Flexible turbine for power generation in straight pipe

A downhole power generation system, comprising:

• a downhole tubular having a generator recess, wherein the generator recess is radially offset from a central bore of the downhole tubular, and wherein the generator recess is connected to the central bore via an opening;
• a generator disposed within the generator recess, wherein the generator includes a rotor and a stator;
• a main shaft secured to the rotor;
• a secondary shaft coupled to the main shaft;
• a flexible coupler configured to couple the secondary shaft to the main shaft, and wherein the secondary shaft is configured to hinge with respect to the main shaft via the flexible coupler;
• at least one turbine blade secured to the secondary shaft and configured to rotate the secondary shaft to drive rotation of the main shaft and the rotor in response to fluid flow through the central bore with the at least one turbine blade in an extended position, wherein at least one turbine blade is disposed at least partially within the central bore in the extended position, and wherein the at least one turbine blade is configured to move at least partially into the generator recess toward a retracted position in response to contact with a downhole tool moving along the central bore;
• and
• a biasing spring having a first end secured to the secondary shaft and a second end secured to an interior surface of the generator recess, wherein the biasing spring is configured to bias the secondary shaft toward the central bore in the extended position and compress to permit the secondary shaft to move into the generator recess in the retracted position.

A downhole power generation system, comprising:

• a downhole tubular having a generator recess, wherein the generator recess is radially offset from a central bore of the downhole tubular, and wherein the generator recess is connected to the central bore via an opening;
• a generator disposed within the generator recess, wherein the generator includes a rotor and a stator;
• a main shaft secured to the rotor;
• a secondary shaft coupled to the main shaft;
• a flexible coupler configured to couple the secondary shaft to the main shaft, and wherein the secondary shaft is configured to hinge with respect to the main shaft via the flexible coupler;
• and
• at least on turbine blade secured to the secondary shaft and configured to rotate the secondary shaft to drive rotation of the main shaft and the rotor in response to fluid flow through the central bore with the at least one turbine blade in an extended position, wherein at least one turbine blade is disposed at least partially within the central bore in the extended position, and wherein the at least one turbine blade is configured to move at least partially into the generator recess toward a retracted position in response to contact with a downhole tool moving along the central bore, and
• wherein the at least one turbine blade and/or the secondary shaft comprise a flexible material, and wherein the at least one turbine blade and/or the secondary shaft is configured to bend in response to contact of the at least one turbine blade with the downhole tool to move the at least one turbine blade toward the retracted position.