Turbine exhaust system and method for modifying the same

A turbine exhaust system for introducing, to a condenser, exhaust steam after having driven a turbine rotor, the system comprising:

• an exhaust hood inner casing that involves the turbine rotor, and that has stationary blades installed on the inner peripheral part thereof, the stationary blades constituting each turbine stage together with corresponding moving blades installed on the turbine rotor;
• a bearing cone that is installed contiguously to the inner peripheral part of a final stage moving blade exit annular plane of the turbine rotor, and that covers a bearing of the turbine rotor in the inner space thereof;
• an exhaust hood outer casing that covers the exhaust hood inner casing and the bearing cone, and that forms an exhaust hood connecting with the condenser, together with the exhaust hood inner casing and the bearing cone;
• a flow guide that is installed contiguously to the outer peripheral part of the final stage moving blade exit annular plane so as to surround the outer peripheral side of the bearing cone, and that forms an annular diffuser flow path between the bearing cone and the flow guide, for discharging, toward the exhaust hood, exhaust steam that has driven a turbine rotor and then passed through the outer peripheral part of the final stage moving blade exit annular plane;
• and
• exhaust hood upper part flow guides each serving as means for separating annular plane upper part exhaust steam that flows within a range including vertical upward flow out of exhaust steam radially discharging from the flow guide into the exhaust hood, from other exhaust steam, to thereby introduce the separated exhaust steam to the condenser, wherein exhaust steam introduction-side end faces thereof each functioning as a separation boundary between the annular plane upper part exhaust steam and the other exhaust steam, are located further toward the upper side than the horizontal plane containing the central axis of the turbine rotor.

A method for modifying a turbine exhaust system that includes an exhaust hood inner casing that involves a turbine rotor;

• an exhaust hood outer casing that covers the exhaust hood inner casing and that constitutes an exhaust hood connecting with the condenser, together with the exhaust hood inner casing;
• and a flow guide that is installed contiguously to the outer peripheral part of the final stage moving blade exit annular plane of the turbine rotor, and that forms an annular diffuser flow path for discharging, toward the exhaust hood, exhaust steam that has driven the turbine rotor and then passed through the outer peripheral part of the final stage moving blade exit annular plane, the method comprising:
• retrofitting the turbine exhaust system with exhaust hood upper part flow guides each serving as means for separating annular plane upper part exhaust steam that flows within a range including vertical upward flow out of exhaust steam radially discharging from the flow guide into the exhaust hood, from other exhaust steam, to thereby introduce the separated exhaust steam to the condenser, wherein exhaust steam introduction-side end faces thereof each functioning as a separation boundary between the annular plane upper part exhaust steam and the other exhaust steam, are located further toward the upper side than the horizontal plane containing the central axis of the turbine rotor.

A method for modifying a turbine exhaust system that includes an exhaust hood inner casing that involves a turbine rotor, and that has stationary blades installed on the inner peripheral part thereof, the stationary blades constituting each turbine stage together with corresponding moving blades installed on the turbine rotor;

• a bearing cone that is installed contiguously to the inner peripheral part of a final stage moving blade exit annular plane of the turbine rotor, and that covers a bearing of the turbine rotor in the inner space thereof;
• an exhaust hood outer casing that covers the exhaust hood inner casing and the bearing cone, and that constitutes an exhaust hood connecting with the condenser, together with the exhaust hood inner casing and the bearing cone;
• and a flow guide that is installed contiguously to the outer peripheral part of the final stage moving blade exit annular plane so as to surround the outer peripheral side of the bearing cone, and that forms an annular diffuser flow path between the bearing cone and the flow guide, for discharging, toward the exhaust hood, exhaust steam that has driven a turbine rotor and then passed through the outer peripheral part of the final stage moving blade exit annular plane, the method comprising:
• retrofitting the turbine exhaust system with exhaust hood upper part flow guides each serving as means for separating annular plane upper part exhaust steam that flows within the range including vertical upward flow out of exhaust steam radially discharging from the flow guide into the exhaust hood, from other exhaust steam, to thereby introduce the separated exhaust steam to the condenser, wherein exhaust steam introduction-side end faces thereof each functioning as a separation boundary between the annular plane upper part exhaust steam and the other exhaust steam, are located further toward the upper side than the horizontal plane containing the central axis of the turbine rotor.