U.S. patent application number 16/079475 was filed with the patent office on 2019-02-14 for centrifugal compressor with leakage-free diffuser blades and method of assembling a centrifugal compressor.
The applicant listed for this patent is Nuovo Pignone Tecnologie Srl. Invention is credited to Daniele PANARA, Emanuele RIZZO.
Application Number | 20190048891 16/079475 |
Document ID | / |
Family ID | 56203834 |
Filed Date | 2019-02-14 |
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United States Patent
Application |
20190048891 |
Kind Code |
A1 |
PANARA; Daniele ; et
al. |
February 14, 2019 |
CENTRIFUGAL COMPRESSOR WITH LEAKAGE-FREE DIFFUSER BLADES AND METHOD
OF ASSEMBLING A CENTRIFUGAL COMPRESSOR
Abstract
A centrifugal compressor includes a rotor with a plurality of
impellers and a stator with at least a first diaphragm, a second
diaphragm, a diffuser, and a plurality of diffuser blades inside
the diffuser; each diffuser blade has a tip portion, a base portion
and an airfoil portion; and are located between the downstream
portion of the first diaphragm and the upstream portion of the
second diaphragm; the base portion of the diffuser blades is
integrated in or mounted to the upstream portion of the second
diaphragm, and the tip portion of the diffuser blades abuts against
the downstream portion of the first diaphragm; alternatively, the
base portion of the diffuser blades is integrated in or mounted to
the downstream portion of the first diaphragm, and the tip portion
of the diffuser blades abuts against the upstream portion of the
second diaphragm.
Inventors: |
PANARA; Daniele; (Florence,
IT) ; RIZZO; Emanuele; (Firenze, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nuovo Pignone Tecnologie Srl |
Florence |
|
IT |
|
|
Family ID: |
56203834 |
Appl. No.: |
16/079475 |
Filed: |
March 20, 2017 |
PCT Filed: |
March 20, 2017 |
PCT NO: |
PCT/EP2017/056499 |
371 Date: |
August 23, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 1/066 20130101;
F04D 29/624 20130101; F04D 29/462 20130101; F04D 17/122 20130101;
F04D 17/10 20130101; F04D 29/444 20130101 |
International
Class: |
F04D 29/44 20060101
F04D029/44; F04D 17/10 20060101 F04D017/10; F04D 29/62 20060101
F04D029/62 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 21, 2016 |
IT |
102016000029251 |
Claims
1. A centrifugal compressor for a fluid, comprising a rotor with a
plurality of impellers and a stator with at least a first
diaphragm, a second diaphragm downstream the first diaphragm, a
diffuser defined between a shroud side of a downstream portion of
the first diaphragm and a hub side of a upstream portion of the
second diaphragm, and a plurality of diffuser blades inside the
diffuser, each diffuser blade having a tip portion, a base portion
and an airfoil portion between the base portion and the tip
portion, wherein the diffuser blades are located between the
downstream portion of the first diaphragm and the upstream portion
of the second diaphragm, wherein the base portion of the diffuser
blades is integrated in or mounted directly or indirectly to the
upstream portion of the second diaphragm so to avoid fluid flow
between the base portion and the hub side of the upstream portion,
and the tip portion of the diffuser blades abuts against the
downstream portion of the first diaphragm so to avoid fluid flow
between the tip portion and the shroud side of the downstream
portion or wherein the base portion of the diffuser blades is
integrated in or mounted directly or indirectly to the downstream
portion of the first diaphragm so to avoid fluid flow between the
base portion and the shroud side of the downstream portion, and the
tip portion of the diffuser blades abuts against the upstream
portion of the second diaphragm so to avoid fluid flow between the
tip portion and the hub side of the upstream portion.
2. The centrifugal compressor of claim 1, wherein the tip portion
of each diffuser blade of the plurality is movable, resiliently
movable, with respect to the first diaphragm or the second
diaphragm whereto it is mounted.
3. The centrifugal compressor of claim 1, wherein each diffuser
blade of plurality comprises a first platform adjacent to the base
portion and a spring acting on the first platform.
4. The centrifugal compressor of claim 1, wherein each diffuser
blade of the plurality comprises a second platform and the spring
is located between the first platform and the second platform and
acts on them.
5. The centrifugal compressor of claim 1, wherein at least the base
portion or the airfoil portion or the tip portion of each diffuser
blade of the plurality is made of elastic material.
6. The centrifugal compressor of claim 1, wherein the base portion
and the airfoil portion and the tip portion of each diffuser blade
of the plurality is made of elastic material, the same elastic
material.
7. The centrifugal compressor of claim 1, wherein each diffuser
blade of the plurality comprises a snap mount for mounting it to
the first diaphragm or the second diaphragm.
8. A method of assembling a centrifugal compressor, wherein: a
plurality of half-diaphragms are bundled together; A) a half-casing
or half-counter-casing is lowered on the bundle; B) the plurality
of half-diaphragms are loosened inside said half-casing or
half-counter-casing; and C) the plurality of half-diaphragms are
fixed to the half-casing or half-counter-casing.
9. The method of claim 8, wherein: the half-casing or
half-counter-casing with half-diaphragms inside is turned upside
down; and D) a rotor of the centrifugal compressor is lowered on
the turned half-casing or half-counter-casing with half-diaphragms
inside.
10. The method of claim 9, wherein E) a plurality of
half-diaphragms are bundled together, F) a half-casing or
half-counter-casing is lowered on the bundle G) the plurality of
half-diaphragms are loosened inside the half-casing or
half-counter-casing, H) the plurality of half-diaphragms are fixed
to the half-casing or half-counter-casing, and I) the half-casing
or half-counter-casing with half-diaphragms inside is lowered on
the assembly.
11. The method of claim 8, wherein diffuser blades are located
between adjacent half-diaphragms and wherein the diffuser blades
are compressible.
12. The method of claim 11, wherein, one or more diffuser blades is
or are compressed during bundling.
13. The method of claim 11, wherein, one or more diffuser blades is
or are mounted to half-diaphragms.
Description
FIELD OF THE INVENTION
[0001] Embodiments of the subject matter disclosed herein
correspond to centrifugal compressors with leakage-free diffuser
blades and methods of assembling centrifugal compressors.
BACKGROUND OF THE INVENTION
[0002] Centrifugal compressors usually have one or more diffusers;
a diffuser is a (stationary) channel or multi-channel that receives
a flow of a working fluid when it exits a (rotary) impeller of a
compressor; a diffuser may comprise diffuser blades; a diffuser
blade is fixed to a diaphragm of the compressor by shrink fitting
or by friction fitting or by screwing or by welding or because it
is integral with the diaphragm.
[0003] At least in the field of Oil & Gas, it is common
practice to start assembling of a compressor by: [0004] providing a
half-casing or a half-counter-casing of the compressor, [0005]
lowering the half-diaphragms of the compressor, one by one, into
the half-casing or half-counter-casing and fixing them, one by one,
to it, [0006] lowering the rotor of the compressor on the
half-casing or half-counter-casing with half-diaphragm already
inside.
[0007] Due to such assembling method, when the half-diaphragms
comprise diffuser blades, there must be a clearance between the
tips of each diffuser blade and the surfaces of the diaphragms
facing the tips.
[0008] In fact, friction or interference between the diffuser
blades and the diaphragms should be avoided during assembling of
the compressor.
[0009] Furthermore, the lowering of the half-diaphragms should be
precise in order to avoid damages to the diffuser blades and/or the
diaphragms due to contact between the diffuser blades and the
diaphragms.
[0010] Such gaps between the tips of each diffuser blade and the
surfaces of the diaphragms facing the tips are disadvantageous as
they cause secondary effects that are related to the flow of
working fluid between the tips and such surfaces during operation
of the compressor.
[0011] Ideally, all the working fluid of the compressor should flow
around the diffuser blades guided by the airfoil portions of the
diffuser blades.
SUMMARY OF INVENTION
[0012] Therefore, there is a general need for improving
turbomachines and their assembling methods.
[0013] This need is particularly high for centrifugal compressors
such as those used in the field of "Oil & Gas", i.e. machines
used in plants for exploration, production, storage, refinement and
distribution of oil and/or gas.
[0014] First embodiments of the subject matter disclosed herein
relate to centrifugal compressors.
[0015] According to such first embodiments, the centrifugal
compressor comprises a rotor with a plurality of impellers and a
stator with at least a first diaphragm, a second diaphragm
downstream said first diaphragm, a diffuser defined between a
shroud side of a downstream portion of said first diaphragm and a
hub side of a upstream portion of said second diaphragm, and a
plurality of diffuser blades inside said diffuser; each diffuser
blade has a tip portion, a base portion and an airfoil portion
between the base portion and the tip portion; said diffuser blades
are located between said downstream portion of said first diaphragm
and said upstream portion of said second diaphragm; the base
portion of said diffuser blades is integrated in or mounted
directly or indirectly to said upstream portion of said second
diaphragm so to avoid fluid flow between said base portion and said
hub side of said upstream portion, and the tip portion of said
diffuser blades abuts against said downstream portion of said first
diaphragm so to avoid fluid flow between said tip portion and said
shroud side of said downstream portion; alternatively, the base
portion of said diffuser blades is integrated in or mounted
directly or indirectly to said downstream portion of said first
diaphragm so to avoid fluid flow between said base portion and said
shroud side of said downstream portion, and the tip portion of said
diffuser blades abuts against said upstream portion of said second
diaphragm so to avoid fluid flow between said tip portion and said
hub side of said upstream portion.
[0016] Second embodiments of the subject matter disclosed herein
relate to methods of assembling centrifugal compressors.
[0017] According to such second embodiments, the method of
assembling a centrifugal compressor provides that: A) a plurality
of half-diaphragms are bundled together, B) a half-casing or
half-counter-casing is lowered on said bundle, C) said plurality of
half-diaphragms are loosened inside said half-casing or
half-counter-casing, and D) said plurality of half-diaphragms are
fixed to said half-casing or half-counter-casing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The accompanying drawings, which are incorporated herein and
constitute an integral part of the present specification,
illustrate exemplary embodiments of the present invention and,
together with the detailed description, explain these embodiments.
In the drawings:
[0019] FIG. 1 shows schematically and partially a cross-section of
an embodiment of a centrifugal compressor,
[0020] FIG. 2A shows schematically an embodiment of a diffuser
blade as it is used in the centrifugal compressor of FIG. 1,
[0021] FIG. 2B shows schematically an embodiment of a diffuser
blade used differently from FIG. 2A,
[0022] FIG. 3 shows in detail another embodiment of a diffuser
blade of the centrifugal compressor of FIG. 1, and
[0023] FIG. 4 comprising FIGS. 4A to 4K shows some steps of an
embodiment of a method of assembling a centrifugal compressor.
DETAILED DESCRIPTION
[0024] The following description of exemplary embodiments refers to
the accompanying drawings.
[0025] The following description does not limit embodiments of the
invention. Instead, the scope of embodiments of the invention is
defined by the appended claims.
[0026] Reference throughout the specification to "one embodiment"
or "an embodiment" means that a particular feature, structure, or
characteristic described in connection with an embodiment is
included in at least one embodiment of the subject matter
disclosed. Thus, the appearance of the phrases "in one embodiment"
or "in an embodiment" in various places throughout the
specification is not necessarily referring to the same embodiment.
Further, the particular features, structures or characteristics may
be combined in any suitable manner in one or more embodiments.
[0027] FIG. 1 shows schematically and partially a cross-section of
an embodiment of a centrifugal compressor 100 for compressing a
fluid.
[0028] Compressor 100 comprises a stator and a rotor.
[0029] The rotor comprises a shaft 103 and some impellers; FIG. 1
shows only a first centrifugal impeller 104 of a first compression
stage and a second centrifugal impeller 105 of a second compression
stage; both impellers 104 and 105 are fixed to the shaft 103; the
second compression stage immediately follows the first compression
stage and both are used for compressing the same fluid; FIG. 1
highlights the hub side 104H and the shroud side 104S of impeller
104.
[0030] The stator comprises a casing 101, a counter casing 102
placed inside the casing 101, and some diaphragms; FIG. 1 shows
only a first diaphragm and a second diaphragm; such diaphragms
consist of a upstream portion and a downstream portion wherein the
words "upstream" and "downstream" take the fluid flow direction
inside the compressor into account; FIG. 1 shows only the
downstream portion 106 of the first diaphragm, the upstream portion
107 of the second diaphragm and the downstream portion 108 of the
second diaphragm.
[0031] In FIG. 1, the fluid flows into the impeller 104, then out
of the impeller 104, then between the downstream portion 106 and
the upstream portion 107, then between the counter casing 102 and
the upstream portion 107, then between the upstream portion 107 and
the downstream portion 108, then into the impeller 105, then out of
the impeller 105.
[0032] Two sets of statory blades are present in the compressor
100: return-channel blades 109 and diffuser blades 110; the blades
109 are located between the upstream portion 107 of the second
diaphragm and the downstream portion 108 of the second diaphragm;
the blades 110 are located inside the diffuser between the
downstream portion 106 (in particular its shroud side 106S) of the
first diaphragm and upstream portion 107 (in particular its hub
side 107H) of the second diaphragm.
[0033] A diaphragm may consist of a single piece or two distinct
pieces fixed to each other or three distinct pieces (i.e. upstream
portion, downstream portion and return-channel blades) fixed to
each other.
[0034] The diffuser blades will now be described in detail
referring to FIG. 1 and FIG. 2A.
[0035] Each diffuser blade 110 has a tip portion 110T, a base
portion 110B and an airfoil portion 110A between the base portion
110B and the tip portion 110T.
[0036] According to a first possibility (shown in FIG. 1 and FIG.
2A), the base portion 110B is integrated in or mounted directly or
indirectly to the upstream portion 107 so to avoid fluid flow
between the base portion 110B and the hub side 107H, and the tip
portion 110T abuts against the downstream portion 106 so to avoid
fluid flow between the tip portion 110T and the shroud side 106S.
It is to be noted that FIG. 2A shows a gap between the tip portion
110T and the shroud side 106S (and a double-headed arrow), but this
represents only the fact that the tip portion 110T is not integral
with the first diaphragm 106 (and may move). In an embodiment, the
whole cross-section of the tip portion at the end of the blade is
in contact with the surface (shroud side) of the downstream portion
of the first diaphragm. In an embodiment, the whole cross-section
of the base portion at the end of the blade is in line with the
surface (hub side side) of the upstream portion of the second
diaphragm. In an embodiment, the area of the surface (shroud side)
of the downstream portion of the first diaphragm is substantially
flat, i.e. it is not recessed with respect to other areas of the
downstream portion. In an embodiment, the area of the surface (hub
side side) of the upstream portion of the second diaphragm is
substantially flat, i.e. it is not recessed with respect to other
areas of the upstream portion.
[0037] According to a second possibility (shown in FIG. 2B), the
base portion 130B of the diffuser blades 130 is integrated in or
mounted directly or indirectly to the downstream portion (106 in
FIG. 1 and FIG. 2B) of the first diaphragm so to avoid fluid flow
between the base portion 130B and the shroud side 106S of the
downstream portion 106, and the tip portion 130T of the diffuser
blades 130 abuts against the upstream portion (107 in FIG. 1 and
FIG. 2B) of the second diaphragm so to avoid fluid flow between the
tip portion 130T and the hub side 107H of the upstream portion
107.
[0038] Abutment without substantial friction may be obtained by
letting the tip portion of the blades move.
[0039] In the following, reference will be made to the embodiment
of FIG. 2A (as well as to FIG. 1); similar considerations apply to
the embodiment of FIG. 2B.
[0040] According to a first approach, movement is obtained through
a resilient component, for example a spring.
[0041] In this case, the tip portion 110T of each diffuser blade
110 may be movable, more particularly resiliently movable, with
respect to the first diaphragm (106 in FIG. 1) or the second
diaphragm (107 in FIG. 1) whereto it is mounted (see e.g. FIG. 2A
and the double-headed arrow).
[0042] The possibility of movement may be provided by a spring
located for example below the surface of the first diaphragm (106
in FIG. 1) or the second diaphragm (107 in FIG. 1) whereto the
blade is mounted.
[0043] According to a second approach, movement is obtained through
a resilient portion of the blade.
[0044] In this case, at least the base portion 110B or the airfoil
portion 110A or the tip portion 110T of each diffuser blade 110 may
be made of elastic material; one or more other portions of the
diffuser blade may be made of elastic material.
[0045] According to a specific embodiment, the base portion 110B
and the airfoil portion 110A and the tip portion 110T of each
diffuser blade 110 is made of elastic material, more particularly
the same elastic material.
[0046] The first approach and the second approach may also be
combined.
[0047] The above-mentioned movement may be in the range of e.g.
0.2-0.4 mm.
[0048] According to the first approach, a spring may be used having
a spring constant in the range of e.g. 0.3-3.0 10.sup.6 N/m.
[0049] According to the second approach, an elastic material may be
used having a Young's Modulus in the range of e.g. 0.1-10.0 GPa.
Suitable materials may be for example polymers (such as PolyEther
Ether Ketone i.e. "PEEK"), including i.a. polyethylenes, and
elastomers. For example, the airfoil portion of the diffuser blades
may be made of e.g. aluminum and the tip portion of the diffuser
blades may be made of e.g. PEEK.
[0050] It is to be noted that the diffuser blades are exposed to
quite hot (for example at 100-300.degree. C.) and quite corrosive
substances (for example a mixture of hydrocarbons); therefore,
their materials should be chosen accordingly.
[0051] In any case (i.e. first approach and/or second approach),
each diffuser blade 110 may comprise a snap mount for mounting it
to the first diaphragm (106 in FIG. 1) or the second diaphragm (107
in FIG. 1).
[0052] FIG. 3 shows a specific embodiment of a diffuser blade 110.
The base portion 110B, the airfoil portion 110A and the tip portion
110T are very thin. The blade 110 comprises a first platform 111
adjacent to the base portion 110B, a second platform 112 and a
spring 113 that is located between the first platform 111 and the
second platform 112 and acts on them. The blade 110 comprises a
snap mount 114 for mounting it to the first diaphragm (106 in FIG.
1) or the second diaphragm (107 in FIG. 1); the snap mount 114 may
comprise two elastic tongues. The platforms 11 and 112, the spring
113 and the mount 114 are designed to be completely inserted into a
blind hole of a diaphragm; the outer surface of the platform 111
will be approximately (depending on the compression of the spring
113) in line with the surface of the diaphragm.
[0053] Thanks to diffuser blades identical or similar to those just
described, other assembling methods may be used.
[0054] An embodiment of a method of assembling a centrifugal
compressor will be described in the following with the aid of FIG.
4.
[0055] According to this embodiment, diffuser blades are located
between adjacent half-diaphragms of the compressor; these diffuser
blades are compressible.
[0056] Initially: [0057] a plurality of half-diaphragms 401 (see
FIG. 4A) are bundled together (see FIG. 4B the single black stripe
at the bottom represents a link or bond between them); the bundling
action results in a light compression of the diffuser blades;
[0058] a half-casing 403 or half-counter-casing is lowered on the
bundle 402 (see FIG. 4C); [0059] the plurality of half-diaphragms
401 are loosened inside the half-casing 403 or half-counter-casing
(see FIG. 4D--the single black stripe at the bottom is no longer
present as the link or bond between is released); the diffuser
blades rearrange slightly inside the half-casing; and
[0060] the plurality of half-diaphragms 401 are fixed to the
half-casing 403 or half-counter-casing (see FIG. 4D--several short
black stripes at the bottom represent fixing devices).
[0061] Due to the light compression of the diffuser blades, each
half-diaphragm reduces its width (or axial size) somewhat, for
example from a minimum of 0.2 mm to a maximum of 0.4 mm. Depending
on the construction of the diffuser blade, such reduction in size
derives from a compression of a resilient component of the diffuser
blade and/or of a resilient portion of the diffuser blade.
[0062] Afterwards, after step D: [0063] the half-casing 403 or
half-counter-casing with half-diaphragms 401 inside is turned
upside down (see FIG. 4E); and [0064] a rotor 404 of the
centrifugal compressor is lowered on the turned half-casing 403 or
half-counter-casing with half-diaphragms 401 inside (see FIG. 4F);
bearings or half-bearings keep the rotor in position.
[0065] Finally, after step F: [0066] a plurality of half-diaphragms
405 (see FIG. 4G) are bundled together (see FIG. 4H--the single
black stripe at the bottom represents a link or bond between them);
the bundling action results in a light compression of the diffuser
blades; [0067] a half-casing 407 or half-counter-casing is lowered
on the bundle 406 (see FIG. 4I); [0068] the plurality of
half-diaphragms 405 are loosened inside the half-casing 407 or
half-counter-casing (see FIG. 4J--the single black stripe at the
bottom is no longer present as the link or bond between is
released); the diffuser blades rearrange slightly inside the
half-casing; [0069] the plurality of half-diaphragms (405) are
fixed to said half-casing (407) or half-counter-casing (see FIG.
4J--several short black stripes at the bottom represent fixing
devices); and [0070] the half-casing 407 or half-counter-casing
with half-diaphragms 405 inside is lowered on the assembly deriving
at step F (see FIG. 4K).
[0071] In step A and/or in step G, one or more diffuser blades is
or are compressed during bundling.
[0072] Prior to step A and/or prior to step G, one or more diffuser
blades is or are mounted to half-diaphragms.
[0073] This written description uses examples to disclose the
invention, including the preferred embodiments, 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.
* * * * *