Patent Application
20150275675
The subject matter disclosed herein relates to the art of turbomachines and, more particularly, to a bucket airfoil for a turbomachine.
Turbomachines include a compressor portion linked to a turbine portion through a common compressor/turbine shaft and a combustor assembly. An inlet airflow is passed through an air intake toward the compressor portion. In the compressor portion, the inlet airflow is compressed through a number of sequential stages toward the combustor assembly. In the combustor assembly, the compressed airflow mixes with a fuel to form a combustible mixture. The combustible mixture is combusted in the combustor assembly to form hot gases. The hot gases are guided along a hot gas path of the turbine portion through a transition piece. The hot gases expand along a hot gas path through a number of turbine stages acting upon turbine bucket airfoils mounted on wheels to create work that is output, for example, to power a generator. In some cases, last stage bucket airfoils are provided with a part span shroud to provide mechanical damping.
According to an aspect of an exemplary embodiment, a turbomachine bucket airfoil includes a root end, a tip end spaced from the root end, and an airfoil surface extending between the root end and the tip end. The airfoil surface includes an upstream edge, a downstream edge, a pressure side and a suction side defining a natural bucket profile. The airfoil surface includes a blade span zone defining a part span shroud zone. A first part span shroud projects outwardly of the pressure side in the part span shroud zone, and a second part span shroud projects outwardly of the suction side in the part span shroud zone. The turbomachine bucket airfoil includes an interruption of the natural bucket profile in the part span shroud zone.
According to another aspect of an exemplary embodiment, a turbomachine includes a compressor portion, a turbine portion operatively connected to the compressor portion, and a combustor assembly fluidically connected to the compressor portion and the turbine portion. A turbomachine bucket airfoil is arranged in one of the compressor portion and the turbine portion. The turbomachine bucket airfoil including a root end, a tip end spaced from the root end defining a blade span zone, and an airfoil surface extending between the root end and the tip end. The airfoil surface includes an upstream edge, a downstream edge, a pressure side and a suction side defining a natural bucket profile. The airfoil surface includes a blade span zone defining a part span shroud zone. A first part span shroud projects outwardly of the pressure side in the part span shroud zone. A second part span shroud projects outwardly of the suction side in the part span shroud zone. The turbomachine bucket airfoil includes an interruption of the natural bucket profile in the part span shroud zone.
According to yet another aspect of an exemplary embodiment, a turbomachine system includes a compressor portion, an air inlet system fluidically connected to the compressor portion, a turbine portion operatively connected to the compressor portion, a combustor assembly fluidically connected to the compressor portion and the turbine portion, and a driven component operatively connected to one of the compressor portion and the turbine portion. A turbomachine bucket airfoil is arranged in one of the compressor portion and the turbine portion. The turbomachine bucket airfoil includes a root end, a tip end spaced from the root end, and an airfoil surface extending between the root end and the tip end. The airfoil surface includes an upstream edge, a downstream edge, a pressure side and a suction side defining a natural bucket profile. The airfoil surface includes a blade span zone defining a part span shroud zone. A first part span shroud projects outwardly of the pressure side in the part span shroud zone, and a second part span shroud projects outwardly of the suction side in the part span shroud zone. The turbomachine bucket airfoil includes an interruption of the natural bucket profile in the part span shroud zone.
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.
A turbomachine system, in accordance with an exemplary embodiment, is indicated generally at 2, in
Air enters air inlet system 18 and flows to compressor portion 6. The air is compressed and passed to combustor assembly 12. A portion of the air is passed into turbine portion 8 for cooling. In combustor assembly 12 the air is mixed with a fuel and or dilluents to form a combustible mixture. The combustible mixture is combusted forming hot gases that pass from combustor assembly 12 to turbine portion 8 via a transition piece (not shown). The hot gases expand through turbine portion 8 at which time buckets 30 convert thermal energy into mechanical energy that drives driven component 20. The hot gases pass through last stage buckets 33 and toward an exhaust system (also not shown).
As best shown in
Airfoil surface 50 also includes a centerline 70 that extends between upstream edge 59 and downstream edge 60 at a position that is equidistant from root end 44 and tip end 46. Airfoil surface 50 is also shown to include a blade span zone 73 that represents a portion of blade span 47. Blade span zone 73 extends from a position at about 25-30% of blade span 47 to about 90-95% of blade span 47. A first part span shroud 90 is mounted to, and projects outwardly of, pressure side 56. A second part span shroud 92 is mounted to, and projects outwardly of, suction side 54. First and second part span shrouds 90 and 92 join with part span shrouds on adjacent buckets to provide mechanical damping for last stage buckets 33. First and second part span shrouds may be mounted to airfoil surface 50 at centerline 70, radially inwardly of centerline 70, or radially outwardly of centerline 70 depending upon desired damping and aerodynamic performance.
In accordance with an exemplary embodiment, first part span shroud 90 and second part span shroud 92 are mounted to airfoil surface 50 in a part span shroud zone 100. Part span shroud zone 100 includes a first portion 104 that extends radially inwardly of centerline 70 toward root end 44, and a second portion 106 that extends radially outwardly of centerline 70 toward tip end 46. In accordance with an aspect of an exemplary embodiment, first portion 104 extends up to 25% of blade span zone 73 radially inwardly of centerline 70 toward root end 44, and second portion 106 extends up to 25% of blade span zone 73 radially outwardly of centerline 70 towards tip end 46. In accordance with another aspect of an exemplary embodiment, first portion 104 extends up to 15% of blade span zone 73 radially inwardly of centerline 70 toward root end 44, and second portion 106 extends up to 15% of blade span zone 73 radially outwardly of centerline 70 towards tip end 46. In accordance with still another aspect of an exemplary embodiment, first portion 104 extends up to 10% of blade span zone 73 radially inwardly of centerline 70 toward root end 44, and second portion 106 extends up to 10% of blade span zone 73 radially outwardly of centerline 70 towards tip end 46. In accordance with another aspect of an exemplary embodiment, airfoil surface 50 includes a first edge interruption 116 and a second edge interruption 118. First edge interruption 116 is formed in upstream edge 59 within part span shroud zone 100 and second edge interruption 118 is formed in downstream edge 60 within part span shroud zone 100. At this point it should be understood that the term “interruption” describes a deliberate, engineered deviation of natural bucket edge profile 63 that exists only in part span shroud zone 100.
In accordance with an aspect of the exemplary embodiment, first and second interruptions 116 and 118 constitute a change in chord length of airfoil surface 50 in part span shroud zone 100. In the exemplary embodiment shown, the change in chord length constitutes an increase in chord length of airfoil surface 50 in part span shroud zone 100. Of course, it should be understood that the change in chord length may be a reduction in chord length or a reduction in one edge and an increase in an opposing edge which may result in no actual net change in length while still achieving the desired result discussed below. First and second edge interruptions 116 and 118 create a change in Zweifel loading coefficient of airfoil surface 50 in part span shroud zone 100. Specifically, first and second edge interruptions 116 and 118 are designed to establish an incompressible Zweifel loading coefficient or number of between about 0.5 and about 0.8 in part span shroud zone 100 in order to reduce efficiency losses in part span shroud zone 100, as shown in
In accordance with another aspect of an exemplary embodiment illustrated in
At this point it should be understood that the exemplary embodiments describe a turbomachine bucket having specific, engineered interruptions in the natural bucket profile designed to achieve a desired Zweifel loading coefficient range at a particular location. The particular Zweifel loading coefficient range reduces a peak Mach number experienced by the bucket in the particular location. By reducing the peak Mach number, enhances bucket loading characteristics leading to an increase in bucket performance or, conversely, a decrease in efficiency losses at the part span shroud zone. It should also be understood that while shown in both the upstream and downstream edges, an interruption may be formed in only one or the other edges. Also, while described as being arranged in both the pressure and suction sides of the bucket, the interruption may be arranged in one or the other of the sides. Additionally, while shown and described in connection with buckets arranged in a final/last turbine stage, exemplary embodiments may be employed in stages arranged upstream of the last stage.
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.
