Rotary kinetic fluid motors or pumps – Working fluid passage or distributing means associated with... – Plural distributing means immediately upstream of runner
Reexamination Certificate
2001-09-24
2003-10-14
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Working fluid passage or distributing means associated with...
Plural distributing means immediately upstream of runner
C415S209200, C415S210100
Reexamination Certificate
active
06632070
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a guide blade for a turbomachine, preferably for a turbine and even more preferably a gas turbine, for use, for example, in a power station for generating electricity. The invention also preferably relates to a guide blade ring made up of such guide blades. The invention relates, even more preferably, to a component for bounding a flow duct in a turbomachine.
BACKGROUND OF THE INVENTION
Such a gas turbine has a shaft or a rotor to which so-called rotor blades are permanently connected. The rotor blades extend in the radial direction into a flow duct of the turbine. A plurality of rotor blades form a rotor blade ring in the peripheral direction of the rotor. A plurality of rotor blade rings are arranged at a distance from one another in the longitudinal direction of the rotor. So-called guide vanes, which extend in the radial direction from, the outside into the flow duct, are arranged on the turbine casing. The guide vanes are likewise arranged in guide vane rings, the individual guide vane rings meshing with the rotor blade rings in the manner of teeth. In contrast to the rotor blades, the guide vanes are solidly and immovably fastened on the casing.
The flow duct enclosed between the rotor blades and the guide vanes is bounded by the guide vanes and rotor blades and is sealed toward the outside. For this purpose, both the rotor blades and the guide vanes have, as a rule, a so-called platform in the region of their blade/vane root, with which they are fastened to the rotor or to the casing. This platform extends essentially at right angles to their blade/vane aerofoil, which protrudes radially into the flow duct.
Very high temperatures occur, particularly in the case of gas turbines in the field of electricity generation. Efforts are made to achieve continually higher gas temperatures in the course of efficiency increases. This increases the demands made on the materials used and on the cooling, which is generally necessary, of the individual components of the gas turbine.
An impingement cooling system for a gas turbine blade/vane is revealed in DE 26 28 807 A1. The gas turbine blade/vane is aligned along a blade/vane axis and has a blade/vane aerofoil and a platform region along the blade/vane axis. In the platform region, the platform extends transverse to the blade/vane axis away from the blade/vane aerofoil outward approximately at right angles. In this way, the platform forms a part of the flow duct for a working fluid (hot gas), which flows through the gas turbine. Due to the very high temperatures in the flow duct, the surface of the platform exposed to the hot gas is subjected to severe thermal effects. In order to cool the platform, a perforated wall element is arranged in front of the surface of the platform facing away from the hot gas. Cooling air enters via the holes in the wall element and meets the surface of the platform facing away from the hot gas. This achieves efficient impingement cooling.
WO 97/12125 A1 shows a sealing element for sealing a gap between components of a gas turbine installation. Two blades/vanes directly adjacent to one another in a blade/vane ring have mutually opposite grooves on opposing edges of their platforms. A sealing element is inserted into these grooves. A gap between the platforms is sealed by this sealing element. At the same time, however, the platforms are not rigidly connected to one another so that sufficient clearance remains for thermal expansions in particular. The sealing element has a profiled surface area and this provides an improved sealing effect.
In addition to being subjected to thermal effects, the rotor blades must withstand high centrifugal forces during operation because of the rotational speed of the rotor. This applies particularly to turbines which are employed as propulsion engines or propulsion turbines, for example in the aeronautical field. Particularly high rotational speeds are provided for such propulsion turbines. Because of the high centrifugal forces associated with the high rotational speeds, efforts are made to achieve the lowest possible mass of the rotor blades, particularly in the case of these propulsion turbines. For this purpose, U.S. Pat. No. 3,294,364 proposes separating the platform from the individual guide blades, i.e. to dispense with an integral unit, consisting of rotor blades and platform, and its advantages. For the multi-part configuration demands, as compared with the integral unit, increased complexity and therefore increased time and cost requirements during the assembly of the rotor blades in the turbine. The separation between the platform and the actual rotor blade is, for example, known from U.S. Pat. No. 5,244,345.
SUMMARY OF THE INVENTION
An object of the invention is to provide a guide blade for a turbomachine which can be manufactured simply and at favorable cost. A further object of the invention is to provide a guide blade ring made up of such guide blades and to provide a component for bounding a flow duct in a turbomachine.
According to the invention, the object directed towards the guide blade is achieved by means of a guide blade for a turbomachine, which guide blade is aligned along a blade/vane axis and has a blade/vane aerofoil arrangement, a fastening region and a platform region arranged between the blade/vane aerofoil region and the fastening region. The platform region is preferably designed to receive a separating region which can be separated non-destructively from the guide blade. The separating region is preferably part of a platform, which is associated with the platform region, for bounding a flow duct in the turbomachine.
The guide blade is therefore no longer configured integrally, as was previously usual in the case of guide blades, but has a platform region which can be separated—the separating region. This multi-part design therefore initiates a new way of constructing guide blades. In contrast to the rotor blades for aircraft turbines, for which such a multi-part construction is known, the construction does not appear to be appropriate for guide blades of a gas turbine in the field of electricity generation. On the one hand, there are of course no centrifugal forces in the case of the guide blades and, on the other, the assembly complexity and therefore the expenditure of time and cost are disadvantageously influenced by the multi-part construction.
In a surprising manner, however, the multi-part design leads to a marked simplification of the manufacturing process for the guide blade per se. Particularly in the case of one-piece cast guide blades, this is due to the casting process being very much simpler because at least part of the platform, which usually protrudes at right angles to the blade/vane axis, does not have to be cast at the same time. This results in a casting mold which is very much simpler to handle and manufacture. This simplification of the casting process is important, particularly in the case of single-crystal or directionally solidified guide blades. Such guide blades have very good material properties. Because attempts are made to achieve continually higher operating temperatures for gas turbines in the field of electricity generation, it is usually only possible to employ such high-quality guide blades.
A further essential advantage of the multi-part configuration for the manufacturing process may be seen in the fact that the individual parts have clearly simplified geometry as compared with the integral configuration. This permits the application of a high-quality coating which protects the turbine guide blades from damage, in particular from thermal damage due to the desired high temperatures. In the case of the integral configuration, a high-quality and enduring coating is only possible with great difficulty in the transition region between the blade/vane aerofoil and the platform extending essentially at right angles to it because, in this transition region, it is almost impossible to achieve a uniform coating, such as is possible in the case of a simple geometry, in
Harness & Dickey & Pierce P.L.C.
Look Edward K.
McCoy Kimya N
Siemens Aktiengesellschaft
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