RADIAL TURBOMACHINE

Abstract

Radial turbomachine includes fixed case; one rotor disc installed in case and having rotor blades mounted on front face thereof; plurality of elements projecting from case and terminating proximity to rotor disc, wherein projecting elements include seal elements acting against rotor disc are operatively active on rear face of rotor disc or stator blades radially interposed between rotor blades of rotor disc; and one support plate bearing projecting elements and installed in case. Support plate is radially extended across from rotor disc and includes plurality of first circular portions concentric with rotation axis of rotor disc and plurality of second circular portions radially interposed between first circular portions. Several of first circular portions bear projecting elements and second circular portions are more deformable, along radial directions, than first circular portions in manner to allow relative movements between first circular portions when support plate is subjected to action of thermal gradients.

Claims

1. A radial turbomachine, comprising: a fixed case (6); at least one rotor disc (2, 2, 2) installed in the case (6) and having rotor blades (3, 3, 3) mounted at least on a front face (4, 4, 4) thereof, in which the rotor disc (2, 2, 2) is rotatable in the case (6) around a respective rotation axis (X-X); a plurality of elements (25, 35) projecting from the case (6) and terminating in proximity to the rotor disc (2, 2, 2); and at least one support plate (17, 37) installed in the case (6); wherein said support plate (17, 37) bears said elements (25, 35) projecting from the case (6); wherein said at least one support plate (17, 37) is radially extended across from the rotor disc (2, 2, 2), wherein the support plate (17, 37) comprises: a plurality of first circular portions (29) concentric with the rotation axis (X-X), wherein said first circular portions (29) bear said projecting elements (25, 35); and a plurality of second circular portions (30) radially interposed between the first circular portions (29), wherein the second circular portions (30) are configured to deform to a greater extent, along radial directions, than the first circular portions (29) in a manner so as to allow relative movements between the first circular portions (29) when the support plate (17, 37) is subjected to action of thermal gradients; wherein each of the second circular portions (30) comprises a plurality of flexible bodies, having a main extension that is transverse with respect to the radial directions; wherein the flexible bodies are substantially cylindrical or conical walls (33) coaxial with the rotation axis (X-X).

2. The turbomachine according to claim 1, wherein, in a section along an axial plane, the support plate (17, 37) has at least one serpentine section defining said substantially cylindrical or conical walls (33).

3. The turbomachine according to claim 2, wherein the serpentine section is defined by annular cavities obtained on both faces of the support plate (17, 37).

4. The turbomachine according to claim 3, wherein the annular cavities on the two faces are radially alternated to define said serpentine section.

5. The turbomachine according to claim 2, wherein a deformation of the second circular portions (30) occurs as a bellow movement of the serpentine section.

6. The turbomachine according to claim 2, wherein the serpentine section comprises radial sections and axial sections, wherein each of the second circular portions (30) comprises two axial sections connected by a radial section and each of the first portions (29) is defined by a radial section.

7. The turbomachine according to claim 2, wherein the serpentine section comprises radial sections and axial sections, wherein each of the second portions (30) comprises an axial section and two radial sections extended from opposite ends of the axial section, wherein each of the first portions (29) has a thickness, measured in an axial direction, equal to an axial length of the axial sections.

8. The turbomachine according to claim 1, wherein the support plate (17, 37) is a single piece.

9. The turbomachine according to claim 1, wherein the support plate (17, 37) is obtained via removal of material and/or via molding.

10. The turbomachine according to claim 1, wherein the projecting elements (25, 35) comprise seal elements (34) acting against the rotor disc (2, 2, 2) and operatively active on a rear face (9, 9, 9) of the rotor disc (2, 2, 2).

11. The turbomachine according to claim 1, wherein the projecting elements (25, 35) comprise stator blades (13) radially interposed between the rotor blades (3) of the rotor disc (2).

Description

DESCRIPTION OF THE DRAWINGS

[0099] Such description will be set forth hereinbelow with reference to the set of drawings, provided only as a non-limiting example, in which:

[0100] FIG. 1 illustrates a meridian section of a first embodiment of a turbomachine in accordance with the present invention;

[0101] FIG. 2 illustrates a meridian section of a second embodiment of a turbomachine in accordance with the present invention;

[0102] FIG. 3 illustrates a rear view of a portion of a support plate belonging to the turbomachines pursuant to FIGS. 1 and 2;

[0103] FIG. 4 is a meridian half-section of the support plate of FIG. 3;

[0104] FIG. 5 illustrates a variant of the support plate of FIG. 3;

[0105] FIG. 6 is a meridian half-section of the support plate of FIG. 5;

[0106] FIG. 7 illustrates a further variant of the support plate of FIG. 3;

[0107] FIG. 8 is a meridian half-section of the support plate of FIG. 7;

[0108] FIG. 9 illustrates a further variant of the support plate of FIG. 3;

[0109] FIG. 10 is a meridian half-section of the support plate of FIG. 9;

[0110] FIG. 11 is an enlarged stator element of the turbomachine of FIG. 1 in a first operative configuration;

[0111] FIG. 12 is the stator element of FIG. 11 in a second operative configuration; and

[0112] FIGS. 13-15 illustrate an enlarged seal element belonging to the turbomachines pursuant to FIGS. 1 and 2 in respective operative configurations;

[0113] FIG. 16 illustrates a stator element and a rotor element belonging to the turbomachine of FIG. 1.

DETAILED DESCRIPTION

[0114] With reference to the abovementioned figures, reference number 1 overall indicates a turbomachine in accordance with the present invention. The turbomachine 1 illustrated in FIG. 1 is an expansion turbine of outflow radial type with a single rotor disc 2. The turbomachine 1 illustrated in FIG. 2 is an expansion turbine of outflow radial type with two counter-rotating rotor discs 2.

[0115] With reference to FIG. 1, the turbine 1 comprises the rotor disc 2, provided with a plurality of rotor blades 3 arranged in series of concentric rings on a respective front face 4 of the rotor disc 2. Each series of rotor blades 3 is part of a rotor stage of the turbine 1. The rotor disc 2 is rigidly connected to a shaft 5 which is extended along a rotation axis X-X. The shaft 5 is in turn connected to a generator (not illustrated). The rotor blades 3 are extended away from the front face 4 of the rotor disc 2 with leading edges thereof substantially parallel to the rotation axis X-X. According to that illustrated in the enclosed figures, first ends of the rotor blades 3 of each series are connected and supported by a respective first rotor ring 301 integral with the rotor disc 2. Opposite ends of the same rotor blades 3 of a series are constrained to a second rotor ring 302 (FIG. 16).

[0116] The rotor disc 2 and the shaft 5 are housed in a fixed case 6 and are supported by the latter in a manner such that they can freely rotate around the rotation axis X-X. The fixed case 6 comprises a front wall 7, placed across from the front face 4 of the rotor disc 2, and a rear wall 8, situated across from a rear face 9 of the rotor disc 2 opposite the front face 4. A sleeve 10 is integral with the rear wall 8 and rotatably houses the shaft 5 by means of the interposition of suitable bearings 11. The front wall 7 has an inlet opening 12 for a work fluid situated at the rotation axis X-X.

[0117] The fixed case 6 also houses a plurality of stator blades 13 arranged in series of concentric rings directed towards the front face 4 of the rotor disc 2. The series of stator blades 13 are radially alternated with the series of rotor blades 3 to define a radial expansion path of the work fluid which enters through the inlet opening 12 and is expanded radially away towards the periphery of the rotor disc 2. The fixed case 6 also comprises a radially peripheral wall 14 which is extended from the front 7 and rear 8 walls and internally delimits an outlet volume 15 for the work fluid.

[0118] The turbine 1 comprises a deflector or nose 16 defined by a convex wall, placed in the inlet opening 12 and directed towards the entering flow.

[0119] The stator blades 13 are supported by a support plate 17 installed in the case 6 and constrained thereto. The support plate 17 is placed across from the front face 4 of the rotor disc 2, parallel thereto, and fit against an internal face 7a of the front wall 7 of the case 6.

[0120] As is visible in FIGS. 3-10, the support plate 17 is a disc provided with a central passage 18. In the central passage 18, a tubular wall 19 is housed that is part of the case 6. The tubular body 19 is extended from the front wall 7 towards the rotor disc 2 and internally delimits the inlet opening 12 of the turbine 1. A clearance is present between a radially internal edge 20 of the support plate 17 and the tubular body 19.

[0121] The support plate 17 has a plurality of through holes 21 at a radially peripheral portion thereof (FIGS. 3-10). Screws 22 housed in the through holes 21 and in threaded holes obtained in the case 6 constrain the support plate 17 to said case 6. A radially peripheral surface 23 of the support plate 17 always lies in abutment against an abutment surface 24 of the case 6. The abutment surface 24 is a cylindrical surface inside the case 6, coaxial with the rotation axis X-X and directed towards said rotation axis X-X (FIG. 1).

[0122] As is visible in FIGS. 1, 11 and 12, each series of stator blades 13 is part of a projecting element 25 that is extended away from the support plate 17. Each projecting element 25 comprises an annular band 26 (cylinder coaxial with the rotation axis X-X) having a first edge joined to a first surface 17a of the support plate 17 and a second edge directed towards the rotor disc 2 and provided with a joint 27 that also has ring form.

[0123] First ends of the stator blades 13 of one series are joined to the joint 27. Second ends, opposite the first, of the stator blades 13 of the same series are all constrained to an end ring 28, it too coaxial with the rotation axis X-X. The end rings 28 are arranged between the series of rotor blades 3 and in proximity to the front face 4 of the rotor disc 2.

[0124] Each joint 27 radially faces a respective second rotor ring 302 and each end ring 28 radially faces a respective first rotor ring 301. Seal elements 303 (e.g. labyrinth seals) are borne by each end ring 28 and by each joint 27 and act against the respective first 301 and second rotor ring 302 in order to delimit the radial expansion path of the work fluid (FIG. 16).

[0125] The annular band 26 has a radial thickness t1 less than a radial size d1 of the respective joint 27. For example, the radial thickness t1 is equal to about of the radial size r1. For example, the ratio between an axial length l1 of the annular band 26 and the respective radial thickness t1 is comprised between about 3 and about 10.

[0126] The support plate 17 is formed by a plurality of first circular portions 29 concentric with the rotation axis X-X and by a plurality of second circular portions 30 radially interposed between the first circular portions 29.

[0127] The projecting elements 25 which bear the stator blades 13 are connected to the and supported by the first circular portions 29.

[0128] The second circular portions 30 are more deformable, along radial directions, than the first circular portions 29 in a manner so as to allow relative movements between the first circular portions 29 (and between different series of stator blades 13) when the support plate 17 is subjected to the action of thermal gradients. According to the embodiment of FIGS. 3 and 4 and the variant of FIGS. 5 and 6, the support plate 17 has a constant thickness (as is visible in FIG. 1). The first portions 29 are defined by solid rings with opposite faces perpendicular to the rotation axis X-X. The second portions 30 have a plurality of through openings 31 arranged along the circumferential extension of each second portion 30. The illustrated through openings 31 are slots with elongated form.

[0129] According to the embodiment of FIGS. 3 and 4, each of the second portions 30 has a radially more internal first series of slots 31 and a radially more external second series of slots 31. Each of the two series comprises a plurality of said slots 31 arranged circumferentially in succession and each of the slots 31 is extended along the circumferential direction. In addition, the slots 31 of the two different series are angularly offset, i.e. mutually rotated around the rotation axis X-X, in a manner such that any radius that extends from said rotation axis X-X intersects at least one of said slots 31. The two series of slots 31 together delimit flexible bodies or arms 32 that are extended along circumferential directions and are arranged circumferentially in succession. The arms 32 are perpendicular to the radial directions.

[0130] According to the variant of FIGS. 5 and 6, each of the second portions 30 has a single series of slots 31. The series comprises a plurality of said slots 31 arranged circumferentially in succession. Each of the slots 31 is curved and tilted with respect to a circumferential direction. Adjacent pairs of slots 31 together delimit an arm or flexible body 32. Each arm 32 is curved and connects two of the radially successive first circular portions 29.

[0131] According to the embodiment of FIGS. 7 and 8 and the variant of FIGS. 9 and 10, each of the (radially more deformable) second circular portions 30 comprises at least one flexible body defined by a substantially cylindrical wall 33 coaxial with the rotation axis X-X.

[0132] According to the embodiment of FIGS. 7 and 8, in a meridian section, the support plate 17 has as a serpentine shape defined by radial sections and axial sections. The axial sections constitute the substantially cylindrical walls 33. Some of the radial sections constitute the first portions 29 that bear the annular bands 26. In other words, each of the second portions 30 comprises two axial sections 33 connected by a radial section. Each of the first portions 29 is defined by a radial section. From a different standpoint, the support plate 17 has annular cavities on both faces which are radially alternated in a manner so as to define the aforesaid serpentine shape.

[0133] According to the embodiment of FIGS. 9 and 10, in a meridian section, the second portions 30 each comprise an axial section constituting the substantially cylindrical wall 33 and two radial sections extended from opposite ends of the axial section 33. The first portions 29 each have a thickness (measured in the axial direction) equal to the axial length of the axial sections 33. From a different standpoint, each of the second portions 30 is defined by two radially successive annular cavities, each formed on one of the faces of the support plate 17.

[0134] The support plate 17, in accordance with the above-described embodiments, is a single piece preferably obtained via removal of material and/or via molding.

[0135] The turbine 1 of FIG. 1 also comprises seal elements 34 (e.g. labyrinth seals) acting at the rear face 9 of the rotor disc 2. The seal elements 34 are borne by projecting elements 35 geometrically similar to the projecting elements 25 that bear the stator blades 13.

[0136] The turbine 1 comprises a plurality of projecting elements 35 coaxial with the rotation axis, arranged radially in succession at at least several of the stages situated on the opposite side of the rotor disc 2.

[0137] As is more visible in FIGS. 13-15, each projecting element 35 comprises an annular band 36 (cylinder coaxial with the rotation axis X-X) having a first edge joined to a first surface 37a of a support plate 37 and a second edge directed towards the rotor disc 2 and provided with a seal-carrier joint 38 that also has ring shape.

[0138] The annular band 36 has a radial thickness t2 less than a radial size d2 of the respective seal-carrier joint 38. For example, the radial thickness t2 is equal to about of the radial size r2. For example, the ratio between an axial length l2 of the annular band 36 and the respective radial thickness t2 is comprised between about 3 and about 10.

[0139] In the illustrated embodiment, the seal elements 34 are flexible appendages which are radially extended towards the rotation axis X-X from the seal-carrier joint 38. On the second face 9 or rear face of the rotor disc 2, the same number of annular reliefs 39 and projecting elements 35 are present. Each of the annular reliefs 39 has a radially external surface 40 facing towards the seal elements 34 of the respective seal-carrier joint 38.

[0140] The support plate 37 that bears the seal elements 34 is structurally identical (apart from the specific sizing) to the support plate 17 that bears the stator blades 13. Therefore, for the detailed description of the support plate 37 that bears the seal elements 34, reference is made to the preceding description relative to the support plate 17 for the stator blades 13 and to the relative FIGS. 3-10. The support plate 37 is placed across from the rear face 9 of the rotor disc 2, parallel thereto, and fit against an internal face 8a of the rear wall 8 of the case 6.

[0141] Also the support plate 37 for the seal elements 34 is constrained to the case 6 by means of screws 22 passing into the through holes 21. A radially peripheral surface 23 of the support plate 37 always lies in abutment against an abutment surface 24 of the case 6. The abutment surface 24 is a cylindrical surface inside the case 6, coaxial with the rotation axis X-X and directed towards said rotation axis X-X (FIG. 1).

[0142] For both support plates 17, 37, a first surface 17a, 37a is connected to the annular bands 26, 36 of the projecting elements 25, 35 and a second surface 17b, 37b, opposite the first, delimits an interspace 41 with the internal face 7a, 8a of the respective wall 7, 8 of the case 6. Annular gaskets 42 (coaxial with the rotation axis X-X) are arranged between the second surface 17b, 37b of the support plate 17, 37 and the wall 7, 8 of the case 6, each at a respective projecting element 25, 35. The annular gaskets 42 are for example elastomeric, made of metal or graphite. The annular gaskets 42 are housed in annular seats 42a obtained on the internal face 7a, 8a of the respective wall 7, 8 of the case 6.

[0143] Pairs of successive projecting elements 25, 35 together delimit annular chambers 43, 43. First annular chambers 43 are delimited between two radially successive projecting elements 25 that bear the stator blades 13, the respective support plate 17 and end of the rotor blades 3. Second annular chambers 43 are delimited between two projecting elements 35 that bear the seal elements 34, the respective support plate 37 and the second face 9 of the rotor disc 2.

[0144] The annular gaskets 42 isolate annular volumes of the interspace 41, each placed at a respective annular chamber 43, 43. Each annular volume of the interspace 41 is in fluid communication with the respective annular chamber 43, 43 through the through openings 31 of the respective support plate 17, 37 of FIGS. 3-6 or through through openings suitably obtained (not illustrated) in the support plates 17, 37 of FIGS. 7-10.

[0145] In the front wall 7 and/or in the rear wall 8 of the case 6, inspection accesses 44 are obtained (one is schematically illustrated in FIG. 1), i.e. holes/openings with suitable seal closure elements that can be removed and repositioned, situated at the through openings 31.

[0146] The counter-rotating turbine 1 of FIG. 2 comprises a fixed case 6 that houses at its interior a first rotor disc 2 and a second rotor disc 2. The rotor discs 2, 2 can freely rotate, each in a manner independent from the other, in the case 6 around a common rotation axis X-X. For such purpose, the first disc 2 is integral with a respective first rotation shaft 5 mounted in the case 6 by means of bearings 11. The second disc 2 is integral with a respective second rotation shaft 5 mounted in the case 6 by means of respective bearings 11, not illustrated.

[0147] The first rotor disc 2 is provided with a plurality of rotor blades 3 arranged in series of concentric rings on a respective front face 4 of the first rotor disc 2. The second rotor disc 2 is provided with a plurality of rotor blades 3 arranged in series of concentric rings on a respective front face 4 of the second rotor disc 2. The front face 4 of the first rotor disc 2 is placed across from the front face 4 of the second rotor disc 2 and the blades 3 of the first disc 2 are radially alternated with the blades 3 of the second disc 2. The blades 3 of the first rotor disc 2 terminate in proximity to the front face 4 of the second rotor disc 2 and the blades 3 of the second rotor disc 2 terminate in proximity to the front face 4 of the first rotor disc 2.

[0148] The turbine 1 of FIG. 2 also comprises seal elements 34 acting at the rear faces 9, 9 of the rotor discs 2, 2. The seal elements 34 are borne by projecting elements 35 mounted on support plates 37. On the second face 9, 9 of each of the rotor discs 2, 2, the same number of annular reliefs 39 and projecting elements 35 are present. Each of the annular reliefs 39 has a radially external surface 40 facing towards the seal elements 34 of the respective seal-carrier joint 38.

[0149] The support plates 37, the projecting elements 35 and the seal elements 34 are entirely similar to those described for the turbine 1 of FIG. 1 and illustrated in FIGS. 3-10 and 13-15 (the same reference numbers have also been used) and therefore will not be newly described herein.

[0150] The counter-rotating turbine 1 of FIG. 2 also comprises an axial stage 45, 45 for each of said first rotor disc 2 and second rotor disc 2 The axial stages are placed at radially peripheral portions of each rotor disc 2, 2. More in detail, a series of rotor blades 46, 46 of the respective axial stage 45, 45 are radially extended from the peripheral edge of the respective rotor disc 2, 2. A series of stator blades 47, 47 of the respective axial stage 45, 45 are radially extended from a portion 48 of the case 6 towards the rotation axis X-X. The rotor blades 46, 46 are placed across from the stator blades 47, 47 along an axial direction. An axial stage, for example of the above-described type, can also be provided in an embodiment variant (not illustrated) of the turbomachine of FIG. 1.

[0151] During use and with reference to the turbine 1 of FIG. 1, the work fluid enters into the turbomachine through the inlet opening 12; being expanded, it transmits work on the rotor blades 3 and finally exits from the turbine 1 crossing through the outlet volume 15. The mechanical work is transmitted by the rotor disc 2 to the generator (not illustrated) through the shaft 5.

[0152] Given the characteristic structure of the radial machine, the temperature profile varies from the inlet towards the outlet, i.e. in radial direction. This variation of the temperature creates an axial temperature gradient on the support discs 17, 37 and on the projecting elements 25, 35.

[0153] The radially more internal first circular portion 29 is heated before the successive first circular portion 29; it tends to expand more and the expansion is absorbed by the radial compression of the second circular portion 30 that lies between the two. This phenomenon, as the disc 17, 37 is progressively heated, is verified throughout the support disc 17, 37 and prevents the generation of excessive internal stresses.

[0154] FIGS. 11 and 12 show, by way of example, the geometric variation of the projecting elements 24 that bear the stator blades 13. The support disc 17, even if provided with the second circular portions 30 that are radially more deformable (than the first 29), tends to be radially expanded less than the joint 27 and the end ring 28 so that under hot (normal operating) conditions, the annular band 26 is deformed and allows the joint 27 and the end ring 28 said expansion (FIG. 11: cold configuration; FIG. 12: configuration at operating conditions).

[0155] FIGS. 13-15 show, by way of example, what happens at the seal elements 34. Starting from a phase (FIG. 13) with the machine off and cold up to an operating condition phase (FIG. 15) passing through a starting phase (FIG. 14). First, (FIG. 14) the seal-carrier joint 38 is radially expanded, due to the flexibility of the annular band 36, then the rotor disc 2 is expanded and also the support disc 37 is slightly expanded. During all these phases, the invention ensures a minimum clearance (1, 2, 3) between the seal elements 34 and the annular reliefs 39. Such clearance, as a function of the starting speed, can only increase with respect to the starting condition, ensuring that there is never interference between rotating and fixed parts.