Axial turbine

Abstract

An axial turbine has a turbine stage including stator blades fixedly provided on a stationary section and moving blades fixedly provided on a rotating section and has a structure in which a flow blowing out from a space formed between the stator blades and the moving blades exists. In order to prevent a decrease in stage output power due to such blowout flow thereby to improve the turbine stage efficiency, the axial turbine comprises a member coupling an inner circumferential side of the stator blades, and a structure provided on a surface of the member opposed to the moving blades for bending a flow blowing out from the side of the rotating section into a space between the stator blades and the moving blades in a rotational direction of the rotating section.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to axial turbines and more particularly to a drum-type rotor turbine.[0003]2. Description of the Related Art[0004]The axial turbine such as a steam turbine or gas turbine comprise a turbine stage including stator blades formed to transform the pressure of a fluid into kinetic energy and moving blades for transforming the pressure or kinetic energy of the fluid into the rotational energy of a rotating section. The stator blades are fixedly provided between an outer circumferential diaphragm and inner circumferential diaphragm forming a stationary section. The moving blades are provided on a rotor that forms the rotating section. A clearance is provided between the inner circumferential diaphragm and the rotor, and the clearance has a seal. This seal reduces a leakage flow that passes through the clearance. This leakage flow passing through the clearance, however, cannot be completely zeroed ...

AI Technical Summary

Benefits of technology

[0007]The method of providing a plurality of balance holes in a circumferential direction cannot be used for an axial turbine not having such a space as a drum-type rotor in which to provide the balance holes. In addition, a stage with significant differences in pressure between the front and rear of the moving blades increases the flow rate of the steam flowing through the balance holes, and takes in this flow between the stator blades and the moving blades. Accordingly, the amount of steam flowing into the moving blades will be reduced and this, in turn, could reduce stage output power.

[0008]In case where the balance holes are not present, the leakage flow that has passed through the clearance will blow out from a space formed between the stator blades and the moving blades. However, this blowout flow will, as detailed later herein, interfere with the flow that has run in from an upstream direction as the main flow of steam between stators, and the interference will disturb the main flow of steam, thus reducing the output power of the stage.

[0009]An object of the present invention is to provide an axial turbine having a structure in which a flow blowing out from a space formed between stator blades and moving blades exists and in which a decrease in stage output power due to such blowout flow is prevented to occur thereby to enable the turbine stage efficiency to be improved.

[0013]According to the present invention, since the flow blowing out from the space between the stator blades and the moving blades is bent in the rotational direction of the rotor, it is possible to suppress interference of the blowout flow with a main flow of steam that has run in from an upstream direction between stator blades, and consequently to prevent a decrease in stage output power to occur, thereby improving turbine stage efficiency.

Problems solved by technology

The method of providing a plurality of balance holes in a circumferential direction cannot be used for an axial turbine not having such a space as a drum-type rotor in which to provide the balance holes.

However, this blowout flow will, as detailed later herein, interfere with the flow that has run in from an upstream direction as the main flow of steam between stators, and the interference will disturb the main flow of steam, thus reducing the output power of the stage.

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