RU2783145C1 - Turbine with a shroud around the rotor blades and method for limiting the working medium leakage in the turbine - Google Patents

Abstract

FIELD: turbines.

SUBSTANCE: described is a gas (or steam) turbine (200) including a rotor with at least one set of rotor blades (213-1), a stator with a body (261), and a shroud (250); the shroud (250) passes around the set of rotor blades (213-1), and the body (261) passes around the shroud (250). The shroud (250) has a radial size independent of the temperature thereof due to the material, and is coupled movably with the body (261) so that the stator body (261) can thermally expand and contract in the process of operation of the turbine while maintaining the radial size of the shroud. The rotor also thermally expands and contracts in the process of operation of the turbine, and at the working temperature, the end areas of the rotor blades (213-1) are in immediate proximity to the inner area of the shroud (250), so that the gap is minimal or even equal to zero in the working state. The bandage (250) is made of or contains a material with a coefficient of thermal expansion (CTE) of less than 10 mcm/m/°C.

EFFECT: possibility of preventing working medium leakage along the periphery of the rotor blades in the process of operation of the turbine, while the efficiency of the turbine in the working state is maximum.

20 cl, 13 dwg

Description

FIELD OF THE INVENTION

[0001] The subject matter described herein generally relates to turbines, and more specifically to gas turbines and steam turbines, an embodiment of a new shroud around their rotor blades, as well as new methods for limiting the leakage of the working medium in the turbine, in particular around ends of the rotor blades in the turbine.

BACKGROUND OF THE INVENTION

[0002] Gas turbines are machines designed to process a working medium, such as air, which flows within a flow channel during operation of the machine; in particular, the gas turbine transfers kinetic energy from the current working medium to the rotor of the machine, thereby rotating its rotor.

[0003] Turbine efficiency can be defined as the ratio of the mechanical power output at the rotor to the mechanical power input of the operating fluid. The efficiency of the turbine is negatively affected by the leakage of the working medium that occurs at the ends of the rotor blades during the power stroke of the turbine.

[0004] In FIG. 1 is a very schematic cross-sectional view of a conventional (hot gas) turbine 100. Turbine 100 includes a rotor 110 and a stator 160. Rotor 110 includes a shaft 111 and, for example, three wheels 112 mounted on a shaft 111; the first wheel 112-1 has a first set of blades 113-1 (corresponding to the first expansion stage); the second wheel 112-2 has a second set of blades 113-2 (corresponding to the second expansion stage); the third wheel 112-3 has a third set of vanes 113-3 (corresponding to the third or last expansion stage). The stator 160 includes a housing with a casing 161 and an internal annular flow channel that guides the working medium from the inlet IL to the outlet OL. The annular flow channel is created by the outer wall 165 of the stator and the inner wall 169 of the stator, and sets of rotor blades are placed inside (in Fig. 1, for example, three sets of rotor blades 113-1, 113-2 and 113-3) and sets of stator blades ( in Fig. 1, for example, four sets of stator blades 167-1, 167-2, 167-3 and 167-4 are available). The outer wall 165 of the stator (which may be made of several rings connected to each other directly and/or indirectly) is fixed to the casing 161, for example, using ring elements; in FIG. 1, for example, two ring members 163-1 and 163-2 are available. The inner wall 169 of the stator (which is made of several rings) is fixed to the outer wall 165, for example, with sets of blades; in FIG. 1, for example, four rings of the inner wall are available, respectively fixed on the outer wall 165, for example, by means of four sets 167-1, 167-2, 167-3 and 167-4 of blades. Rotor 160 is rotatably coupled to stator 110; for this purpose in Fig. 1, two bearings 190-1 and 190-2 are available, each placed between the inner wall ring and the shaft.

[0005] However, in the hot gas turbine of FIG. 1, the working medium may leak into the gap between the ends of the rotor blades 113-1, 113-2, 113-3 and the outer wall 165 of the stator; however, this clearance avoids contact and thus damage to both the outer wall (which is stationary) and the blades (which rotate) during operation of the turbine. With proper selection of the clearance, contact (and therefore damage) can be avoided under all operating conditions.

[0006] US Pat. No. 4,784,569 proposes a solution for limiting leakage in a (hot gas) turbine. According to this solution, by means of a properly shaped shroud around the ends of the rotor blades, a satisfactory gas seal can be achieved so that most of the working fluid passes between the blades for efficient energy recovery, with only a very small part lost by passage around the periphery of the blades. However, in a (hot gas) turbine at operating temperature, any shroud is subject to deformation (eg, it warps inward or outward in the radial direction), and such deformation can lead to damaging contact between the shroud and the blades. The shape of the shroud in the '569 patent is such that it thermally deforms but maintains an operating clearance relative to the blades. Thus, with this type of bandage, leakage of the working medium is still possible.

[0007] Thus, it would be desirable to provide a new turbine with less or no leakage around the periphery of the rotor blades during turbine power stroke (and therefore with smaller clearances than were previously possible or provided by prior art and designs (including zero clearance ) between the ends of the rotor blades and the shroud surface) and with very little or no risk of damaging contact; in particular, it would be desirable to avoid damage to the rotor blades due to stator contact: not only A) under power stroke conditions where the blades are rotating at full speed and both rotor and stator are at high temperature, but also B) when starting and stopping when the blades rotate slowly and both the rotor and stator are at low temperature, and C) during acceleration, when the blades increase their speed, the rotor is at high temperature and the stator is at low temperature, and D) during braking, when the blades reduce their speed, the rotor has a low temperature, and the stator has a high temperature.

SUMMARY OF THE INVENTION

[0008] According to one aspect, the subject matter described herein relates to a turbine including a rotor, a stator, and a shroud; the rotor includes at least one set of rotor blades, the shroud extends around the set of rotor blades, the stator includes a housing extending around the shroud; the shroud is movably connected to the housing so that the housing can thermally expand and contract, thereby changing the radial distance between the housing and the shroud during operation of the turbine.

[0009] Although the scope of the present invention is gas turbines (specifically their first expansion stages, more specifically their first expansion stage), it is also quite applicable to steam turbines.

[0010] According to another aspect, the subject matter described herein relates to a method for limiting leakage of a working fluid between a turbine rotor and stator during a turbine power stroke; wherein the turbine includes at least one rotor wheel with a set of rotor blades and a stator housing extending around the set of rotor blades; the stator housing has a radial size depending on its temperature; the rotor wheel has a radial size depending on its temperature; wherein the method includes the steps of: manufacturing a bandage having a radial size substantially independent of its temperature, placing the bandage concentrically around the rotor wheel, between the set of rotor blades and the stator housing, and mechanically mating the bandage with the housing in such a way that the mating is maintained regardless of bandage temperature and body temperature; moreover, at the operating temperature of the turbine, the areas of the ends of the rotor blades of the specified set are in close proximity to the inner region of the shroud or in contact with it.

[0011] As will be better explained below, the stator housing is made from one or more materials, typically metallic materials, that expand when heated and contract when cooled; therefore, such a stator housing increases its dimensions, including the radial dimension, when heated, and decreases its dimensions, including the radial dimension, when cooled. On the contrary, the new bandage is made of a material (or several materials) that expands very little when heated and contracts very little when cooled, this is achieved, for example, by a coefficient of thermal expansion of less than 10 µm/m/°C; therefore, there is a very slight increase in the dimensions of such a brace, including the radial dimension, upon heating, and a very slight decrease in the dimensions, including the radial dimension, upon cooling.

[0012] It should also be noted that, as will be better explained below, when the rotor blade tip regions of said set are in contact with the inner region of the shroud, only slight abrasion is possible without any contact damage.

BRIEF DESCRIPTION OF GRAPHICS

[0013] The described embodiments of the invention and many of its attendant advantages can be more fully appreciated and understood in the course of studying the following detailed description, considered in connection with the accompanying drawings, and:

in FIG. 1 is a schematic longitudinal sectional view of a prior art turbine;

in FIG. 2 is a partial schematic longitudinal sectional view of a first embodiment of a turbine;

in FIG. 3 is a partial schematic longitudinal sectional view of the turbine stator of FIG. 2;

in FIG. 4 is a partial schematic longitudinal sectional view of the turbine rotor of FIG. 2;

in FIG. 5 is a partial schematic longitudinal sectional view of the turbine shroud of FIG. 2;

in FIG. 6 is a sectional view A-A of the stator casing, shroud and some of the turbine keyways of FIG. one;

in FIG. 7 is a partial enlarged sectional view A-A of the turbine keyway of FIG. 1 in the first position/state;

in FIG. 8 is a partial enlarged sectional view A-A of the turbine keyway of FIG. 1 in the second position/state;

in FIG. 9 is a partial schematic longitudinal sectional view of the turbine of FIG. 1 in the first working condition;

in FIG. 10 is a partial schematic longitudinal sectional view of the turbine of FIG. 1 in the second working condition;

in FIG. 11 is a partial schematic longitudinal sectional view of the turbine of FIG. 1 in the third working condition;

in FIG. 12 is a partial schematic longitudinal sectional view of a second embodiment of a turbine; and

in FIG. 13 is a flow diagram of an embodiment of a turbine leakage limiting method.

DETAILED DESCRIPTION OF EMBODIMENTS

[0014] When a (hot gas) turbine is operating, its components have and maintain substantially constant operating temperatures. In this context, the inventors of the present invention have found that it is possible to ideally select the shape and size of the turbine components in such a way as to avoid leakage of the working medium along the periphery of the rotor blades during operation of the turbine. In fact, it has been found that, in contrast to prior art turbine designs, the clearance between the ends of the turbine rotor blades (see, for example, blades 113-1, 113-2 and 113-3 in Fig. 1) and the stator element, for example, the fixed shroud passing around the rotor blades (see, for example, the outer wall 165 in Fig. 1) is equal to zero. Thus, the efficiency of the turbine in operation is maximized, which is a desirable option.

[0015] During the acceleration of the turbine, the temperatures of the turbine components change significantly, for example, temperature increases of 100-400°C are possible; to be precise. It should be noted that each turbine component experiences a different temperature increase and that temperature increases do not occur everywhere at the same time; in general, the turbine rotor is heated first, and then the turbine stator is heated.

[0016] In the process of braking the turbine, a corresponding decrease in temperature is observed, but in this case, the turbine rotor cools first, after which the turbine stator cools down.

[0017] When the temperature of a turbine component changes, its size changes; in particular, an increase in temperature corresponds to an increase in size, and a decrease in temperature corresponds to a decrease in size.

[0018] In the case of the above ideal choice during turbine start and stop, the gap between the ends of the turbine rotor blades and the surrounding stator element is zero or small, which is a good option.

[0019] However, in the case of the above ideal choice, during the acceleration of the turbine, the rotor blades will come into contact with the stator element passing around them, since at least one turbine wheel, together with its blades, will thermally expand before the surrounding stator element; as a result, damage to the blades and the element will occur.

[0020] It has been found that the leakage of working fluid around the periphery of the turbine rotor blades during start-up, stop, acceleration and braking has a negligible effect on the overall efficiency of the turbine, since these operating phases have a relatively short duration compared to the turbine power stroke phase.

[0021] As described herein, the design of the new turbine provides little or no leakage when the rotor is hot, and thus high efficiency is achieved, in particular in the operating condition, i.e., during operation of the turbine. For this purpose, a shroud is placed around at least one set of turbine rotor blades to provide a satisfactory seal to the working fluid when the rotor is hot. Such a bandage is not rigidly connected to the turbine stator; the mechanical connection of the shroud to the stator, in particular to the turbine housing, is designed in such a way that the housing can thermally expand (and contract) without affecting the position of the shroud and thus leakage in any operating state of the turbine. The bandage (see, for example, element 250 in Fig. 7) and the turbine housing (see, for example, element 261 in Fig. 7) can be radially slidable using a set of keyways (see, for example, elements 280-1, 280-2, 280-3, 280-4 in Fig. 7).

[0022] Preferably, the new turbine shroud is sized substantially independent of its temperature. Initially, with a cold rotor, there is some leakage in the gap between the rotor and the shroud; at this stage, the stator has a low temperature and is coupled to the rotor, see, for example, Fig. 9. Then, as the rotor heats up, this rotor expands, the gap decreases to zero or almost zero, and, as a result, the leakage decreases to zero or almost zero; at this stage, the stator is still at a low temperature and is coupled to the rotor, see, for example, FIG. 10. Finally, the rotor heats up and expands, and both clearance and leakage remain zero or near zero; at this stage, the stator heats up and expands but remains mated to the rotor, see for example FIG. eleven.

[0023] Although the scope of the present invention is gas turbines (specifically their first expansion stages, more specifically their first expansion stage), it is also quite applicable to steam turbines.

[0024] Below will be given detailed references to embodiments of the description, one or more examples are illustrated in the drawings. Each of the examples is provided to clarify the description and not to limit the present description. As such, it will be apparent to those skilled in the art that various modifications and variations can be made within the scope of this disclosure without departing from the scope or spirit of this disclosure. Reference in this specification to "one embodiment" or "an embodiment" or "some embodiments" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the described subject matter. Thus, the occurrence of the phrase "in one embodiment", "in an embodiment" or "in some embodiments" in various places throughout this specification does not necessarily refer to one(s) and the same(s) ) implementation of the invention. In addition, specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0025] When representing elements of various embodiments, the singular and plural forms and the word "specified" are intended to indicate that one or more elements exist. The terms "comprising", "including" and "having" are intended to indicate inclusion and mean that additional elements may exist in addition to the listed elements.

[0026] In FIG. 2-8 are different views of the same first embodiment of a (hot gas) turbine made using a new type of shroud. In particular, these figures show views of the first turbine expansion stage. However, the same solution or a similar solution can be used for any turbine expansion stage. In addition, the same solution or a similar solution can be used in several turbine expansion stages.

[0027] The difference of this first embodiment from the prior art turbine can be better understood by comparing the structure in the first expansion stage (corresponding to blades 113-1) of turbine 100 in FIG. 1 with the structure in the first expansion stage (corresponding to blades 213-1) of turbine 200 in FIG. 2; it should be noted that the reference designations of the respective elements in FIG. 1 and FIG. 2 differ by a hundred, so that, for example, item 212-1 in FIG. 2 corresponds to item 112-1 in FIG. one.

[0028] The improved turbine 200 of the first embodiment of the present invention having the features of the invention includes a rotor 210, a stator 260, and a shroud 250; unlike the prior art, the new shroud 250 is associated with the stator 260, but has a certain amount of movement, thus, strictly speaking, it cannot be considered as a component of the turbine stator.

[0029] The rotor 210 includes at least one set of blades 213-1, which are components of a wheel 212-1 mounted on a shaft 211; as a rule, the rotor includes several wheels (with blades) mounted on a single shaft. Bandage 250 passes around a set of blades 213-1; as will be explained better with reference to the second embodiment, the band may extend around one or two or three or more sets of blades. Stator 260 includes a housing extending around shroud 250; according to the first embodiment, the casing 261 extends around the brace 250.

[0030] As shown in FIG. 2, the first set of stator blades 267-1 may be mounted before the rotor blade set 213-1 and/or the second set of stator blades 267-2 may be mounted behind it. The flow passage is formed by the stator outer wall 265 and the stator inner wall 269, and inside is at least one set of rotor blades 213-1 and optionally also sets of stator blades 267-1 and 267-2. According to the embodiment of FIG. 2 stator blades 267-1 are fixed on the first outer wall ring 265 and the first inner wall ring 269, and stator blades 267-2 are fixed on the second outer wall ring 265 and the second inner wall ring 269; in addition, the first ring of the outer wall 265 is associated with the casing 261, and the first ring of the inner wall 269 is associated with the bearing 290-1. According to the embodiment of FIG. 2, the brace 250 is located axially between the first ring of the outer wall 265 and the second ring of the outer wall 265.

[0031] The geometry of the brace 250 according to the first embodiment can be better understood from FIG. 5; alternative shapes and geometries are possible as long as they are designed to provide zero or substantially zero leakage of the operating fluid around the tips of the rotor blades. Band 250 includes a first annular inner portion 251 in the form of a sleeve (eg, a cylindrical or conical sleeve) and a second annular outer portion 254 in the form of a flange; the first annular inner part 251 is used to create a seal for the working environment at the ends (214 in Fig. 4) of the blades 213-1; the second annular outer part 254 serves to mate with the housing 261, in particular with the node 270 (see, for example, Fig. 3) of the housing 261, which will be described later.

[0032] Bandage 250 (having an annular shape, as can be seen, for example, in Fig. 6) is associated with the ability to move with a housing, in particular with a casing 261 (having an annular shape, as can be seen, for example, in Fig. 6), so that the housing can thermally expand and contract during turbine operation (i.e., during the time interval from start to stop), thereby changing the radial distance between them. For example, in FIG. 6 casing 261 and band 250 are installed concentrically and with radial clearance; the aforementioned mating can provide changes (eg, from about 0.5 to about 5.0 mm) in the radial distance between the casing and the shroud while maintaining concentricity.

[0033] The interface between the brace 250 and the housing, in particular the housing 261, substantially prevents rotation of the brace 250 relative to the housing. In reality, the casing is configured to substantially fix the relative angular position of the shroud and casing during operation of the turbine (i.e., during the time interval from startup to shutdown); a detailed description of the node 270 of the casing 261 is given below.

[0034] The interface between the brace 250 and the housing, in particular the housing 261, substantially prevents the brace 250 from moving axially relative to the housing. In fact, the casing is configured to substantially fix the relative axial position of the shroud and casing during operation of the turbine (i.e., during the time interval from startup to shutdown); a detailed description of the node 270 of the casing 261 is given below.

[0035] The band 250 and the housing, in particular the casing 261, can be considered to be divided into parts, as shown, for example, in FIG. 6; such a division may correspond to connected elements or, simply and usually, to different zones of a single element. Parts 250-1, 250-2, 250-3, 250-4 of the brace 250 are slidable with the corresponding parts 261-1, 261-2, 261-3, 261-4 of the casing 261 of the body with a change in their relative radial position.

[0036] Such radial sliding can be maintained by having the band part having a radially oriented protrusion and the body part having a corresponding radially oriented recess, the protrusion being able to slide within the recess.

[0037] In an alternative embodiment, such radial sliding can be maintained by having the body part have a radially oriented protrusion and the bandage part have a corresponding radially oriented recess, the protrusion being able to slide within the recess.

[0038] In another and preferred embodiment, and as shown in the figures (see in particular Fig. 7 and Fig. 8), such radial sliding can be supported by at least one oriented in the radial direction of the device, in particular the groove -key 280. Such a device, in particular the groove-key 280, is made with the possibility of radial sliding in the recess 255 (see Fig. 7 and Fig. 8) of the bandage 250, in particular the second annular outer part 254, and/or in the recess 262 (see Fig. 7 and Fig. 8) housing, in particular the casing 261.

[0039] In accordance with this last possible alternative embodiment, it is preferable that the device, in particular the keyway 280, be fixed on the housing, in particular the casing 261; in the embodiment of FIG. 7 and FIG. 8, the keyway 280 is fixed to the housing 261 by means of a screw 282. In this case, the device, in particular the keyway 280, is slidable radially (for example, by about 1.0 to about 5.0 mm) in a corresponding recess. 255 bandage 250; in addition, some possibility of (limited) movement around the circumference (for example, from about 0.1 to about 0.2 mm) between the keyway 280 and the recess 255 is provided; with reference to Fig. 7 and FIG. 8 “radial” means vertically, and “circumferential” means horizontally.

[0040] When pairing with a device is selected, multiple devices are typically used. In this case, as shown, for example, in FIG. 6, the turbine includes a plurality of radially oriented devices, in particular a plurality of keyways; in accordance with the first embodiment, four slot keys 280-1, 280-2, 280-3, 280-4 are used, but another number is possible, for example, from three to sixteen. Each device from this set is made with the possibility of radial sliding in the corresponding recess of the bandage and/or in the corresponding recess of the housing.

[0041] According to the first embodiment shown in FIG. 2-8, flange 254 of shroud 250 is configured to mate with turbine casing assembly 270 261 . Assembly 270 includes a first annular flange 272, an annular rib 274, an annular seat 276 to accommodate an annular washer 277 (when installing the assembly), a second annular flange 278; radial recesses 262 are formed in annular rib 274. Flange 254 is configured to be positioned between first flange 272 and washer 277 with some (limited) axial movement (eg, from about 0.2 to about 0.5); it should be noted that the flange 254 of the brace 250 is placed in place before the washer 277 is placed in its place.

[0042] The bandage 250 is preferably made from a low thermal expansion (CTE) material, such as a CTE of less than about 10 µm/m/°C, preferably less than about 8 µm/m/°C, more preferably less than about 6 µm/m /°C; thus, its dimensions, in particular its radial dimension, are substantially independent of its temperature. Band 250 may be made of or may comprise a metal alloy material or a ceramic material.

[0043] In contrast, the rotor 210 and/or the stator 260 have dimensions, in particular the radial dimension, depending on their temperature. In fact, rotor 210 and/or stator 260 are typically made from one or more high CTE materials, in particular CTE greater than about 10 µm/m/°C, in particular greater than about 12 µm/m/°C, and more specifically more than about 14 µm/m/°C. Rotor 210 and stator 260 may be made from one or more metallic materials.

[0044] From FIG. 9, Fig. 10 and FIG. 11, it can be understood how the components of the turbine may change their radial dimensions during operation of the turbine 200; Fig. 9 corresponds to a possible starting state when the rotor 210 is at a low temperature and the stator 260 is at a low temperature, FIG. 10 corresponds to a possible acceleration state when rotor 210 is at high temperature (and expanded) and stator 260 is at low temperature, FIG. 11 corresponds to a possible operating state when the rotor 210 is at high temperature (and expanded) and the stator 260 is at high temperature (and expanded); it should be noted that the shape, size and position of the brace 250 are the same in these three figures. On FIG. 9, a large gap G1-1 is available between the blades 213-1 and the shroud 250; in FIG. 10, a small gap G1-2 is available between the blades 213-1 and the shroud 250; in FIG. 11, a small gap G1-2 is available (or there is no gap at all) between the blades 213-1 and the shroud 250; the gap G1 has decreased due to the expansion of the rotor 210, in particular the wheel 212-1. Accordingly, in FIG. 9, a small gap G2-1 is available between the shroud 250, in particular the flange 254, and the casing 261, in particular the rib 274 (see also FIG. 7); in FIG. 10, a small gap G2-1 is available between the band 250, in particular the flange 254, and the casing 261, in particular the rib 274 (see also FIG. 7); in FIG. 11, a large gap G2-2 is available between the band 250, in particular the flange 254, and the casing 261, in particular the rib 274 (see also FIG. 8); gap G2 has increased due to the expansion of the stator 260, in particular the casing 261.

[0045] As described above, the tip regions 214 of the blades 213-1 may be in close proximity to the inner region 252 of the shroud 250 at least in the power stroke state of the turbine 200.

[0046] In an alternative embodiment, it is advantageous that the tip regions 214 of the blades 213-1 can be in contact with the inner region 252 of the shroud 250 at least in the power stroke state of the turbine 200. However, in this case, it is preferable that the shroud 250 includes a layer 253 of abrasive material on the inner region 252 and that the blades 213 include a layer 215 of abrasive material (or at least one device of abrasive material) on the regions 214 of the ends. Thus, upon contact of layer 215 with layer 253, slight abrasion occurs without damaging the blades and/or the shroud. In addition, in this case, at least in the state of the power stroke of the turbine 200, the regions 214 of the ends of the blades 213-1 partially penetrate into the inner region 252 of the shroud 250, which advantageously ensures that there is no leakage of the working medium, in particular along the periphery of the blades, at least in the process working stroke of the turbine.

[0047] FIG. 12 refers to the second embodiment of the turbine 900, which is similar to the first embodiment. In accordance with this embodiment, the shroud 950 (which may consist of one or more fragments) passes around two sets of rotor blades 913-1 (parts of the first wheel 912-1) and 913-2 (parts of the second wheel 912-2); in an alternative embodiment, the shroud may extend around three or more sets of rotor blades. The shroud 950 is coupled, for example, to the assembly 970 of the shroud 961 of the stator housing of the turbine 900 by means of a flange 954. 2 (in the form of a cylindrical or conical sleeve) shroud 950 passes around the second set of rotor blades 913-2.

[0048] An additional advantage is the installation of a set of blades 967-2 in the shroud 950, in particular in the third part 953 (in the form of a cylindrical or conical sleeve) of the shroud 950. The blades 967-2 can be considered stator blades.

[0049] Although the scope of the present invention is gas turbines (specifically their first expansion stages, more specifically their first expansion stage), it is also quite applicable to steam turbines.

[0050] As should be understood from the above description, in the first embodiment, the second embodiment, and other similar turbines, a method is implemented to limit leakage between the rotor and stator of the turbine, at least during its power stroke.

[0051] In FIG. 13 is a flow diagram 1300 of an embodiment of a method for limiting fluid leakage around the tips of the rotor blades, at least during operation of the turbine. The method begins at an initial step 1310 and ends at step 1390. In this embodiment, it is assumed that the turbine includes at least one rotor wheel with a set of rotor blades and a stator housing extending around the set of rotor blades; in addition, the radial size of the stator housing depends on its temperature, and the radial size of the rotor wheel depends on its temperature.

[0052] In accordance with this embodiment, the method includes the steps of:

- (step 1320) manufacturing a band with a radial size substantially independent of its temperature,

- (step 1350) placing the shroud concentrically around the rotor wheel, between the set of rotor blades and the stator housing, and

- (step 1360) mechanically pairing the brace with the body in such a way that the pairing is maintained regardless of the temperature of the brace and the temperature of the body, in particular, without damaging the brace and/or the body;

according to this method, at least at the operating temperature of the turbine, the blade tip regions are in close proximity (eg, from about 0.1 to about 1.0 mm) to or in contact with the inner region of the shroud.

[0053] As a rule, with the above mechanical interface, radial movement of the band relative to the body is provided.

[0054] The mechanical interface between the shroud and the housing is advantageously implemented using a plurality of keyways.

[0055] In accordance with this embodiment, the method may include additional steps:

- (step 1330) applying a layer of abradable material to the inner region of the brace, and

- (step 1340) applying layers of abrasive or material or at least one device of abrasive material on the area of the ends of the blades;

in this case herein, at least at the operating temperature of the turbine, the end regions or the abrasive devices partially penetrate into the inner region of the band through the abrasion of the abradable layer with the abrasive material.

Claims (29)

1. Turbine (200) including rotor (210), stator (260) and shroud (250); moreover, the rotor (210) includes at least one set of rotor blades (213-1), while the band (250) passes around the set of blades (213-1) of the rotor, and the stator (260) includes a housing (261) passing around the band (250), and at the same time, the band (250) is made of or contains a material with a thermal expansion coefficient (TEC) of less than 10 μm/m/°C and is associated with the body (261) with the possibility of movement so that the body (261) can thermally expand and contract, thereby changing the radial distance between the casing (261) and the shroud (250) during operation of the turbine (200). 2. Turbine (200) according to claim 1, in which the housing (261) is configured (270) to substantially fix the relative angular position of the shroud (250) and housing (261) during operation of the turbine (200). 3. Turbine (200) according to claim 1 or 2, in which the housing (261) is configured (270) to essentially fix the relative axial location of the shroud (250) and housing (261) during operation of the turbine (200). 4. The turbine (200) according to claim 1, or 2, or 3, in which the part (250-1, 250-2, 250-3, 250-4) of the shroud (250) is slidably associated with the part (261- 1, 261-2, 261-3, 261-4) of the body (261) with a change in their relative radial position. 5. Turbine (200) according to claim 4, additionally including at least one radially oriented device (280), in particular a groove-key, moreover, said device (280) is made with the possibility of radial sliding in the recess (255) of the shroud ( 250) and/or recess (262) of the housing (261). 6. Turbine (200) according to claim. 5, including a plurality of radially oriented devices (280-1, 280-2, 280-3, 280-4), in particular groove keys, each device from the specified set is made with the possibility of radial sliding in the corresponding recess of the bandage (250) and/or the corresponding recess of the body (261). 7. Turbine (200) according to claim 5 or 6, in which each device (280) is fixed (282) on the specified housing (261), and each device (280) is made with the possibility of radial sliding in the corresponding recess (255) of the shroud ( 250). 8. Turbine (200) according to any one of the preceding claims, wherein said band (250) includes a layer (253) of abradable material on the inner region (252). 9. Turbine (200) according to claim 8, in which one or more rotor blades (213) of the specified set includes a layer (215) or device of abrasive material on the area (214) ends. 10. A turbine (200) according to any one of the preceding claims, wherein said shroud (250) is made of or contains a material with a CTE of less than 8 µm/m/°C, preferably less than 6 µm/m/°C. 11. Turbine (200) according to any one of the preceding claims, wherein said shroud (250) is made of or contains a metal alloy material or a ceramic material. 12. A turbine (200) according to any one of the preceding claims, wherein the rotor (210) and/or stator (260) are made from one or more materials with a CTE greater than 10 µm/m/°C. 13. Turbine (200) according to any of the preceding claims, wherein the rotor (210) and/or stator (260) are made from one or more metallic materials. 14. A turbine (900) according to any of the preceding claims, wherein said shroud (950) extends around one, or two, or three or more sets of rotor blades (913-1, 913-2). 15. Turbine (900) according to claim 14, wherein the stator includes at least one set of stator blades (967-2), said blades (967-2) being mounted on said shroud (950). 16. Turbine (200) according to any one of the preceding claims, which is a gas turbine or a steam turbine. 17. A method for limiting the leakage of the working medium between the rotor (210) and the stator (260) in the turbine (200) during the power stroke of the turbine (200), and the turbine includes at least one wheel (212-1) of the rotor with a set of blades (213 -1) a rotor and a stator housing (261) passing around a set of rotor blades (213-1), while the radial size of the stator housing (261) depends on its temperature, and the radial size of the rotor wheel (212-1) depends on its temperature , while the method includes the steps: - manufacturing (1320) a bandage (250) from or containing a material with a coefficient of thermal expansion (CTE) of less than 10 μm/m/°C, - placement (1350) of the shroud (250) concentrically around the wheel (212-1) of the rotor, between the set of blades (213-1) of the rotor and the housing (261) of the stator, and - mechanical interfacing (1360) of the shroud (250) with the housing (261) in such a way that the mating is maintained regardless of the temperature of the shroud and the temperature of the housing; moreover, at the operating temperature of the turbine, the regions (214) of the ends of the blades (213-1) of the specified set are in close proximity to the inner region (252) of the shroud (250) or in contact with it. 18. The method according to claim 17, in which, during mechanical coupling, radial movement of the bandage (250) relative to the housing (261) is provided. 19. The method of claim 18, wherein the mechanical interfacing between the band (250) and the housing (261) is performed using a plurality of keyways (280). 20. The method according to claim 17, or 18, or 19, further comprising the steps: - applying (1330) a layer (253) of abradable material to the inner region (252) of the bandage (250), and - applying (1340) layers (215) of abrasive or material, or device of abrasive material on the area (214) ends of the blades (213-1) of the rotor of the specified set; moreover, at the operating temperature of the turbine, said end regions (214) or said devices partially penetrate said inner region (252).

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