Patent Grant
9828858
The invention relates to turbine blade design, and particularly to gas turbine blade airfoil shape and tip shroud shape for maximum aerodynamic efficiency and structural life.
In a gas turbine engine, air is pressurized in a compressor, then mixed with fuel and burned in a combustor to generate hot combustion gases. The hot combustion gases are expanded within the turbine section where energy is extracted to power the compressor and to produce useful work, such as turning a generator to produce electricity. The hot combustion gas, also called the working gas, travels through a series of turbine stages that are numbered starting at 1 from front to back of the turbine section. A turbine stage includes a circular array of rotating turbine blades, and may also include a circular array of stationary vanes. The blades extract energy from the working gas for powering the compressor and providing output power. Commonly, each blade is removably mounted on the circumference of a disk.
A turbine blade has a tip that closely clears a surrounding shroud. The shroud channels the working gas through the turbine section. The inner lining of the shroud is made abradable so the blade tips can cut a path in it to minimize the tip-to-shroud clearance, and minimize leakage of the working gas from the pressure side to the suction side of each blade. Some blade designs include a tip shroud as shown in
The invention is explained in the following description in view of the drawings that show:
The present inventors have recognized a need for blades with an improved tip shroud and transitional structure between the airfoil and the tip shroud in order to reduce mechanical loading at the blade airfoil inner radial span and root regions, reduce tip shroud deflection, reduce aerodynamic losses, improved turbine efficiency and power generation, and increase blade tip thermo-mechanical fatigue life compared to known blade configurations.
A blade airfoil conforming to the replacement profiles 31T, 31M, and 31R provides the following aerodynamic improvements over the prior art blade of profiles 31T, 30M, 30R:
a) Increased tolerance to variations 41 in the angle of incidence of the working gas inflow at the leading edge of the airfoil.
b) Substantially reduced suction surface diffusion over most of the span of the blade. Suction surface diffusion is the increase in static pressure from airfoil trailing edge to a minimum static pressure location of the blade suction surface divided by velocity head (Pt-Ps) at the minimum pressure location.
c) Reduction in aerodynamic losses on the suction side of the airfoil, due to reduced friction on the airfoil surfaces.
d) Reduced peak Mach number in the trailing edge region, resulting in reduced trailing edge losses and increased aerodynamic efficiency.
e) Improved mass distribution resulting in reduced structural loading in the lower span and root of the blade.
Tables 1a-1k herein specify eleven sectional profiles of a blade airfoil according to an embodiment of the invention at successive 10% radial increments of the span of the airfoil starting at the root. The absolute values of the coordinates define one blade in inches. However, the coordinates may used as relative values that may be scaled up or down proportionally, along with the tolerance below, for larger or smaller turbines. Each radial profile is characterized by a smooth curve connecting the nominal X and Y coordinates in each table. The term “nominal” herein means a design goal implemented within acceptable tolerance. An acceptable manufacturing tolerance is +/−0.050 inches in a direction normal to the surface at each location at a temperature of 20° C. (293.15 K, 68° F.). The coordinates represent the uncoated outer surface of the airfoil. The airfoil surface is a smooth surface connecting the sectional profiles defined below from 0% to 100% of the span.
Table 2a specifies the shape of an axially forward edge of the tip shroud along the portion spanned by line 58. Table 2b specifies the shape of an axially aft edge profile spanned by line 60. The absolute values of the coordinates in inches define one airfoil. However, the coordinates may used as relative values that can be scaled up or down proportionally, along with the tolerance below, for larger or smaller turbines. Each profile 58, 60 is characterized by a smooth curve connecting the nominal X and Y coordinates in each table. An acceptable manufacturing tolerance is +/−0.050 inches in a direction normal to the tip shroud edge at each location at a temperature of 20° C. (293.15 K, 68° F.). The coordinates represent the uncoated outer surface of the tip shroud. The X (axial), Y (circumferential) origin 0.0 of the coordinates for tables 2a, 2b is on the same turbine radius with the X, Y origins of tables 1a-1k. The Z or radial coordinate depends on the radius of the turbine shroud inner surface. The radially outer surface of the tip shroud 56 may form a cylindrical or conical surface of rotation parallel to that of the turbine shroud inner surface. The specified shape may be scaled circumferentially for turbines with fewer or more blades per disk, such that the tip shrouds have close clearance in the circular array of blades.
While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.
This application is the US National Stage of International Application No. PCT/US2014/038750 filed May 20, 2014, and claims the benefit thereof. The International Application claims benefit of the 21 May 2013 filing date of United States provisional patent application number 61/825,642. All applications are incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2014/038750 | 5/20/2014 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2014/189902 | 11/27/2014 | WO | A |
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| 102009003794 | Oct 2009 | DE |
| Number | Date | Country | |
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| 20160115795 A1 | Apr 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61825642 | May 2013 | US |
