Flow passage sealing of turbine and streamline structure thereof

Abstract

The root region of a flowpath through a turbine includes a sealing configuration for minimizing leakage flow and secondary aerodynamic losses. Entrance and exit root radial seals are provided between upstream and downstream nozzles at locations radially inwardly of the root region of the flowpath to minimize radial leakage flow. To minimize intrusion flow into the flowpath from rotor pumping action and consequent aerodynamic losses, an exit flow guide on each bucket turns the exiting radial flow in a predominantly axial direction. Additionally, the upstream bucket root radius and nozzle root radius are faired or tapered to minimize the possibility of a protuberance projecting into the flowpath at steady state operation. An additional entrance root axial fin is provided on the buckets to reduce the flow coefficient and afford further reduction in leakage flow.

Description

technical field [0001] The present invention relates to a flow path structure for a turbomachine which facilitates streamlined flow characteristics and sealing along the flow path, and more particularly to a flow path structure for a steam turbine which is used to minimize the Leakage flow and secondary gas power loss. Background technique [0002] The flow path through the turbine along the root radius is defined locally by the inner bands or rings of the nozzle and the flow surface along the platform at the blade root of the rotor. Any fluid flow that exits this passage along the root boundary leaks past the vanes and directly reduces the power output of the turbine stage. Typical nozzle and blade designs for example for the low pressure section of a steam turbine include a nozzle root diameter equal to the blade root diameter, which results in a very likely upstream facing step under steady state flow conditions which disturbs the fluid flow in the flow channel. Streaml...

AI Technical Summary

Problems solved by technology

Typical nozzle and blade designs for example for the low pressure section of a steam turbine include a nozzle root diameter equal to the blade root diameter, which results in a very likely upstream facing step under steady state flow conditions which disturbs the fluid flow in the flow channel. streamlined features

A large wheel gap also increases the rotor suction effect of the leakage flow, thereby increasing the radial intrusion flow leading to further aerodynamic losses

In particular, the radial re-entrant flow caused by the rotor suction effect results in fluid flow separation along the flow channel, resulting in aerodynamic losses

Images