Fluid reaction surfaces (i.e. – impellers) – Specific blade structure – Concave surface
Reexamination Certificate
2003-05-09
2004-08-03
Verdier, Christopher (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Specific blade structure
Concave surface
C416S22300B, C416SDIG002, C416S092000, C416S09700R, C416S24100B, C416S24100B
Reexamination Certificate
active
06769878
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a turbine blade for a gas turbine engine and more specifically to an improved airfoil profile having reduced heat load to the airfoil leading edge resulting in improved life.
2. Description of Related Art
As the demand for more efficient turbine engines continues to increase, higher firing temperatures are required in order to optimize turbine performance. This, in turn, requires enhanced airfoil configurations to accommodate these higher firing temperatures. Known airfoil failure modes, such as creep, which is when an airfoil is exposed to high operating temperatures and a given stress level for an extended period of time, are being addressed through redesigns involving enhanced cooling to reduce airfoil operating temperatures. Further enhancements have also been made to address performance issues caused by boundary layer flow separation. Early turbine blade technology often had airfoils with a blunt or rounded leading edge. A rounded leading edge had a constant radius of curvature, which made for an abrupt transition to the pressure side and suction side of the airfoil body, due to the discontinuous radii of curvature for each surface when compared to the constant radius of curvature of the leading edge. This transition section created regions of rapid acceleration followed by deceleration resulting in performance loss by the turbine blade. To correct this transition, some airfoil designers chose to provide an airfoil having a sharper leading edge, as disclosed in U.S. Pat. No. 5,980,209, and hereby incorporated by reference. The sharper leading edge contained a more elliptical shape that provided a smoother transition to the pressure side and suction side surfaces, thereby reducing the amount of overspeed and improving performance.
While enhancements have typically focused on lowering operating temperatures of the airfoil to increase creep margin and airfoil life as well as to address minor performance issues, there are other failure modes that must be addressed when enhancements are made to an airfoil. One specific area that should be addressed is the “heat load”, of the airfoil leading edge. Heat load is defined as the product of the heat transfer coefficient for a particular airfoil design and the relevant airfoil surface area. While changing the airfoil leading edge to a more elliptical design smooths the transition to the pressure side and suction side surfaces of the airfoil, it has been determined that the heat load experienced by the airfoil leading edge is adversely impacted. Due to the geometry changes, the airfoil leading edge is more difficult to cool than the rounded leading edge configuration of the prior art, resulting in increased heat load. If too large of a heat load is experienced by a specific region of the airfoil, such as the leading edge, it can cause a life limiting condition to be present.
Therefore, what is needed is an airfoil design that incorporates performance and life enhancements of the prior art while minimizing heat load to the leading edge.
SUMMARY AND OBJECTS OF THE INVENTION
In accordance with the present invention, there is provided a novel and improved airfoil having improved performance and reduced operating temperatures for increased creep life, while simultaneously minimizing the amount of heat load experienced by the airfoil leading edge, thereby extending airfoil life. To accomplish this, airfoil geometry is disclosed that contains a semi-elliptical leading edge allowing sufficient cooling to reduce exposure of the leading edge to excessive heat, while maintaining the flow benefits of the transition between an elliptical leading edge and the pressure side and suction side surface curvatures.
In the preferred embodiment of the present invention, an airfoil for a turbine blade having an attachment with a platform extending radially outward from the attachment is disclosed with the airfoil having an uncoated profile substantially in accordance with Cartesian coordinate values of X, Y, and Z as set forth in Table 1, carried only to three decimal places, wherein Z is a distance measured radially from the platform to which the airfoil is mounted.
In an effort to reduce the overall blade heat load, the turbine blade containing the disclosed airfoil geometry contains a reconfigured leading edge, pressure side surface, and suction side surface as well as a plurality of radially extending holes for passing a cooling medium through the airfoil. The cooling medium can vary depending on engine conditions, but is typically compressed air or steam. To protect the airfoil surfaces from oxidation a metallic coating is applied.
It is an object of the present invention to provide a turbine blade having a novel and improved airfoil geometry with improved performance, lower heat load to the airfoil leading edge, enhanced cooling, increased creep margin, and extended life.
In accordance with these and other objects, which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings.
REFERENCES:
patent: 3928026 (1975-12-01), Hecht et al.
patent: 5980209 (1999-11-01), Barry et al.
patent: 6129991 (2000-10-01), Warnes et al.
patent: 6450770 (2002-09-01), Wang et al.
patent: 6461110 (2002-10-01), By et al.
patent: 6474948 (2002-11-01), Pirolla et al.
patent: 6503059 (2003-01-01), Frost et al.
patent: 6685434 (2004-02-01), Humanchuk et al.
patent: 6715990 (2004-04-01), Arness et al.
Wilson, D.G. et al, “The Design and Peformance Prediction of Axial Flow Turbines”, The Design of Gas Turbine Engines Thermodynamics and Aerodynamics 2nd Ed, 1995, pp. 185-200, IGT1-ASME.
Ainley & Matheson, “A Method of Performance Estimation for Avial Flow Turbines”, Aeronautical Research Council Report No. 2974, 1957, pp. 1-30.
Dunham & Came, “Improvements to the Ainley—Mathieson Method of Turbine Performance Prediction”, Journal of Engineering for Power, Jul. 1970, pp. 252-256.
Kacker & Okapuu, “A Mean Line Prediction Method for Axial Flow Turbine Efficiency”, Journal of Engineering for Power vol. 104, Jan. 1982, pp. 111-119.
Pritchard, “An Eleven Parameter Axial Turbine Airfoil Geometry Model” ASME Paper 85-GT-219, Mar. 1985.
Johnston Christopher
Parker David G.
Strohl J. Page
Taylor Jeffrey S.
Mack Brian R.
Power Systems Mfg. LLC
Verdier Christopher
LandOfFree
Turbine blade airfoil does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Turbine blade airfoil, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Turbine blade airfoil will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3308447