higher flow rates.

A method of extending the flow range of a downhole turbine comprising a rotor impelled by a fluid flow, and a shaft coupled to the rotor, comprising:

• providing a stator, in hydraulic communication with the rotor, for imparting tangential and axial vector flow components on a fluid flowing past the stator;
• attaching one or more restriction assemblies on the rotor to selectively control a flow velocity of a fluid through the rotor;
• installing one or more braking vanes on the rotor to impart a drag force on the rotor as the rotor and braking vanes rotate, wherein the one or more braking vanes are sized and configured such that the drag force increases in proportion to a square of a rotation speed so that a higher drag force is induced at higher speeds as compared to lower speeds;
• and,
• increasing the fluid flow rate to activate the movement of the turbine while concurrently activating the restriction assemblies to moderate the flow velocity through the rotor, wherein the restriction assemblies increase the flow velocity at lower flow rates, wherein said downhole turbine is used for power generation downhole.

A method of extending the flow range of a downhole turbine comprising a rotor impelled by a fluid flow, and a shaft coupled to the rotor, comprising:

• attaching one or more restriction assemblies on the rotor to selectively control a flow velocity of a fluid through the rotor;
• installing one or more braking vanes on the rotor to impart a drag force on the rotor as the rotor and braking vanes rotate, wherein the drag force increases at higher flow rates;
• and,
• increasing the fluid flow rate to activate the movement of the turbine while concurrently activating the restriction assemblies to moderate the flow velocity through the rotor, wherein the restriction assemblies increase the flow velocity at lower flow rates.