Fluid reaction surfaces (i.e. – impellers) – Specific blade structure – Having wear liner – sheathing or insert
Reexamination Certificate
2001-01-09
2002-07-23
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Specific blade structure
Having wear liner, sheathing or insert
C416S228000, C416S23600R, C416S092000, C416S09700R
Reexamination Certificate
active
06422821
ABSTRACT:
BACKGROUND OF THE INVENTION
This application relates generally to gas turbine engine rotor blades and, more particularly, to methods and apparatus for reducing rotor blade tip temperatures.
Gas turbine engine rotor blades typically include airfoils having leading and trailing edges, a pressure side, and a suction side. The pressure and suction sides connect at the airfoil leading and trailing edges, and span radially between the airfoil root and the tip. To facilitate reducing combustion gas leakage between the airfoil tips and stationary stator components, the airfoils include a tip region that extends radially outward from the airfoil tip.
The airfoil tip regions include a first tip wall extending from the airfoil leading edge to the trailing edge, and a second tip wall also extending from the airfoil leading edge to connect with the first tip wall at the airfoil trailing edge. The tip region prevents damage to the airfoil if the rotor blade rubs against the stator components.
During operation, combustion gases impacting the rotating rotor blades transfer heat into the blade airfoils and tip regions. Over time, continued operation in higher temperatures may cause the airfoil tip regions to thermally fatigue. To facilitate reducing operating temperatures of the airfoil tip regions, at least some known rotor blades include slots within the tip walls to permit combustion gases at a lower temperature to flow through the tip regions.
To facilitate minimizing thermal fatigue to the rotor blade tips, at least some known rotor blades include a shelf adjacent the tip region to facilitate reducing operating temperatures of the tip regions. The shelf is defined within the pressure side of the airfoil and disrupt combustion gas flow as the rotor blades rotate, thus enabling a film layer of cooling air to form against the pressure side of the airfoil. The film layer insulates the blade from the higher temperature combustion gases.
BRIEF SUMMARY OF THE INVENTION
In an exemplary embodiment, a rotor blade for a gas turbine engine includes a tip region that facilitates reducing operating temperatures of the rotor blade, without sacrificing aerodynamic efficiency of the turbine engine. The tip region includes a first tip wall and a second tip wall that extend radially outward from an airfoil tip plate. The first tip wall extends from adjacent a leading edge of the airfoil to a trailing edge of the airfoil. The second tip wall also extends from adjacent the airfoil leading edge and connects with the first tip wall at the airfoil trailing edge to define an open-top tip cavity. At least a portion of the second tip wall is recessed to define a tip shelf. A notch extends from the tip plate and is defined between the first and second tip walls at the airfoil leading edge. The notch is in flow communication with the tip cavity.
During operation, as the rotor blades rotate, combustion gases at a higher temperature near each rotor blade leading edge migrate to the airfoil tip region. Because the tip walls extend from the airfoil, a tight clearance is defined between the rotor blade and stationary structural components that facilitates reducing combustion gas leakage therethrough. If rubbing occurs between the stationary structural components and the rotor blades, the tip walls contact the components and the airfoil remains intact. As the rotor blade rotates, combustion gases at lower temperatures near the leading edge flow through the notch and induce cooler gas temperatures into the tip cavity. The combustion gases on a pressure side of the rotor blade also flow over the tip region shelf and mix with film cooling air. As a result, the notch and shelf facilitate reducing operating temperatures of the rotor blade within the tip region, but without consuming additional cooling air, thus improving turbine efficiency.
REFERENCES:
patent: 5261789 (1993-11-01), Butts et al.
patent: 5503527 (1996-04-01), Lee et al.
patent: 6059530 (2000-05-01), Lee
Lee Ching-Pang
Prakash Chander
Rinck Gerard Anthony
Shelton Monty Lee
Singh Hardev
Andes William Scott
Armstrong Teasdale LLP
General Electric Company
Look Edward K.
McCoy Kimya N.
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