U.S. patent application number 14/103526 was filed with the patent office on 2014-06-19 for methods of manufacturing divided blades of turbomachines by additive manufacturing.
This patent application is currently assigned to Nuovo Pignone Srl. The applicant listed for this patent is Nuovo Pignone Srl. Invention is credited to Lorenzo Cosi, Iacopo Giovannetti, Mirco Innocenti, Frencesco Piraccini, Pierluigi Tozzi.
Application Number | 20140165398 14/103526 |
Document ID | / |
Family ID | 47631577 |
Filed Date | 2014-06-19 |
United States Patent
Application |
20140165398 |
Kind Code |
A1 |
Giovannetti; Iacopo ; et
al. |
June 19, 2014 |
METHODS OF MANUFACTURING DIVIDED BLADES OF TURBOMACHINES BY
ADDITIVE MANUFACTURING
Abstract
The method is used for manufacturing a turbomachine blade that
comprises an airfoil portion and is divided into two parts at an
intermediate region of the airfoil portion; each of the two parts
of the airfoil portion is obtained by additive manufacturing; the
two parts are joined by brazing.
Inventors: |
Giovannetti; Iacopo;
(Florence, IT) ; Cosi; Lorenzo; (Florence, IT)
; Innocenti; Mirco; (Florence, IT) ; Piraccini;
Frencesco; (Florence, IT) ; Tozzi; Pierluigi;
(Florence, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nuovo Pignone Srl |
Florence |
|
IT |
|
|
Assignee: |
Nuovo Pignone Srl
Florence
IT
|
Family ID: |
47631577 |
Appl. No.: |
14/103526 |
Filed: |
December 11, 2013 |
Current U.S.
Class: |
29/889.71 |
Current CPC
Class: |
Y10T 29/49337 20150115;
B23P 15/04 20130101; B22F 5/04 20130101; F01D 5/3061 20130101; Y02P
10/25 20151101; B22F 3/1055 20130101; B33Y 80/00 20141201; F01D
5/147 20130101; F01D 5/32 20130101; Y02P 10/295 20151101 |
Class at
Publication: |
29/889.71 |
International
Class: |
F01D 5/30 20060101
F01D005/30 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2012 |
IT |
CO2012A000058 |
Claims
1. A method of manufacturing a turbomachine blade comprising an
airfoil portion and being divided into two parts (P1, P2) at an
intermediate region of the airfoil portion, wherein each of said
two parts (P1, P2) of said airfoil portion is obtained by additive
manufacturing, and wherein said two parts are joined by
brazing.
2. The manufacturing method of claim 1, wherein said two parts (P1,
P2) are directly brazed together.
3. The manufacturing method of claim 1, wherein leading edge
portions and intermediate portions of said two parts (P1, P2) are
joined by brazing and trailing edge portions of said two parts (P1,
P2) are joined through one or more dowel pins.
4. The manufacturing method of claim 1, wherein the turbomachine
blade comprises a root portion adjacent to a first part (P1) of
said two parts (P1, P2) of the airfoil portion and a shroud portion
adjacent to a second part (P2) of said two parts (P1, P2) of the
airfoil portion, wherein said root portion and said first part (P1)
are obtained in a single piece by additive manufacturing and
wherein said shroud portion and said second part (P2) are obtained
in a single piece by additive manufacturing.
5. The manufacturing method of claim 1, wherein said airfoil
portion extends longitudinally for a length and has a first end
region and a second end region, wherein said airfoil portion has at
least one internal cavity extending along said length.
6. The manufacturing method of claim 5, wherein the turbomachine
blade is associated to a longitudinal axis, and wherein said
airfoil portion is divided into two parts by a plane transversal to
said longitudinal axis, said plane transversal and said
longitudinal axis forming an angle greater than 0.degree. and
smaller than 45.degree..
7. The manufacturing method of claim 5, wherein at least one of
said parts of said airfoil portion has at least one hole at said
intermediate region, and at least one dowel pin is inserted into
said at least one hole.
8. The manufacturing method of claim 5, wherein said at least two
parts of said airfoil portion are joined together by a push fit,
wherein a first part of said parts of said airfoil portion has a
male-type lipped rim, and wherein a second part of said parts of
said airfoil portion has a female-type lipped rim, so that a
female-male connection between said parts of said airfoil portion
is established.
9. The manufacturing method of claim 5, wherein a cross-section of
said at least one internal cavity is reduced at said intermediate
region of said airfoil portion.
10. The manufacturing method of claim 5 being arranged as a stator
blade of an axial flow steam turbine, wherein said airfoil portion
has holes and/or slots extending from an airfoil surface to said
internal cavity, wherein one or more of said at least two parts is
made of metallic material.
Description
BACKGROUND TO THE INVENTION
[0001] Embodiments of the subject matter disclosed herein generally
relate to methods of manufacturing blades for turbomachines.
[0002] In steam turbines, partial condensation of the steam occurs
at their last stage or stages.
[0003] In particular condensation occurs on the airfoil portion of
the stator blades of a so-called "condensing stage", typically the
last stage of the turbine.
[0004] If droplets are generated as a consequence of condensation,
they leave the static stator blades and they hit the rotating rotor
blades; therefore, damages to the rotor blades may occur.
[0005] In order to reduce the damages caused by the droplets, the
rotation speed of the rotor blades may be reduced; but in this way,
the efficiency of the turbine is also reduced.
[0006] Alternatively, in order to reduce any damage on the rotor
blades, solutions exist for collecting the condensation before the
generation of droplets.
[0007] The most typical of these solutions consists in using hollow
stator blades where condensation is likely to occur, providing
holes or slots through the airfoil portion of the blades extending
from the airfoil surface to the internal cavity, and sucking from
the internal cavity so to that any condensation leaves the airfoil
surface and enters the internal cavity. In this way, droplets on
the airfoil surface of the stator blades are not generated and
released.
[0008] These hollow blades are typically obtained through milling
two metal bars, welding them together and mill finishing the
assembled component, in order to produce the blades with a
reasonable precision while avoiding the high cost of casting.
[0009] In gas turbines, hollow blades are sometime used for rotor
blades in order to reduce weight of the rotating element.
[0010] These hollow blades are typically obtained through casting,
particularly "investment casting", in order to obtain a rotating
element having an extremely precise shape and size.
BRIEF DESCRIPTION OF THE INVENTION
[0011] Therefore, there is a general need for improving the blades
of turbomachines both in terms of performance and
manufacturing.
[0012] For example, it is always desirable to have a high precision
and a low production cost.
[0013] Ideally, in order to achieve high performances, the shape,
size and material(s) of the blade should be freely selectable along
its whole length.
[0014] Such general need is particularly felt for the hollow stator
blades of steam turbines; these blades are generally located at the
last stage or stages of a multistage steam turbine; these blades
are very often made of metal.
[0015] A main aspect of the present invention is a method of
manufacturing a turbomachine blade.
[0016] According to embodiments thereof, the method is used for
manufacturing a turbomachine blade comprising an airfoil portion
and being divided into two parts at an intermediate region of the
airfoil portion; each of said two parts of said airfoil portion is
obtained by additive manufacturing; said two parts are joined by
brazing.
[0017] Such method allows to manufacture very long blades.
[0018] It is to be noted that the trailing edge of the blade, which
is usually very thin, is not spoiled by the brazing operation;
furthermore, the use of one or more dowel pins assure a perfect
alignment and stability of the trailing edges of the two parts if
brazing is not carried out on these portions.
[0019] Advantageous technical features of embodiments of the
present invention are set out in the detailed description.
BRIEF DESCRIPTION OF DRAWINGS
[0020] The accompanying drawings, which are incorporated herein and
constitute a part of the specification, illustrate an embodiment of
the present invention and, together with the description, explain
this embodiment. In the drawings:
[0021] FIG. 1 shows a side view of a blade according to an
embodiment of the present invention,
[0022] FIG. 2 shows a perspective view of a first part of the blade
of FIG. 1 comprising a root portion,
[0023] FIG. 3 shows a perspective view of a second part of the
blade of FIG. 1 comprising a shroud portion, and
[0024] FIG. 4 shows a perspective and cross-section view of a
detail of the blade of FIG. 1 where the first part and the second
part of the blade are joined together.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The following description of an exemplary embodiment refers
to the accompanying drawings. The same reference numbers in
different drawings identify the same or similar elements. The
following detailed description does not limit the invention.
Instead, the scope 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] In the following, a hollow stator blade of a multistage
steam turbine entirely made of metal will be described as it is a
very typical application of an embodiment of the present invention;
in particular, this blade is designed for an axial flow
turbine.
[0028] The blade of the embodiment FIG. 1 comprises an airfoil
portion 1 that extends longitudinally for a length and has a first
end region 2, a second end region 3 and an intermediate region 5;
according to the embodiment of FIG. 1, the intermediate region 5 is
exactly in the center of the airfoil portion 1 and is separate and
distant from both the first end region 1 and the second end region
3. The airfoil portion 1 is defined laterally (and externally) by
an airfoil surface and has at least one internal cavity 4 (not
shown in FIG. 1) extending along said length; the internal cavity 4
reduces the weight of the blade, the quantity of material necessary
for its production and collects condensation from the airfoil
surface.
[0029] It is to be noted that instead of a single internal cavity
extending along the airfoil portion a set of internal cavities
extending along the airfoil portion may be provided in the airfoil
portion; in this case, the cavities may be isolated from each other
in order to provide independent suctions of condensation and/or
blows of cold or hot gases.
[0030] The airfoil portion 1 is divided into at least two parts P1
and P2; the division is located at the intermediate region 5; in
particular, the division is made according to a plane, but, more in
general, the division could be made according to a
three-dimensional surface. According to the embodiment of FIG. 1,
the division plane is a plane TP that is transversal to the airfoil
portion 1, specifically to a longitudinal axis LA of the airfoil
portion 1; the plane TP and the axis LA form an angle more
particularly greater than 0.degree. and smaller than 45.degree.,
more particularly approximately equal to 10.degree..
[0031] According to the embodiment of FIG. 1, the internal cavity 4
extends entirely along the length of the airfoil portion 1; anyway,
according to alternative embodiments, it may extends less in the
direction of the first end region 2 and/or in the direction of the
second end region 3.
[0032] It is to be noted that although the blade of FIG. 1 is
divided into two parts, a division into three or more parts could
be implemented according to alternative embodiments. In this case,
one or more of the parts will not be adjacent
[0033] In order to collect condensation, the airfoil portion may
have holes and/or slots extending from the airfoil (external)
surface to its internal cavity. According to the embodiment of FIG.
1, a set of slots 12 are used; these slots are arranged in two
parallel lines in order to provide a sufficient passage for the
condensation liquid and to avoid excessive weakening of the blade.
As is shown in FIG. 1, the slots are located only in the second
part P2, especially in the second end region 3, where condensation
is more likely to occur.
[0034] It is to be noted that instead of a single set of holes or
slots located close to each other a plurality of sets may be
provided in the airfoil portion in order to, for example, optimize
suction of condensation in different areas of the airfoil
surface.
[0035] The blade of the embodiment FIG. 1 comprises also a root
portion 6 and a shroud portion 7; the root portion 6 is adjacent to
the first end region 2 of the airfoil portion 1 and the shroud
portion 7 is adjacent to the second end region 3 of the airfoil
1.
[0036] For best performances and construction of the stator blades
row of the turbine stage, the root portion 6 and the first part P1
of the airfoil portion 1 are made in a single piece and the shroud
portion 7 and the second part P2 of the airfoil portion 1 are made
in a single piece.
[0037] It is to be noted that although the blade of FIG. 1 is
divided into two parts, a division into three or more parts could
be implemented according to alternative embodiments. In this case,
only one part will be adjacent to the root portion, only one part
will be adjacent to the shroud portion, and one or more of the
parts will not be adjacent either to the root portion or to the
shroud portion. A multiple division allows a higher design
flexibility even if a higher construction complexity.
[0038] The first P1 and the second part P2 of the airfoil portion 1
are joined together; push fit is used in combination with
brazing.
[0039] A first measure for obtaining a good and stable join of the
two parts P1 and P2 is to provide at least one hole-pin pair on
these two parts. According to the embodiment of FIG. 1, a part of
the airfoil portion 1, in particular part P1, is provided with a
dowel pint 9 (see FIG. 2) at the intermediate region 5,
specifically at the interface between the two parts P and P2;
correspondingly, the other part of the airfoil portion 1, in
particular part P2, is provided with a hole 8 (see FIG. 3) at the
intermediate region 5, specifically at the interface between the
two parts P1 and P2; by coupling the two parts P1 and P2 together,
the dowel pin 9 is inserted into the hole 8; it is to be noted that
the hole-pin pair of the embodiment of FIG. 1 is located in the
trailing edge region of the airfoil portion 1 of the blade, i.e.
where the airfoil portion is quite thin. It is to be that,
according to alternative embodiments, the number of hole-pin pairs
may be more than one. It is also to be noted that, according to
alternative embodiments, the dowel pin may be a separated component
(i.e. not integrated in one of the parts); in this case both parts
have a hole and the pin is inserted in both holes.
[0040] According to the embodiment of FIG. 1, the parts P1 and P2
of the airfoil portion 1 are joined together by push fit; no
brazing is carried out where the hole 8 and the dowel pin 9 are
located, i.e. at the trailing edge portions of the two parts P1 and
P2.
[0041] A second measure for obtaining a good and stable join of the
two parts P1 and P2 is to provide these two parts with lipped rims.
According to the embodiment of FIG. 1, a part of the airfoil
portion 1, in particular part P1, is provided with a male-type
lipped rim 10 (see FIG. 2 and FIG. 4) at the intermediate region 5,
specifically at the interface between the two parts P and P2;
correspondingly, the other part of the airfoil portion 1, in
particular part P2, is provided with a female-type lipped rim 11
(see FIG. 3 and FIG. 4) at the intermediate region 5, specifically
at the interface between the two parts P and P2; in this way, a
female-male connection (see FIG. 4) between these parts is
established.
[0042] According to the embodiment of FIG. 1, the parts P1 and P2
of the airfoil portion 1 are joined together by brazing where rim
10 and rim 11 are located, i.e. at the leading edge portions and
the intermediate (i.e. intermediate between leading edge and
trailing edge) portions of the two parts P1 and P2.
[0043] In order to facilitate the realization of the connection
means between the two parts of the airfoil portion, it might be
necessary to reduce the cross-section of the internal cavity at the
intermediate region of the airfoil portion; in other words, to
increase the width of the walls of the two parts at the
intermediate region of the airfoil portion without modifying the
airfoil, i.e. external, surface of the airfoil portion; more
particularly the cross-section reduction is gradual. According to
the embodiment of FIG. 1, the cross-section reduction, i.e. the
wall increase, is localized where the lipped rims 10 and 11 are
located (see FIG. 4).
[0044] The surface defining the internal cavity 4 is free from
steps, in particular smooth; this facilitates and optimizes the
production of the blade by means of additive manufacturing.
[0045] Apart from the intermediate region 5, it is possible that
the cross-section of the internal cavity 4 increases gradually from
the first end region 2 to the intermediate region 5 and/or that it
increases gradually from the second end region 3 to the
intermediate region 5.
[0046] As already explained, one of the reasons for the internal
cavity of the airfoil portion of the blade may be to collect
condensation; in this case, condensation must be discharge from the
cavity; different alternatives may be provided for the condensation
discharge.
[0047] A first possibility is that the internal cavity reaches the
first end region next to the root portion and the discharge occurs
through the root portion.
[0048] A second possibility is that the internal cavity reaches the
second end region next to the shroud portion and the discharge
occurs through the shroud portion.
[0049] A third possibility is that the internal cavity ends before
the first end region, next to the root portion, and there are one
or more through holes starting from the internal cavity and
reaching the first end region so that the discharge occurs through
the root portion.
[0050] A fourth possibility is that the internal cavity ends before
the second end region, next to the shroud portion, and there are
one or more through holes starting from the internal cavity and
reaching the second end region so that the discharge occurs through
the shroud portion.
[0051] As explained above the condensation may reach either the
root portion and/or the shroud portion; afterwards the condensation
may flow along these two portions (for example in case of hollow
root or shroud portions) or through these two portions.
[0052] The structure of the blade just described is particularly
suitable for being produced by additive manufacturing, and this is
an important feature of the present invention.
[0053] Additive manufacturing has many advantages with respect to
the traditional technologies used for turbomachines blades, in
particular for stator blades of steam turbines, as it allows a
great design flexibility for the external shape of the blade as
well as for the internal shape of the blade (in particular its
internal cavity or cavities), as it allows to realize even small
details in a shape (this includes the production of small blades),
as it allows to realize graded materials in a blade (for example
the material may vary along the length or height of a blade
according to the mechanical and/or chemical requirements of the
various specific points of the blade), as it allows a simpler
manufacturing process and a lower manufacturing cost.
[0054] As far as manufacturing is concerned, it must be considered
that in the field of "Oil & Gas" small-lot production is common
also because solutions are studied (or at least customized) for a
specific client. In general, it is always desirable to have a high
precision and a low production cost.
[0055] According to a method of manufacturing a turbomachine blade
one or each of the divided parts of the airfoil portion is obtained
by additive manufacturing.
[0056] According to a method of manufacturing a turbomachine blade,
the divided parts of the airfoil portion are joined by brazing.
[0057] More particularly, the additive manufacturing of the first
part, i.e. the one adjacent to the root portion, starts from the
first end region, i.e. the area close to the root portion, and the
additive manufacturing of the second part, i.e. the one adjacent to
the shroud portion, starts from the second end region, i.e. the
area close to the shroud portion.
[0058] In the case of turbomachines blades, in particular stator
blades of steam turbines, it is best to provide that additive
manufacturing comprises binding granular material or
materials--different materials might be used in different places.
Typically, the blades are made of metal, and the granular material
or one of the granular materials or each of the granular materials
is metallic.
[0059] In the embodiments (like the embodiment of FIG. 1), that are
very advantageous, wherein the blade comprises a root portion
adjacent to a first part of the two parts of the airfoil portion,
the root portion and the first part are obtained in a single piece
by additive manufacturing. In this case, due to the fact that the
root portion has a cross-section bigger than the airfoil portion
and that the increase in cross-section is typically in the form of
one or more steps, in order to facilitate and optimize the
production of the blade part by means of additive manufacturing,
additive manufacturing of the first part should start from the root
portion. It is to be noted that, in this way, production of the
first part do not require any further subtractive process operation
(such as turning, milling, electron discharge machining).
[0060] In the embodiments (like the embodiment of FIG. 1), that are
very advantageous, wherein the blade comprises a shroud portion
adjacent to a second part of the two parts of the airfoil portion,
the shroud portion and the second part are obtained in a single
piece by additive manufacturing. In this case, due to the fact that
the shroud portion has a cross-section bigger than the airfoil
portion and that the increase in cross-section is typically in the
form of one or more steps, in order to facilitate and optimize the
production of the blade part by means of additive manufacturing,
additive manufacturing of the second part should start from the
shroud portion. It is to be noted that, in this way, production of
the second part do not require any further subtractive process
operation (such as turning, milling, electron discharge
machining).
[0061] After producing the parts of the airfoil portion (including
the root portion and the shroud portion, if the case) separately,
they are joined and fixed together.
[0062] Fixing is carried out by brazing; prior to brazing a push
fit may be provided so that the two parts are correctly and firmly
positioned between each other during the brazing operation.
According to the embodiment of FIG. 1, push fit derives from the
two lipped rims 10 and 11.
[0063] More particularly, a male-type lipped rim of any of the two
parts is inserted into a female-type lipped rim of any other of
said two parts, and the brazing operation is carried out where the
female-type lipped rim and said male-type lipped rim are located
after insertion, precisely where the two lips are located.
Referring for example to FIG. 1, after fitting the two parts P1 and
P2 together, the whole blade (including root and shroud) can be
placed in a brazing oven.
[0064] Finally, in the case of a stator blade of a steam turbine,
holes and/or slots extending from the external surface of the
airfoil portion to the internal cavity of the airfoil portion (i.e.
holes and/or slots transversal to the airfoil portion and to its
longitudinal axis) are realized. The best technologies to be used
for this operation are EDM (Electrical Discharge Machining)
drilling and/or cutting or laser drilling and/or cutting; it is to
be noted that, if using a laser-based technology, it is important
to control the laser beam and to avoid unintentional drilling
and/or cutting of both walls of the airfoil portion.
[0065] The blade design according to an embodiment of the present
invention, as described in the present description, is used in a
turbomachine.
[0066] The blade design according to an embodiment of the present
invention is particularly suitable for being used as stator blade
of a steam turbine, especially in the last stage or stages of a
multistage turbine.
[0067] More in general, the blade design according to an embodiment
of the present invention may be used as (static or moving) phase
separator device for a turbomachine (e.g. a turbine, a compressor,
a pump) that gets in contact with a multiphase fluid, typically a
combination of liquid and gas.
[0068] It is to be noted that the holes or slots may be used for
sucking condensation and, alternatively, for ejecting a fluid,
typically a hot fluid. It is to be noted that the internal cavities
may be more than one and may have the same function or different
functions (lightening the blade, cooling the blade, heating the
blade, sucking fluid, ejecting fluid).
[0069] 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.
* * * * *