U.S. patent application number 12/472590 was filed with the patent office on 2010-12-02 for system and method to reduce acoustic signature using profiled stage design.
This patent application is currently assigned to DRESSER-RAND COMPANY. Invention is credited to Stephen S. Rashid, Joseph A. Tecza.
Application Number | 20100303604 12/472590 |
Document ID | / |
Family ID | 42227941 |
Filed Date | 2010-12-02 |
United States Patent
Application |
20100303604 |
Kind Code |
A1 |
Tecza; Joseph A. ; et
al. |
December 2, 2010 |
SYSTEM AND METHOD TO REDUCE ACOUSTIC SIGNATURE USING PROFILED STAGE
DESIGN
Abstract
To reduce noise and thereby increase turbine efficiency, the end
walls and airfoils of a turbine are designed to reduce or eliminate
radial pressure gradients on rotor blades and their incipient
secondary flow vortices which may noisily excite downstream blade
and vane rows. Instead of generating inefficient noise, the fluid
energy may be properly directed into the shaft as efficient
work.
Inventors: |
Tecza; Joseph A.; (Scio,
NY) ; Rashid; Stephen S.; (Wellsville, NY) |
Correspondence
Address: |
Edmonds Nolte, PC
16815 ROYAL CREST DRIVE, SUITE 130
HOUSTON
TX
77058
US
|
Assignee: |
DRESSER-RAND COMPANY
Olean
NY
|
Family ID: |
42227941 |
Appl. No.: |
12/472590 |
Filed: |
May 27, 2009 |
Current U.S.
Class: |
415/1 ; 415/119;
415/208.2 |
Current CPC
Class: |
F02C 7/045 20130101;
F02K 1/825 20130101; F01D 5/143 20130101 |
Class at
Publication: |
415/1 ;
415/208.2; 415/119 |
International
Class: |
F01D 9/04 20060101
F01D009/04 |
Claims
1. A turbine, comprising: at least one set of rotor blades mounted
radially symmetrically about a rotating shaft, wherein each rotor
blade has a hub and a tip; and at least one stator axially-spaced
from the at least one set of rotor blades and mounted radially
symmetrically about the rotating shaft, wherein the at least one
stator defines a plurality of radially-spaced vanes having inner
and outer end walls that define end wall passages, wherein the end
wall passages have a profile shaped to direct a working fluid to a
plane substantially tangent to the inner and outer end walls.
2. The turbine of claim 1, wherein the profile of the end wall
passages is configured to substantially eliminate the radial
pressure gradient incident between the hub and the tip of each
rotor blade, whereby the resultant acoustic signature of the
turbine is attenuated.
3. The turbine of claim 1, wherein the turbine is a multiple-stage
steam turbine.
4. The turbine of claim 1, wherein each of the radially-spaced
vanes have a convex surface and a concave surface with the convex
surface of one vane and the concave surface of an adjacent vane
defining the end wall passages.
5. The turbine of claim 4, wherein the convex and concave surfaces
are configured to cause the working fluid passing through the end
wall passages to follow a path defined by a mean of the adjacent
convex and concave surfaces.
6. The turbine of claim 1, wherein the inner and outer end walls
are configured to make the working fluid pressure at the hub
substantially equal to the working fluid pressure at the tip.
7. The turbine of claim 1, wherein the vanes are configured to
direct fluid passing through the end wall passages
circumferentially about and radially-spaced from a center line of
the turbine.
8. A stator for a turbine, comprising, an inlet and an outlet,
wherein the outlet is adjacent to at least one rotor blade having a
hub and a tip; and a plurality of inner and outer end walls
extending from the inlet to the outlet and defining a plurality of
end wall passages having inner and outer radial limits, wherein the
end wall passages have a profile configured to direct a working
fluid to a plane substantially tangent to the inner and outer
radial limits, wherein the plurality of inner and outer end walls
are configured to substantially eliminate the radial pressure
gradients incident between the hub and the tip of the at least one
rotor blade, thereby attenuating resultant acoustic signature.
9. The stator of claim 8, wherein, taken along an axial
cross-sectional view, the tip of the at least one rotor blade is
substantially tangent to the outer radial limit and the hub of the
at least one rotor is substantially tangent to the inner radial
limit.
10. The stator of claim 8, wherein the profile is configured to
direct fluid passing through the end wall passages
circumferentially about and radially-spaced from a center line of
the turbine.
11. A method of reducing turbine acoustic signature, comprising:
introducing a working fluid into a turbine having at least one
stator adjacent to and axially-spaced from at least one rotor
blade, wherein the stator comprises a plurality of radially-spaced
vanes, each vane having an inlet and an outlet and defining a
profile of an end wall passage including an inner and outer end
wall; receiving the working fluid through the inlet of the end wall
passage; channeling the working fluid through the profile of the
end wall passage; and directing the working fluid out the outlet of
the vane and substantially tangent to the inner and outer end
walls, thereby substantially decreasing the radial pressure
gradient incident between a hub and a tip of the at least one rotor
blade, and thereby attenuating resultant acoustic signature.
12. The method of claim 11, wherein the turbine is a multiple-stage
turbine and the working fluid is steam.
13. The method of claim 11, wherein each of the radially-spaced
vanes have a convex surface and a concave surface with the convex
surface of one vane and the concave surface of an adjacent vane
defining the end wall passages
14. The method of claim 11, wherein, taken along an axial
cross-sectional view, the tip of the at least one rotor blade is
substantially tangent to the outer end wall of the end wall passage
and the hub of the at least one rotor blade is substantially
tangent to the inner end wall of the end wall passage.
15. The method of claim 11, wherein each of the radially-spaced
vanes have a convex surface and a concave surface with the convex
surface of one vane and the concave surface of an adjacent vane
defining the end wall passages.
16. The method of claim 15, wherein the convex and concave surfaces
are configured to cause the working fluid passing through the end
wall passages to follow a path defined by the mean of the adjacent
convex and concave surfaces.
17. The method of claim 11, wherein the convex and concave surfaces
are configured to cause the working fluid passing through the end
wall passages to follow a path defined by the concave surface.
18. The method of claim 11, wherein the convex and concave surfaces
are configured to cause the working fluid passing through the end
wall passages to follow a path defined by the convex surface.
19. The method of claim 11, wherein the working fluid one of air,
products of combustion, or a process fluid such as carbon dioxide.
Description
BACKGROUND
[0001] When the radial pressure gradient in the fluid stream of a
turbine is minimized or eliminated, turbine stage efficiency can be
significantly improved. Typical turbine inefficiencies may include
noise production from several fluid dynamic sources, including wake
cutting, high velocity fluid, and turbulent flow fields, including
secondary flow vortices. The noise generally results from
reflecting and turbulent wave fields incident upon the several
stationary and moving blades downstream from a blade set that
receives irregular pressure differentials and converts them into
secondary flow vortices. As explanation, when a pressure gradient
incident on a rotating blade set is intense enough, transient or
sustained separation of fluid flow may occur in the vicinity of the
trailing edges of the blades. This separation of fluid flow can
result in secondary flow vortices directed downstream at stationary
and moving blades, thus producing high-intensity noise instead of
directing the fluid energy into the output shaft for power
generation.
[0002] What is needed, therefore, is a system designed to reduce
radial pressure gradients incident upon rotating blades and thereby
direct the fluid energy into the output shaft instead of into the
creation of noise.
SUMMARY
[0003] Embodiments of the disclosure may provide a turbine having a
working fluid. The turbine may include at least one set of rotor
blades mounted radially symmetrically about a rotating shaft,
wherein each rotor blade has a hub and a tip, and at least one
stator axially-spaced from the at least one set of rotor blades and
mounted radially symmetrically about the rotating shaft, wherein
the at least one stator defines a plurality of radially-spaced
vanes having inner and outer end walls that define end wall
passages, wherein the end wall passages have a profile shaped to
direct a working fluid to a plane substantially tangent to the
inner and outer end walls.
[0004] Embodiments of the disclosure may further provide a stator
for a turbine. The stator may include an inlet and an outlet,
wherein the outlet is adjacent to at least one rotor blade having a
hub and a tip, and a plurality of inner and outer end walls
extending from the inlet to the outlet and defining a plurality of
end wall passages having inner and outer radial limits, wherein the
end wall passages have a profile configured to direct a working
fluid to a plane substantially tangent to the inner and outer
radial limits, wherein the plurality of inner and outer end walls
are configured to substantially eliminate the radial pressure
gradients incident between the hub and the tip of the at least one
rotor blade, thereby attenuating the resultant acoustic
signature.
[0005] Embodiments of the disclosure may further provide a method
of reducing turbine acoustic signature. The method may include
introducing a working fluid into a turbine having at least one
stator adjacent to and axially-spaced from at least one rotor
blade, wherein the stator comprises a plurality of radially-spaced
vanes, each vane having an inlet and an outlet and defining a
profile of an end wall passage including an inner and outer end
wall, receiving the working fluid through the inlet of the end wall
passage, channeling the working fluid through the profile of the
end wall passage, and directing the working fluid out the outlet of
the vane and substantially tangent to the inner and outer end
walls, thereby substantially decreasing the radial pressure
gradient incident between a hub and a tip of the at least one rotor
blade, and thereby attenuating the resultant acoustic
signature.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] 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.
[0007] FIG. 1 illustrates a partial diagrammatic, longitudinal
sectional view of an exemplary turbine according to one or more
aspects of the present disclosure.
[0008] FIG. 2 illustrates a fragmentary view of a pair of turbine
stages according to one aspect of the present disclosure.
[0009] FIG. 3 illustrates an axial depiction of the defining lines
for the profiles of the end wall sections, according to one aspect
of the present disclosure.
[0010] FIG. 4 illustrates a radial view of the convex and concave
surfaces of an exemplary set of stator vanes.
DETAILED DESCRIPTION
[0011] 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.
[0012] 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.
[0013] According to an exemplary embodiment of the present
disclosure, to reduce noise and thereby increase turbine
efficiency, the end walls and airfoils of a turbine may be designed
to reduce or eliminate radial pressure gradients and their
potential secondary flow vortices which may excite downstream blade
and vane rows into the production of noise. In particular, by
channeling reflecting and turbulent flow waves into a
continuously-flowing shape through the end walls and airfoils, the
fluid flowpath of the working fluid becomes generally linear in the
desired direction of flow. Consequently, with a generally linear
flowpath, the working fluid may be channeled directly into the
succeeding rotor row with a minimal hub to tip velocity
differential. Thus, the fluid energy may be directed into the shaft
to create work, rather than into the generation of inefficient
noise.
[0014] FIG. 1 illustrates an exemplary turbine 100 according to at
least one aspect of the present disclosure. In an exemplary
embodiment, the turbine 100 may be a multiple-stage steam turbine.
The turbine 100 may be composed of a plurality of stages wherein a
first stage 101 may include a set of rotor blades 102,
axially-spaced from and interleaved with a set of stator vanes 104.
The first stage 101 may be followed by any number of succeeding
stages, The rotor blades 102 may be configured as a circular moving
blade set, while the stator vanes 104 may be configured as a
circular or semi-circular stationary blade set, each blade set
having blades mounted symmetrically radial about a rotating shaft
106. In an exemplary embodiment, the first stage 101 may be an
impulse turbine stage, but may also be a reaction turbine stage.
The present disclosure, however, may be less effective in a
reaction machine since there is no real danger of the hub pressure
at the rotor inlet dropping below the pressure at the rotor
exit.
[0015] The rotor blades 102 may each be provided with a root 108
configured to couple the blades 102 to the rotating shaft 106 which
rotates around a central axis of the turbine 100. The stator vanes
104 may be in a fixed arrangement, typically mounted
circumferentially to the outer casing 110 of the turbine 100 and
extending inwardly therefrom.
[0016] In exemplary operation, a fluid, such as steam, air,
products of combustion, or a process fluid such as CO.sub.2 or
other fluid may be used as the working fluid. In an embodiment
using steam, the fluid may include injected into the turbine 100
and follow a plurality of channels or passageways, depicted by the
arrows 112, thus channeling itself through the various stages of
rotor blades 102 and stator vanes 104. As the steam passes through
the various stages of the turbine 100, the stator vanes 104 may be
configured to direct the fluid into contact with the subsequent set
of rotor blades 102, thereby causing the shaft 106 to rotate and
produce work.
[0017] However, if the fluid flow directed at the rotor blades 102
is composed of a heightened hub-to-tip pressure gradient, the rotor
blades 102 may become agitated and create noise, or they may
produce secondary flow vortices, potentially exciting downstream
blades 102 or vanes 104 whose vibrations will also create noise.
According to one aspect of the present disclosure, to reduce or
eliminate the production of noise, the passageways 112 of the vanes
104 may be profiled in a manner that directs the fluid flow in a
generally uniform pressure toward the rotor blades 102.
[0018] Referring now to FIG. 2, illustrated is an exemplary
embodiment of a pair of turbine stages 201a, 201b according to at
least one aspect of the present disclosure. The stages 201a, 201b
may each consist of a plurality of stator vanes 104 followed by a
plurality rotating blades 102, wherein the arrow 112 denotes the
direction of fluid flow through the particular stages 201 a, 201 b.
Although not fully illustrated, each stage 201 a, 201 b may consist
of a body of revolution about the rotational axis of the turbine
100.
[0019] In particular, FIG. 2 illustrates a pair of stator vanes 104
and a pair of rotating blades 102, wherein each rotating blade 102
may include a tip 212 and a hub 214. As illustrated, each stator
vane 104 may define an end wall passage 202 extending from an inlet
203a to an outlet 203b and configured to direct fluid flow into the
subsequent set of rotating blades 102. The end wall passage 202 may
include an outer section 204 and an inner section 206, wherein each
section 204, 206 may incorporate a given profile 208, 210,
respectively.
[0020] When fluid flows in the end wall passage 202 the flow is
considered "attached" if it flows continuously in one direction in
the space defined between the outer section 204 and the inner
section 206. Although the velocity profile of the flow will
generally proceed in an equivalent direction, it may change
depending on whether the flow is laminar or turbulent. In typical
operations, there will be a small boundary layer of slower flow
adjacent to each profile 208, 210, but the flow in this boundary
layer will be in the same direction as the flow in the rest of the
space. If the boundary layer gets too thick that the flow within it
reverses, a phenomenon called "hub separation" may occur,
potentially creating eddy currents.
[0021] In turbines, the flow being accelerated through the end wall
passage 202 generally flows in a direction tangent to the
circumference at the point in the end wall passage 202 where it
turns from the axial direction and is thereby accelerated. The flow
continues "straight" in space, but the boundary profiles 208, 210
both curve inward or downward, tending to bunch up the flow at the
outer profile 208 (locally curving toward it) and flow away from
the inner profile 210 (locally curving away from it). As can be
appreciated, this results in an uneven velocity flow distribution,
and is the type of behavior that the present disclosure is designed
to prevent or remedy.
[0022] During turbine 100 operation, a pressure gradient incident
across the tip 212 and hub 214 of a rotor blade 102 may also
generate "hub separation." For example, the centrifugal
acceleration of the working fluid in a turbine 100 generally
forces, or "stirs," the fluid away from the hub 214 and creates a
substantially higher pressure near the tip 212 of the rotating
blade 102 than at the hub 214. However, suppressing the pressure at
the hub 214 may potentially cause a negative reaction, typically in
the form of a significant potential pressure rise across the hub
214 sections of the blade 102. Blade 102 reaction may be
characterized by the pressure drop across the blade 102 row divided
by the pressure drop across the end wall passage 202. Since this
pressure rise at the hub 214 cannot generally be supported, the hub
214 sections of the blade 102 may "separate," resulting in a radial
pressure gradient flowing out of the end wall passage 202.
[0023] The result of this pressure gradient on the rotating blade
102 is that secondary flow vortices may potentially develop and
excite or vibrate downstream objects, such as rotor blade 102 and
stator vane 104 rows. The excitation or vibration of rotor blade
102 and/or stator vane 104 rows may produce high-intensity noise
representing fluid energy that is inefficiently wasted as noise
production instead of being directed into the output shaft 106 for
generation of power.
[0024] According to one exemplary embodiment of the present
disclosure, the profiles 208, 210 may be configured to provide a
constant and equalized pressure gradient across the rotating blades
102, thereby reducing or eliminating secondary flow vortices.
Particularly, the specific profiles 208, 210 of the end wall
passages 202 may be configured to mimic the tangential fluid flow
exiting the stator vane 104 and make the exiting pressure
substantially uniform as it extends from the hub 214 to the tip 212
of the subsequently located rotating blade 102. Uniform pressures
incident on the rotating blades 102 minimize and/or prevent hub 214
"separation" that would normally result in the production of
downstream noise, as described above.
[0025] The curvature, or shape, of the end wall 202 profiles 208,
210 may be derived via axial and radial projections, upstream from
the rotating blades 102, from a pair of lines of revolution about a
centerline of the turbine 100. Referring to FIG. 3 (in combination
with FIG. 2), illustrated is a depiction of the lines of revolution
302, 304 for the outer section 204 and the inner section 206,
respectively, of the end wall 202. As shown, the lines of
revolution 302, 304 may be drawn from the centerline 306 of the
turbine 100. In the axial direction, the outer end wall section 204
may have its profile defined by an extent, tangent to the tip 212
of the rotating blade 102, obtaining between points "a" and "b".
Also, in the axial direction, the inner end wall section 206 has
its profile defined by an extent, tangent to the hub 214 of the
rotating blade 102, obtaining between points "c" and "d".
[0026] FIG. 4 shows a radial view of an exemplary stator vane 104
body, where the convex and concave surfaces 402, 404, respectively,
are illustrated. Inscribed between the surfaces 402,404 is a mean
line 406 which radially extends between points "e" and "f". In an
exemplary embodiment of the disclosure, the mean line 406 may be
the axially-defining component for the profiles 208, 210 and
configured to allow the profiles 208, 210 to mimic tangential fluid
flow. In alternative exemplary embodiments, in lieu of the mean
between the surfaces 402, 404, the axially-defining component for
the profiles 208, 210 can comport to either the convex surface 402
or the concave surface 404, or any other representative flow line
derived through geometric or fluid dynamic calculation.
[0027] According to the present disclosure, with a substantially
tangential fluid flow exiting the end wall 202, the incident
pressures on the rotating blades 102 from the hub 214 to the tip
212 may be substantially uniform, and thus reducing or completely
eliminating any secondary flow vortices. Particularly, using a
profiled end wall 202 may direct a working fluid onto the rotating
blades 102 such that the pressure at the hub 214 is equal to the
pressure at the tip 212. By reducing the hub 214 to tip 212
pressure gradient incident on the rotating blades 102, as explained
above, a reduction of downstream turbine 100 acoustic signature may
result, thereby increasing turbine 100 efficiency.
[0028] 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.
* * * * *