Patent Application
20140037439
The subject matter disclosed herein relates to turbomachines. More particularly, aspects of the disclosure relate to turbomachine exhaust diffusers.
Turbomachine (e.g., steam turbine) designs generally include several sections: a high pressure (HP) section, an intermediate pressure (IP) section and a low pressure (LP) section. The LP section includes an inlet, a plurality of stages, and an exhaust diffuser (or, exhaust hood) opposite the inlet. The diffuser is typically used to recover the static pressure in the steam exiting the last stage bucket.
Conventionally, the diffuser is located axially downstream of the last stage bucket in the LP section, and provides a linear flow path for the steam exiting the LP section. The conventional diffuser inherently has spatial and geometric constraints which make it difficult to recover a desired amount of static pressure from the exiting steam. This conventional diffuser configuration can cause inefficiencies in the steam turbine system.
Various embodiments include a turbomachine exhaust diffuser. In some embodiments, the turbomachine diffuser includes an inlet, an outlet opposing the inlet along a primary axis of the turbomachine diffuser, and a diffuser region between the inlet and the outlet. The diffuser region can include: a radially outer wall and a radially inner wall opposing the radially outer wall. The radially inner wall can include: a first section including a substantially uniform slope, and a second section continuous with the first section, the second section having a non-uniform slope.
A first aspect of the invention includes a turbomachine diffuser including: an inlet; an outlet opposing the inlet along a primary axis of the turbomachine diffuser; and a diffuser region between the inlet and the outlet, the diffuser region including: a radially outer wall; and a radially inner wall opposing the radially outer wall, the radially inner wall having: a first section including a substantially uniform slope; and a second section continuous with the first section, the second section having a non-uniform slope.
A second aspect of the invention includes a turbomachine system having: a turbomachine having a low pressure (LP) section; and a turbomachine diffuser fluidly connected with an exhaust of the LP section, the diffuser including: an inlet; an outlet opposing the inlet along a primary axis of the turbomachine diffuser; and a diffuser region between the inlet and the outlet, the diffuser region including: a radially outer wall; and a radially inner wall opposing the radially outer wall, the radially inner wall having: a first section including a substantially uniform slope; and a second section continuous with the first section, the second section having a non-uniform slope.
A third aspect of the invention includes a power plant system having: a dynamoelectric machine; and a turbomachine system operably connected with the dynamoelectric machine, the turbomachine system including: a turbomachine having a low pressure (LP) section; and a turbomachine diffuser fluidly connected with an exhaust of the LP section, the diffuser including: an inlet; an outlet opposing the inlet along a primary axis of the turbomachine diffuser; and a diffuser region between the inlet and the outlet, the diffuser region including: a radially outer wall; and a radially inner wall opposing the radially outer wall, the radially inner wall having: a first section including a substantially uniform slope; and a second section continuous with the first section, the second section having a non-uniform slope.
These and other features of this invention will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings that depict various embodiments of the invention, in which:
It is noted that the drawings of the invention are not necessarily to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements between the drawings.
As noted, the subject matter disclosed herein relates to turbo-machines. More particularly, aspects of the disclosure relate to turbo-machine exhaust diffusers.
As described herein, steam turbine designs generally include several sections: a high pressure (HP) section, an intermediate pressure (IP) section and a low pressure (LP) section. The LP section includes an inlet, a plurality of stages, and an exhaust diffuser (or, exhaust hood) opposite the inlet. The diffuser is typically used to recover the static pressure in the steam exiting the last stage bucket. More particularly, as a working fluid such as steam flows from an area of relatively smaller volume to an area of relatively greater volume, the kinetic energy of that fluid will decrease. This decrease in kinetic energy causes an increase in static pressure. Generally speaking, the more effective the diffuser is at reducing the kinetic energy of the fluid, the greater the diffuser is said to perform.
Conventionally, the diffuser is located axially downstream of the last stage bucket in the LP section, and provides a linear flow path for the steam exiting the LP section. The conventional diffuser inherently has spatial and geometric constraints which make it difficult to recover a desired amount of static pressure from the exiting steam. This conventional diffuser configuration can cause inefficiencies in the steam turbine system.
Two conventional diffuser configurations are employed in order to increase recovery of back pressure in steam traversing the diffuser. These approaches include: 1) The angled outer wall configuration; and 2) The “adjustable” inner wall configuration.
In the first scenario (angled outer wall), the radially outer wall of the diffuser is designed such that its angle is relatively steep relative to the axis of the turbine. This provides for a greater internal volume in the diffuser, which allows for increased diffusion and consequently greater static pressure recovery. While this angled outer wall configuration can increase the static pressure recovery relative to a flat, planar outer wall configuration, the outer wall angle is limited by the physical dimensions of the diffuser.
In the second scenario (adjustable inner wall), the inner wall is connected to an adjustment apparatus which can modify a position of the inner wall to effectively expand the volume within the diffuser for improved static pressure recovery. However, this adjustment apparatus can be expensive, and also consumes an undesirably large amount of space within the diffuser.
In contrast to these conventional approaches, various embodiments of the invention are directed toward a turbomachine diffuser with an inner wall that includes a recess (or, divot). In particular embodiments of the invention, a turbomachine diffuser is disclosed including: an inlet; an outlet opposing the inlet along a primary axis of the turbomachine diffuser; and a diffuser region between the inlet and the outlet, the diffuser region including: a radially outer wall; and a radially inner wall opposing the radially outer wall, the radially inner wall having: a first section including a substantially uniform slope; and a second section continuous with the first section, the second section having a non-uniform slope. It is understood that in various alternative embodiments of the invention, the second section having the non-uniform slope can extend substantially an entire length of the diffuser 4.
The diffuser 4 can further include a diffuser region 14 between the inlet 6 and the outlet 12. The diffuser region 14 can include a substantially cavernous area where working fluid (e.g., steam) entering the diffuser 4 from the inlet 6 can expand (diffuse) before leaving the diffuser 4 at its outlet 12. The diffuser 4 in this case is an axial diffuser, in that the diffusion region 14 generally expands in cross-sectional area (and consequently, volume) from the axial inlet 6 to the axial outlet 12.
As shown in
More particularly, the second section 22 can include: a first sub-section 30 with a positive slope relative to the primary axis (A) of the turbomachine system 2, and a second subsection 32 connected with the first subsection 30, where the second subsection 32 has a negative slope relative to the primary axis (A) of the turbomachine system 2. In some embodiments, the second subsection 32 can be welded, brazed or otherwise connected with the first subsection 30 after formation of each of the first and second subsection 30, 32, respectively. However, in other embodiments, the first subsection 30 and the second subsection 32 can be formed concurrently.
In various embodiments of the invention, the second section 22 of the radially inner wall 18 is located proximate the inlet 6. That is, the second section 22 (and particularly, the recess 24) is located within a first axial half (or in some cases, a first axial third) of the diffuser 4 as measured from the inlet 6. In particular embodiments, the second subsection 32 is located proximate (adjacent or near) the inlet 6. In comparison with conventional diffusers, where recess 24 is located proximate the inlet 6 as in the various embodiments of the invention, the diffuser 4 is able to improve diffusion of the working fluid because of its larger volume proximate the LSB 9 (and the inlet 6). This enhanced diffusion causes a greater increase in static pressure recovery in the diffuser 4 according to various embodiments of the invention, when compared with conventional approaches.
It is understood, however, that in various alternative embodiments, the first subsection 30 can extend a substantial length of the diffuser 4, occupying the space where first section 20 is depicted in
As shown herein, the first subsection 30 and the second subsection 32 can meet at an apex 34 (or, junction) (indicated by dashed circle for clarity of illustration) at the radial bottom of the radially inner wall 18. In various embodiments of the invention, the first subsection 30 and the second subsection 32 are separated an angle (β) of approximately 150 degrees to approximately 179 degrees. In some particular embodiments, (β) can span between approximately 160-175 degrees, and in even more particular embodiments, (β) can span between approximately 165-170 degrees.
It is understood that the diffuser 4 shown and described according to various embodiments of the invention is able to realize increased efficiency over the conventional diffusers known in the art. This diffuser 4 can realize an increase in static pressure recovery when compared with the conventional diffusers, and can consequently increase the efficiency of a turbomachine system (e.g., turbomachine system 2) in which the diffuser 4 operates.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It is further understood that the terms “front” and “back” are not intended to be limiting and are intended to be interchangeable where appropriate.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
