Patent Application
20130039758
The subject matter disclosed herein relates to turbines. More particularly, the subject matter relates to an airfoil to be positioned in a turbine.
In a gas turbine engine, a combustor converts chemical energy of a fuel or an air-fuel mixture into thermal energy. The thermal energy is conveyed by a fluid, often air from a compressor, to a turbine where the thermal energy is converted to mechanical energy. Several factors influence the efficiency of the conversion of thermal energy to mechanical energy. The factors may include blade passing frequencies, fuel supply fluctuations, fuel type and reactivity, combustor head-on volume, fuel nozzle design, air-fuel profiles, flame shape, air-fuel mixing, flame holding, combustion temperature, turbine component design, hot-gas-path temperature dilution, and exhaust temperature. For example, high combustion temperatures in selected locations, such as the combustor and turbine nozzle areas, may enable improved combustion efficiency and power production. In some cases, high temperatures in certain combustor and turbine regions may shorten the life and increase wear and tear of certain components. Accordingly, it is desirable to control temperatures in the turbine to reduce wear and increase the life of turbine components.
According to one aspect of the invention, a turbine airfoil includes a platform and a blade extending from the platform. The airfoil also includes a slot formed in a slashface of the platform, the slot being configured to receive a pressurized fluid via passages and configured to direct the pressurized fluid to a selected region of the turbine airfoil to improve airfoil life.
According to another aspect of the invention, a method for cooling a turbine airfoil is provided, wherein the method includes flowing a pressurized fluid into a passage formed in a platform of the turbine airfoil. The method also includes flowing the pressurized fluid from the passage into a slot formed in a slashface of the platform, the slot being configured to direct the pressurized fluid to a selected region of the turbine airfoil to improve airfoil life.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
In an aspect, the combustor 104 uses liquid and/or gas fuel, such as natural gas or a hydrogen rich synthetic gas, to run the turbine engine. For example, fuel nozzles 110 are in fluid communication with a fuel supply and pressurized air from the compressor 102. The fuel nozzles 110 create an air-fuel mix, and discharge the air-fuel mix into the combustor 104, thereby causing a combustion that creates a hot pressurized exhaust gas. The combustor 104 directs the hot pressurized exhaust gas through a transition piece into a turbine nozzle (or “stage one nozzle”), causing turbine 106 rotation as the gas exits the nozzle or vane and gets directed to the turbine bucket or blade. The rotation of turbine 106 causes the shaft 108 to rotate, thereby compressing the air as it flows into the compressor 102. In an embodiment, airfoils (also nozzles or buckets) are located in various portions of the turbine, such as in the compressor 102 or the turbine 106, where hot gas flow across the airfoils causes wear and thermal fatigue of turbine parts, due to non-uniform temperatures. Controlling the temperature of parts of the turbine airfoil can reduce wear and enable higher combustion temperatures in the combustor, thereby improving performance. Controlling the temperature of regions of and proximate to parts, such as airfoils, to improve component life is discussed in detail below with reference to
As depicted, a hot gas path 214 flows from a leading edge 216 to a trailing edge 218 of the blade 204. The pressurized fluid barrier formed within the slot 208 restricts flow of the hot gas across the slashface 210 to a cavity 220 (also called a “shank cavity”) in the lower portion 206. A recess 222 to receive a pin is located below the platform 202. In embodiments, the pressurized fluid is also configured to cool the recess 222 and pin region. By restricting the hot gas flow across the slashface 210, the cooling fluid within the slot 208 reduces wear and tear on the lower portion 206. In an embodiment, the pressurized fluid is pressurized air used to cool selected portions of the airfoil 200, wherein passages are used to direct the cooling fluid to the selected portions. Further, the passages may include passages 212, wherein the pressurized fluid is distributed by the slot 208 to cool the platform 202. In the embodiment, the slot 208 comprises a substantially semicircular cross section geometry. As depicted, the pressurized fluid is configured to flow in the direction of the hot gas path 214 flow, wherein the fluid exits the open trailing edge side of the slot 208. In other embodiments, both ends of the slot 208 may be closed. The slot 208 with closed ends may be configured to direct the pressurized fluid to other regions of the airfoil 200. In embodiments, the slot 208 in the slashface 210 may also provide stress relief for high stress regions of the airfoil 200, such as the trailing edge 218 and platform 202, wherein the slot 208 weakens the slashface to divert a load from the high stress region. As depicted, the cross sectional geometry of the slot 208 is a portion of a circle, ellipse or oval. In other embodiments, the cross sectional geometry will include any suitable shape, such as triangles, rectangles or trapezoids. Further, the slot 208 may have a substantially uniform cross-section across the slashface 210. Other embodiments may have a variable cross-section for the slot 208, such as a slot 208 that varies in cross section shape or size along its length. For example, the slot 208 may have a decreasing cross-section size in one direction to force flow out of the slot 208, or with increasing size to reduce flow velocity at the slot exit. In another example, the slot 208 could transition from a shape optimized for heat transfer at one part of the slash face 210 to one that is optimized for stress relief at another part of the slash face 210.
In aspects, turbine parts, including airfoils, are formed of stainless steel or an alloy, where the parts may experience thermal fatigue if not properly cooled during engine operation. It should be noted that the apparatus and method for controlling temperature in turbine parts may apply to cooling of turbine buckets, as shown in
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
