Fluid reaction surfaces (i.e. – impellers) – With heating – cooling or thermal insulation means – Changing state mass within or fluid flow through working...
Patent
1994-07-19
1995-10-24
Look, Edward K.
Fluid reaction surfaces (i.e., impellers)
With heating, cooling or thermal insulation means
Changing state mass within or fluid flow through working...
416191, 415115, F01D 522, F01D 518
Patent
active
054604869
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a turbine blade of a gas turbine comprising at least one cooling air duct extending in the blade as well as a shroud band segment which is arranged on the blade tip and which, together with additional segments of adjacent blades, forms a blade reinforcing band, a cooling air branch duct is provided which extends in the shroud band segment essentially perpendicularly to the blade axis, is connected with the blade cooling air duct situated in the leading area of the blade and from which cooling air bores lead to the surface of the shroud band segment.
Such a cooled gas turbine blade is shown in German Patent Document 39 30 324 A1. By means of this type of a cooling of not only the blade but also of the shroud band segment, it can be achieved and the thermal stress and the geometrical deformations can be kept low to which the blade and the segment are subjected as a result of thermal influences. Although the thermal stress to a turbine blade is already considerably reduced by means of the known cooling air guiding, additional improved cooling measures are desirable which are the object of the present invention.
SUMMARY OF THE INVENTION
For achieving this and other objects, the present invention provides that at least one additional cooling branch duct extends in the shroud band segment and is connected with another blade cooling duct situated in the trailing area of the blade or in the blade center and from which cooling air bores also lead to the surface of the shroud band segment.
Since, as known, a shroud band segment extends along the whole blade cross-section and may therefore have a relatively large surface, an effective cooling by means of only a single cooling air branch duct as well as the cooling air bores branching away from it cannot be sufficient. According to the invention, at least two cooling air branch ducts are therefore provided which preferably extend essentially in parallel and which are each supplied directly by a separate blade cooling air duct and which cause, in each case, particularly via branching film cooling holes or convection cooling bores, an effective cooling of essentially the whole shroud band segment. While, in this case, on the leading side of the blade or in the blade center area, a sufficiently large amount of cooling air is still available in a blade cooling duct for supplying a connected cooling air branch duct, on the trailing side of the blade in the blade cooling air duct, this amount of cooling air is already reduced to such an extent that a cooling air branch duct which would be supplied by a blade cooling air duct on the trailing side of the blade would receive hardly any cooling air. It is therefore provided in certain embodiments in the shroud band segment close to the trailing area of the blade, in addition, a so-called parallel duct which is supplied with cooling air by an adjacent cooling air branch duct and, for this purpose, is connected with the latter preferably via several cooling air bores. These bores may be the same as those which lead out as film cooling holes on the surface of the shroud band segment. Several cooling air branch ducts as well as the cooling air bores which branch away from them therefore run in a virtually net-type manner through the interior of the shroud band segment and are therefore capable of covering the largest area of the shroud band segment for the purpose of cooling.
The cooling air branch duct as well as the cooling air bores, which clearly have a smaller diameter than the cooling air branch duct, may be placed in the shroud band segment by means of drilling. While, however, the cooling air bores should lead out on the surfaces of the shroud band segment and in this case form film cooling holes or convection cooling bores, the cooling air branch ducts should not lead out on the surface of the shroud band segment because an excessive partial cooling air flow would uselessly escape via the respective cooling air branch duct which has a relatively large cross-section.
REFERENCES:
patent: 3529902 (1970-09-01), Emmerson
patent: 3628880 (1971-12-01), Smuland
patent: 4017213 (1977-04-01), Przirembel
patent: 4127358 (1978-11-01), Parkes
patent: 4353679 (1982-10-01), Hauser
patent: 4946346 (1990-08-01), Ito
patent: 5344283 (1994-09-01), Magowan et al.
Evans Neil M.
Hayton Paul
Hill Stephen H.
BMW Rolls-Royce GmbH
Lee Michael S.
Look Edward K.
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