Rotary kinetic fluid motors or pumps – Bearing – seal – or liner between runner portion and static part – Between blade edge and static part
Reexamination Certificate
2001-11-29
2004-01-06
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
06672831
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a device for setting the gap dimension for a turbomachine, in particular for a gas turbine, with a multiplicity of moving blades arranged in at least one moving-blade row of a rotor arrangement, with a guide-vane carrier surrounding the rotor arrangement and also a turbine casing surrounding the guide-vane carrier, with a multiplicity of heat accumulation segments which are arranged on the guide-vane carrier of the rotor arrangement and at least opposite the moving-blade tips and, together with the moving-blade tips, enclose a gap, and also with at least one drive means which projects radially through the turbine casing and the guide-vane carrier and is operatively connected kinematically to at least one heat accumulation segment and which, when actuated, brings about a radial spacing of the heat accumulation segment.
BACKGROUND OF THE INVENTION
Turbomachines of the abovementioned type serve primarily either for the controlled compression of gases, as is the case in compressor stages, known as compressors in turbo plants, or for the controlled expansion of highly compressed and fast-flowing media for the drive of gas turbines which are used in a way known per se for energy recuperation. In order to make energy recuperation by means of gas turbine plants as efficient as possible, a declared aim of efforts toward optimization is to increase the efficiency of turbomachines of this type. Attempts are made, by a series of technical measures, to counteract loss mechanisms which occur both when compressing the working media to be compressed and when driving of turbines.
In this connection, it is expedient, in particular, to keep the radial gaps forming in thermal turbomachines between the rotating and the stationary plant components as small as possible, in order to keep as low as possible the loss streams which pass through these gaps and constitute small, but still existing part mass streams of the working medium passing through the turbomachine, without at the same time participating in the desired energy conversion. Loss streams thus constitute loss mechanisms which may considerably reduce the efficiency of turbomachines. Moreover, the hot loss streams lead to heating or overheating of the blade tips. If attempts are made to keep the gaps small, with the result that the loss streams and therefore the heating of the blade tips also remain low, cooling measures are possible more easily or at a lower outlay.
The particular problem with regard to the reduction of loss streams is, on the one hand, the need for a discrete spacing between the stationary and rotating components of a turbomachine, in order to ensure the free running of the rotor arrangement; on the other hand, it is expedient, for the reasons mentioned, to keep this very interspace as small as possible, this being made more difficult by the fact that the plant components of the turbomachine expand under thermal and mechanical load, with the result that the relative positions of the individual components change during the operation of a turbomachine on account of different thermal expansion behaviors. This makes it difficult, moreover, to have as minimal a gap dimensioning as possible for the entire operating range of a turbomachine which, depending on the type of turbomachine, is exposed to a wide temperature spectrum. Thus, because of the centrifugal forces acting on the rotating components and their natural heating, they are subject to more rapid expansion, which would lead, in principle, to a gap reduction, than the complex thermally insulated components of the stator which experience slower heating and, in a thermally stationary operating state, contribute by expansion to an enlargement of the gap dimension. It is expedient, however, to keep this gap dimension as small as possible during operation.
Both active and passive measures are known for monitoring or influencing the gap dimension, passive precautions superficially seeming to be more advantageous, especially since active control precautions implemented by mechanical setting systems for gap control have high complexity and are suitable only to a limited extent for robust machines subjected to high thermal load, such as, for example, gas turbine plants.
One possibility for implementing gap control passively is the specific optimization of material combinations having specifically selected coefficients of thermal expansion, which brings about thermal expansion in all the plant components determining the gap, with the result that, on the one hand, the gap assumes a minimum size and, on the other hand, this minimum gap width is maintained over the entire operating range, that is to say temperature range, of the turbomachines.
Due to the highly complex configuration of known turbomachines, the possibilities for any desired choice of material combinations for stator and rotor components in order to improve the thermal behavior are very limited. Although the choice of material can be made, while taking into account the problem of the gap width, it has nevertheless not been possible hitherto to solve satisfactorily the problem of reducing the gap dimension merely by the choice of the material combination alone.
Another possibility for keeping the gap dimension small is to take into account abrasive surface actions on stator and rotor components. In this case, the surfaces located opposite one another and almost in contact are provided at least partially with abrasive surface coatings which, when the turbomachine is in operation, are stripped away in a controlled manner by being intentionally ground off or down and which thus result in an optimized gap.
However, after only one operating cycle of the turbomachine, the gap forming as a result of abrasive action has an optimized maximum gap width, but one which cannot be reduced again.
Finally, structural measures for a uniform expansion of the rotor and stator components of a turbomachine are also possible, but, overall, entail a considerable extra outlay in structural terms and, moreover, are not suitable for robust use with long-time stability in gas turbines.
Thus, a device for setting the gap between turbine blades and a heat accumulation segment may be gathered from U.S. Pat. No. 5,228,828. The following statements refer to the exemplary embodiment illustrated in FIG. 1 of the US publication. A heat accumulation segment 18, 82 is arranged opposite the individual turbine blade tips 14, 16. The two components enclose a gap. Through the turbine casing wall 36 projects a rotary shaft 12 which is connected to a control cam 44 within the turbine casing. The control cam 44 spaces the flanks 48 and 54 from one another, especially since the components 46 and 52 are clamped together by means of the spring 76. The components 46 and 52 then engage, on the other hand, into corresponding extensions 84 and 86 of the heat accumulation segment 18, in such a way that, in the event of a relative movement of the two components 46 and 52, the heat accumulation segment 18 moves radially away from the turbine blade tips 14 and 16 or toward these. A relative movement of the two components 46 and 52 may be carried out by means of a rotation of the rotary shaft 12 and of the control cam 44 connected to the latter.
The illustration of this known device clearly shows a complicated construction involving a high outlay, with the result that the operation of the gas turbine becomes more susceptible to repair and maintenance.
SUMMARY OF THE INVENTION
The object on which the invention is based is to develop a device for setting the gap dimension for a turbomachine, in particular a gas turbine with a multiplicity of moving blades arranged in at least one moving-blade row of a rotor arrangement, with a guide-vane carrier surrounding the rotor arrangement and also a turbine casing surrounding the guide-vane carrier, with a multiplicity of heat accumulation segments which are arranged on the guide-vane carrier of the rotor arrangement and at least opposite the moving-blade tips and which, together with the
Brandl Herbert
Busekros Armin
Marx Peter
Rathmann Ulrich
Wellenkamp Ulrich
Alstom Technology Ltd
Burns Doane Swecker & Mathis L.L.P.
Edgar Richard A.
Look Edward K.
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