Fluid reaction surfaces (i.e. – impellers) – With heating – cooling or thermal insulation means – Changing state mass within or fluid flow through working...
Reexamination Certificate
1999-06-30
2001-01-16
Verdier, Christopher (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
06174135
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to turbine engines and, more particularly, to apparatus and methods for cooling a turbine blade trailing edge.
A turbine engine typically includes a core engine having, in serial flow relationship, a high pressure compressor which compresses an airflow entering the core engine, a combustor in which a mixture of fuel and compressed air is burned to generate hot propulsive gases, and a high pressure turbine which is rotated by the hot propulsive gases. The high pressure turbine is connected to the high pressure compressor by a shaft so that the high pressure turbine blades drive the high pressure compressor. Additional compressors and turbine blades (e.g., a low pressure compressor and a low pressure turbine) may be positioned in serial flow relationship with the core engine. As used herein, the term “turbine blades” refers to the high pressure turbine blades and low pressure turbine blades.
A turbine blade typically includes an airfoil, a platform, a shank, and a dovetail. The platform is connected to a root of the airfoil and the shank. The shank is connected to the dovetail, through which the cooling air is directed. The airfoil includes a leading edge and a trailing edge, with the trailing edge being relatively thin in comparison to the leading edge. The airfoil further includes an upper portion, a lower portion, and a tip. The tip and the root are connected to the leading edge and the trailing edge at the upper portion and the lower portion of the airfoil, respectively.
A greater operating efficiency and power output of the turbine engine is achieved through higher operating temperatures. Operating temperatures are limited, however, by a maximum temperature tolerable by the rotating turbine blades, along with problems associated with tension and stress caused by increased rotation of the turbine blades. Typically, cooling air is extracted from an outlet of the compressor and utilized to cool, for example, turbine blades.
Optimization of aerodynamic efficiency creates problems with operating conditions of the airfoil, and optimization of the operating conditions creates problems with the aerodynamic efficiency. In operation, aerodynamic losses predominately occur at the upper portion of airfoils with a thick trailing edge due to radial distribution of the hot propulsive gases. However, a thin trailing edge increases the likelihood that the lower portion of the airfoil will fail due, at least in part, to high centrifugal stresses during operation, when combined with the high operating temperatures.
BRIEF SUMMARY OF THE INVENTION
In an exemplary embodiment of the invention, a turbine blade airfoil includes a plurality of slots on an upper portion of the airfoil and a plurality of trailing edge openings through a lower portion of the airfoil. The turbine blade also includes a shank, a platform, and a dovetail. The airfoil is connected to the platform at a root and further includes at least one cooling cavity located between a pressure side wall and a suction side wall which extend from a leading edge of the airfoil to a trailing edge of the airfoil.
More specifically, the upper portion of the airfoil includes a thin trailing edge. The slots extend from the pressure side wall of the airfoil to the trailing edge. The lower portion of the airfoil includes a thicker trailing edge than the upper portion trailing edge. The trailing edge openings extend through the trailing edge and provide convection cooling to the lower portion of the trailing edge. The slots cool the upper portion of the airfoil utilizing a combination of convection cooling for the airfoil and film cooling for the upper portion of the trailing edge.
Utilizing the above described airfoil with the combination of slots and trailing edge openings improves the performance and durability of the turbine blade. The performance of the turbine blade is improved by utilizing a thin trailing edge at the upper portion of the airfoil which is effectively cooled by the slots. The durability of the turbine blade is improved by including a trailing edge at the lower portion of the airfoil which has a greater width than the upper portion trailing edge and which is cooled by the trailing edge openings extending through the lower portion trailing edge.
REFERENCES:
patent: 4726104 (1988-02-01), Foster et al.
patent: 5215431 (1993-06-01), Derrien
patent: 5342172 (1994-08-01), Coudray et al.
patent: 5503527 (1996-04-01), Lee et al.
patent: 5503529 (1996-04-01), Anselmi et al.
patent: 5772398 (1998-06-01), Noiret et al.
General Electric Company
Hess Andrew C.
Verdier Christopher
Young Rodney M.
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