Patent Application
20110110763
The present invention relates to turbines, and more particularly to reducing turbine acoustic signature. In the exhaust end of a turbine, a nacelle is commonly braced with multiple pylons or struts. During turbine operation, bow waves may originate from these pylons or struts as fluid flow comes into contact with such pylons or struts. When these bow waves propagate upstream, they may back-pressure the rotor. Excitation of the rotor's blades by these bow waves generates noise.
Noise generation, which increases a turbine's acoustic signature, indicates an increase in aerodynamic losses caused by fluid energy that is not directed into the rotor assembly for power generation. Such aerodynamic losses contribute to turbine inefficiency.
Thus, there is a need for apparatus and methods for guiding non-uniform flow fields around downstream obstructions in order to reduce turbine acoustic signature and thereby increase turbine efficiency.
Embodiments of the disclosure may provide a turbine. The turbine may include a casing, at least one stage of rotor blades disposed in the casing, at least one stage of stator blades projecting inwardly from the casing and operatively associated with the rotor blades, and at least one fluid flow obstruction disposed downstream from the at least one stage of rotor blades. The turbine may further include an exhaust ring disposed downstream from the at least one stage of rotor blades and upstream from the at least one fluid flow obstruction, the exhaust ring including a plurality of non-uniform exhaust guide vanes that extend circumferentially around and project inwardly from the exhaust ring, the exhaust guide vanes configured to direct a fluid flow around the at least one fluid flow obstruction in a manner that suppresses formation of a bow wave at the fluid flow obstruction.
Embodiments of the disclosure may further provide an exhaust ring subject to a fluid flow from an upstream stage of turbine rotor blades. The exhaust ring may include a plurality of non-uniform exhaust guide vanes, the exhaust guide vanes having camber angles that are varied in a predetermined manner to cause a fluid flow traversing the exhaust guide vanes in a downstream direction to be diverted around at least one fluid flow obstruction disposed downstream of the exhaust ring in a manner that suppresses formation of a bow wave at the fluid flow obstruction.
Embodiments of the disclosure may further provide a method of reducing the acoustic signature of a turbomachine. The method may include identifying a fluid flow obstruction in an exhaust path of the turbomachine, providing a plurality of vanes upstream of the fluid flow obstruction, and adjusting a camber angle of a portion of the plurality of vanes, the camber angle directing a portion of the fluid flow around the at least one fluid flow obstruction in a manner that suppresses formation of a bow wave at the fluid flow obstruction.
The present disclosure is best understood from the following detailed description when read with the accompanying Figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure. However, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various Figures. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure.
Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Further, in the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.” All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope.
Referring to
The rotor assembly 104, having axis X-X, includes a plurality of roots 108, upon which a plurality of rotor blades 110, or airfoils, are mounted. The plurality of roots 108 and corresponding rotor blades 110 are axially spaced from, and adjacent to, the stator blades 106. The plurality of roots 108 and corresponding rotor blades 110 are positioned at equally spaced intervals. In other embodiments, the plurality of roots 108 and corresponding rotor blades 110 may be spaced at varying intervals. As illustrated, the stator blades 106 and the rotor blades 110 are positioned in an alternating interdigitated pattern, and the general direction of fluid flow through turbine 100 is shown by arrow A, i.e., from left to right. After passing through the stator blades 106 and rotor blades 110, the fluid enters an exhaust section 112 where it is exhausted in the direction of arrow B.
The exhaust section 112 includes an exhaust nacelle 114 that is mounted to the casing 102 in any appropriate manner. The nacelle 114 may be structurally supported against the resulting pressure and structural forces by at least one pylon 116, or strut. While only one pylon 116 is shown, in other embodiments, any number of pylons 116 may be used to provide a structural load bearing member for supporting the nacelle 114 in the exhaust region 112. A bearing housing 118 is located in the exhaust section 112, and is also supported by the at least one pylon 116. The at least one pylon 116 may be constructed with additional thickness in order to support the weight of the bearing housing 118 and the rotor assembly 104.
During exemplary operation of the turbine 100, a fluid is introduced at the left end of the turbine 100 and generates work as the fluid expands through the turbine stages in the direction of the arrow A. The fluid may include steam, air, products of combustion, or a process fluid, such as CO2, or other fluid. The stator vanes 106 act as fixed nozzles configured to orient the fluid flow into high speed jets that are directed into general contact with the subsequent set of rotor blades 110. The fluid velocity increases and is directed into the rotor blades 110, which receive and convert the fluid flow into useful work, such as rotating the rotor assembly 104.
The fluid flowing out of the rotor blades 110 is generally relatively uniform in character. However, bow waves may originate from downstream stationary objects, such as the pylons 116, when the fluid flow comes into contact with such downstream stationary objects. When these bow waves propagate upstream, they cause circumferential pressure variation behind the rotor blades 110. Such pressure variation excites the rotor assembly 104, and may result in turbine 100 noise. Noise and rotor assembly 104 excitation are examples of inefficiencies that increase the acoustic signature of the turbine 100, and represent fluid energy that is not directed into the rotor assembly 104 to produce useful work. A reduction in the unsteady-state differential pressures across stationary downstream objects, including the pylons 116, may effectively attenuate resultant turbine 100 noise generation, and thereby increase turbine 100 efficiency.
According to at least one aspect of the present disclosure, a system of stator matching, or pylon matching, may be implemented to direct fluid flow substantially around stationary objects that are located downstream from any row of rotor blades 110 in order to suppress the non-uniform pressure field caused by the stationary objects. In an exemplary embodiment, as explained below, fluid flow may be substantially directed around a pylon 116. This reduces the strength of the pressure fields incident thereupon and thereby attenuates the resultant acoustic signature of the turbine 100.
Referring to
As illustrated in
The vanes 204 include concave and convex opposite sides, and are cambered at diverse angles so as to substantially direct the fluid flow around the individual pylons 116. Each of the vanes 204 have substantially the same leading edge geometry. However, the vanes 204 vary in geometry along the trailing edge.
As illustrated in
The embodiment shown in
Still referring to
Directing the fluid flow around the pylons 116 suppresses the formation of bow waves at the pylons 116. If such bow waves were allowed to form, they could propagate upstream and cause back pressure on the rotor blades 110. Such back pressure may in turn cause excitation of the rotor blades 110. Thus, it may be appreciated that reducing the excitation of the rotor blades 110 by suppressing the formation of bow waves may reduce turbine 100 noise, and thereby increase the overall efficiency of the turbine 100.
In alternative exemplary embodiments of the present disclosure, the total number of non-uniform exhaust guide vanes 204 having non-uniform cambers disposed within the exhaust ring 202 may be reduced, and may instead be generally focused in an area closer to the downstream obstructions. For example, in an embodiment, the exhaust ring 202 includes a minimal number of vanes 204 disposed in a general area closer to a downstream obstruction, and the minimal number of vanes 204 are configured to direct the fluid flow around the downstream obstruction. Reducing the number of vanes 204 can advantageously decrease the turbine 100 weight, materials cost, and fabrication cost.
Referring now to
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Although the present disclosure has been described with respect to directing flow around pylons 116, embodiments of the present disclosure may be used to direct flow around other downstream stationary objects. In addition, there are potentially other geometries where embodiments of the present disclosure could be useful. For example, if the casing 102 is circumferentially non-uniform, embodiments of the present disclosure may be used to direct flow between opposing sides of an exhaust 112, induction, or extraction portion of the turbine 100. Additionally, to further minimize fluid flow obstruction, the pylons 116, or any downstream obstruction, may also be formed to be aerodynamically streamlined in a generally symmetrical tear drop shape that reduces pressure losses therefrom.
The foregoing has outlined features of several embodiments so that those skilled in the art may better understand the detailed description that follows. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.
