Fluid reaction surfaces (i.e. – impellers) – With heating – cooling or thermal insulation means – Changing state mass within or fluid flow through working...
Reexamination Certificate
1999-10-05
2001-12-11
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
With heating, cooling or thermal insulation means
Changing state mass within or fluid flow through working...
Reexamination Certificate
active
06328531
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a cooled turbine blade comprising a platform and an aerofoil portion having a suction face and a pressure face extending between leading and trailing edges, and a number of slots opening adjacent the trailing edge on the pressure face side for the escape of cooling air flowing through an internal cavity of said aerofoil portion. Such cooled blades are used, in particular, in turbine blading which is subjected to high temperatures.
2. Summary of the Prior Art
Conventionally, the slots adjacent the trailing edge of cooled turbine blades open into recesses which are formed near the trailing edge on the pressure face side and which are separated by stiffeners which locally constitute the aerodynamic profile of the aerofoil near the trailing edge. European Patent No. 0785339 discloses an arrangement of this kind.
It has been found that the alternating arrangement of recesses through which cool air flows and stiffeners which are locally subjected to the high temperatures of the combustion gases, leads to strong thermal fields in the trailing edge region. This induces high thermal stresses which can cause damage to the aerofoil portion in the trailing edge region.
SUMMARY OF THE INVENTION
The object of the invention is to provide a new trailing edge geometry which alleviates these drawbacks and makes it possible to lengthen the service life of the cooled blades.
To this end, according to the invention there is provided a cooled turbine blade comprising a platform and an aerofoil portion extending from said platform, said aerofoil portion having at least one internal cavity for the flow of cooling air, a leading edge, a trailing edge, first and second walls between said leading and trailing edges, and an outer edge remote from said platform and defining the tip of said blade, said first and second walls having external surfaces respectively defining a suction face and a pressure face of said aerofoil portion, and said first and second walls having internal surfaces bounding said at least one internal cavity, said second wall terminating short of said trailing edge and defining an end surface which is substantially perpendicular to said pressure face defined by said second wall, said end surface and said internal surface of said first wall defining a rebate in said aerofoil portion adjacent said trailing edge and extending from said platform to said tip of said blade, and said aerofoil portion including means defining a plurality of slots opening in said end surface for the escape of cooling air from said at least one internal cavity to said trailing edge on the pressure face side of said aerofoil portion, the slot nearest said platform opening partly in the platform, and said rebate extending into said platform facing said slot.
With this arrangement the thermal field in the region of the trailing edge is more uniform, and this area experiences much weaker thermal stresses.
Preferably, the slots are separated by small bridges which interconnect the first and second walls of the aerofoil portion.
Other preferred features and advantages of the invention will become apparent from the following description of the preferred embodiment, which is given by way of nonlimiting example and with reference to the appended drawings.
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Bariaud Christian Bernard
Bil Eric Stephan
Look Edward K.
Nguyen Ninh
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Societe Nationale d'Etude et de Construction de Moteurs d&a
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