Rotary kinetic fluid motors or pumps – With passage in blade – vane – shaft or rotary distributor...
Reexamination Certificate
1999-10-18
2001-06-05
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
With passage in blade, vane, shaft or rotary distributor...
C415S200000, C416S09700R, C416S09700R, C416S22900R, C416S230000, C416S24100B
Reexamination Certificate
active
06241469
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a turbine blade with a metal blade body and a protective coating constructed of a porous intermetallic felt, and in the blade body of the turbine blade cooling air channels are constructed that end at the intermetallic felt in order to supply it with cooling air.
2. Brief Description of the Related Art
DE 42 41 420 C1 describes a compressor blade consisting of a titanium alloy that is provided with an abrasive blade armor. The blade armor consists of a nickel matrix with enclosed boron nitride particles. This blade armor is provided preferably at the blade tip.
DE 32 03 869 A1 describes a turbine blade consisting of a basic body (core) of the metal turbine blade and a ceramic hollow body (blade shell). The blade shell is attached with metal retention pins to the turbine blade core. Insulation bodies inserted between the ceramic and metal contact surfaces are intended to reduce the heat flow from the blade shell to the turbine blade core.
DE 29 50 150 A1 introduces a sealing arrangement designed to seal a passage between a rotating and a non-rotating part. The sealing arrangement is provided with a surface seal and an edge part that is located opposite from the surface seal and is attached to the other part. The edge part has teeth that protrude into the surface seal that cut grooves into the surface seal when rotated, so that the seal arrangement forms a labyrinth seal.
The surface seal of this known seal arrangement is composed of metal fibers that form a mat-like or felt-like construction. This material is produced by sintering a matrix of randomly oriented metal fibers at a high temperature and reduced pressure, whereby a completely felted structure of metal fibers is formed which has metal bonds at all contact points of the fibers. The sintered material is characterized by an apparent density that is substantially lower than the density of the fibers themselves. The low density of the sintered fiber material is approximately in the range from 14 to 30%, and in this way these materials differ from sintered, pulverized materials with a density of more than 30%. This type of surface seal was used successfully because it has both the required strength, rigidity, and compactness and is also elastic, and can be comminuted and abraded.
GB 2 053 367 A describes a cooled gas turbine with a shield located opposite from the rotating blades. The shield is formed by a tubular ring with a rectangular cross-section which is able to hold cooling air in its interior. Holes have been provided in the ring wall opposite from the blades, and this wall is provided on the outside with a porous layer through which the cooling air is able to penetrate. The porous layer consists of a material sintered from small spheres. The spheres are constructed of a nickel-based super-alloy.
DE 2 038 047 describes a construction feature on guide vanes that is located inside the flow space of a steam turbine, in particular of saturated and wet steam turbines, and is used to drain water from the surfaces of the individual guide vanes. To reduce or completely prevent the erosion caused by water drop condensation on the surfaces of the turbine blades of wet steam turbines, the guide vane has drainage channels that are filled with porous, liquid-permeable material made from metallic materials or their alloys. The use of porous, liquid-permeable material has as its goal the specific drainage of water from the interior of a steam turbine.
DE 33 27 218 A1 describes a thermally highly stressed, cooled component, in particular a turbine blade, that is coated for reasons of reducing the heat stress with a metal felt layer that again is covered with an additional, ceramic heat insulation layer. In principle, the metal felt layer functions as an elastic carrier material for the ceramic heat insulation layer (see page 4, line 33 to page 5, 2; page 6, 1st paragraph and page 7, lines 2 to 7), but the metal felt layer also has a heat-dissipative action, especially since cooling air is supplied via cooling air grooves
3
(see
FIG. 1
) to the underside of the metal felt layer in order to cool it locally and in this way achieve an optimum heat dissipation of the heat flowing through the heat insulation layer
6
.
With respect to the arrangement of the above quoted publication it can be said that metal felt is applied to the surface of turbine blades for thermal protection, but this protective effect is insufficient to protect the material from which the turbine blades are made from overheating, when the turbine blades encounter high thermal stresses.
SUMMARY OF THE INVENTION
The invention is based on the objective of further developing a turbine blade with a metal blade body and a protective coating constructed from a porous intermetallic felt and in the blade body of the turbine blade cooling air channels are constructed that end at the intermetallic felt in order to supply it with cooling air in such a way that the turbine blade can be cooled better than this is possible with the state of the art. In addition, the degree of effectiveness of the turbine is increased.
The objective is realized by a turbine blade with a protective coating constructed from a porous intermetallic felt and in the blade body of the turbine blade air cooling channels are constructed that end at the intermetallic felt in order to supply it with cooling air.
The turbine blade according to the invention is characterized in that the intermetallic felt is based on an iron or nickel aluminide alloy with mixing ratios of Fe:Al and Ni:Al of approximately 50:50, whereby the ratio here is an atomic ratio. Such a mixing ratio, which is intended to include mixing ratios between 40:60 to 60:40, produces metallic felts with a very slight oxidizability, which, on the one hand, crucially increases the life span of such metallic felts and, on the other hand, preserves their felt structure for a longer time.
In addition to the iron or nickel alloy, additional substances or elements can be added to the respective alloy, for example, Ta, Nb, Cr, B, Si, Zr or Ga. The essential factor in adding additional elements is that the atomic mixing ratio of Fe to Al or Ni and Al remains in the magnitude of 50:50.
In normal felts, oxidative processes, for example, damage the felt structure during its use to such a point that its capacity with respect to cooling air permeability, for example, is crucially reduced. This results in an overheating of the turbine blade.
According to the invention, the protective coating is furthermore provided with cooling channels that are facing the blade body and end in the area of the cooling channels. In this way, it can be ensured that more cooling air additionally flows through the intermetallic felt. This, then, is able to prevent the risk of turbine blade overheating.
In principle, the fact that a porous intermetallic felt is provided on the surface of the blade body does not immediately have as a result that the cooling air introduced into the latter contacts the hot gases of the turbine, but it passes through the intermetallic felt in a gradual manner and is distributed over a larger area. The intermetallic felt, which may have higher surface temperatures than standard materials for turbine blades, is, hereby, cooled in the most intensive manner, whereby the turbine blade, hereby, can be maintained at operating temperature with an extremely small amount of cooling air in comparison to a turbine blade where the cooling air channels exit immediately at the surface. Since the cooling air amount is much smaller because of the better heat transfer, the degree of effectiveness of the turbine is correspondingly increased, since less cooling air is required in the energy supply of the combustor.
The gradual flow of the cooling air through the intermetallic felt has the result that the exit speed of the cooling air at the surface of the turbine blade is very low and does not negatively influence the aerodynamics as was the case previously. This is in particular true if the
Beeck Alexander
Nazmy Mohamed
Asea Brown Boveri AG
Burns Doane Swecker & Mathis L.L.P.
Look Edward K.
Nguyen Ninh
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