Rotary kinetic fluid motors or pumps – Including heat insulation or exchange means
Reexamination Certificate
2001-09-12
2003-02-04
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Including heat insulation or exchange means
C415S191000, C415S208200, C415S211200
Reexamination Certificate
active
06514041
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a carrier for a guide vane and a heat protection shield for a guide vane in a thermal turbo machine, such as, for example, a turbine part or compressor of a gas turbine, in order to achieve minimal radial vane play.
BACKGROUND OF THE INVENTION
In thermal turbo machines, radial vane clearance(a) exists between the rotating vanes and stationary housing, as well as between guide vanes and rotor. This vane clearance is determined during operation by mechanical and thermal movement of the various machine parts. In the process, different vane clearance are created during the various operating conditions, such as, for example, during start-up and shut-down, constant performance operation, and load changes, because the vanes, housing and rotor expand and contract differently. If the vane clearance is made sufficiently large to prevent a rubbing of the machine parts in all operating situations, this will provide an undesired, large vane clearance in certain operating conditions that will cause a reduction in the performance of the gas turbine or pumping limit of a compressor.
Previous attempts to decrease vane clearance and thereby increase the performance of the turbo machine always included efforts to maintain the level of production costs and life span of the machine. In order to limit the expansion of the stationary housing, this included, for example, the forced cooling of the stationary housing or materials with low coefficients of expansion.
DE 1 057 827 describes a vane wheel rim with a groove facing the rotating vane tips. Into the groove are inserted heat-resistant and abradable sealing elements consisting of a thermically designed expansion body whose mass distribution, clamping and positioning is such that the vane clearance is maintained approximately constant during temperature changes. This is achieved, for example, by a curvature of the sealing element in an axial direction, whereby the curvature changes during cooling or heating in such a way that a small gap is maintained. On the other hand, a small gap is achieved in that the abradable surfaces rest against the guide vane tips during the installation of the sealing elements and abradable off when the machine starts up. The abradable also achieves the smallest gap possible and prevents a breaking of the vane tips.
DE 43 09 199 describes a device for attaching heat shield segments and guide vanes in turbines with an axial flow. Here, the heat shield segments are attached to a massive stator ring that is inserted into recesses in the exterior housing of the turbine. The guide vanes are thereby attached, separately from the heat shield segments, directly to the exterior housing. The massive stator rings are sized relatively small so that their temperature and the vane play between the massive stator ring and vane tips can be better controlled. The temperature of the massive stator ring can also be controlled with cooling by air or fluids or by electrically heating, so that the vane plays can be controlled.
U.S. Pat. No. 5,927,942 and U.S. Pat. No. 5,380,150 describe a heat shield segment in a gas turbine that is attached radially opposite from the rotating vane tips on the stationary housing. Each heat shield segment consists of a substrate with a abradable layer. It is connected radially and axially on both sides as well as in the center of the heat shield segment by means of rails that have a hook-shaped cross-section to a carrier unit on the housing of a turbine machine, whereby the hooks are provided in recesses in the carrier unit. A segmented, spring-loaded band furthermore extends between the hooks on both sides of the heat shield segment. The band permits, in particular, a springing attachment of the heat shield segment at the carrier unit, thus absorbing any instances of thermal expansion and deformation of the heat shield segment and carrier unit. This attachment enables a radial as well as axial movement of the heat shield segment, whereby the rail in the center of the heat shield segment prevents a radial inward movement. The segmented band furthermore ensures a seal that prevents the coolant from flowing out of the space between the heat shield segment and the segmented band. And finally, the heat shield segment has a abradable layer for minimizing the rotating vane play.
The disadvantage of the heat shield segment or heat protection shield according to the described state of the art is, on the one hand, the abradable layers. In most machines, for example in gas turbines, the worn-off material remains inside the machine housing in the form of particles and may damage surfaces and obstruct cooling channels. The vane play created in this way does not necessarily have the optimally small size. When the turbo machine is started, the rotor first expands, while the housing of the turbo machine expands more slowly. If the abradable layers are worn off during the start-up, the vane play is again increased by the expansion of the housing and is not necessarily optimal during steady state operation.
In addition, heat shield segments of this type and their individual attachment on the housing of the turbo machine only regulate the rotating vane play, while the guide vane play must be adjusted with a separate construction.
SUMMARY OF THE INVENTION
This results in the objective of the invention, which is to create a carrier for guide vanes and a heat shield segment arranged radially opposite from the rotor vane tips for a thermal turbo machine, where said carrier and heat shield segment achieve a minimal, radial play between the tips of the . . . vanes and the rotor and between the tips of the guide vanes and the heat shield segment, whereby this minimal vane play should be maintained in as many operating conditions as possible. In particular, damage caused by material from abradable layers should be avoided. The production costs and life span of the components hereby should be at least maintained at the current or reduced level. The seal between the heat shield segment and housing also should be improved.
A thermal turbo machine with a rotor, rotor vanes, a stationary housing, and guide vanes is provided with a guide vane carrier that is attached to the housing of the turbo machine. The guide vane carrier is provided with a guide vane platform, to which are attached one or more guide vane airfoils. Heat shield segments are arranged radially opposite from the tips of the rotor vanes. According to the invention, an entire, axially adjoining heat shield segment or a part of two axially adjoining heat shield segments are part of the guide vane platform. Also, at least two braces extend at an angle to the guide vane platform, in part radially outward, towards a band. The braces hereby each extend in different directions relative to each other, in the manner of open scissors, from the guide vane platform towards the band. The radially outer ends of the braces are connected by the band, whereby the band is attached to the stationary housing. Furthermore, the guide vane platforms as well as the braces are made, in particular, from a first material with a high coefficient of expansion, whereby the band consists of a second material with a coefficient of expansion that is lower in comparison to the first material.
By integrating guide vane platform and heat shield segment, both the radial play between the guide vane tip and rotor, as well as the one between the rotating vane tip and the heat shield segment are simultaneously determined by a single construction. As a result of material choice for the band on the one hand and for the braces and integrated guide vane platform on the other hand, the guide vane carrier with the heat shield segment exhibits a thermal behavior that results in minimal vane play during the various operating conditions of the turbo machine. Since the coefficient of expansion of the band is lower than that of the material of the braces and guide vane platform, the band expands less quickly than the braces. During the warming of the machine, the angled arrange
Beeck Alexander
Matheny Alfred Paul
Alstom (Switzerland Ltd
Look Edward K.
Nguyen Ninh
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