Radial outflow turbine

Abstract

1. A radial outflow turbine (1), comprises an inlet stator (16) mounted in a case (5), at an inlet duct (9), fixed with respect to the case (2) and comprising a plurality of inlet stator vanes (21) distributed around an axis of rotation (X-X) of a rotor disk (5) of the turbine (1). The inlet stator vanes (21) are curved outside of radial planes containing the axis of rotation (X-X) and all in one and the same direction about said axis of rotation (X-X), to delimit among them a plurality of curved channels (31). Each of the curved channels (31) has an inlet section (I) and an outlet section (O), wherein a direction orthogonal to the inlet section (I) forms with the axis of rotation (X-X) an inlet angle (Ω) so as to receive the working fluid along an axial or substantially axial direction (A). Each curved channel (31) is further shaped to direct the outgoing working fluid through the respective outlet section (O) along a direction tangent (T) to a circumference coaxial to the axis of rotation (X-X).

Description

[0001] “Radial outflow turbine”

[0002] DESCRIPTION

[0003] Field of the finding

[0004] The present invention has as its object a radial outflow turbine.

[0005] As radial outflow turbine is intended a drive turbomachine wherein the fluid flow with which it exchanges energy is mainly directed in a radial direction with respect to the axis of rotation of the turbine and from the center towards the periphery of the turbine.

[0006] Preferably but not exclusively, the present invention refers to radial expansion turbines used in apparatuses for energy production by means of the water-steam Rankine cycle or organic Rankine cycle (ORC).

[0007] The present invention specifically refers to the inlet structure of the working fluid in the radial outflow turbine.

[0008] Background of the finding

[0009] The public document WO0216775A2 shows an expansion turbine with axial inlet and radial outlet. The turbine comprises a stator provided with a conical deflector and a plurality of fixed and inclined vanes arranged around the axis of the turbine. The public document W02015140707A1 shows a radial outflow turbine comprising a support disk having a face with a radial rotor stage formed by an array of vanes arranged in succession along a respective circular path. The disk has through inlet channels provided with inlet rotor vanes and located in a position radially outer to a respective shaft and radially inner to the radial rotor stage. The turbine also comprises a first fixed portion provided with a plurality of fixed inlet openings axially placed alongside the inlet rotor vanes of the support disk. The fixed inlet openings have inlet stator vanes defining an axial stator stage.

[0010] The public document WO2016128925A1 shows a centrifugal radial turbomachine comprising a rotor disk installed in a case and rotating in the case around a respective axis of rotation, a ring of rotor vanes mounted on a front face of the rotor disk, a ring of stator vanes that extend axially between the case and the front face of the rotor disk. The case has a radially axial inlet inner with respect to the stator vane ring and an adjustment device operatively active at the axial inlet. The adjustment device comprises an annular member placed at the axial inlet, a drive shaft and an actuator configured to move the annular member. The adjustment device also comprises radial elements with an aerodynamic profile that connect the annular member to the drive shaft.

[0011] The public document US3378229A shows a radial outflow turbine comprising nozzles placed radially upstream of the respective rotor vanes to receive a radial flow and direct it in the direction of rotation of the rotor.

[0012] Summary

[0013] In the field of radial outflow turbines, which are characterized by low volumetric flow rates and high enthalpy jumps, the performance of the turbine can be increased by raising the rotational speed of the machine.

[0014] The Applicant however, has observed that the increase in the rotation speed of the machine requires the reduction of the inlet radius of the first stator. Since the inflow of the fluid into the machine takes place along an axial or substantially axial direction and then the fluid is deflected along radial directions and towards a first vaned stator array, the reduction of the inlet radius of the first stator involves that the fluid is forced to suddenly change direction, with a possible detachment of the fluid vein and consequent impairment of the machine performance.

[0015] The Applicant retains that the presence of stator vanes at the inlet such as those shown in the above-mentioned documents W02015140707A1 and WO2016128925A1 , is not able to solve this drawback. Nor would the stator vanes shown in document WO0216775A2 and US3378229A appear to be effective since, when the fluid meets them, it has already changed direction from axial to radial and therefore the possible detachment of the fluid vein has already occurred.

[0016] The Applicant has therefore realized the need to guide the fluid flow entering the radial outflow turbine such as to be able to increase its rotation speed without drawbacks and therefore to improve the performance of the turbine itself.

[0017] The Applicant has found that the above indicated goals and still others can be reached by placing a particular stator at an inlet of the machine, which is able to guide the flow and avoid the formation of recirculations.

[0018] More specifically, according to a 1stindependent aspect, the present invention refers to a radial outflow turbine, comprising: a case; a rotor disk mounted in the case and supported in the case such as to be able to rotate around its own axis of rotation passing through a center of the rotor disk and perpendicular to the rotor disk; at least one array of rotor vanes arranged on a face of the rotor disk and around the axis of rotation, wherein leading edges of the rotor vanes face the axis of rotation; wherein the case has an inlet duct located at the axis of rotation; wherein said face of the rotor disk bounds with the case a transit volume for a working fluid, the transit volume being in fluid communication with the inlet duct and with a radially peripheral outlet; an inlet stator mounted in the case, at the inlet duct, fixed with respect to the case and comprising a plurality of inlet stator vanes distributed around the axis of rotation.

[0019] The inlet stator vanes are curved outside of radial planes containing the axis of rotation and all in one and the same direction about said axis of rotation, to delimit among them a plurality of curved channels; each of the curved channels having an inlet section and an outlet section; wherein a direction orthogonal to the inlet section forms with the axis of rotation an inlet angle such as to receive the working fluid along an axial or substantially axial direction, optionally the inlet angle being between 0° and 45°, preferably but not necessarily the inlet angle being equal to 0°; wherein each curved channel is shaped to direct the outgoing working fluid through the respective outlet section along a direction tangent to a circumference coaxial to the axis of rotation.

[0020] The inlet angle is such that the inlet section receives the working fluid along an axial or substantially axial direction; optionally the inlet angle is between 0° and 45°; optionally the inlet angle is equal to 30°; optionally the inlet angle is equal to 0°. Each curved channel is shaped to direct the outgoing working fluid through the respective outlet section along a direction tangent to a circumference coaxial to the axis of rotation, such as to transform the direction of the working fluid from axial to radial and to confer a rotational component to said working fluid.

[0021] An observer placed outside of the case and on the axis of rotation who observes the inlet stator through the inlet duct sees at least part of the inlet sections.

[0022] The Applicant has verified first of all that the solution according to the invention allows to transform the direction of the flow from axial to radial and to confer a rotational component to the fluid, reducing or eliminating the risks of a detachment of the fluid vein. The Applicant has verified that the solution according to the invention allows to realize a vaned stator array located at the inlet and to ensure that an absolute speed at the outlet of the vaned stator array is the correct one for the inflow of the fluid into the rotor array placed immediately downstream.

[0023] The Applicant has actually verified that the curvature of the inlet stator vanes diverts the flow, increasing the absolute speed and the “rotation” thereof, with an increase of the outlet angle. The solution therefore combines two functions (transforming the direction of the flow from axial to radial and realizing a vaned stator array) in a single component.

[0024] The Applicant has also verified that the solution according to the invention allows to realize the first rotor array, placed on the rotor disk, with a reduced diameter with respect to known solutions.

[0025] The Applicant has then verified that the solution according to the invention allows to increase the rotation speed of the machine and therefore its performance. In this way, with the same available enthalpy jump, it is possible to realize machines with smaller radial dimensions and higher rotation speeds, with a consequent increase in efficiency.

[0026] Further aspects of the invention are below described.

[0027] In a 2ndaspect according to the 1staspect, the inlet stator comprises a central body carrying the plurality of inlet stator vanes.

[0028] In a 3rdaspect according to the 2ndaspect, the central body has a first axial end located at the inlet sections of the curved channels and / or the central body has a second axial end located at the outlet sections of the curved channels.

[0029] In a 4thaspect according to the 3rdaspect, a diameter of the first axial end is smaller than a diameter of the second axial end.

[0030] In a 5thaspect according to the 2nd, 3rdor 4thaspect, the inlet stator vanes develop from a surface of the central body and said surface of the central body bounds the curved channels together with said inlet stator vanes.

[0031] In a 6thaspect according to at least one of the aspects 2 to 5, the surface of the central body has at least one portion that diverges toward the second axial end.

[0032] In a 7thaspect according to the 6thaspect, the portion that diverges is substantially conical.

[0033] In an 8thaspect according to the 6thor 7thaspect, the portion that diverges is concave. In a 9thaspect according to the aspect 3 or 4 or to at least one of the aspects 5 to 8 when the 5thaspect is according to the aspect 3 or 4, the surface of the central body has a substantially cylindrical portion close to the first axial end and coaxial to the axis of rotation; optionally, said substantially cylindrical portion defines an inlet nose, optionally having a rounded or tapered ogival shape.

[0034] In a 10thaspect according to the aspect 3 or 4 or to at least one of the aspects 5 to 9 when the 5thaspect is according to the aspect 3 or 4, the surface of the central body has a radially peripheral portion and close to the second axial end that lies in a plane orthogonal to the axis of rotation.

[0035] In a 11thaspect according to at least one of the aspects 1 to 10, an inner surface of the inlet duct is associated to the inlet stator vanes and bounds the curved channels together with said inlet stator vanes.

[0036] In a 12thaspect according to at least one of the aspects 1 to 10, the inlet stator comprises an annular body having an inner surface associated to the inlet stator vanes and bounding the curved channels together with said inlet stator vanes.

[0037] In a 13thaspect according to at least one of the aspects 1 to 12, each inlet stator vane has: a leading edge, a trailing edge, a radially inner side edge joining the leading edge with the trailing edge and a radially outer side edge joining the leading edge with the trailing edge.

[0038] In a 14thaspect according to the aspect 13, the leading edges border the inlet sections of the curved channels; optionally the leading edges are positioned at the first axial end of the central body.

[0039] In a 15thaspect according to the aspect 13 or 14, the trailing edges border the outlet sections of the curved channels.

[0040] In a 16thaspect according to at least one of the aspects 13 to 15, the leading edges of the inlet stator vanes bound with the axis of rotation angles complementary to said inlet angles.

[0041] In a 17thaspect according to at least one of the aspects 13 to 16, the leading edges of the inlet stator vanes extend along radial directions.

[0042] In a 18thaspect according to at least one of the aspects 13 to 17, the trailing edges of the inlet stator vanes extend along respective axial directions.

[0043] In a 19thaspect according to at least one of the aspects 13 to 18, a median surface of each inlet stator vane placed at the respective leading edge is tangent to a plane forming with the axis of rotation an angle between 0° and 30°. In a 20thaspect according to at least one of the aspects 13 to 19, a median surface of each inlet stator vane placed at the respective trailing edge is tangent to a plane in turn tangent to a circumference coaxial to the axis of rotation.

[0044] In a 21staspect according to at least one of the aspects 1 to 20, each inlet stator vane has a substantially concave intrados.

[0045] In a 22ndaspect according to at least one of the aspects 1 to 21 , each inlet stator vane has a substantially convex extrados.

[0046] In a 23rdaspect according to at least one of the aspects 1 to 22, each inlet stator vane is warped.

[0047] In a 24thaspect according to at least one of the aspects 13 to 20 or according to at least one of the aspects 21 to 23 when according to the aspect 13, the radially inner side edge is associated to a surface of the central body.

[0048] In a 25thaspect according to at least one of the aspects 13 to 20 or with the aspect

[0049] 24 or according to at least one of the aspects 21 to 23 when according to the aspect 13, the radially outer side edge is associated to an inner surface of the inlet duct or to an inner surface of an annular body part of the inlet stator and bounding the curved channels together with said inlet stator vanes.

[0050] In a 26thaspect according to at least one of the aspects 1 to 25, the rotor vanes of said at least one array are arranged around the outlet sections of the curved channels and are adjacent to said outlet sections of the curved channels.

[0051] In a 27thaspect according to at least one of the aspects 1 to 26, the radial outflow turbine comprises a plurality of concentric arrays of rotor vanes arranged on the face of the rotor disk and around the axis of rotation; wherein the rotor vanes of a more radially internal array are arranged around the outlet sections of the curved channels and are adjacent to said outlet sections of the curved channels.

[0052] In a 28thaspect according to the aspect 26 or 27 when according to one of the aspects 13 to 20, a height of the inlet stator vanes at the trailing edges is equal or substantially equal to a height of the adjacent rotor vanes.

[0053] In a 29thaspect according to at least one of the aspects 13 to 20, a height of the inlet stator vanes at the leading edges is higher than a height of the inlet stator vanes at the trailing edges.

[0054] In a 30thaspect according to at least one of the aspects 1 to 29, the radial outflow turbine comprises at least one array of stator vanes arranged around the axis of rotation and on an internal face of the case placed in front of the face of the rotor disk.

[0055] In a 31staspect according to the aspect 30 when according to the aspect 29, the radial outflow turbine comprises a plurality of arrays of stator vanes interposed among the arrays of rotor vanes.

[0056] In a 32ndaspect according to the aspect 30 or 31 , the radial outflow turbine comprises a support disk fixed in the case and placed in front of the face of the rotor disk carrying said at least one array of rotor vanes, wherein the support disk carries said at least one array of stator vanes.

[0057] In a 33rdaspect according to at least one of the aspects 1 to 32, the face of the rotor disk carrying said at least one array of rotor vanes is flat.

[0058] In a 34thaspect according to at least one of the aspects 1 to 33, leading edges of the rotor vanes lie substantially parallel to the axis of rotation.

[0059] In a 35thaspect according to at least one of the aspects 1 to 34, the inlet stator is removably mounted in the case, optionally by means of screws.

[0060] In a 36thaspect according to the aspect 35, the inlet stator is fixed to a wall of the case facing the face of the rotor disk carrying said at least one array of rotor vanes. In a 37thaspect according to the aspect 36 when the aspect 35 is according to the aspect 32, the inlet stator is fixed to the support disk.

[0061] In a 38thaspect according to the aspect 37, the inlet stator is fixed to the support disk that in turn is fixed to the case.

[0062] In a 39thaspect according to the aspect 36, 37 or 38 when the aspect 35 is according to the aspect 12 or 25, the annular body is fixed to said wall of the case.

[0063] In a 40thaspect according to the aspect 39, through screws in the annular body are screwed in said wall of the case.

[0064] In a 41staspect according to at least one of the aspects 1 to 40, the radial outflow turbine comprises a shaft mounted in the case, optionally by means of bearings, to rotate about said axis of rotation; wherein the rotor disk is mounted on the shaft to rotate integrally with said shaft.

[0065] In a 42ndaspect according to the aspect 41 , the rotor disk is mounted at one end of the shaft and the inlet stator is located in front of said end of the shaft.

[0066] In a 43rdaspect according to at least one of the aspects 1 to 42, the inlet duct of the radial outflow turbine is in connection with a working fluid and the radial outflow turbine is mechanically connected to a generator to generate electrical energy by means of the rotation of the rotor disk caused by the passage of the fluid in the transit volume.

[0067] In a 44thaspect, the present invention is also related to an organic Rankine cycle plant (ORC) comprising a radial outflow turbine according to one or more of the aspects 1 to 43.

[0068] In a 45thaspect according to the aspect 44, the organic Rankine cycle plant comprises: an organic working fluid; a heat exchanger combined with a high temperature source and configured to exchange heat between the high temperature source and the organic working fluid so as to heat and evaporate said organic working fluid; said radial outflow turbine fed with the organic working fluid in vapor phase exiting the heat exchanger to realize a conversion of the energy of the working fluid into mechanical energy according to a Rankine cycle and then into electrical energy through a generator mechanically connected to the radial outflow turbine; a condenser configured to condense the organic working fluid exiting the radial outflow turbine; a pump configured to feed with the organic working fluid coming from the radial outflow turbine said heat exchanger.

[0069] In a 46thaspect according to the aspect 44 or 45, the organic working fluid is chosen among hydrocarbons, ketones, siloxanes, fluorides.

[0070] Further characteristics and advantages will become more apparent from the detailed description of preferred, but not exclusive, embodiments of a radial outflow turbine according to the present invention.

[0071] Description of the drawings

[0072] This description will be explained below with reference to the attached drawings, provided solely for illustrative and, therefore, non-limiting purpose, in which:

[0073] ■ figure 1 shows a partial half-section according to a radial plane of a radial outflow turbine according to present invention;

[0074] ■ figure 2 shows a front view of a rotor disk belonging to the turbine of figure 1 ;

[0075] ■ figure 3 is a 3D view of an inlet stator of the radial outflow turbine of figure 1 with some parts removed to better highlight others;

[0076] ■ figures 3A and 3B show respective enlarged portions of figure 3;

[0077] ■ figure 4 is a side elevation view of the inlet stator of figure 3;

[0078] ■ figure 4A is a magnification of figure 4; ■ figure 5 is a front view of the inlet stator of figure 3;

[0079] ■ figure 6 is a sectional view of the inlet stator according to the VI-VI plane of figure 4;

[0080] ■ figure 6A is a magnification of figure 6;

[0081] ■ figure 7 is a 3D view of a stator vane of the inlet stator as referred to in the preceding figures;

[0082] ■ figures 8 - 10 show respective variants of the radial outflow turbine of figure 1 .

[0083] Definitions

[0084] In the present description and in the attached claims, the terms “radial” and “axial” and “circumferential” are intended to refer to the axis of rotation of the turbine.

[0085] In the present description and in the attached claims, with “median surface of a vane” (stator or rotor) is intended the surface defined by the assembly of the median lines of the wing profile of said vane.

[0086] Detailed description

[0087] With reference to the mentioned figures, a radial outflow turbine (ROT - Radial Outflow Turbine) according to the present invention has been overall indicated with the reference number 1 .

[0088] The radial outflow turbine 1 comprises a case 2 that houses an impeller comprising a shaft 3 supported by means of bearings 4 in the case 1 such as to rotate about its own axis of rotation “X-X”. The impeller comprises furthermore a rotor disk 5 positioned at one end of the shaft 3 (keyed on the shaft 3 or realized as one piece with the shaft 3), such as to rotate together with the shaft 3 around the axis of rotation “X-X” that passes through a center of the rotor disk 5. In the exemplary embodiment shown in figure 1 , the case 2 comprises a front wall 6, a rear wall 7 and a sleeve 8 that extends from the rear wall 6 and internally carries the bearings 4 and the shaft 3.

[0089] The front wall of the case 2 has an inlet duct 9 located at the axis of rotation “X-X”. In the shown exemplary embodiment, the inlet duct 9 has a circular section and is coaxial to the axis of rotation “X-X”. The rotor disk 5 is interposed between the front wall 6 and the rear wall 7 and has an its own face 10 facing the front wall 6. This face 10 is flat and supports a first array of rotor vanes 11 and a second array of rotor vanes 12 arranged around the axis of rotation “X-X” and concentric to each other (figures 1 and 2).

[0090] An inner face of the front wall 6 of the case 2 carries an array of stator vanes 13 arranged around the axis of rotation “X-X” and interposed between the first array of rotor vanes 11 and the second array of rotor vanes 12 (figure 1 ). In the embodiment of figure 1 , the stator vanes 13 are carried by a support disk 14 placed side by side and fixed to the front wall 6 by means of screws 15.

[0091] Leading edges of the rotor vanes 11 , 12 lie substantially parallel to the axis of rotation “X-X” and face said axis of rotation “X-X”.

[0092] The face 10 of the rotor disk 5 that carries the rotor vanes 11 , 12 bounds, with the front wall 6 or with the support disk 14, a transit volume for a working fluid “F” that enters through the inlet duct 9. The transit volume is in fluid communication with the inlet duct 9 and with a radially peripheral outlet (not shown).

[0093] An inlet stator 16 is mounted fixed in the case 2, at the inlet duct 9 and is located in front of the end of shaft 3 that carries the rotor disk 5. The inlet stator 16 is positioned at the axis of rotation “X-X”, near the flat face 10 of the rotor disk 5 and in a position radially internal with respect to the first array of rotor vanes 11 .

[0094] The inlet stator 16 comprises a central body 17 axial-symmetrical with respect to the axis of rotation “X-X”. The central body 17 has a first axial end 18 and a second axial end 19. The first axial end 18 faces the inlet duct 9. The central body 17 converges starting from the second axial end 19 toward the first axial end 18. In fact, a diameter of the first axial end 18 is smaller than a diameter of the second axial end 19. The first axial end 18 has a rounded or tapered ogival shape. The second axial end 19 has the shape of a disk.

[0095] The central body 17 has a surface 20 that connects the first axial end 18 to the second axial end 19 and diverges toward the second axial end 19 like a kind of cone but with a certain concavity. The surface 20 of the central body 17 has a portion substantially cylindrical and coaxial to the axis of rotation “X-X” close to the first axial end 18 and a portion radially peripheral and close to the second axial end 19 that lies in a plane orthogonal to the axis of rotation “X-X”.

[0096] On the surface 20 of the central body 17 are positioned inlet stator vanes 21 distributed around the axis of rotation “X-X”. Each inlet stator vane 21 has a leading edge 22, a trailing edge 23, a radially inner side edge 24, joining the leading edge 22 with the trailing edge 23, and a radially outer side edge 25, joining the leading edge 22 with the trailing edge 23 (figure 7).

[0097] In the embodiments shown in figures 1 , 3-7, 9 and 10, the leading edges 22 are close to the first axial end 18 and extend along radial directions (figure 5), i.e. bound with the axis of rotation “X-X” angles “|3” of 90°. The trailing edges 23 are close to the second axial end 19, are positioned on the radially peripheral portion of the surface 20 and extend along respective axial directions (figure 3 and 4). A height “hi” of the inlet stator vanes 21 at the leading edges 22 is higher than a height “h2” of the inlet stator vanes 21 at the trailing edges 23 (figure 9). In the shown exemplary embodiments, “hi” is about three times “h2”.

[0098] The inlet stator vanes 21 are curved and warped outside of radial planes containing the axis of rotation “X-X”, all in one and the same direction about said axis of rotation “X-X”. Each inlet stator vane 21 has sections of a wing profile with a substantially concave thrust face 26 and a substantially convex suction face 27.

[0099] A median surface “M” of each inlet stator vane 21 placed at the respective leading edge 22 is tangent to a plane “P1” forming with the axis of rotation “X-X” an angle of attack “a” between 0° and 30° (figure 4A). This median surface “M” at the respective trailing edge 23 is instead tangent to a plane “P2” in turn tangent to a circumference coaxial to the axis of rotation “X-X” (figure 6A).

[0100] The radially inner side edge 24 of each inlet stator vane 21 is associated with the surface 20 of the central body 17 (connected or realized as one piece).

[0101] The inlet stator 16 comprises furthermore an annular body 28 arranged around the central body 17, coaxial to the central body 17 and having an inner surface 29 connected (jointed or realized as one piece) to the radially outer side edge 25 of each inlet stator vane 21. In figures 3-6, this annular body has not been shown to better highlight the inlet stator vanes 21 , while it is visible in cross-section in figures 1 , 8, 9 and 10.

[0102] In the embodiment of figures 1 and 8, the inlet stator 16 is removably mounted in the case 2, by means of screws 30 engaged in the annular body 28 and in the support disk 14. The screws 30 fix the inlet stator 16 to the support disk 14 that is in turn fixed to the front wall 6 by means of the respective screws 15. The screws 15, 30 are arranged around the inlet duct 9. The inlet stator vanes 21 bound among them and together with the surface 20 of the central body 17 and the inner surface 29 of the annular body a plurality of curved channels 31 .

[0103] Each of the curved channels 31 has an inlet section “I” and an outlet section “0” (figures 3A and 3B).

[0104] The inlet section “I” is defined by a flat surface wherein two adjacent leading edges 22 lie and is bounded between said two adjacent leading edges 22.

[0105] The outlet section “0” is defined from a flat surface wherein two adjacent trailing edges 23 lie and is bounded between said two adjacent trailing edges 23.

[0106] A direction orthogonal to the inlet section “I” forms with the axis of rotation “X-X” an inlet angle “Q” (figure 8), preferably between 0° and 45°, such as to receive the working fluid that enters through the inlet duct 9 along an axial or substantially axial direction “A” (schematically shown in figures 3 and 4). This inlet angle “Q” is complementary to the angle “|3” formed by the leading edges 22 with the axis of rotation “X-X”. In the embodiments of figures 1 , 9 and 10, the inlet angle “Q” is equal to 0° and the angle “|3” is equal to 90°.

[0107] Each curved channel 31 is shaped to direct the outgoing working fluid through the respective outlet section “O” along a direction tangent “T” to a circumference coaxial to the axis of rotation “X-X” (figures 3 and 6).

[0108] As can be seen in figures 1 , 8, 9 and 10, the rotor vanes 11 of the first array are arranged around the outlet sections “O” of the curved channels 31 and are adjacent to said outlet sections “0”. The height “h2” of the inlet stator vanes 21 at the trailing edges 23 is equal or substantially equal to a height “h3” of the rotor vanes 11 of the first array.

[0109] The embodiment variant of figure 8 differs from that of figure 1 in that the leading edge 22 of the inlet stator vanes 21 is backward with respect to that of figure 1 and is inclined such as to form with the axis of rotation “X-X” an angle “|3” less than 90°, for example of about 60°. Then, the inlet angle “Q” is of about 30°.

[0110] The embodiment variant of figure 9 differs from that of figure 1 in that the annular body 28 is attached to the front wall 6 of the case 2 by means of screws 15 which pass through said annular body 28 and also through the support disk 14.

[0111] The embodiment variant of figure 10 differs from that of figure 1 in that the annular body 28 is attached to the front wall 6 of the case 2 by means of screws 15 which pass through said annular body 28 and screw directly into the front wall 6, because the support disk 14 is not present and the stator vanes 13 are carried by the front wall 6.

[0112] In not shown embodiment variants, the inlet stator 16 is not provided with the annular body 28 and an inner surface of the inlet duct 9 is associated to the inlet stator vanes 21 and bounds the curved channels 31 together with said inlet stator vanes 21. In other words, the annular body 28 is an integral part of the front wall of the case 2 or of the support disk 14. The radially outer side edge 25 of the inlet stator vanes 21 is associated with the inner surface of the inlet duct 9.

[0113] In use, the working fluid that enters through the inlet duct 9 according to a substantially axial direction, is guided and deviated by the curved channels 31 so that an outlet speed from the outlet sections “0” of the curved channels is the correct one for the inlet of the working fluid into the subsequent first array of rotor vanes 11 . The described radial outflow turbine 1 is preferably but not necessarily used within the organic Rankine cycle plants (ORC).

[0114] An organic Rankine cycle plant, not shown in its entirety as it is a known type, comprises: an organic working fluid (for example chosen among hydrocarbons, ketones, siloxanes, fluorides); a heat exchanger combined with a high temperature source and configured to exchange heat between the high temperature source and the organic working fluid so as to heat and evaporate said organic working fluid; the radial outflow turbine 1 supplied with the organic working fluid in vapor phase exiting from the heat exchanger to realize a conversion of the energy of the working fluid into mechanical energy according to a Rankine cycle and then into electrical energy through a generator mechanically connected to the shaft 3 of the radial outflow turbine 1 ; a condenser configured to condense the organic working fluid exiting from the radial outflow turbine 1 ; a pump configured to supply with the organic working fluid coming from the radial outflow turbine 1 again the heat exchanger.

[0115] List of elements

[0116] 1 radial outflow turbine

[0117] 2 case

[0118] 3 shaft

[0119] 4 bearings

[0120] 5 rotor disk

[0121] 6 front wall 7 rear wall

[0122] 8 sleeve

[0123] 9 inlet duct

[0124] 10 face of the rotor disk

[0125] 11 first array of rotor vanes

[0126] 12 second array of rotor vanes

[0127] 13 stator vanes

[0128] 14 support disk

[0129] 15 screws

[0130] 16 inlet stator

[0131] 17 a central body

[0132] 18 first axial end

[0133] 19 second axial end

[0134] 20 surface of the central body

[0135] 21 inlet stator vanes

[0136] 22 leading edges

[0137] 23 trailing edges

[0138] 24 radially inner side edge

[0139] 25 radially outer side edge

[0140] 26 concave thrust face

[0141] 27 convex suction face

[0142] 28 annular body

[0143] 29 inner surface

[0144] 30 screws

[0145] 31 curved channels

[0146] X-X axis of rotation

[0147] M median surface a angle of attack

[0148] [3 angle

[0149] Q inlet angle hi inlet stator vanes height at the leading edges h2 inlet stator vanes height at the trailing edges h3 rotor vanes height

Claims

CLAIMS1. Radial outflow turbine, comprising:- a case (2);- a rotor disk (5) mounted in the case (2) and supported in the case (2) such as to rotate about its own axis of rotation (X-X) passing through a center of the rotor disk (5) and perpendicular to the rotor disk (5);- at least one array of rotor vanes (11 , 12) arranged on a face (10) of the rotor disk (5) and around the axis of rotation (X-X), wherein leading edges of the rotor vanes (11 , 12) face the axis of rotation (X-X); wherein the case (2) has an inlet duct (9) located at the axis of rotation (X-X); wherein said face (10) of the rotor disk (5) bounds with the case (2) a transit volume for a working fluid, the transit volume being in fluid communication with the inlet duct (9) and with a radially peripheral outlet;- an inlet stator (16) mounted in the case (5), at the inlet duct (9), fixed with respect to the case (2) and comprising a plurality of inlet stator vanes (21 ) distributed around the axis of rotation (X-X); characterized in that the inlet stator vanes (21 ) are curved outside of radial planes containing the axis of rotation (X-X) and all in one and the same direction about said axis of rotation (X-X), to delimit among them a plurality of curved channels (31 ); each of the curved channels (31 ) having an inlet section (I) and an outlet section (O); wherein a direction orthogonal to the inlet section (I) forms with the axis of rotation (X-X) an inlet angle (Q) such that the inlet section (I) receives the working fluid along an axial or substantially axial direction (A); wherein each curved channel (31 ) is shaped to direct the outgoing working fluid through the respective outlet section (O) along a direction tangent (T) to a circumference coaxial to the axis of rotation (X-X), such as to transform the direction of the working fluid from axial to radial and to confer a rotational component to said working fluid.

2. Turbine according to claim 1 , wherein the inlet angle (Q) is between 0° and 45° or is equal to 0° or is equal to 30°.

3. Turbine according to claim 1 or 2, wherein the inlet stator (16) comprises a central body (17) carrying the plurality of inlet stator vanes (21 ); wherein the central body (7) has a first axial end (18) located at the inlet sections (I) of the curved channels (31 ) and / or wherein the central body (7) has a second axial end (19) located at the outlet sections (0) of the curved channels (31 ); wherein a diameter of the first axial end (18) is smaller than a diameter of the second axial end (19); wherein the inlet stator vanes (21 ) develop from a surface (20) of the central body (17) and said surface (20) of the central body (16) bounds the curved channels (31 ) together with said inlet stator vanes (21 ).

4. Turbine according to claim 3, wherein the surface (20) of the central body (17) has at least one portion diverging toward the second axial end (19) and one substantially cylindrical portion close to the first axial end (18) and coaxial to the axis of rotation (X-X).

5. Turbine according to any of claims 1 to 4, wherein an inner surface of the inlet duct (9) is associated to the inlet stator vanes (21 ) and bounds the curved channels (31 ) together with said inlet stator vanes (21 ); or wherein the inlet stator (16) comprises an annular body (28) having an inner surface (29) associated to the inlet stator vanes (21 ) and bounding the curved channels (31 ) together with said inlet stator vanes (21 ).

6. Turbine according to any of claims 1 to 5, wherein each inlet stator vane (21 ) has: a leading edge (22), a trailing edge (23), a radially inner side edge (24) joining the leading edge (22) with the trailing edge (23) and a radially outer side edge (25) joining the leading edge (22) with the trailing edge (23); wherein the leading edges (22) bound the inlet sections (I) of the curved channels (31 ); wherein the trailing edges (23) bound the outlet sections (0) of the curved channels (31 ).

7. T urbine according to claim 6, wherein the leading edges (22) of the inlet stator vanes (21 ) bound with the axis of rotation (X-X) angles (|3) complementary to said inlet angles (Q).

8. Turbine according to claim 6 or 7, wherein the leading edges (22) of the inlet stator vanes (21 ) extend along radial directions and wherein the trailing edges (23) of the inlet stator vanes (21 ) extend along respective axial directions.

9. Turbine according to any of claims 6 to 8, wherein a median surface (M) of each inlet stator vane (21 ) placed at the respective leading edge (22) is tangent to a plane (P1 ) forming with the axis of rotation (X-X) an angle of attack (a) between 0° and 30°.

10. Turbine according to any of claims 6 to 9, wherein a median surface (M) of each inlet stator vane (21 ) placed at the respective trailing edge (23) is tangent to a plane (P2) in turn tangent to a circumference coaxial to the axis of rotation (X-X).

11. Turbine according to any of claims 1 to 10, wherein each inlet stator vane (21 ) is warped.

12. Turbine according to any of claims 6 to 10 when claim 6 depends on any of claims 3 or 4, wherein the radially inner side edge (24) is associated with the surface (20) of the central body (17).

13. Turbine according to any of claims 6 to 10 when claim 6 depends on claim 5, wherein the radially outer side edge (25) is associated with the inner surface (29) of the inlet duct (9) or of the annular body (28).

14. Turbine according to any of claims 1 to 13, wherein the inlet stator (16) is removably mounted in the case (2).

15. Turbine according to any of claims 1 to 14, wherein the rotor vanes (11 ) of said at least one array are arranged around the outlet sections (0) of the curved channels (31 ) and are adjacent to said outlet sections (0) of the curved channels (31 ).

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