DESCRIPTION
TECHNICAL FIELD
Erabodimenis of the subjeci matter disclosed herein generally relaie lo composite centrifuga! impellers for turboinachines and related production inelhods. parlicularly, but not exclusively, for oil and gas applications
Otiier Embodiments generally relates to a mold for producing this centrifugal impeller, some particular components to make this centrifugiU impeller with this mold, and a lurbomachine in which said impeller could be used. BACKGROUND ART
A component of a centrifugal turbomachine is the centrifugal impeller, which transfers, in general, energy from the motor thai drives the turbomachine to a working fluid being compressed or pumped by accelerating the fluid outwards from the center of rotation; the kinetic energy imparted by the impeller to the working fluid is transformed into pressure energy when the outward movement of the fluid is confined by a diffuser and the machine casing. This centrifugal machine is called, in general, a compressor (if the worfcing fluid is gas) or a pump (if the working fluid is a liquid).
•Another type of centrifugal lurbomachine is an expander, which uses the pressure of a working fluid to generate mechanical work on a shaft by using an impeller in which the fluid can be expanded.
US 4,676.722 describes a wheel for a centrifugal compressor made by a plurality of fiber loaded scoops. A disadvantage of this particular impeller is that the various scoops have direct fiber reinforcement substantially in the

radial direction, so U is difficult to balance circumferential stress as generated by centrifugal forces at a high speed of rolaiion. After manufacluring, the sectors are joined lo each other by the adhesive strength of a bonding agent, which limits the maximum speed of operation Also, the method of manufacture, in which the assembly is drawn into place by filaments, is restricted to relatively simple geometries (e.g. with straight-edged sectors) which maj' have low aerodynamic efficiency.
US .5,944,485 describes a turbine of thermo-structural composite material, particularity one of large diameter, and a method for manufacturing the turbine that provides mechanical coupling for its assembly by means of bolts, grooves, slots, and so on. A disadvantage of fhts impeller is that the mechanical coupling cannot ensure a high resistance at high rotatiwtai velocitN when using either a corrosive or erosive working fluid Therefore the reliability of this component may decrease dramatically. In addition, the scheme for attaching the airfoil to the hub provides user continuous fibers around the internal corners of the passages. Smce these are typically areas of high stress, it is desirable to have fibers that are continuous from the airfoil to the cover and from the airfoil to the hub.
US 6.854,960 describes a segmented composite impeller or propeller arrangement and a manufacturing method. The main disadvantage of this impeller is that it relies on adhesive bonding to join identical .segments. As a result, it does not have a high mechanical resistance to work at high rotational velocity, and centrifugal forces can separate identicai segments and destroy the impeller itself. Another disadvantage is that it is not possible to build an impeller v\ith vanes with complex geometry, as is the case with three
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dimensional or simitar impellers.
In general, a disadvantage of all the aforesaid impellers is that ihey present a relaiiveiy complex mechanical structure, because they are composed of several different components that need to be made independently a«d then mechanically as>sembled together. .Vloreover, the components made of fibers have to be built in general by expensive metal molds, increasing the cost of manufacture. Also, different metal molds have to be used to build t)iese fiber components for each different type of impeller, which significantly increases the cost of manufacture. Again, these mechanical assemblies are not easily achievable by means of automated machinery, further increasing the time and cosi of manufacture.
Another disadvantage is thai the vanes of these impellers are not protected in any way from solid or acid particles suspended in the working flow, therefore erosion and corrosion problems could be significant and may lead to the destruction of the component.
Yet another disadvantage is that it may be difficult to achieve the mechanical assembly of all the components needed for optimal operations of the impeller at high speed. .Moreover, any distortion produced by tlie tensions and forces created during use can cause problems during operation, especially at high speed; vibrations may occur during operation, caused by wesu^ and/or by a faulty assembly of various components. Therefore, the impeller may fail
To date, notwithstanding (he developments in technology, these disadvantages pose a problem and create a need to produce simple and inexpensive centrifugal impeller for turbomachineri' in an even faster and less expensive way, while at the same time producing an improved and high
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quality finished product. A particular need exists (o produce an innovative centrifugal impeller by taking advantage of composite and fibtsr technoiogies, whilemoslly preserving the mechanical, fluid-dynamic and aerodynamic properties of metallic impeller, m order (o effectjvely use this innovative impeller in the turfjomachinery field. Design improvements are needed to take greater advantage of the inherent strengths of composites, and to enable safe operation at higher tip speeds than is possible with typical metallic impellers. SUMMARY
An object of the present invention is to produce a simple, fast and cheap mold for building a centrifugal impeller, overcoming at least some of the drawbacks mentioned above.
A further object is to develop a method for the production of said impeller, particularly a method for creating the impeller using composite materia!.
A further object is to produce some components to make said impeller by said mold in an easy and cheap way.
According to a first aspect, there is a centrifugal impeller for a turbomachine comprising a plurality of aerodynamic vanes; each of these vanes comprising internal walls on which is associated at least a fabric element.
In other words, the aerodynamic vanes are the empty spaces between adjacent blades, During the use of the impeller, in a few words, the working fluid enters into an inlet eye of each aerodynamic vane, passes through the vane, in which the fluid is pushed radially by the geometry of the vane itself

and b\' the rotation of the impeller, and finally goes oui through an eye outlet of each vane.
U must be understood that, in this description and in the attached claimB. the term "fabric" is used to imply a number of one or more of a variety of different fibrous structures wo\en into a paltern, such as a braid pattern, a stitched pattern, or an assembly of layers {and not woven arrangements only). See the descriptions below.
In a particularly advantageous embodiment of the subject matter disclosed, first fabric element.^ are configured to surround each aerodynamic vane in order to substantially reproduce the shape of the aerodynatnie vane such that the aerodynamic characteristics of said vane are preserved. The fabric comprises fibers that are advantageously and preferably continuous around the entire infernal surface of each vane thereby providing a high resistance to mechanical stresses generated at these locations. In this way a single vane becomes particularly resistant to the mechanical stress and at the same time is able to preserve its aerodynamic characteristics.
In another advantageous embodiment of the invention, a second fabric element is configured to alternately surround an upper wall of a vane and a lower wall of an adjacent vane passing along the respective blade therebetween such that the aerodynamic characteristics of said vane are preserved.
In another advantageous embodiment, a third fabric element has a substantially conical surface with fabric blades stretching out from the surface; these fabric blades being able to reproduce substantially the blades of the finished impeller .
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It is clear thai the aforesaid three embodiiflenfs could be realized in different ways according to specific needs of manufacturing or use; also, it doijs not exclude restlizing these embodiments in combinations one to the other,
In another embodiment, a shaped contponent is associated inside each of the aerodynamic vanes in order to act against the erosion or corrosion phenomena caused by the working fluid.
In fact, the working fluid could be a gas, a liquid or in general a mixture thereof, and the erosion or corrosion process could be aggravated by the high rotational speed of the impeller, which causes the liquid or solid particles in the flow to strike the blade with higher force.
In another advantageotis form of imiplementation. the impeller comprises a fourth fabric element placed over the aerodynamic vanes; this fourth fabric element could substantially have a centjrifugal shroud shape and function.
Moreover, the impeller could coijnprise a fifth fabric element having substantially an annular planar shape that reali/es substantially a rear-plate for the impeller itself.
A sixth fabric element could be fitted under the aerodynamic vanes; this element has .substantially an annular shape and is able to be matched with the external inferior surface of the \ anes.
A seventh fabric element could be advantageously fitted around an axial hole inside which a rotor of the turbomachine fits. The fourth, fifth, sixth and seventh fabric elements could be provided, preferably in comhination one to the other, to increase the mechanical resistance of the finished impeller, however, it must be understood that these fabric elements could be used alone
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or in various combinations according to the specific needs of manufacturing or use.
In an advantageous embodiment, all the aforesaid tlabric elements - when provided are enclosed or associated m the filling material, typically called "malrix'", in order lo obtain a more rigid shape for the impeller.
In a particularly advantageous embodiment, all of (he aforesaid fabric elements •- when provided - are matched or pressed togetlier m order to niinim^ce she empty spaces between them. In this case, ihe filling material ased to nil the spaces between adjacent fiber elements is reduced as much as possible, in order to maximii^e the amount of structural fiber within the volume. This will further increase the mechanical resistance of the finished impeller.
In a further advantageous embodiment, an inner core element is placed under the aerodynamic vanes in order to facilitate the manufacturing process of the impeller, in particular to facilitate the deposition of the said fourth, fifth, sixth, and seventh fiber elements in place, and, when provided, providing a base for the fiber deployment. Also, the core element could be configured advantageously to give a higher strength and stiffness during the work of the finished impeller at high rotational velocities.
The core could be made at least by a material more rigid than the filling material before it's cured, for example: wood (for example balsa), foam (for example epoxies, phenolics, polypropelyne, polyurethane, polyvinyl chloride PVC, acrylonitrile hutadiene-styrene ABS, cellulois acetate), honeycomb (for example krafl paper, aramid paper, carbon or glass reinforced plastic, aluminum alloys, titanium, and other metal alloy.s), polymers (for example
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phcnolics, polyimides, pofyetherimides, poiyelherelherketones), or metaliic materials or others.
In parliculariy advantageous embodiments, the core consists of unfilled cavities that decrease the overall dertsiiy of the core, so that it is substantially lower than that of the fabric or filling niateriiU. This will result in lower forces on the adjacent structure when subjected to high rotational velocities
in particular embodiments, the core could be surrounded, in part, by al least one of the aforesaid fabric elements - alone or in various combinations, when provided in order lo obtain a particularly compact, rigid and resistant system.
According to a preferred embodiment of the invention, the above fabric elements are made by a plurality of unidirectional or multidirectional fibers, realized substantially to have a high anisotropy along at least a preferential direction. These fibers could have a substantially thread-like shape, as for example carbon fibers, glass fibers, quartz, boron, basalt, polymeric (such as aromatic poiyamide or extended-chain polyethylene) polyethylene, ceramics (such as silicon carbide or alumina) or others.
It doe.s not exclude, however, thai these fabric elements could be realized with two or more layers of fibers, with a combination of fibers of different types or with different tvpes of elements, as for example vvitJi granular, lamellar or .spheroidal elements or woven, stitched, braided, non-crimp or other fabrias, unidirectional tapes or tows, or any other fiber architectures. .
The above filling material could be realized by a material able lo hold together, to evenly distribute the tensions inside, and to provide high resistance to high temperatures and wear for the fabric elements; on the

coritran'. the fabric clcmenls are able mainly to provide high resistance to the lensians during the work of the impeller. Moreover, the filling material can be arranged to present a low specific mass or densitv- in order to reduce the weight of the impeller and thus the cemrtfugai force generated during the work.
The filling material could be preferably an organic, natural or synthetic polymer material, whose main component,^ are polymers with high molecular weight molecules, and which are formed by a large number of basic units (monomers) joined togeiher by chemical bonds. Structurally, these molecules may be formed from linear or branched chains, tangled with each other, or three-dimensional lattices, and mainly composed of carbon and hydrogen atoms and. in some cases, oxygen, niirogen, chlorine, silicon, fluorine, sulfur, or others In general, polymeric materials are a very large family of hundreds and hundreds of different substances.
One or more auxiliarj compounds can also be added to the polymer materials, such as micro- or nanoparlicles, which have different functions depending on the specific needs, for example to strengthen, toughen, stabilize, preserve, liquefy, color, bleach, or protect the polymer from oxidation.
In an advantageous form of implementation of the invention, the polymer filling material is constituted, at least in psurt, from a thermoplastic polymer such as PPS (polyphenylene sulphides), PA (polyamide or nylon), PMMA (or acryiic). LCP (liquid crystal polymer), POM (acetal), PAl (polyamide imide), PEEK (poly-ether-ether-ketone), PEKK (poly-ether-ketone-keione). P.AEK (poly-aryl-ether-ketone) . PPT (Polyethylene lereptalato), PC (poly
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carbonate), PK (polyethylene), FEI (Poly-ethcr-imide). PKS fpolyefher), PPA (poliptalamide), PVC (polyvinyl chloride). PU (polyurelhane), PP (polypropylene), PS (polvstvrene), PPO (polifenilene oxide), PI (polyimide; exisi as tliermosetting), or more. For particularly high temperature applications various poiyimides such as polyrjierized monomeric reactant (PMR) resins, 6F-Polyimides with a phenylethynyl endcap (HFPE), and phenyiethynyl-lerminated imide (PETl) oiigomers may be preferred.
In another advantageous form of implementation of the invention, the polymer filling material i.s at least partly con.stiluied of a thenno,<;etting polymer, such as Epoxy, phenolic, polyester, vinylester, Amin, furans, PI (exist also as thermoplastic material), BMI (Bismaleimides). CE (c>ajiate ester), Pthalanonitrile. benzoxazines or more. For particuiarh high temperature appitcations various thermosetting polyimides such as polymerized monomeric reactani (PMR) resin.s, 6F-Po!yimide8 with a phenylethynyl endcap (HFPE). and phenylethynyl-terminated imide (PETl) oligomers msy be preferred.
According to another advantageous embodiment of the invention, the filling material is composed of a ceramic materia! (such avS silicon carbide or alumina or other) or even, at least in part, from a metai (such as aluminum, titanium, magnesium, nickel, copper or their alloys), carbon (as in the case of oarbon-carbon composites), or others
An advantage of the impeller created according to the invention is that it presents high quality and innovative characteristics.
In particular, (he impeller is extremely light while, at the same time, has a comparable resistance with respecl to the known impeller made of metal used
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in the turbomacbine field (for high rotational velocity and for high pressure ratio).
In fact, a traditional metallic impeller could weigh from about 10 to 2000 kg depending on the impeller size, and the iinpeller accorditxg to the invention could weigh from about 0.5 to 20 kg (for the same type of impeller). Therefore, the weight reduction is greater than 75%.
Another advantage is that an impeller made according to the invention could be used with a lot of different fluids O'Cjuid, gas or a mixture thereof) and with fluid.s that present high corrosive or erosive characteristics.
A further advantage is comes from the fact that it is particularly ine.xpensive and simple to produce and to handle. See description below.
Another advantage is that it is particularly easy to apply more components or elements to improve the quality or the mechanical characteristics of the impeller according to specific requirements, like the .shaped components or fiber elements made by specific shape or other.
Again, another advantage is that an impeller made according the present invention could be of different types, preserving at the same time aerodynamic and mechanical characteristics For example, the impeller could be a three dimensional impeller, a two dimensional impeller, or others.
According to a second aspect, there is a turbomacbine wherein at least a centrifugal impeller as described above is implemented
In particular, this turbomacbine could be a centrifugal compressor (for gas) or pump (for liquid), or else it could be a centriliigal expander; in any case, the turbomacbine has preferably a plurality of these impellers associated on a common shaft in metal or other material (for example a composite

ma(eriaf),
According lo a third aspect, there is a mold to build a centrifugal impeller for a turbomachine comprising of. at least, an annular insert comprising a plurality of aerodynamic vane inserts reproducing the aerodynamic vanes of the finished impeller.
\n particular, the annular insert could be made by a single piece or, preferably, by joining together a plurality of pieces, see below.
The mold comprises preferably and advantageously a base plate having an internal face and an e.xternal face, the internal face being configured to reproduce a rear-surface of the impeller and the external face being substantially opposite to the mternal face; an upper-ring having m internal face and an external face, the iniernal face being configured to reproduce a front-surface of the impeller and the external face being substantially opposite to the intertml face.
In other embodiments, the mold comprises the aforesaid fabric elements having preferably atid advarUageously a (serai) ngid shape and bemg made separately before placed inside the mold.
In a particularly advatttageous embodiment of the invention, the mold comprises the inner core associated under the centrifugal impeller preform imd over the base plate; the inner core could be realized in numerous different embodiments according lo different technical needs or requirements of use. See below.
In another advantageoas embodiment of the invention, the mold comprise.s a pluralitv of shaped components able to be associated on an external surface of each aerodynamic vane in.serf, these shaped component.s are configured to

act against the erosion or corrosion of the working fluid during the work of ihe finished impeller.
In particular, these shaped components could be associated between one of the atbresaid fabric elements and the surfaces of the annular insert corresponding to the walls of the vanes, m a position where the erosion or corrosion process caused by the working fluid is higher
A closure system could be provided to close the preform betwe«i the base-plate and the upper/ring, in order to center and lock said impeller preform between them. This sy.stem could be realized in a plurality of different types, for example in a mechanical system (centering pins. scre\vs or others), a geometrical system (shaped holes, shaped grooves, shaped teeth, shaped surfaces or others), or others systems.
An injection system is provided to inject the fUhng material inside the mold by means of injection channels made inside the ba.ve plate and/or the upper-ring.
An advantage of the mold according to Ihe present invention is that the finished impeller the mold produces is high quality and has innovative characteristics for the turbomachiners- field.
Another advantage is that ihe material used for the annular insert could be something low-cost and easy to machine, such as high-density foam or ceramic.
Moreover, the material is ver)^ compact and yet e.stremely versatile, because it is possible to make a lot of different types of impellers providing m annular insert with specific geometry and shape (in particular three or two dimension impellers).

Yet another advantage of (he mold design is that it allows a single-step infusion and cure of the filling material through the entire part. This provides for a high strength part and eliminates the need for secondary Joining operations such as bonding, machining, or mechanical attachment which can be costK and time-consuming. In addition, the possibility for part contamination or handling damage between operations is eliminated.
According to a fourth aspect, there is an aerodynamic vane insert configured to reproduce at least an aerodynamic vane of the finished centrifugal impeller such that the aerodynamic characteristics of the vane of ihe llnished impelter are preserved.
Advantageously, the aerodynamic vane insert comprises at least a central region configured to properly reproduce the aerodynamic vane and end-regions coniigured to be associated with end-regions of an adjacent insert forming Ihe annular assembly.
In a particularly advantageous embodiment, these shaped end-regions are configured to be associated with end-regions of an adjacent msert m order to create the inlet and respective outlet eyes for the working fluid and for handling, positioning tJie insert within the moid, and containing resin chaimels. More, the shaped end-regions could be provided with sealing elements to avoid a leakage during the injection of the filling material.
In a preferred embodiment, the aerodynamic vane inserts are made by at least a single piece; however it does not exclude that the inserts could be made of two or more pieces or, on the contrary', a single insert could produce two or more aerodynamic vanes according to the particular embodiments.
The advantage of this a,spect of the invention is that it allows the
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fabrication of vanes with complex 3D geome(n' such that the inserts can readily be removed from the impelier after the filling material has cured.
According to another exemplars- embodiment, an aerodynamic vsuie insert is joined with other vane inserts to form an aitnular assembly reproducing of all the aerodv naniic vanes of the finished impeller such that the aerodynamic characteristics of the vanes of the finished impeller are preserved
This annular insert could be made also by a single piece. See below.
In 3 preferred embodiment, the annular insert comprises, preferably and advantageously, a first face, a second face, a plurality of shaped slots, arid an axial hole.
The first face is configured to reproduce the upper surface of Ihe annular jjsserabiy of all the aerodynamic vanes of the fmished impeller; the second face !S substantially opposite to the first face and configured to reproduce the lower surface of the aforesaid annular assembly; the plurality of shaped slots are provided to reproduce substantially the lateral walls of the vanes; and the im axial hole reproduces substantially (he axial hole of the finished impeller in which a rotor of the turbomachine is placed.
Adv^itageously, tlie aerodynamic vane insert and the annular insert can be made by an appropriate material according to the fabrication process or the lype of finished impeller, and it could be a soluble or breakable material, a reforroable material, or u solid material that can be extracted in multiple pieces, such as - but not limited lo - metal, ceramic, polymer, wood, or wax. Some specific examples include water soluble ceramics (for example .Aquapour'^ from Advanced Ceramics Manufacturing), state-change materials (for example "Rapid Reformahle Tooling .Systems" from 2Phase
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f
I'echnoiogies), shape memory polymers (for example VcriflexD Reusable Mandfels fiom Cornerstone Research Gfoup).
AJI advanfage of (he aerodynamic vane inserts and rtie annular insert according to the present invention is that the>' are able to build a tmtshed impeller of high quality and with innovative characteristics for the turbomachinerv' field.
Another advantage is that they are extremely versatile, because it is possible to make many different types of aerodynamic vanes providing a specific geometry and shape thereof, for example impeller of two or three dimensional types, or others.
Still another advantage is - in general • that the finished impeller could be made in a single injection and docs not require subsequent assembly and bonding. This reduces raanufacturtng time and improves the structural integrity of the part. However, if does not excluded injecting and curing each vane individually and then combining these vanes in a subsequent step with the hub and shroud.
According to a fifth aspect, there is a method for building a centrifugal impeller for a turbomachine, that comprise at least a step to fabricate an annular insert comprising a plurality of aerodynamic vane inserts reproducing the aerodynamic vanes of the finished impeller such that the aerodynamic characteristics of the vane« and the finished impeller are preserved
The aerodynamic vanes are the empty spaces between two adjacent blades through which the working fluid can flow when the impeller is working See also the description before
In an advantageous embodiment of the invention, this method comprises a
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step to build a plurality of fwsrodynamic vane inserts made by said appropriate material, each of them reproducing ai least an aerodynamic vane of the impeller and each configured to associate with each other to realise the arjnular insert.
In an alternative embodiment of the invention, it provides a step to build the annular insert from a single piece using a specific mold.
In another embodiment of the invention, il provides a step to build a first fabric element able to be associated around each of the said aerodynamic vane inserl-s.
In yet another embodiment, another step is provided to build a second fabric element able to be associated on an upper wall of a vane and on a lower wall of the adjacent vane of ihe annular insert.
More, other steps are prov tded to build a third fabric element able to form continuously a plurality of blade walls and a wall between the Wades.
It's clear however that there could be a lot of ways to build fabric elements and to associate them on the impeller mserls according to assembly or application needs.
In another embodiment of the invention, another step is provided to associate, at least, a shaped component on the external surface of each iierodynamic vane insert before associating the fabric element on it. In this way it is possible to enclose the shaped component between the aerodynamic vane insert and the respective fabric element.
In yet another embodiment of the invention, another step is provided to associate an inner core under the annular insert in order to give a higher strength and stiffness during the work of the finished impeller at the high
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rotation velocities and, at the same time, to facilitate its construction providing a solid base for the fibers deploymtsnt.
Advaatageously, the fiiiing malerial could be fifled inside the mold by an infusion process, such as resm transfer molding (RFM). vacuum assisted resin transfer moldling (VARTM), structural reaction injection molding (SRIM), reinforced reaction injection itwlding (RRIM), or others, it's clear thai it does not exclude using other methods according to specific needs of construction or use.
in another preferred embodiment, another step is provided to remove the annular insert after the infusion and curing process of the filling material; this could be achieved by Hushing with liquid or gas, in the case of a soluble insert, heating, in the case of meltable insert, breaking, in the case of breakable insert, or designing the geometrx- of the annular insert such that it can be removed without change, in the case of solid insert. Anyhow, this removing step is such that the annular insert could be extracted or dissociated from the finished impeller after the inru.sion process in such a way that the aerodynamic characteristics of the vanes of the finished impeller are preserved.
In another preferred embodiment, still another step is provided to fabricate all or portions of the aerodynamic vane mserts and of tlte annular insert using an additive manufacturing technique to minimize the need for machining the inserts. These additive manufacturing methods include, but are not limited to, stereoiithography, fused deposition modeling, laser sintering, and electron beam melting, The choice of method will depend on many factoi-s including the molding temperature and desired dimensional tolerances

of the impeller. This is especialiy attractive for applications where small quaiililies of impdlers with llie same shape will be produced.
In yet anolher preferred embodiment, ail or portions of the insert would be cast using dies made with one of the additive manufacturing methods mentioned above. In this case, the insert material could consist of a ceramic that is sohibie.
An advantage of the method according to the invention is that the finished impeller produces by the method is of high quality and has the aforesaid innovative characteristics for the turbomachinery field.
Another advjuitage is that it is particularly easy to provide further phases to add components or elements to improve the quality or the mechanical characteristics of the finished impeller according to specific requirements.
A further advantage is that this method is extremely versatile, because it is possible to built different types of impellers preserving aerodynamic and mechanical characteristics thereof, for example two or three dimensional impeller or others BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more apparent by following the description and the accompanying drawings, which show schematically and not in scale non-limiting practical embodiments. More specifically, in the drawings, where the same numbers indicate the same or corresponding parts;
Figures lA, IB and IC show cross-sections of an impeller according to different embodiments;
Figure 2 shows an exploded assembly of a mold according to one embodiment of the invention;
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Figure 3 shows a ialera! and exploded view of a moid similar to Fig 2;
Figure 4 shows a compoaenl for (he mold of Fig.3.
Figures 5 and 6 show a pluraiily of views of a coinpoflem of the mold of Fig.2 or 3;
Figures 7 and 8 show other components according (o particular embodiments of the invention;
Figures 9A, ^)B ajid 9C show a respective fiber element according to particular embodiments of the invention;
I Figure 10 shows a cross-section of the mold of Figg.2 or 3: and
Figures HA to 11L show a piurality of fibers used with different embodiments of the invention. DETAILED DESCRIPTION
In the drawings, m which the same numbers correspond to the same parts in all the various Figures, a finished centrifugal impeller for a lurbomachine according to a first embodiment of the invention is indicated generically with Ihe numeral lOA, see Figure I A. This impeller lOA comprises a plurality of aerodynamic vanes 13 formed between aerodynamic blades 15 made by first fabric elements lA (see also Fig.9A) and impregnaled witli a first filling material M, typically referred to as a "matrix".
Its clear that the number and the shape of the fabric elements, the aerodynamic blades, and the corresponding vanes will varj' depending on the particular embodiment of the impeller. See description above.
A working fluid enters in the inlet eye of each Aane 13 along an incoming direction A. goes through the vane 13, and goes out from the outlet eyes of (he same vane along a direction B
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A shaped component 19 - shown not to scale in Fig.i A - is disposed on an inferior uaJI 131 of the vane B betvveen each blade 15 to prevent the erosion of the working fluid during the work of the impeller lOA. A fourth fabric element 4 is advsntageouslv provided over the vane 13 having substantially a centrifugal shroud shape and function. An inner core elenvent 21 is: associated under the vanes 13 and could be surrounded by a pluralixy of further fabric elements 5, 6, 7, See description below.
In the embodiment, (see also description of the Fig. 7) this shaped component 19 reproduces sub.staniially the shape of the inferior walls 131 of the vane 13 where the erosion process caused by the How of the working fluid could be higher; however it's not to exclude that these components 19 could be made with another shape or other materials. See description below.
The Fig. !B .^hows a second embodiment in which an impeller I OB is provided with a second fabric element IB (see also description of Fig.9B) configured to surround alternately an upper wall of a vane 13 and a lower wail of an adjacent vane 13 passmg along the respective blade 15 therebetween.
|The Fig.lC shows a third embodiment in which an impeller IOC is provided with a third fabric element IC (see also de.scription of Fig.9C) configured lo form the blades 15 and a superior wall 13S of the vane 13 between each blade 15; this third fabric element IC is composed substantially by an annular plate with a plurality of shaped sheets stretching out from the plate to form the blades.
In both of the embodiments lOB and IOC could be provided the same elements described for in the first embodiment of Fig. lA, as .shown in the
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Figures themselves, as the shaped component 19, the inner core 21, and ortiers.
in Fig.2 is shown an exploded view of a mold 100 to build said centrifugal impeller lOA, lOB or IOC which comprises basically an annular insert 110 (shown itself in exploded view in this Figure) and the inner core element 21 between a base plate 113 and an upper-ring 115.
The annular insert 110 is made, in this particular embodiment, by associating a plurality of aerodynamic vane inserts 200, each of them reproducing an aerodynamic vane 13 of the fmished impeller, to form an assembly substantially annular or toroidal. See below.
The base plate 113 has an internal face 113A configured to reproduce a rear-surface of the finished impeller lOA. iOB or IOC and an external face II3B bemg substantially opposite to the mternal f^ce I ISA. The upper-rmg 11.5 has an internal face 115.A conllgured to reproduce a front-surface of the impeller and an e.vtemai face 115B substantially opposite to the internal face 115 A.
ITte inner core element 21 is associated under the annular insert 110 and presenKi a tUvSt face 21A (see also Figg.2, 3 and 9), an opposed second face 21B and an axial bole 21C The first face 21A has advantageously a shroud form, similar to a bell, or a tutipan configured to match the inferior surface of the preform 110; the opposed second face 21B is configured to reproduce substantially the rear-surface of the finished impeller and the axial hole 21C is able to be associated on a shaft R of a machine where the finished impeller can be installed.
In this drawing, the core element 21 is surroimded by a fifth fiber element

5, a sixth fiber clement 6, and a seventh fiber element 7, Sec below.
It has to be noted thai in these drawings the shape of the core element 21 is presented to fill completely the space between the shaft and the perform 110; it does not exclude realizing the core element 21 to fill partially this space in order to decrease the stress and at the same time the weight of the finished impeller.
In another advantageous embodiment, these further fabric elements 5, 6 or 7 could be not provided when the core element 21 is made by metallic material.
Moreover, shaped cavities or holes could be provided on the core element 21 made by metallic material and inserted with part of the fabric elements to fix more stably these elements on it.
Moreover, in Fig.2 it is shown a closure system 119 comprises - in this advantageous embodiment - a plurality of closure pins 119A fixed on the edge of the internal face 113A of the base plate 113 and with corresponding closure holes 119B made on tlie edge of the internal face 1 !5A of the upper-ring 115; insertion holes 119C are provided on each aerodynamic vane insert 200 in a particular position, see description below.
It's clear that the closure system 119 is described here as an example of a realization; this system can varv enormously depending on the particular embodiment.
In Fig.2 it is shown furthermore an axial insert 121 to form the axial hole 21C of the finished impeller made with a speciHc material, eventually the same material of the perform 110 and/or of the inserts 200.
U has to be noted that Fig 2 shows also a plurality of first fabric elements

lA. each of them associated on the external surface of a respective aerodynamic vane insert 200, it's cleai tJiat the mold JOO could comprise also ihe second and third fabric element IB and respectively IC {not shown in Fig.2 for simplicity) to realize the finished impeller shown schematically in Fig.IB and respectively IC.
Fig.3 shows an exploded and faterat view of a mold similar to that of Fig.2 in which the inserts 200 are associated together to form the annular insert 110. In this Figure it is not shown the first fabric element 1A nor the second or third fabric element IB and IC for simplicity.
More, in Ibis drawing is shown the forth, fifth and sixth fabric elements 4, 5, 6 that could be provided inside the mold 100 to form the finished impeller in an advantageous embodiment of the invention.
In particular, the fonrth fabric element 4 is configured to be associated between tiie annular Insert 110 and the upper-ring 11.5; the fifth fabric element 5 is configured to be associated between the core 21 and the internal face 113A of the base plate 113; the sixth fabric element 6 is configured to be associated between the annular insert 110 and the core 21; the seventh fabric element 7 is configured to be associated inside the axial hole 21C of the core 21. These fabric elements 4, 5, 6, 7 could be impregnated with the first filling material M during the nmnufactruing process.
Moreover, in Fig.3 ii is also shown the annular insert 110 partially in section and configured to reproduce an annular assembly of a plurality of aerodynamic vanes of the finished impeller such that the aerodynamic characteristics of the finished impeller are preserved.
In a preferred embodiment here described, the annular insert 110

comprises a first face 1 lOA made by jhe upper surface of the vanes annular assembly ami having substanlialiy a form similar to a bell or a tulipan, and able (0 be matched witti the fourth fabric element 4. A second fucn HOB is substantially opposite to the first face llOA and made by the lower surface of the vanes annular assembly, a plurality of shaped slots 137 are provided to reproduce substantially ihe blades !5 of each vane 13 and the axial hole 21C being able to be associated to the rotor R of the turbomachine.
This annular insert 110 could be made by joining lo each other a plurality of said aerodynamic vane inserts 200 (as shown in these Figures) or by a single piece, as said above.
In Fig.4 it is shown schematically a segmented fabric element 37 (see also Fig. I A) able to be fated inside the space at the comer of said shaped slots 137 to increase the rigiditv of the whole assembly of the finiished impeller, eliminate preferential flovvpaths for the filling material, and avoid regions containing only filling material with no fiber where cracking might initiate during cure.
In a prel'erred embodiment, all the fabric elements 1 to 7 and 37 are made by fabric material that present soil or (semi) rigid features, so they could be made separately and associated together during the mold assembling. The fabric material however could be made by otlier typt^ according to ditTerent embodiments or needs of use of the finished impeller. Moreover, these fabric eiemenis could be made of different types of fiber material according to differeni embodiments, see below.
In Figg.5 and 6 it is shown schematically the aerodynamic vane insert 200 according lo an advantageou.s embodiment of (be invention, in which it

comprises a central region 2()0A configured to reproduce a vane 13 of the finished impeller and opposite shaped end regions 200B, 20()C configured lo be sissociated with shaped end regions 200B and respectively 200C of an adjacent vane insert 200 to arrange the annular assembly realixing tlte annular inseri 110. In particular, the end regions 200B, 200C comprise a lateral surfaces 200D and respectivel> 20()E are able to engage with the lateral surfaces 20UD and respectively 2()0E of the adjacent vane insert 200.
Advantageously, the opposite shaped end regions 20()B, 200C reproduce the inlel eye and respectively the outlet eye of the vane 13.
Moreover, in this particular embodiment, the end regions 200B. 200C are shaped in order to match with end regions of an adjacent inseri 200 and, at the same lime, for handling and positioning the vane insert 200 within the mold 100.
ft"s clear that the form and the shape of these end regions 200B. 200C could be changed according to the particular embodiments of the invention.
U has to be noted that the vane insert 200, shown here, represents a three-dimensional vane; but it's clear that this insert 200 could be made according to other different types, for example a two-dimensional vane or other.
In Fig 7 it is shown schematically the aforesaid shaped element 19 according to an advantageous embodiment of the invention, able to cover just the portion of a vane 13 of the finished impeller where the erosion process is higher, for example the bottom part thereof (see Fig.lA.)
In particular, this shaped element 19 is realized by a first surface SI able to reproduce the shape of and to be associated on the inferior wall 131 of a vane 13, see also Fig.lAi and by lateral edges S2 and S3 to reproduce

parliaily ihc shape of and to be associated on ihe lateral walls of the blades 15 inside ihe vane 13. Acivantageousiy, this shaped element 19 can be associated on the central region 2()0A of the \ aae insert 2U0 and enclosed by the first, second or third fabric elements 1 A, IB or IC, see also Ftgg.5 and 6,
In Fig.8 it is shown a different embodin»en{ with respect to Fig.7 in which a shaped component 20 is able to coat or cover completely the walls of the vane 13; in other words, this shaped component 20 forms substiuitially a closed channel able to reproduce entirely the vane 13 in which ihe working fluid flows.
I In particular, this shaped element 20 is realized by a first inferior surface LI able lo reproduce the shape of and to be associated on the inferior wall !3l of a vane 13; by lateral edges L2 and L3 to reprodtice the shape of and to be associated on the lateral walls of the blades 15 inside the vane 13 and by a second superior surface L4 lo reproduce the shape of and lo be a.ssociirted on the superior wail 13S of a vane 13.
At tlie same time, this shaped element 20 can be associated on the central region 200A of the insert 200 and enclosed by the first, second or third fabric elemenl 1 A. IB or IC.
These shaped elements 19, 20 could be made by a material resistant to erosion or corrosion (as for example metal or ceramic or polymers or other) and can also be used to further increase the mechtmical resistance of the finished impeller.
It's clear that the shaped elements 19. 20 have to reproduce the shape of The vane, so lhe>' could be of the three or two dimensional types, or other types according to the shape of the particular vane in which they have to be
n

associated.
It has to be noted tSiat the shaped elements 19, 20 can be fixed inside the vitne 13 by tlve filling materiai M and also by its shaped form in a simple aad useful way.
|Fig.9A shows the first fiber element lA (see also Fig.lA) that presents a shape reproducing approximately the shape of the vane 13. In this case, this element 1.4 could be made by any type of fibers - as described before - and it coyld be advantageously semi-elastic or conformable so as to enlarge itself to pass over the end regions 200B or 200C of tlte insert 200 and then to close around (he central region 200A. h is clear that, in a further embodiment, the insert 200 could not include the end regions 200B. 2t)0C. In another embodiment, the element IA could be braided, or otherwise produced, directly onto the insert 2O0, so no fabric deformation would be required.
Fig.9B shows the second fiber element IB (see also .Fig.IB) that presents a shape configured to surround alternately the superior wall I3S of the vane 13 and the inferior wail 131 of an adjacent vane 13 passing along the respective blade 15 therebetween. In particular, this second element IB is made substantially by a shroud plate shaped so as to form continuously all the vanes 13 of tlie annular assembly placing a vane insert 200 and the adjacent vane insert 200 opposed on its surface during the assembly of the mold 100,
Fig.'X.' shows the third fiber element IC (see also Fig. IC) that presents a configuration substantially made by an annular plate to form the superior or inferior wall I3S or 131 with blade surfaces stretching out from this plate to form the blade 15 of the finished impeller: this third fabric element IC can be placed substantially above the annular in.sert 110 (as shown in Fig.9C) or

under the annulaT insert 110 (as shown in Fig. IC) during the assembly of the mold 100.
in Fig.10 it is shown schematically a cross-section of the mold 100 of Figg.2 and 3. in which you can see m particular the vane inserts 200 and the empty spaces inside which is contained the aforesaid fabric elements 1 to 7 and in which the fdling material M is filled,
In a particularly adv^itageous embodiment, (Jie empty spaces are made so as to match or press together the fabric elements 1 to 7 placed inside so iliat the adjacent fabric elements are strictly in contact each other.
In this way it is possible to decrease the empty spaces between two adjacent fiber elements 1 lo 7 as much as possible; the filling material M being able to fill the spaces between fibers of the same fiber element 1 to 7 in order to provide a high, and controlled, fiber volume fraction, see above; in particular, using a closed mold it is possible to control these spaces to provide a high, and controlled, fiber volume fraction.
The filling material M can be injected from a plurality of injection holes 12.1 made in the base plate 113 and/or in the upper-ring i 1.5.
In the Figg.llA to ML there are shown a plurality of fibers that can be used to make the fiber elements lA, IB, IC. 4, 5, 6,7 or 37 according to different embodiments of tlte invention.
I In particular, shown in Fig. 11A is a composite material comprising the filling material M inside which are enclosed a plurality of continuous fibers R.2 which ma\ be oriented in a preferential direction in order to have optimal strength distribution on the fiber elements during the use of the finished impeller.
20

in Figg.llB and IIC are shown composite maleriais composed of the filling nisUerial M inside which are enclosed a plurality of particle fibers R3 and respective^ discontinuous fibers R4.
In Figg. f ID 10 IIL are sbo^vs respectively fibers composed of a biaxia! mesh R5, a sewed mesh R6, a tri-axial mesh R7, a multilayer warping mesh R8, a three-dimensional twister fiber R9, a cyiindricfJ three-dimensic^ia! mesh RiO and respectively a three-dimensional interwoven mesh RM. All these tjpes of fibers or mesh can be various!) oriented in order to have optimal strength distribution on the fiber elements.
It has to be noted that over the years many types of synthetic fibers have developed presenting specific characteristics for particular applications that can be used according lo the particular enibodimenis.
For example, the Dyneema tO (also known as "Gel Spuji Polyethylene, or flDPR) of the Company "High Performance Fibers b.v. Corporation" is a synthetic fiber suitable for production of cables for traction, and it is used for sports such as kite surfing, climbing, fishing and the production of armors; another fiber similar to the Dyneema is the Spectra *■ patented by an U.S. Company; and another fiber available on tlie market is the Nomex #, a meta-aramjd sub-stance made in the early sixties by DuPont.
The disclosed exemplary embodiments provide objects and methods to realize an impeller with innovative features It should be understood that this description is not intended to limit the invention. On the contrar>, the exemplary embodiments are imended lo cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by (he appended claims Further, in the detailed description of the
5t

exemptar>- embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.
Although the features and elements of the present exemplar^' embodiments are described in the embodiments in particular combinations, each feature or element caji be used alone without (he other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein.
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 example are intended to be within the scope of the claims if (hey have structural elements tlial do not dilTer from the literal Ijwiguage of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
A ft A 3^ lit ft ^
5x

WE CLAIM:
1. A centrifugal impeller for a Uirbomachine comprising a plurality of aerodynamic vanes (13), each of ibem (13) having internal walls on which is associated a fabric element {1 A; IB; iC; 4: 5; 6; 7; 37).
2. The impeller of claim I. wtierein the first fabric elements (lA) are configured to surround each of said aerodynamic vanes (13).
3. The impeller of claim 1 or 2, wherein a second fabric element (IB) is configured to surround alternateh an upper wall (t3S) of a vaxie (13) and a lower wall (131) of an adjacent vane (13) passing along the respective blade (15) there between.
4. The impeller of at least one of the precedent claims, wherein a third fabric element (tC) has a conical surface with blades stretching out from said surface.
5. The impeller of at least one of the precedent claims, wherein if comprises at least one of the followings;

- a fourth fabric element (4) associated over said aerodynamic vanes (13); said fourth element (4) having substantially a centrifugal shroud shape and function:
- a fifth fabric element (5) provided to realize substantially a rear-plaie for the finished impeller; said fifth element (5) having substantially art annular planar shape:
- a sixth fabric element (6) associated under said aerodynamic vanes (13); said sixth element (6) having substantially an annular shape able to be matched with the e.\tema1 inferior surface of said aerodynamic vanes (13);
- a sevemh fabric element (7) associated around an axial hole (21C) used to associate a rotor for the turbomachine;
- a .segmented fabric element (37) able to he fitted inside the space at the corner
S3

of shaped slots (115) of the vanes (13) to increase the rigidity of the whole assembly of the finished impeller, eliminate preferential flowpaths fos the filling niateriaK and avoid regions containing only filling material with no fiber where cracking might initiate during cure;
- a shaped component (19; 20) associated inside each of said aerodynamic vanes (13) in order to act against the erosion of the working tluid. 6, The impeller of at least one of the precedent claims, wherein said fabric elements (i A, IB; IC, 4; 5; 6; 7; 39) are impregnated with a filling material (M). 7 The impeller of at least one of the precedent claims, wherein an inner core element (21) is associated under said aerodynamic vanes (13) in order to facilitate the manufacturing process of said impeller.
8. The impeller of claim 7. wherein said core eiemeni (21) is surrounded by at
least one of the following: said fourth, fifth, sixth, seventh fiber elements (4; 5; 6;
7)
9. The impeller of at least one of the precedent claims, wherein said fabric elements (1A, IB: l(^; 4; 5; 6; 7; 37) are made by a plurality of unidirectional or multidirectional fibers, realized substantially to have a high aiiisotropy along at least a prefereniiat direction.
10. A turboroachine wherein it comprises at least a centrifugal impeller as described from at least one of claim i to 9
MANISHA SINGH NAIR
Agent for the Applicant riN/PA-7401
LEX ORBIS ^
Intellectual Property Practice 709/710, Tolstoy House, 15-17, Tolstoy Marg, New Delhi-110001
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