Improved turbine and blade for protecting roots from flow path hot gases

Abstract

A turbine, particularly a low-pressure turbine, is disclosed. The turbine includes a plurality of rotor components and spacers arranged between the rotor components to prevent intake air from a hot gas flow path from reaching the inter-wheel spacing. Each rotor component includes a deflector. The deflector is positioned corresponding to each spacer and deflects purge air pumped upward from the inter-wheel spacing through the rotor components to prevent the intake air from heating the blade roots.

Description

Technical Field

[0001] The present disclosure relates to a gas turbine capable of protecting the edges of the wheels of a rotor assembly from being drawn into the inter-wheel space during operation. Background Art

[0002] As we all know, a gas turbine is an energy conversion device, which generally includes a compressor for extracting and compressing gas, a combustor (or burner) for adding fuel to heat the compressed air, a high-pressure turbine including multiple rotor assemblies for extracting power from the hot gas flow path and driving the compressor, and a low-pressure turbine also including multiple rotor assemblies and mechanically connected to the load, etc.

[0003] In the design of low-pressure turbines, in particular, precautions are often taken to reduce gas ingestion from the hot gas flow path, which can have a detrimental effect on non-hot gas components such as wheels and spacers. This phenomenon of gas ingestion from the hot gas flow path can occur when the engine is operating at part load.

[0004] More specifically, as described above, a typical low pressure turbine includes a plurality of rotor assemblies, each rotor assembly having a rotor wheel having a rim to which a plurality of blades are coupled.

[0005] Each blade comprises a male dovetail or root designed to mate with a corresponding groove formed on the edge of the rotor wheel. The wheel is typically made of a cheaper material than the blades.

[0006] Between two adjacent and facing rotor wheels, an inter-wheel space is provided between the two rotor wheels of the two rotor components.

[0007] The phenomenon of gas ingestion from the hot gas flow path typically occurs when some of the hot gas flows into the wheel gap, causing the wheel rim to operate above or near its material temperature limit. The rim, made of less expensive materials, can be damaged, reducing the useful life of the wheel. This means that this phenomenon can be the cause of dovetail failure (e.g., severe deformation) in the wheel, which can lead to subsequent blade separation.

[0008] In addition to the above, the interwheel space is typically purged. To this end, gas turbines are equipped with a ducting system to provide purge air from the compressor to the low-pressure turbine. Specifically, the purge air is introduced into the interwheel space of the low-pressure turbine. To some extent, this reduces the overall temperature of the interwheel space.

[0009] Hot gas ingestion is generally prevented when the purge air volume is equal to or greater than the air volume pumped by the wheels. If the purge air volume is less than the pumping air volume, the pumping effect will compensate for the amount of hot gas that the purge system cannot provide with hot gas, which will be sucked in from away from the wheels and pumped out near the wheels (recirculation). Recirculation can occur when the engine is running at low power, and the compressor will then provide less purge air to the low-pressure turbine, which can still run at its high speed.

[0010] In order to reduce the phenomenon of gas being sucked into the inter-wheel space through the hot gas flow path of the low-pressure gas turbine, some solutions have been proposed in the prior art.

[0011] Specifically, spacers can be added between the wheels. These spacers can have edges that axially cover the gaps not covered by the wheels. These spacer edges can also extend radially to the same outer diameter as the wheels to minimize the portion of the wheel rim that overlies the inter-wheel gap cavity. While the spacers act as a physical barrier to hot gas ingestion, they generally do not contact the edges of adjacent wheels, allowing hot gas to flow inside the gap and into the inter-wheel gap. By maintaining a tapered edge on the spacers, the spacers can provide protection to adjacent wheels even if the wheels have different outer diameters.

[0012] Therefore, it is of technical interest to provide improved turbines and blades that can reduce any gas that may be drawn from the hot gas flow path. Summary of the Invention

[0013] The improvement to the spacers described above is the provision of a near flow path seal (NFPS) that is capable of facilitating the sealing of the wheel spacing in the vicinity of the hot gas path. The NFPS replaces the more traditional spacers, better protecting the wheel rim from the effects of inhaled hot gases, which may not only occur within the wheel cavity, but may also enter through the labyrinth seals. Structurally, the NFPS is a segment (i.e., an arm member) rather than a ring (like a spacer), so the NFPS introduces leakage between adjacent rotor members. In addition, the NFPS requires a multi-connection system, which necessarily increases the complexity of the solution in order to engage the NFPS with the internally supported rotor wheel. As compared to traditional spacers, the NFPS is indeed a smaller component and can therefore be made of more expensive materials.

[0014] However, recently, in order to increase the power and efficiency of gas turbines, the temperature of the hot gas flow path has increased. For this reason, the purge air flow from the compressor has also been reduced, resulting in an increased risk of gas ingestion from the hot gas flow path.

[0015] Furthermore, when the low-pressure turbine rotates at a slower speed, the hot gas path changes in proportion to the pressure reduction because the hot gas flow path has a slower expansion at a lower speed from one stage to another or from one rotor assembly to another. Also, as mentioned above, the pumping effect is reduced when the low-pressure turbine rotates at a slower speed.

[0016] Finally, the temperature of the wheel rim gap is typically monitored using suitable thermocouples. However, as turbine layouts become increasingly compact, thermocouple installation has become more complex, resulting in lower reliability. Furthermore, thermocouple installation becomes more complex when spacers or other mechanical barriers are placed between the two rotor assemblies. Consequently, the number of installed thermocouples often decreases, leading to a reduced risk of increased wheel rim temperature and potential deterioration.

[0017] Thus, in one aspect, the subject matter disclosed herein relates to a turbine comprising a plurality of rotor components that rotate due to the expansion of hot combustion gases flowing into a hot gas flow path channel. Each rotor component comprises a rotor wheel. An inter-wheel spacer is provided between two adjacent rotor wheels. Furthermore, each rotor component comprises a protective spacer disposed between two facing rotor components, the protective spacer being configured to prevent intake airflow from the hot gas flow path channel from reaching the inter-wheel spacer. Furthermore, the turbine comprises stator spacers. A channel is defined between each stator spacer and the associated protective spacer. The rotor components further comprise a deflector configured to deflect purge air pumped upward from the inter-wheel spacer through the rotor components into a channel having a pressure lower than that of the gas deflected by the deflector.

[0018] In another aspect, the subject matter disclosed herein is directed to a deflector disposed on the shank of each blade.

[0019] In another aspect, the subject matter disclosed herein relates to a deflector disposed on an edge of a rotor wheel of a blade and capable of covering a gap between a spacer and the wheel.

[0020] In another aspect, disclosed herein is a deflector having an upper surface configured to deflect gas that may be drawn from the hot gas flow path passage toward the upper surface of the spacer.

[0021] In another aspect, the deflector is configured to direct the intake gas flow over the upper surface of the shank while allowing the purge air gas to flow in a radial direction to the hot gas flow path passage when the turbine is operating under base load conditions to prevent hot gas ingestion. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] A more complete understanding of the disclosed embodiments of the present invention and many of its attendant advantages will be readily obtained by reference to the following detailed description when considered in conjunction with the accompanying drawings, which likewise become better understood, wherein:

[0023] Figure 1 A schematic diagram of a gas turbine is shown;

[0024] Figure 2 An exploded view of the blade is shown;

[0025] Figure 3 shows a partial cross-sectional view of a low power turbine according to a first embodiment;

[0026] Figure 4 shows a partial cross section of a low power turbine section according to a first embodiment showing the purge air flow under normal operating conditions;

[0027] Figure 5 Shown Figure 4 Cross section of a low-power turbine showing less gas intake;

[0028] Figure 6 Shown Figure 4 a cross section of a low-power turbine with a purge flow at so-called base load conditions; and

[0029] Figure 7 It is a partial cross-sectional view of a low-power turbine according to a second embodiment. DETAILED DESCRIPTION

[0030] This article presents improvements to gas turbines. Gas turbines have many components, including a low-pressure turbine. These low-pressure turbines are composed of numerous blades radiating from a central hub and angled to direct air through the engine. Some areas of the gas turbine are very hot, while other areas are relatively cool. A known problem is that some of the hot gas moved by the blades can flow towards the central hub under certain conditions, causing damage to the turbine and reducing its service life.

[0031] The inventors have discovered that this problem can be mitigated and / or resolved by placing a novel deflector element corresponding to the shank of each blade and interposing it between the blade itself and a spacer disposed between two adjacent wheels. The deflector is shaped to deflect the purge air between two adjacent rotor components toward the low-pressure passage 74, and in particular toward the upper surface of the spacer, and subsequently upwards to deflect any incoming hot air. This protects the turbine's internal components and prevents an increase in the average temperature therein.

[0032] Figure 1A gas turbine is schematically shown and generally designated by reference numeral 1. The gas turbine 1 comprises a compressor 11 for extracting and compressing gas, which is fed to a burner or combustor (not shown) for adding fuel to heat the compressed air; a high-pressure turbine 12 comprising a plurality of rotor assemblies for extracting power from the hot gas flow path and driving the compressor 11; a shaft 13 connecting the compressor 11 and the high-pressure turbine 12; and a low-pressure turbine 14 also comprising a plurality of rotor assemblies for driving, for example, a gearbox and a centrifugal compressor or any other load via another shaft 15.

[0033] In addition, the gas turbine 1 includes a purge system 16 to provide purge air to the low-pressure turbine 14. The purge system generally comprises an air extractor 161 connected to a cooler 163 via a connecting pipe 162, which in turn is connected to the low-pressure turbine 14 via a purge pipe 164 to purge the inter-wheel space between the rotor assemblies (see below). This has the effect and function of reducing the overall temperature of the inter-wheel space to a certain extent.

[0034] Also refer to Figure 2 and Figure 3 The low-pressure turbine 14 generally includes a plurality of rotor components, indicated herein with reference numeral 2 , which rotate about an axis of rotation R and are coupled to a shaft 15 .

[0035] More specifically, each rotor member 2 includes a rotor wheel 3 coupled to the shaft 15 and having an edge 31 and a plurality of circumferentially spaced concave dovetail slots or grooves 32 surrounding the edge 31. In this embodiment, each groove 32 has a fit-three shape. However, in some embodiments, the grooves may have different shapes.

[0036] Each rotor component 2 further comprises a plurality of blades 4, each blade in turn comprising a male dovetail or root 41 designed to mate, along the insertion direction, with a corresponding groove 32 of the rotor wheel 3. Thus, each root 41 has almost the same shape as the corresponding groove 32.

[0037] The root 41 of the blade 4 has only a mechanical function to securely couple the blade 4 to the rotor wheel 3 , in particular to the groove 32 of the rotor wheel 3 .

[0038] Each blade 4 also includes a platform or shank 42 to which the root 41 is connected, and a wing 43 coupled to the shank 42. The wing 43 is made of expensive materials because it is subject to significant thermal and mechanical stresses. At the top of the wing 43, there is also a wing shroud 44 that is used to connect each blade 4 to its neighbor.

[0039] As mentioned above, between two adjacent and facing rotor wheels, an inter-wheel gap 5 is provided between the two rotor wheels 3 of the two rotor components 2 .

[0040] Figure 3 Also shown is a stator spacer 6 of a stator (not shown) of the low-pressure turbine 14 , which is inserted between the two rotor components 2 and the nozzle 6 ′.

[0041] The hot gas flow path flows in a hot gas flow path channel, which is indicated by arrows F, which of course passes through the airfoil 43 of the blade 4 .

[0042] A protective spacer 7 is arranged between two adjacent rotor wheels 3. It functions as a barrier to prevent gas from the hot gas flow path F from being drawn into the inter-wheel gap 5. This gas ingestion could cause the temperature in the upper side of the inter-wheel gap 5 to rise, thereby affecting the temperature of the root portion 41 of the blade 4. As described above, excessive thermal stress on the root portion 41 is detrimental to its operation. In this embodiment, the protective spacer 7 is conical. However, in some embodiments, the protective spacer 7 may be cylindrical or have another shape, as long as it functions to define and protect the inter-wheel gap 5. In addition, a labyrinth seal 72 is present on the upper surface 71 of each protective spacer 7 facing the stator spacer 6. This seal is used to minimize the amount of purge flow P required to prevent heat ingestion through the gap between the protective spacer 7 and the stator spacer 6 (commonly referred to as a diaphragm).

[0043] Still refer to Figure 3 , arrow P shows the path of the purge air from the purge system 16. The purge air has the function of lowering the temperature of the inter-wheel gap 5 and forming a pressure barrier by its pressure to block the inhalation of gas from the hot gas flow path channel F. The shank 42 of each blade 4 has a deflector 8 obtained on the shank 42 of each blade 4 and arranged corresponding to the protective spacer 7, specifically arranged corresponding to the edge thereof, so as to be arranged to cover the gap 73 between each protective spacer 7 and the rotor member 2, specifically with reference to Figure 3 The embodiment shown in FIG. 1 shows a gap between the protective spacer 7 and the edge 31 of the rotor wheel 3 .

[0044] The pressure of passage 74 is lower than the pressure of the gas deflected by deflector 8. More specifically, the pressure along passage 74 decreases in the direction of hot gas flow path passage F. In practice, in the field of considering the coupling of adjacent rotor components, the rotor component 2 upstream of the hot gas flow path passage F is referred to as the forward rotor component, and the purge air or gas surrounding such forward rotor component 2 has a higher pressure, and the rear rotor is referred to as the rear rotor component. The deflector is then arranged on the forward rotor component 2, which necessarily has a higher pressure than passage 74.

[0045] In other words, in some embodiments, the deflector 8, which is actually annular, has a protruding edge facing forward of the edge of the protective spacer 7 so as to correspond to each other to close the gap between the protective spacer 7 and the rotor wheel 3. In practice, the protective spacer 7 is also annular, with its edge facing the rotor wheel 3. The surface of the deflector 8 can deflect the hot gas, as will be explained further below.

[0046] exist Figure 3 In the embodiment shown, and with particular reference to the enlarged frame shown in the same figure, the deflector 8 is shaped to have an upper surface 81 intended to deflect gases that may be drawn from the hot gas flow path channel F back to the hot gas flow path channel F. Figure 5 and a lower surface 82 intended to allow purge air or gas from the inter-wheel spacing 5 to pass through the gap 73 between each protective spacer 7 and the rotor member 2 .

[0047] In some embodiments, the deflector 8 can be arranged at different locations and, more specifically, can be obtained on the rotor wheel 3, almost corresponding to the edge 31 (see the notes below). Figure 7 ).

[0048] Typically, whenever, for example, the pressure of the purge air P from the inter-wheel space 5 is generally insufficient to prevent hot gases from entering the inter-wheel space 5 , a deflector 8 is required to be able to deflect any possible gas ingestion from the hot gas flow path channel F that could overcome the mechanical barrier of the protective spacer 7 .

[0049] The operation of the low-pressure turbine 14 and the deflector 8 is as follows.

[0050] When the low-pressure turbine 14 operates and the rotor component 2 rotates, purge air P from the compressor 11 and delivered by the purge pipe 164 cools the inter-wheel space 5. Simultaneously, due to the rotational speed of the low-pressure turbine 14, i.e., the rotor component 2, the combined effect of the pumping effect and the barrier formed by the protective spacer 7 prevents gas from the hot gas flow path F from being drawn into the inter-wheel space 5. Furthermore, the action of the deflector 8 further prevents any possible, even localized, gas ingestion. The deflector, due to its alignment with the protective spacer 7, is able to deflect any localized gas ingestion from the hot gas flow path F via its upper surface 81 while also allowing the purge air P to pass through the gap 73. Localized gas ingestion can also occur because the pressure field caused by the hot gas flow in the hot gas flow path F is not always circumferentially uniform. Referring to the deflector 8, in some embodiments, its alignment with the protective spacer 7 means that it is able to deflect the hot gas upwards back toward the shank 42 of the blade 4.

[0051] The operation of the deflector is particularly affected when the rotational speed of the low-pressure turbine 14 is reduced, for example, when the low-pressure turbine 14 is operated at 50% of its normal operating speed. In this case, the protective effect of the pumping effect is reduced in proportion to the reduced speed.

[0052] Specifically, in order to better describe the operation of the deflector 8, Figure 4 、 Figure 5 and Figure 6 Some operating conditions of the low pressure turbine 14 are shown. Figure 4 A typical flow path for purge air P is shown in FIG, where no suction gas is foreseen. In this case, purge air P from compressor 11 passes through inter-wheel spacing 5 and reaches hot gas flow path passage F, thereby protecting inter-wheel spacing 5 from the high temperatures of the hot gas. In this operating condition, deflector 8 does not function as a deflector, as it does not cover protective spacer 7. Rather, it serves as a component that reduces gap 73.

[0053] Now refer to Figure 5 , illustrates the prevention of gas ingestion during low-power operation of the gas turbine. In this case, a portion of the hot gas of hot gas flow path channel F (see arrow F') does not reach protective spacer 7, specifically channel 74, upper surface 71, and labyrinth seal 72. In effect, deflector 8 deflects purge air P pumped upward from inter-wheel space 5 through rotor member 2. The purge air P is deflected by deflector 8 into channel 74 and ingested by channel 74 itself, as it is at a lower pressure than the purge air P.

[0054] Furthermore, due to the shape of the upper surface 81 of the deflector 8, the intake gas flow F' is forced to turn radially upward. In other words, the deflector 8 reverses the direction of the intake airflow F'. In particular, the intake airflow F' turns above the upper surface of the handle 42. In this case, the deflector 8, and in particular the purge air P from the compressor 11, prevents the inhalation of gas into the inter-wheel space 5. The deflector 8 helps prevent the possibility that the intake hot gas F' from the hot gas flow path F could leak into the inter-wheel space 5 and thus heat the rim 31.

[0055] exist Figure 6 FIG. 8 shows the operation of the deflector 8 when the gas turbine 1 is operated under base load conditions, ie when the rotor member 2 is rotating at nominal speed. Figure 6As shown, the purge air P from the inter-wheel space 5 is divided into two flows, P' and P", one of which (P') is driven by the deflector 8, specifically by the lower surface 82, through the pressure variation on the channel 74 (the pressure along the channel 74 is lower than the pressure of the purge gas P); while the other flow P" into which the purge air P is separated is driven by the pumping effect toward the wing 43. It can be seen that in this case, the deflector 8 does not interfere with the pumping effect of the rotor member 2, thereby allowing the purge air P to flow to the flow path F, thereby preventing it from being sucked in.

[0056] refer to Figure 7 , shows a second embodiment of the improved low-pressure turbine 14. In the figures already described, the same reference numerals designate the same reference numerals as those already described. Figure 3 , and the same or corresponding parts, elements, or components are shown in FIG and described above, and will not be described again. However, in this case, the protective spacer 7 is not conical, but cylindrical. Also, in this case, the deflector 8 is placed on the shank 42 or the edge 31 of the rotor wheel 3 in correspondence with the protective spacer 7.

[0057] Figure 7 Also shown are several paths that the purge air P from the compressor 11 takes through the purge duct 164 .

[0058] In this case, the operation of the low-pressure turbine 14 is identical to that disclosed in the preceding figures.

[0059] Although the present invention has been described in terms of various specific embodiments, it will be apparent to those skilled in the art that many modifications, variations, and omissions are possible without departing from the spirit and scope of the claims. Furthermore, unless otherwise indicated herein, the order or sequence of any process or method steps may be changed or re-sequenced according to alternative embodiments.

[0060] Reference has been made in detail to embodiments of the present disclosure, one or more examples of which are shown in the accompanying drawings. Each example is provided by way of explanation of the disclosure, not limitation thereof. Indeed, it will be apparent to those skilled in the art that various modifications and variations may be made to the present disclosure without departing from the scope or spirit of the present disclosure. References throughout this specification to "one embodiment" or "an embodiment" or "some embodiments" mean that the particular features, structures, or characteristics described in conjunction with the embodiment are included in at least one embodiment of the disclosed subject matter. Therefore, the phrases "in one embodiment" or "in an embodiment" or "in some embodiments" appearing in multiple places throughout the specification do not necessarily refer to the same embodiment. Furthermore, in one or more embodiments, the particular features, structures, or characteristics may be combined in any suitable manner.

[0061] When introducing elements of various embodiments, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

Claims

1. A turbine (14), comprising: a plurality of rotor components (2) configured to rotate due to expansion of hot combustion gas flowing into the hot gas flow path channel (F), wherein each rotor component (2) includes a rotor wheel (3), wherein an inter-wheel space (5) is provided between two rotor wheels (3) of two adjacent rotor components (2); a protective spacer (7) arranged between two facing rotor members (2) and configured to prevent an intake airflow (F') from the hot gas flow path channel (F) from reaching the inter-wheel space (5); and a plurality of stator spacers (6), each stator spacer being arranged between two adjacent rotor components (2); wherein a channel (74) is defined between each guard spacer (7) and the corresponding stator spacer (6); Characterized in that at least one rotor member (2) comprises a deflector (8) configured to deflect purge air (P) pumped upwards from the inter-wheel space (5) through the rotor member (2) to the channel (74), The pressure of the channel (74) is lower than the pressure of the gas deflected by the deflector (8).

2. The turbine (14) according to claim 1, wherein the deflector is arranged corresponding to the protection spacer (7).

3. A turbine (14) according to any one of the preceding claims, wherein each rotor wheel (3) has an outer edge (31), and The deflector (8) is arranged on the outer edge (31) of the rotor wheel (3).

4. The turbine (14) according to claim 1 or 2, wherein the deflector (8) covers a portion of a gap (73) between the protection spacer (7) and the rotor wheel (3).

5. The turbine (14) of claim 1 or 2, wherein each rotor member (2) comprises: a rotor wheel (3) configured to rotate about an axis of rotation and having an outer edge (31) and a plurality of circumferentially spaced grooves (32) around the outer edge (31); and a plurality of blades (4), wherein each blade (4) comprises: a shank (42); a root (41) coupled to the shank (42) and designed to mate with a corresponding groove (32) of the rotor wheel (3); and a wing (43) for rotating the rotor member (2) by intercepting the hot gas flow path passage (F); wherein the deflector (8) is arranged on the handle (42); and The deflector (8) covers a portion of a gap (73) between the protection spacer (7) and the rotor wheel (3).

6. The turbine (14) according to claim 1, wherein the deflector (8) is configured to reverse the direction of the suction air flow (F').

7. The turbine (14) of claim 5, wherein the deflector (8) is configured to reverse the direction of the intake airflow (F') above the upper surface of the shank (42).

8. The turbine (14) according to claim 6 or 7, wherein the deflector (8) has an upper surface (81) configured to deflect so as to reverse the direction of the suction air flow (F').

9. The turbine (14) according to claim 1 or 2, wherein when the turbine (14) operates under base load conditions, the deflector (8) allows the purge air (P) to flow in a radial direction to reach the hot gas flow path channel (F) to prevent the hot gas from being inhaled.

10. The turbine (14) according to claim 1 or 2, wherein an inter-wheel spacing (5) is defined between two adjacent rotor wheels (3), wherein purge air (P) is introduced into the turbine (14), wherein the purge air (P) passes through the inter-wheel space (5) to the hot gas flow path passage (F), and wherein the deflector (8) has a lower surface (82) configured to drive a portion (P') of the purge air from the inter-wheel space (5) through pressure variations on the passage (74) and another portion (P") of the purge air (P) into the hot gas flow path passage (F) in which the hot combustion gas flows.

11. The turbine (14) according to claim 1 or 2, wherein a labyrinth seal (72) is interposed between the stator spacer (6) and the protection spacer (7).

12. The turbine (14) of claim 5, wherein the deflector (8) is integral with the shank (42).

13. The turbine according to claim 1 or 2, wherein the turbine is a low-pressure turbine (14).

14. A blade (4) for a turbine (14) according to any one of the preceding claims, the blade (4) comprising: a shank (42); a root (41), said root being coupled to said shank (42); and a wing portion (43) configured to intercept the hot gas flow path; Characterized in that the blade (4) comprises the deflector (8).

15. The blade (4) according to claim 14, comprising: a shank (42); a root (41) coupled to the shank (42) and designed to mate with a corresponding groove (32) of a rotor wheel (3); and a wing (43) for rotating the rotor member (2) by intercepting the hot gas; The deflector (8) covers the gap between the protective spacer (7) and the rotor wheel (3).

16. The blade (4) according to claim 14 or 15, wherein the deflector (8) has an upper surface (81) configured to deflect gas that may be drawn from the hot gas flow path channel (F).

17. The blade (4) according to claim 14 or 15, wherein the deflector (8) has a lower surface (82) configured to allow purge air (P) to flow into the hot gas flow path channel (F) in which the hot combustion gas flows.

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