RU2809677C1 - Improved turbine and blade to protect blade root from hot gases from flow channel - Google Patents

Abstract

FIELD: turbine.

SUBSTANCE: turbine (14), in particular a low-pressure turbine, is described, comprising a plurality of rotor elements (2) and separators configured to be placed between the rotor elements and prevent the penetration of the gas flow from the passage (F) for the passage of the hot gas flow into the internal space (5) of the wheel. Each rotor element includes a deflector (8). A deflector is placed in line with each separator and it deflects the intruded gas flow towards the upper surface of the separator, thereby preventing the blade roots (4) from heating.

EFFECT: improved turbine design is proposed.

8 cl, 7 dwg

Description

FIELD OF APPLICATION OF THE INVENTION

[0001] The present description relates to a gas turbine configured to protect the rim on the wheels of the rotor units from the penetration of hot gases into the internal spaces of the wheels during operation.

PREREQUISITES FOR CREATION OF THE INVENTION

[0002] As is well known, a gas turbine is an energy conversion unit that typically contains, among other things, a compressor that draws in and compresses gas, a combustion chamber (or burner) into which fuel is added to heat the compressed air, and a high-pressure turbine , containing a plurality of rotor assemblies, which extracts energy from a stream of hot gas and drives a compressor and a low-pressure turbine, also containing a plurality of rotor assemblies, mechanically connected to the load.

[0003] In particular, low pressure turbine designs typically take precautions to reduce gas infiltration from the hot gas stream, which can have an adverse effect on components not designed to come into contact with the hot gas, such as wheels and separators. The phenomenon of gas infiltration from a hot gas stream may occur when the engine is running at partial load, and/or when parts of the engine have not been manufactured in full accordance with design requirements, and/or when some parts (eg seals, vent pipes) have been damaged or worn during operation.

[0004] More specifically, a typical low pressure turbine comprises, as described above, a plurality of rotor elements, each having a rotor wheel with a rim to which a plurality of blades are attached.

[0005] Each blade includes a male dovetail or blade root configured to fit into one corresponding groove provided on the rim of the rotor wheel. Wheels are usually made of less noble material than blades.

[0006] Between two adjacent rotor wheels facing each other, the inner space of the wheel is defined as the space between the two rotor wheels of two rotor elements.

[0007] Typically, the phenomenon of hot gas leakage occurs when some of the hot gas flows into the interior of the wheel, causing the wheel rims to operate at temperatures close to or above the material temperature limits, and because they are made of non-precious material, under such conditions damage and reduction in the service life of the wheels is possible. This means that this phenomenon can cause the dovetail joint on the wheel to break (eg severe deformation) and subsequently release the blades.

[0008] In addition to the above, wheel interiors are typically cooled. To achieve this, gas turbines are equipped with a piping system to provide scavenging air from the compressor to the low pressure turbine. In particular, purge air is introduced into the internal spaces of the wheels of low-pressure turbines. This partially reduces the overall temperature of the inner spaces of the wheels.

[0009] Hot gas penetration is typically prevented when the amount of purge air matches or exceeds the amount of air pumped into the wheels. With a smaller amount, the pumping effect will compensate for what the purge system does not provide: the hot gas-air mixture will be taken at a considerable distance from the wheel and released near the wheel (in recirculation mode). Recirculation can occur while the engine is running at low power, and subsequently the compressor supplies less scavenging air to the low pressure turbine, and the low pressure turbine can continue to operate at maximum speed.

[0010] To reduce the risk of gas leakage from the hot gas stream passing through the low pressure gas turbine into the interior of the wheels, a number of solutions are available in the art.

[0011] In particular, spacers may be added between the wheels, the spacers may have rims that axially cover the space not covered by the wheels, and these spacer rims may also extend radially to the same outer diameter of the wheels so that minimize the part of the wheel rim located above the cavity of the inner space of the wheel. Although spacers provide a physical barrier against hot gas penetration, they typically do not contact the rims of adjacent wheels, and therefore hot gas can flow through the gaps and reach the interior of the wheels. Spacers can protect adjacent wheels even when the wheels have a different outside diameter if the spacer rim is tapered.

[0012] Accordingly, there is a need in this technology for an improved turbine and blade configured to reduce any possible gas infiltration from the hot gas stream.

SUMMARY OF THE INVENTION

[0013] Improvements to the above-mentioned separators include the provision of a seal near the gas flow passage (NFPS) configured to seal the interior of the wheel adjacent to the hot gas passage. NFPS replace more traditional spacers to provide better protection to wheel rims from hot gas penetration, which can be directed not only into the wheel cavities, but also through the labyrinth seal. From a design standpoint, NFPS seals are a segment (i.e., arm elements) rather than a ring (like spacers), and therefore allow leakage between adjacent rotor elements. In addition, a multi-connection system is required, which inevitably increases the complexity of the solution due to the need to engage with the internal rotor support wheels. NFPS components are indeed smaller compared to traditional separators and can therefore be made from a more noble material.

[0014] However, recently, in order to increase the power and efficiency of gas turbines, the temperature of the hot gas stream has been increased. This is done by reducing the purge air flow from the compressor, which increases the risk of gas infiltration from the hot gas stream.

[0015] In addition, when the low pressure turbine wheels rotate at a lower speed, the pressure changes proportionally to the decrease in pressure because the hot gas stream expands by a smaller factor when moving at a lower speed along the path from one stage to another or from one rotor assembly to another. At the same time, as stated above, when the low pressure turbine wheel rotates at a lower speed, the pumping effect is reduced.

[0016] Finally, wheel interior temperatures are typically monitored using appropriate thermocouples. However, due to the more compact layout of the turbines, the installation of thermocouples becomes more difficult, resulting in reduced thermocouple reliability. In addition, thermocouple installation is further complicated when separators or any other mechanical barrier are located between the two rotor assemblies. As a result, the number of thermocouples installed tends to be reduced, resulting in less control over the risk of increased rim temperatures and possible rim damage.

[0017] Accordingly, in one aspect, the subject matter of the invention described herein relates to a turbine comprising a plurality of rotor elements configured to rotate as a result of expansion of hot combustion gas flowing in a hot gas flow path. A separator is installed between each two rotor elements facing each other. The function of the separator is to prevent the infiltrated gas flow from the hot gas flow passage from entering the interior of the wheel. Each rotor element also contains a deflector located next to the corresponding separator and configured to deflect the gas flow that has penetrated inside along the upper surface of the separator.

[0018] In another aspect of the subject matter described herein, a deflector is located on the root of each blade.

[0019] In another aspect of the subject matter described herein, the deflector is located on the rim of the blade rotor wheel and may close the gap between the spacer and the wheel.

[0020] In another aspect described herein, the baffle has an upper surface configured to deflect possible permeated gas from the hot gas flow passage toward the upper surface of the separator. In addition, the deflector may have a bottom surface configured to direct scavenging air from the interior of the wheel through a gap between each spacer and the rotor element.

[0021] In another aspect, a blade is described herein comprising a shank, a blade root coupled to the shank, and a blade for rotating a rotor element that includes a deflector configured to deflect an entrained gas flow.

BRIEF DESCRIPTION OF GRAPHIC MATERIALS

[0022] The described embodiments of the invention and the many attendant advantages thereof may be more fully appreciated and understood by reference to the following detailed description taken in conjunction with the accompanying drawings, wherein:

in Fig. 1 shows a diagram of a gas turbine;

in Fig. Figure 2 shows an disassembled view of the blade;

in Fig. 3 is a partial cross-section of a low power turbine according to the first embodiment;

in Fig. 4 is a cross-sectional view of a low power turbine section in accordance with the first embodiment, also showing the purge air flow under normal operating conditions;

in Fig. 5 shows a cross-section of the low power turbine shown in FIG. 4, which is characterized by low gas penetration;

in Fig. 6 is a cross-section of the low power turbine shown in FIG. 4, which is characterized by high gas penetration; And

in Fig. 7 is a partial cross-sectional view of a low power turbine according to the second embodiment.

DETAILED DESCRIPTION OF IMPLEMENTATION OPTIONS

[0023] Improvements in gas turbine design have been identified. Gas turbines have many components, including low pressure turbines. These low-pressure turbines are formed from multiple blades radiating from a central hub and are angled to move air through the engine. Some areas of the gas turbine are very hot. Others are colder. A known problem is that some of the hot gas moved by the blades flows towards the center hub, causing breakdowns and shortening the life of the turbines.

[0024] The inventors have discovered that this problem can be alleviated and/or solved by installing a new deflector element so that it follows the shape of the root of each blade and is located between the blade itself and the spacer located between each blades. The baffle is shaped to deflect any possible infiltrated gas from the hot gas stream towards the top surface of the separator. Thus, the deflector protects the internal parts of the turbine by preventing the average temperature increase inside it.

[0025] In FIG. 1 schematically shows a gas turbine, which is generally designated by the reference number 1. The gas turbine 1 includes, among other things: a compressor 11, which sucks and compresses gas supplied to the combustion chamber or to the burner (not shown in the figure), to which is added fuel for heating the compressed air, a high-pressure turbine 12 containing a plurality of rotor units that extracts energy from the hot gas stream and drives the compressor 11, a shaft 13 connecting the compressor 11 and the high-pressure turbine 12, and a low-pressure turbine 14 also containing a set of rotor units, which, through an additional shaft 15, drives, for example, a gear reducer, a centrifugal compressor or any other load.

[0026] In addition, the gas turbine 1 includes a purge system 16 that provides purge air to the low pressure turbine 14. The scavenging system essentially comprises an air intake 161 connected by a connecting pipe 162 to a cooler 163, which in turn is connected to a scavenging pipe 164 to a low pressure turbine 14 for cooling the wheel interiors (see below) between the rotor assemblies. This provides the effect and function of partially reducing the overall temperature of the internal spaces of the wheels.

[0027] As also shown in FIG. 2 and 3, the low pressure turbine 14 typically includes a plurality of rotor elements, herein designated by reference numeral 2, rotating about a rotation axis R and connected to a shaft 15.

[0028] More specifically, each rotor member 2 includes a rotor wheel 3 coupled to a shaft 15 and having a rim 31, and a plurality of female dovetails or grooves 32 arranged circumferentially around the rim 31. In the present embodiment, each groove 32 has the shape of a fir-tree groove. However, in some embodiments, the grooves may have a different shape.

[0029] Each rotor element 2 also includes a plurality of blades 4, each of them comprising in turn a male dovetail or blade root 41 configured to fit into one corresponding groove 32 of the rotor wheel 31 along the insertion direction. Thus, each blade root 41 has substantially the same shape as the corresponding groove 32.

[0030] The roots 41 of the blade 4 perform only the function of a strong mechanical connection of the blade 4 with the rotary wheel 3, and in particular with the grooves 32 of the rotor wheel 31.

[0031] Each blade 4 also includes a platform or shank 42 to which the blade root 41 is attached, and a blade 43 connected to the shank 42. The blade 43 is made of a noble material because the blade 43 is subject to significant thermal and mechanical stress. At the top of the airfoil 43 there is also an airfoil shroud 44 for connecting each blade 4 to adjacent blades to prevent bending of the blades 4 during turbine rotation under the influence of the changing pressure field on the airfoils 43.

[0032] As indicated, between two adjacent and facing each other rotor wheels, the inner wheel space 5 is defined as the space between the two rotor wheels 3 of the two rotor elements 2.

[0033] In FIG. 3 also shows a stator separator 6 for the turbine stator 14 (not shown in the figures), located between the two rotor elements 2 and the fitting 6'.

[0034] The hot gas flow passes through the hot gas flow passage, indicated by arrow F, which passes through the blades 43 of the blades 4.

[0035] Between two adjacent blades 4 is located a separator 7, which functions as a barrier to prevent the penetration of gas from the passage F for hot gas flow into the inner space 5 of the wheel, which can lead to an increase in temperature on the upper side of the inner spaces 5 of the wheels and, consequently, , temperatures of the roots 41 of the blades 4. As stated above, excessive thermal stress on the roots 41 of the blades has a negative impact on their operation. In this embodiment, the separator 7 has a conical shape. However, in some embodiments, the separator 7 may have a cylindrical or other shape, but it always has the function of defining boundaries and creating protection for the inner spaces of the wheels 5. In addition, on the upper surface 71 of each separator 7, which faces the stator separator 6, there is a labyrinth seal 72 that controls the flow of gas flowing between the separator 7 and the stator separator 6.

[0036] In FIG. 3, arrow P indicates the purge air path, which comes from the purge system 16. The purge air helps to reduce the temperature in the internal spaces of the 5 wheels, as well as to create, due to its own pressure, a pressure barrier that protects against the injection of gas from channel F for the flow of hot gas. The root 42 of each blade 4 has a deflector 8 formed on the root 42 of each blade 4 and positioned in correspondence with the spacer 7, and in particular the edge thereof, so as to bridge the gap 73 between each spacer 7 and the rotor element 2, and in particular with reference to the embodiment shown in FIG. 3, between the separator 7 and the wheel rim 31 there are 3 rotors.

[0037] In other words, in some embodiments, the deflector 8, which is actually annular in shape, has a protruding edge positioned in front of the edge of the spacer 7 and following its shape so as to bridge the gap between the spacer 7 and the rotor wheel 3. In fact, the separator 7 is also annular in shape with the edge facing the rotary wheel 3. The surface of the deflector 8 is such that it can deflect hot gases, as described in more detail below.

[0038] In the embodiment shown in FIG. 3, and in particular with reference to the enlarged portion shown in the same figure, the baffle 8 is formed with an upper surface 81 designed to deflect possible penetration of gas from the passage F for hot gas flow to the upper surface 71 and over the labyrinth seal 72 of the separator 7 , and with a lower surface 82, which is designed to supply scavenging air coming from the inner space 5 of the wheel, through the gap 73 between each separator 7 and the rotor element 2.

[0039] In some embodiments, the deflector 8 may be located in different positions, and in particular it may be placed on the rotor wheel 3 in approximately aligned manner with the rim 31.

[0040] In general, it is necessary that the deflector 8 can deflect any possible amount of infiltrated gas from the channel F to allow a flow of hot gas to pass, which can overcome the mechanical barrier of the separator 7 whenever, for example, the scavenging air pressure P from the inner space 5 of the wheel not enough to prevent the overall penetration of hot gas into the internal spaces of the 5 wheels.

[0041] The low pressure turbine 14 and the deflector 8 operate as follows.

[0042] When the low-pressure turbine 14 operates and the rotor members 2 rotate, the scavenging air P coming from the compressor 163 and transported through the scavenging pipe 164 cools the internal spaces of the wheels 5. At the same time, the combined action of the pumping effect determined by the rotational speed of the impeller of the low-pressure turbine 14, namely the rotor elements 2, together with the barrier formed by the separator 7, prevents the penetration of gas from the channel F for the flow of hot gas into the internal spaces of the wheels 5. In addition, any possible penetration of gas, even local, is further prevented by the action of the deflector 8, which, on the one hand, thanks to its position in accordance with the separator 7, deflects possible penetrations of local gas from the channel F for the passage of the hot gas flow by the first surface 81, and , on the other hand, also allows the purge air P to pass through the gap 73. Local gas penetration may occur due to the fact that the pressure field generated by the hot gas flow in the passage F of the hot gas flow is not always constant. Returning to the deflector 8, the location in accordance with the separator 7 in some embodiments means that it is configured to deflect hot gases back to the top surface of the separator 7.

[0043] The operation of the baffle has a particular effect when the impeller speed of the low pressure gas turbine 14 is reduced, for example when the low pressure gas turbine 14 is operating at 50% of its rated impeller speed. In this case, the protective effect of the pump effect decreases in proportion to the decrease in rotation speed.

[0044] In particular, in order to better describe the operation of the deflector 8, FIG. 4, 5 and 6 show some operating conditions of the low pressure turbine 14. In FIG. Figure 4 shows a typical purge air path P under conditions where no gas penetration is expected. In this case, the purge air P coming from the compressor 11 passes through the inner spaces of the wheels 5 and reaches the hot gas flow channel F, protecting the inner spaces of the wheels 5 from the high temperature of the hot gases.

[0045] As shown in FIG. 5, this document illustrates the phenomenon of minor gas penetration in which part (see arrow F') of the hot gas in the hot gas flow passage F reaches the separator 7, and in particular, thanks to the separator 8, also the upper surface 71 and the labyrinth seal 72. In this case, the penetration of gas into the internal spaces 5 of the wheel is at least partially prevented by the deflector 8, as well as by the purge air P coming from the compressor 163, which allows the infiltrated gas F' from the hot gas stream F to be cooled due to the shape of the lower surface 82 of the deflector 8 The hot gas reaches the shank 42, increasing its temperature and thus creating a potential risk for the roots 41 of the blades 4. The deflector 8 prevents the possible leakage of hot gas flow F' coming from the hot gas flow from the hot gas flow passage F into the internal spaces of 5 wheels, and, accordingly, heating of the shank 42.

[0046] In FIG. Figure 6 illustrates the phenomenon of significant gas penetration, for example, in the case of a low pressure turbine operating at low speed. In particular, it shows the first arrow F'', which indicates the hot gas from the passage F for the flow of hot gas penetrated in the case where the blade 4 is not equipped with a deflector 8, it is obvious that the hot gas reaches the internal spaces of the wheels 5 and heats the shank 42 and, consequently, the root 41 of the blade 4, which leads to its damage; and a second arrow F''', which denotes the hot gas from the channel F for the flow of hot gas F to penetrate in the case where the blade 4 is equipped with a deflector 8. It is easy to understand that in this latter case the hot gas is deflected and is not allowed to reach the internal spaces 5 wheels.

[0047] In the operating condition mentioned above, where the low pressure turbine 14 is said to be operating at low speed, the scavenging air P coming from the wheel interiors 5 is not sufficient to cool the infiltrated gas F''', and as a result the baffle 8 deflects the gas flow F''' that has penetrated inside to the upper surface 71 of the separator 7 and the labyrinth seal 72. The upper surface 81 of the deflector 8, on the one hand, makes it difficult for the penetrated gas F''' to access the internal spaces 5 of the wheels, and, on the other hand, deflects, as stated above, the hot gas through the separator 7 from the shank 42, thus ensuring a decrease in the temperature of the shank 42 itself and, consequently, the root 41 of the blade 4.

[0048] In FIG. 7 a shows a second embodiment of an improved low pressure turbine 14. In the above figure, like reference numerals denote the same or corresponding parts, elements or components already shown in FIG. 3 and described above, and will not be described again. However, in this case, the separator 7 is not conical, but cylindrical. In addition, in this case, the deflector 8 is located on the shank 7 or on the rim 31 of the rotor wheel 3, repeating the shape of the separator 7.

[0049] In FIG. 7 also shows several paths of purge air P coming from compressor 11 through purge pipe 164.

[0050] In this case, the operation of the low power turbine 14 is similar to that described in the previous figures.

[0051] Although the invention has been described in terms of various specific embodiments, those skilled in the art will appreciate that many modifications, variations, and exceptions are possible without departing from the spirit and scope of the claims. In addition, unless otherwise indicated, the order or sequence of any steps of the process or method may be varied or rearranged in accordance with alternative embodiments.

[0052] Reference will now be made in detail to embodiments of the description, with one or more examples illustrated in the drawings. Each of the examples is provided to clarify the description and not to limit the 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 the present disclosure without departing from the scope or spirit of the disclosure. Reference herein to “one embodiment” or “an embodiment” or “certain embodiments” means that the particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the described subject matter inventions. Thus, the appearance of the phrase “in one embodiment,” “in an embodiment,” or “in some embodiments” in various places throughout this specification does not necessarily refer to the same embodiment(s). ) implementation of the invention. Particular features, structures, or characteristics may be further combined in any suitable manner in one or more embodiments.

[0053] When representing elements of various embodiments, the singular form and the word “specified” denote the presence of one or more elements. The terms “comprising,” “including,” and “having” are intended to indicate inclusion and mean that additional elements may exist in addition to the listed elements.

Claims (20)

1. Turbine (14), containing: a plurality of rotor elements (2) configured to rotate as a result of expansion of the hot combustion gas flowing in the channel (F) for passing the hot gas flow, and each element (2) of the rotor contains: rotor wheel (3), configured to rotate around the axis of rotation and having an outer rim (31); And a separator (7) placed between two elements (2) of the rotor facing each other and configured to prevent the gas flow (F', F''') from the channel (F) from entering the internal space ( 5) wheels, characterized in that at least one rotor element (2) contains a deflector (8) located on the outer rim (31) of the rotor wheel (3) and configured to deflect the gas flow (F') that has penetrated inside to the upper surface (71) separator (7). 2. Turbine (14) according to claim 1, in which the deflector is located in accordance with the separator (7) so that hot gases are deflected to the upper surface of the separator (7). 3. Turbine (14) according to any of the previous paragraphs, in which the deflector (8) closes the gap (73) between the separator and the wheel (3). 4. Turbine (14) according to any one of paragraphs. 1 or 2, in which each rotor element (2) contains: a plurality of circumferential grooves (32) around the outer rim (31) of the rotor wheel (3); And a plurality of blades (4), each blade (4) containing a shank (42), a root (41) of the blade connected to the shank (42) and configured to fit into one corresponding groove (42) of the rotor wheel (3), a feather ( 43) to rotate the rotor element (2) by blocking (F) the flow (F) of hot gas. 5. Turbine (14) according to any of the previous paragraphs, in which the separator (7) has an upper surface (71) facing the penetrated hot gas (F'), and in this case, the deflector (8) has an upper surface (81) configured to deflect possible penetrated gas from the hot gas flow (F) to the upper surface (71) of the separator (7). 6. Turbine (14) according to any of the previous paragraphs, in which the internal space (5) of the wheel is defined as the space between two adjacent wheels (3) of the rotor, wherein scavenging air (P) is introduced into the turbine (14), wherein the scavenging air (14) passes through the internal spaces (5) of the wheels and enters the passage (F) for the flow of hot gas, and wherein the deflector (8) has a lower surface (82) configured to direct purge air (P) coming from the inner space (5) of the wheel through the gap (73) between each separator (7) and the rotor element (2). 7. Turbine (14) according to any of the previous paragraphs, in which each separator (7) forms a gap (73) with the corresponding element (2) of the rotor, and the deflector (8) is made and located in accordance with the gap (73) so that close the gap (73) between the separator (7) and the rotor element (2) and ensure the deflection and prevention of possible penetration of local gas from the channel (F) into the gap (73) for the passage of the hot gas flow, and, on the other hand, also allow the purge air (P) to pass through the gap (73). 8. Turbine (1) as claimed in any one of the preceding claims, wherein the turbine is a low pressure turbine (14).