Exhaust gas diffuser for a gas turbine and a method for operating a gas turbine that comprises such an exhaust gas diffuser

Abstract

The invention relates to an exhaust gas diffuser (20) for a gas turbine (1) having an annular outer wall (28) for guiding the diffuser flow (30) and in which an annular guiding element (32), arranged concentrically to said outer wall (28), is provided to influence the diffuser flow (30). In order to improve the aerodynamic effect of the exhaust gas diffuser (20) and to adapt this simultaneously and in an optimal manner for a plurality of operational gas turbine states, it is suggested that the guiding element (32) has a surface (34) which is radially directed inwards and which has a circumferential contour that is convex in the longitudinal section so as to form a displacement element, and that the guiding element (32) is axially displaceable between two positions such that said guiding element (32), when in a first position, allows a flow between the guiding element (32); and outer wall (28) and, when in a second position, largely prohibits a flow between the guiding element (32) and outer wall (28). In addition, the invention discloses a method for operating a gas turbine (1) in which, in order to reduce aerodynamic losses and to increase pressure recovery, the guiding element (32) is displaced in the direction of the second position or until in said second position as the mass flow increases and / or the guiding element (32) is displaced in the direction of the first position or until in said first position as the mass flow reduces.

Description

technical field [0001] The invention relates to an exhaust gas diffuser for a gas turbine having an annular outer wall for guiding a diffuse flow, in which an annular guide element arranged concentrically to the outer wall for influencing the diffuse flow is arranged. . Furthermore, the invention relates to a method for operating a gas turbine having an exhaust gas diffuser of the type described. Background technique [0002] Gas turbines and exhaust diffusers for such gas turbines are known from the prior art for a long time. Exhaust diffusers with relatively large opening angles of 10° and more are known, for example, from DE 198 05 115 A1. The exhaust gas diffuser achieves a large opening angle by providing, in the center of the diffuser channel, a guide extending in the axial direction for extending the otherwise short gas turbine hub. The exhaust diffuser is formed as a ring diffuser by using guide bodies. As a result, a larger area of ​​the recirculation zone behin...

AI Technical Summary

Problems solved by technology

This leads to backfiring even with the afterburner installed there, whereby the combined operation of the gas turbine and afterburner is strongly limited

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