Rotary kinetic fluid motors or pumps – Working fluid passage or distributing means associated with... – Plural distributing means immediately upstream of runner
Reexamination Certificate
1999-10-07
2001-07-17
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
C415S208200, C415S209400
Reexamination Certificate
active
06261058
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to a gas turbine stationary blade and, more particularly, to a gas turbine stationary blade of such a construction that a thermal barrier coating (TBC) can be applied to the blade surface and cracks can be prevented from being made by thermal stresses at the shroud portion of the blade.
FIG. 4
is a perspective view of a conventional gas turbine stationary blade, and
FIG. 5
is a plan cascade view of a plurality of blades. One inside shroud
11
and one outside shroud
12
are provided with respect to one stationary blade
1
as shown in FIG.
4
.
The stationary blade
1
has a construction such that a seal plate (not shown) is put between the shrouds, which are adjacent to each other, by which the leakage of cooling air is decreased. When a single blade construction, in which blades are divided separately, is used because of the need for applying a thermal barrier coating to the blade surface, the number of portions where seal plates are inserted increases, resulting in increased leakage of cooling air.
In order to decrease the leakage of cooling air, several stationary blade can be cast as an integrated, one-piece segment, or single cast blades can be joined by welds into an integrated segment. In these cases, however, a thermal barrier coating cannot be applied to the whole surface of the blade.
As describe above, the decrease in leakage of cooling air caused by blade division is prevented conventionally by one-piece casting of a plurality of stationary blades as an integrated segment or by welding individual cast blades into an integrated segment. However, if singly cast blades are welded into an integrated segment, high thermal stresses cannot be relieved by the temperature difference between the dorsal side and ventral side of blade, so that the potential for the generation of cracks in the shroud is increased.
With the recent increase in gas turbine inlet temperatures, thermal barrier coatings etc. are applied to the blade surface by spraying, using a coating gun, to reduce the thermal load of blade surface to the utmost. In this case, if multiple stationary blades are cast as a one-piece cast integrated segment, or if singly cast blades are welded into an integrated segment, the coating gun typically does not enter a curvedly space formed between the blades, so that the coating cannot be readily applied to the whole blade surface.
SUMMARY OF THE INVENTION
The present invention was made to address the above problems. Accordingly, an object of the present invention is to provide a gas turbine stationary blade of integrated segment construction, in which a thermal barrier coating can be applied to the whole blade surface, and in which excessive stresses are not produced in the shroud, and to a manufacturing method for such blades.
To achieve the above object, the present invention provides a gas turbine stationary blade segment having a plate seat connector adapted to receive a bolt, affixed at each end face portion of inside and outside shrouds affixed to a gas turbine stationary blade. Each plate seat connector protrudes outwardly away from the respective shroud to which it is affixed and includes a flat seat face which is not contiguous with the end face of the shroud. The stationary blade segments are integrated by joining the plate seat connectors of adjacent shrouds in face to face contact by means of bolts and nuts.
In the stationary blade of integrated segment construction in accordance with the present invention, it is preferable that a thermal barrier coating be applied to the whole surface of the stationary blade to reduce thermal load on the stationary blade surface.
To manufacture the above-mentioned stationary blade of integrated segment construction in accordance with the present invention, after a thermal barrier coating is applied to the blade portion of each stationary blade segment, several stationary blade segments are integrated by the joining the plate seat connectors by means of bolts and nuts. Accordingly, an integrated segment stationary blade having a thermal barrier coating applied to the whole surface of each blade can be manufactured easily.
By employing the stationary blade of integrated segment construction in accordance with the present invention, the number of seals inserted between the blades can be decreased, so that the leakage of cooling air can be reduced, whereby the performance of gas turbine is improved.
Preferably, the width of each plate seat connector, i.e., across the seat face, is small compared to the width of the corresponding shroud. In addition, preferably each plate seat connector includes a flexible leg portion which connects the outermost seat face portion of the plate seat connector with the shroud and which is constructed to flex in response to stress applied to the connector as a result of thermal deformation of the shroud.
Because the seat face of each plate seat connector is separate from, i.e., non-contiguous, with the end face of the shroud, when an excessive force is applied to the stationary blade segment of the present invention as a result of thermal expansion, a relative slide can occur at the seating face of the bolted plate seat connector, by which excessive stress in the shroud portion of the segment can be prevented, i.e., relieved. Also, because the stationary blade segments can easily be disassembled into individual blade segments by removing the bolts, a coating gun can readily reach the whole blade surface, so that the whole blade surface can be coated.
As described above, in the gas turbine stationary blade segment in accordance with the present invention, the plate seat connector is provided at each end face portion of the inside shroud and the outside shroud of the gas turbine stationary blade segment, and several stationary blade segments are integrated by joining the plate seat connectors of the adjacent shrouds by means of bolts and nuts. Because a plurality of the stationary blade segments are mechanically joined in an integrated segment construction, the number of locations where seals are inserted can be decreased so that the leakage of cooling air can further be reduced, whereby the performance of gas turbine can be improved.
Also, with the stationary blade segment in accordance with the present invention, since a thermal barrier coating can be applied to the whole blade surface by performing the thermal barrier coating operation before joining the plate seats by means of bolts and nuts, the thermal load on the blade can be reduced, so that the blade segment can tolerate higher gas turbine temperatures.
Further, since the thermal deformation caused by the temperature difference between the dorsal side and ventral side of turbine blade can be absorbed by relative sliding between the bolted faces of the plate seat connectors, an excessive stress created in the shroud can be prevented, so that the reliability of the blade is increased. Moreover, in preferred embodiments in which a flexible leg connects the seat face portion of the plate seat connector to the shroud, flexing of the leg provides additional relief of stress between the shroud and the plate seat connector.
As described above, the present invention achieves substantial and desirable effects contributing to increased reliability and performance of gas turbines.
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Hashimoto Yukihiro
Kataoka Masahito
Terazaki Masao
Alston & Bird LLP
Look Edward K.
McAleenan James M
Mitsubishi Heavy Industries Ltd.
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