Rotary kinetic fluid motors or pumps – Bearing – seal – or liner between runner portion and static part – Between blade edge and static part
Reexamination Certificate
2001-09-24
2003-08-05
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Bearing, seal, or liner between runner portion and static part
Between blade edge and static part
Reexamination Certificate
active
06602050
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a covering element for the protection of components in a machine subjected to high thermal load, in particular of components in a gas turbine. The invention relates, furthermore, to an arrangement with a covering element and with a carrying structure.
BACKGROUND OF THE INVENTION
Components in a machine subjected to high thermal load are exposed to high temperatures during the regular operation of this machine. In a thermal machine, in particular in a gas turbine, a hot medium, for example a hot gas, subjects to a very high thermal load, primarily the surfaces, limiting the hot medium and the associated components. Furthermore, as a result of the transport of heat through these limiting surfaces, such as occurs, for example, in the form of heat conduction or heat radiation, even components which are not directly exposed to the hot medium and are often installed in the casing of the machine are subjected to high thermal loads. The components exposed to the hot medium thus perform two functions: enclosing the hot medium and protecting other, possibly less heat-resistant components from overheating or thermal destruction. Consequently, above all, material properties and the design and mounting of these components subjected to high thermal load must satisfy stringent requirements. Moreover, requirements regarding the coolability of such components must often also be taken into account.
For example, when a gas turbine is in operation, loads arise from mechanical stress (for example, due to internal pressure, centrifugal force, external forces and moments) and as a result of thermal stresses which occur because the thermal expansion of components in the event of temperature differences is prevented. Whereas, during steady-state operation, the temperature differences and therefore the thermal stresses are generally low, as compared with the mechanical stress, during transient operation in the event of load changes and in start-up and shut-down actions the transient thermal stresses are usually decisive, since load changes are necessarily associated with temperature changes. In the case of high working temperatures and large temperature differences between the individual load states, therefore, corresponding thermal expansions occur which affect primarily the casings and the rotors.
U.S. Pat. No. 3,892,497 describes an axial gas turbine with an inner and an outer casing insert. Guide blades and moving blades are arranged along a turbine axis in the gas turbine. A guide blade has in each case a platform (guide blade root) which serves for fastening the guide blade to the inner casing insert. Between in each case two adjacent guide blades spaced axially from one another, a guide ring is arranged on the inner casing insert in such a way that the guide ring is contiguous to the corresponding platforms of the guide blades. The platforms and guide rings are held from inside by the inner casing insert and are connected to the latter by a carrying element. Each carrying element is in this case connected fixedly to the inner casing insert by means of a combination consisting of a locking plate with a screw engaging into the inner casing insert.
The platforms of the guide blades and the guide rings have grooves into which the carrying element engages. A carrying element in this case engages into a groove either in a platform or in a guide ring, engagement taking place in the axial direction in each case at the edge of the platform or guide ring. This fastening to some extent allows relative thermal expansion and contraction between mutually contiguous components in the axial direction and, furthermore, permits simplified assembly and maintenance of the gas turbine. Moreover, a fastening for a guide ring may be gathered from the patent specification, in which a rigid connection to the guide ring is made directly by means of a fixing screw guided radially through the inner casing insert. In this case, the fixing screw secures the guide ring locally at a point between the axial edges of the latter. This embodiments results, when the guide ring is under thermal load, in considerable local thermal stresses in the axial direction and, above all, in the radial direction, since thermal expansions are possible only to a very restricted extent.
SUMMARY OF THE INVENTION
An object on which the invention is based is to specify a component capable of being subjected to high thermal load and at the same time of being cooled as efficiently as possible. The component, in this context, is to be suitable for use in the case of high working temperatures and large temperature differences between various states of load. Another object of the invention is to specify an arrangement with a component and with a carrying structure, which makes it possible, in particular, to fasten the component in the carrying structure in a way which is tolerant to thermal expansion.
The first-mentioned object is achieved, according to the invention, by means of a covering element which has a longitudinal axis and a transverse axis, comprising a wall with a hot side capable of being exposed to a hot medium and with a cool side which is located opposite the hot side and which has a cooling surface capable of being acted upon by a coolant, and further comprising a first bearing region, contiguous to the wall along the longitudinal axis and having a first bearing surface, and a second bearing region, located opposite the first bearing region along the longitudinal axis and having a second bearing surface, and further comprising a first edge region contiguous to the wall along the transverse axis and a second edge region located opposite the first edge region along the transverse axis, there being provided on the cool side a holding element which is arranged between the first and the second bearing region.
The invention proceeds from the notion that a component in a thermal machine, said component being exposed to a hot medium, for example a hot gas or steam, is subjected to very high thermal load by the temperature of the medium. These high temperatures or large temperature changes are associated with heat-induced deformations, above all thermal expansions, which are to be taken into account in the design and mounting of such components. The invention affords a novel possibility for designing and arranging components in a way which is tolerant to thermal expansion in machines subjected to high thermal load.
An above covering element forms, with its hot side capable of being exposed to the hot medium, a defined limitation of the hot medium, for example of the hot gas, in the combustion chamber or in the flow duct of a gas turbine. Furthermore, the covering element, as a component capable of being subjected to high thermal load, serves for the protection of further, possibly less heat-resistant components which are not exposed to the hot medium directly and are arranged in the casing of the thermal machine, in particular of the gas turbine. In this function, the covering element prevents the thermal overloading or even destruction of these components. Provided on the cool side of the covering element is a holding element which is arranged between the first and the second bearing region. The holding element is a fixed integral part of the covering element and has the task of ensuring an additional hold between the first and the second bearing region. The covering element is in this case held via the holding element from the cool side in such a way that, in particular, forces directed perpendicularly to the wall, for example as a result of mechanical and/or thermal load on the wall, can be absor-bed efficiently and, if appropriate, also transmitted efficiently.
At the same time, very good cooling properties of the cooling element can be ensured. This is implemented in that the first and the second bearing region are contiguous to the wall along the longitudinal axis. The side of the wall which is located opposite the hot medium is thereby available virtually completely as a cooling surface. By vi
Scheurlen Michael
Tiemann Peter
Look Edward K.
McCoy Kimya N
Siemens Aktiengesellschaft
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