Exhaust gas diffuser of a gas turbine

Abstract

An exhaust gas diffuser for a gas turbine includes a flow duct which widens towards a diffuser outlet. The flow duct includes an axially extending guide body, wherein the guide body, at least in an axial section of its longitudinal extent, has a plurality of recesses which are distributed over the circumference and arranged between guide elements. Each guide element extends along a spiral line along the longitudinal extent of the guide body. Further, a gas turbine plant with such an exhaust gas diffuser is provided.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is the US National Stage of International Application No. PCT / EP2011 / 056210 filed Apr. 19, 2011, and claims the benefit thereof. The International Application claims the benefits of European Patent Application No. 10004244.9 EP filed Apr. 21, 2010. All of the applications are incorporated by reference herein in their entirety.FIELD OF INVENTION[0002]The invention relates to an exhaust gas diffuser for a gas turbine, having a flow duct which widens towards the diffuser outlet and in the center of which provision is made for an axially extending guide body.BACKGROUND OF INVENTION[0003]Such an exhaust gas diffuser serves for decelerating the exhaust gas flow of a gas turbine and for recuperating at least some of the dynamic pressure. In order to disclose an exhaust gas diffuser with a comparatively large opening angle of 10° and more, it is known from DE 198 05 115 A1, for example, to provide an axially extending guide body ...

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Benefits of technology

[0008]As a result of the pitched orientation of the guide elements (pitch) in relation to the center axis, both an exceptionally efficient and space-saving construction for de-swirling of the flow is disclosed. The pitch of the spiral line is comparatively large in this case so that the spiral lines are only slightly inclined in relation to the center axis of the exhaust gas diffuser. The pitch can also become smaller along its extent. Preferably, it increases, however, in order to obtain an outflow from the exhaust gas diffuser which has as little swirl as possible. This arrangement is particularly advantageous in the case of an axial exhaust gas diffuser in which the number of guide elements is the same as a number of support struts which are provided in the exhaust gas diffuser or directly upstream thereof for the turbine-side support of the gas turbine rotor.

[0009]In an advantageous embodiment, the guide body has a cross-sectional contour which is arranged perpendicularly to the center axis of the exhaust gas diffuser and which is in the shape of a star, the points of which are formed by the respective guide elements. By means of the star-shaped cross-sectional contour, significantly greater rigidity of the inner wall of the exhaust gas diffuser, now formed as an annular diffuser, can be achieved. The tendency of the guide body towards vibrating on account of the flow is significantly reduced as a result. Consequently, it is also possible to design the guide body in a way in which it is fastened on only one side so that its end facing the diffuser outlet overhangs in the exhaust gas diffuser in a freely suspended manner. An aerodynamically disturbing and cost-increasing outlet-side support of the guide body can consequently be avoided on account of the greater rigidity of the guide body.

[0010]In an expedient development, each guide element has an outer tip which projects radially outward from the center axis of the exhaust gas diffuser, the shortest distance of which to the center axis (that is to say in the cross section arranged perpendicularly to the center axis) reduces with decreasing axial distance to the diffuser outlet. In this case, each recess has a radially inward disposed base, the shortest distance of which to the center axis (that is to say in the cross section arranged perpendicularly to the center axis) also reduces with decreasing axial distance to the diffuser outlet. As a result of this, a widening of the flow cross section of the exhaust gas dif

Problems solved by technology

It is disadvantageous, however, that the guide body is comparatively long and therefore has to be supported by additional

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