Inner blade support ring of turbine compressor stator

Abstract

The present invention relates to an inner ring (17) for supporting variable pitch blades of an axial compressor stator of a turbine, the inner ring comprising at least two annular sectors (170) assembled to form the inner ring, each annular sector comprising a plurality of accommodating portions (172) for receiving a pivot shaft of one of the blades. The ring is characterized in that it is assembled on the mating plane between the ends (171) of two consecutive annular sectors (170) by engaging an assembly pin (174) and a cavity (175) for receiving the pin, the assembly pin (174) being fixed on the end (171) of one of the two consecutive annular sectors (170), the cavity (175) being formed on the end (171) of the other of the two consecutive annular sectors, the cavity (175) being constructed and sized to receive the assembly pin (174), with an installation clearance allowing for assembly by sliding fit, the assembly pin (174) being made of a material with a coefficient of thermal expansion higher than that of the material constituting the consecutive annular sectors (170).

Description

Technical Field

[0001] This invention belongs to the field of turbines, particularly axial flow compressors for aircraft turbines.

[0002] More specifically, the present invention relates to an inner ring for supporting variable-pitch blades of an axial-flow compressor stator of a turbine. The invention also relates to a stator having such an inner support ring, an axial-flow turbine compressor including at least one such stator, and a turbine equipped with such a compressor.

[0003] Preferably, the compressor is a high-pressure compressor. Background Technology

[0004] Figure 1 An exemplary embodiment of an axial-flow turbine compressor is shown.

[0005] The compressor 1 extends along the longitudinal axis X-X'. The compressor includes multiple axial stages 10 arranged in series, each stage including a rotor 11 and a bladed stator or stator 12.

[0006] At each point of stator 12, the following are defined:

[0007] - Axial direction x, which is parallel to the longitudinal axis X-X' of the compressor.

[0008] - The radial direction y, which extends perpendicularly to the axial direction x along the radius of the compressor, and

[0009] - Circumferential direction z, which is perpendicular to the axial direction x and the radial direction y.

[0010] Each stator 12 includes a plurality of blades 13 extending radially or substantially radially between the housing 14 and the inner ring 15. These blades 13 are variable-pitch blades, meaning they can pivot about their pivot axes to occupy different angles and optimize gas flow within the stator. Therefore, each blade 13 includes a radially outer pivot axis 131 housed in the housing 14 and a radially inner pivot axis 132 housed in the inner ring 15 (see [link to relevant documentation]). Figure 3 The servo control device 16 (e.g., having a rotating periphery and a connecting rod) enables the blade to pivot.

[0011] The inner ring 15 consists of multiple ring sectors 150 (most commonly two 180° ring sectors, such as...). Figure 2 As shown, the multiple annular sectors are assembled circumferentially end-to-end (along direction z) by a cylindrical body, forming a complete 360° ring once these annular sectors are joined together. The fact that it preferably has two 180° annular sectors is due to the assembly constraints of the compressor, which consists of two half-shells.

[0012] like Figure 3 As shown, each annular sector 150 has a contact surface 151 at its two opposite ends, preferably a planar contact surface. Figure 2 As can be seen, when the two ring sectors 150 are assembled end to end, their respective contact surfaces 151 are in contact with each other, and there is a parting line P between the two sectors, more specifically between the two contact surfaces 151 of the two sectors.

[0013] exist Figure 2 In the diagram, the inner ring 15, represented by a solid line, corresponds to the normal position of the ring, that is, the cold position of the ring when the compressor is not in use.

[0014] However, it has been found that during compressor operation, the inner ring 15 frequently exhibits torsion related to its mechanical and / or thermal environment. Therefore, due to thermal expansion, deformation of the ring sector 150 can be observed at the parting line P of these sectors. The expansion location of sector 150 is... Figure 2 The dashed line indicates the direction of deformation (the direction of deformation is indicated by the arrow F).

[0015] As in Figure 3 and Figure 4 As can be seen, each annular sector 150 has a plurality of accommodating portions 152 that open to the radially outer surface 153 of the annular sector, and each accommodating portion is capable of receiving the radially inner pivoting shaft 132 of the pivoting blade 13. For simplicity, in Figure 3 A single receiving portion 152 is schematically shown in the diagram.

[0016] As in Figure 4 As can be better seen, as long as the annular sector 150 supports the pivoting blades 13, an initial operating clearance J1 exists between the base 133 of each blade 13 and the outer surface 153 of the annular sector 150. However, the twisting and opening of the annular sector 150 (the deformed position of the annular 150 is indicated by dashed lines) causes this operating clearance to decrease significantly. The reduced clearance between the base 133 of each blade 13 and the radial outer surface 153 of the annular sector 150 is marked J2. This reduced clearance J2 leads to contact between the base of the blade 13 and the annular sector 150, resulting in obstruction of the blade 13.

[0017] The incident deviation of different blades 13 can cause the compressor to pump, that is, the aerodynamic stall of blade 13 causes the energy of the airflow in the compressor 1 to reverse. Therefore, this obstruction will have a destructive effect on the compressor.

[0018] Currently, this problem is addressed by increasing the initial clearance J1, which prevents contact between the base 133 of the blade 13 and the annular sector 150 even if the annular sector deforms due to thermal expansion. However, this solution is not satisfactory. Summary of the Invention

[0019] The present invention aims to provide an inner ring for supporting the variable pitch blades of the stator of an axial compressor of a turbine. The inner ring includes at least two annular sectors that are heat-sensitive and inseparable during compressor use (to avoid the aforementioned problems), and that at least two annular sectors can be cold-assembled or cold-disassembled when the compressor is not in use, for example for maintenance operations.

[0020] Therefore, the present invention relates to an inner ring for supporting variable pitch blades of a stator of an axial compressor for a turbine, the inner ring comprising at least two annular sectors assembled end-to-end circumferentially to form the inner ring, each annular sector comprising a plurality of receiving portions for receiving a radially inner pivot shaft of one of the blades.

[0021] According to the invention, on each mating plane between the ends of two consecutive annular sectors, assembly is performed by the cooperation of an assembly pin and a cavity for receiving the assembly pin, the assembly pin being fixed at the end of one of the two consecutive annular sectors, the cavity being formed at the end of the other of the two consecutive annular sectors, the cavity being constructed and sized to receive the assembly pin, with an installation clearance allowing for installation by sliding fit, the assembly pin being made of a material with a coefficient of thermal expansion greater than that of the material constituting the consecutive annular sectors, such that during a temperature rise due to the use of the axial compressor, the assembly pin expands more within the cavity than the cavity itself, thereby ensuring the inseparable assembly of the two consecutive annular sectors, and allowing the assembly pin to retract within the cavity during a temperature drop due to the cessation of the use of the axial compressor by allowing the two consecutive annular sectors to be disassembled.

[0022] Because of these features of the present invention, the assembly of the two annular sectors is reversible.

[0023] This technical solution is also easy to implement and inexpensive.

[0024] Finally, this invention enables the limitation of blade wear and reduces the maintenance and replacement costs of components.

[0025] Other advantageous and non-limiting features according to the invention, which are employed individually or in combination:

[0026] - Each annular sector has a cavity at one of its two ends for receiving an assembly pin, which is secured to the other end of each annular sector;

[0027] - At least one of the annular sectors has a receiving cavity at each of its two ends, and at least another of the annular sectors has an assembly pin at each of its two ends;

[0028] - The ring includes two ring sectors, which are assembled end-to-end to form the inner ring;

[0029] - The ratio between the coefficient of thermal expansion of the material constituting the assembly pin and the coefficient of thermal expansion of the material constituting the annular sector is greater than or equal to 1.3 and less than 2;

[0030] - The ratio between the coefficient of thermal expansion of the material constituting the assembly pin and the coefficient of thermal expansion of the material constituting the annular sector is greater than or equal to 2;

[0031] - The material constituting the assembly pin is selected from aluminum or nickel-based steel, and the material constituting the annular sector is selected from steel or titanium;

[0032] - The assembly pin is cylindrical, and the cavity for receiving the assembly pin is cylindrical.

[0033] The present invention also relates to a stator of an axial-flow turbine compressor, the stator comprising a plurality of variable-pitch blades pivotally mounted between a housing for supporting the blades and an inner ring for supporting the blades, the inner ring being as described above.

[0034] The present invention also relates to an axial flow turbine compressor comprising at least one stator as described above.

[0035] Finally, the present invention relates to a turbine equipped with an axial compressor as described above. Attached Figure Description

[0036] Other features, objects, and advantages of the invention will become apparent from the following description, which is illustrative only and not restrictive, and should be read with reference to the accompanying drawings, in which:

[0037] - Figure 1 A perspective view of a turbine compressor is shown.

[0038] - Figure 2 This is a schematic diagram of an inner ring used to support stator blades, based on existing technology.

[0039] - Figure 3 This is a schematic diagram of a ring sector based on existing technology.

[0040] - Figure 4 This is a detailed schematic diagram of the end of a ring sector based on existing technology.

[0041] - Figure 5 This is a front view of the inner ring used to support the variable pitch blades of the stator of an axial compressor for a turbine, according to the present invention.

[0042] - Figure 6 This is a detailed view of a portion of the inner ring according to the present invention. Detailed Implementation

[0043] Now we will combine Figure 5 The inner ring according to the invention is used to support the variable pitch blades of the stator of an axial compressor for a turbine. This ring is generally indicated by reference numeral 17.

[0044] Like the inner ring 15 described above, the inner ring 17 includes at least two ring sectors 170, which are assembled end-to-end circumferentially to form the complete ring extending 360°. Preferably, the inner ring 17 includes only two ring sectors 170, each extending at an angle of 180°. However, the inner ring 17 may also include a greater number of such sectors.

[0045] Each annular sector 170 includes two ends 171, which form a contact surface with the ends 171 of adjacent annular sectors 170. Therefore, when assembling two consecutive annular sectors, a mating plane exists between the contacting ends 171 of the two consecutive annular sectors. The ends 171 are preferably planar.

[0046] Furthermore, as described above, each annular sector 170 includes a plurality of accommodating portions 172 for receiving the radially inner pivot shaft 132 of the pivot blade 13. These accommodating portions 172 open to the radially outer surface 173 of each annular sector 170.

[0047] At the mating plane (contact plane) between the respective ends 171 of two consecutive annular sectors, assembly is performed by engaging the assembly pin 174 with the cavity 175 for receiving the pin.

[0048] More specifically, the assembly pin 174 is secured to the end 171 of one of the two consecutive annular sectors, and the receiving cavity 175 is arranged at the end 171 of the other annular sector in the two consecutive annular sectors.

[0049] Pin 174 extends along an axis perpendicular to the plane of end 171, and cavity 175 leading to end 171 also extends along an axis perpendicular to the plane of end 171.

[0050] Preferably, the assembly pin 174 is cylindrical, and the receiving cavity 175 is also a cylindrical hole.

[0051] Pin 174 can be fixed to the annular sector 170 by an interference fit, i.e., by a shrink fit. In this case, a notch (not shown) is formed at the end 171, and the dimensions of pin 174 are determined such that the pin is forced into the notch and remains fixed in the notch even when the compressor is not in use.

[0052] Pin 174 can also be fixed to the annular sector 170 by welding, bonding or screwing.

[0053] Furthermore, according to the first variant, such as Figure 5 As shown, each annular sector 170 has a cavity 175 at one of its two ends 171 and an assembly pin 174 at the other end of its two ends 171.

[0054] According to the second variant (not shown in the figure), it may also have at least one annular sector (e.g., a half-ring) and at least one other annular sector (e.g., another half-ring), wherein an assembly pin 174 is provided at each of the two ends 171 of the at least one annular sector, and a cavity 175 is provided at each of the two ends 171 of the at least one other annular sector.

[0055] In addition, such as in Figure 6 As best seen in the image, the cavity 175 is constructed and sized relative to the assembly pin 174 to receive the assembly pin 174, with an installation clearance J3 allowing for installation via a sliding fit. In other words, the pin 174 and the cavity 175 are fitted very precisely so that the pin can slide axially into the cavity 175.

[0056] As a purely indicative example, the mounting clearance J3 between the side wall of pin 174 and the inner wall of cavity 175 is very small, approximately a few hundredths of a millimeter. Still by way of example, for cylindrical pins with a diameter of a few millimeters (preferably between 3mm and 8mm), an ISO-compliant H6g5 type fit can be used.

[0057] The mounting gap J3 is very small, but it still allows for cold mounting of the component.

[0058] Finally, a material pair is selected that can manufacture the pin 174 on one hand and the annular sector 170 with cavity 175 on the other hand, such that the coefficient of thermal expansion of the material constituting the pin 174 is greater than the coefficient of thermal expansion of the material constituting the annular sector.

[0059] Therefore, during turbine and compressor operation, the compressor temperature rises, and pin 174 expands more than cavity 175. Pin 174 then exerts a force on the cavity wall due to its expansion (see...). Figure 6(As indicated by arrow F1 in the diagram), the components thus form a contraction fit, making the two adjacent (continuous) annular sectors inseparable. Therefore, the previously described annular sectors no longer problematically open at the parting line.

[0060] Conversely, when the compressor stops, the components cool down, and the pins recover their original diameter through reverse expansion, which eliminates the shrinkage fit with the annular sector. Then, if necessary, the different annular sectors can be disassembled.

[0061] The annular sector is advantageously made of steel and has a 12×10 -6 The average coefficient of thermal expansion is 8.6 × 10⁻⁶ °C. The annular sector can also be made of titanium, then it has a coefficient of thermal expansion equal to 8.6 × 10⁻⁶ °C. -6 The coefficient of thermal expansion is relatively low at / ℃. Therefore, in the latter case, a higher expansion ratio is obtained through pin 174.

[0062] As described below, steel is preferred in hot environments, while titanium is preferred in cold environments.

[0063] Preferably, in order to achieve the aforementioned technical effect, the ratio between the coefficient of thermal expansion of the material constituting the assembly pin and the coefficient of thermal expansion of the material constituting the annular sector is greater than or equal to 1.3.

[0064] For thermal environments (temperatures above 150°C), the following ratio is preferably selected: the coefficient of thermal expansion of the material constituting the assembly pin / the coefficient of thermal expansion of the material constituting the annular sector is greater than or equal to 1.3 and less than 2.

[0065] For example, the material of pin 174 can be an average coefficient of thermal expansion of 18 × 10⁻⁶. -6 Inconel-type nickel-based steel at / ℃ or with an average coefficient of thermal expansion of 23×10 -6 For aluminum at / ℃, the ratios relative to the steel ring sector are 1.5 and 1.91, respectively.

[0066] For cold environments (temperatures below 150°C), the following ratio is preferably selected: the coefficient of thermal expansion of the material constituting the assembly pin / the coefficient of thermal expansion of the material constituting the annular sector is greater than or equal to 2.

[0067] For example, the material of pin 174 can be an average coefficient of thermal expansion of 23 × 10⁻⁶. -6 For aluminum at / ℃, the ratio to the titanium ring sector is 2.67.

[0068] In the case of a high-pressure compressor, the first stage of the stator will be in a cold environment, while the last stage will be in a hot environment, and the temperature of the compressor will gradually increase from the compression stage to the compression stage.

[0069] Therefore, by combining the sliding component gap with the aforementioned ratio of expansion coefficients, clamping is achieved by causing the pin to expand in the cavity, which is accomplished at a low temperature of approximately 100°C.

[0070] The present invention also relates to a stator, such as the aforementioned stator 12, which, as previously described, includes blades 13 and a housing 14; however, the stator has a ring 17 according to the invention, which replaces the inner ring 15, as shown below. Figure 1 As better illustrated in the figure (Figure 17 in parentheses).

[0071] Similarly, the present invention relates to a compressor 1 comprising at least one stage 10, each stage comprising a rotor 11 and a stator 12, the stator 12 comprising an inner ring 17, and finally, the present invention relates to a turbine comprising such a compressor 1 having a ring 17.

Claims

1. An inner ring (17) for supporting variable pitch blades (13) of a stator (12) of an axial compressor (1) of a turbine, the inner ring comprising at least two annular sectors (170) assembled circumferentially end-to-end to form the inner ring, each annular sector comprising a plurality of accommodating portions (172) for receiving a radially inner pivot shaft (132) of one of the blades (13). Its features are, On each mating plane between the ends (171) of two consecutive annular sectors (170), assembly is performed by the cooperation of an assembly pin (174) and a cavity (175) for receiving the assembly pin, the assembly pin (174) being fixed at the end of one of the two consecutive annular sectors (170), and the cavity (175) being formed at the end of the other of the two consecutive annular sectors. The cavity (175) is constructed and sized to receive the assembly pin (174), with an installation clearance that allows for installation via a sliding fit. Furthermore, the assembly pin (174) is made of a material with a coefficient of thermal expansion greater than that of the material constituting the continuous annular sector (170), such that during a temperature rise due to the use of the axial compressor (1), the assembly pin (174) expands more in the cavity (175) than the cavity (175) itself, thereby ensuring the inseparable assembly of the two continuous annular sectors (170), and allowing the assembly pin (174) to retract in the cavity (175) during a temperature drop due to the cessation of the use of the axial compressor (1).

2. The inner ring (17) according to claim 1, characterized in that, Each annular sector (170) has a cavity (175) at one of its two ends (171) for receiving an assembly pin, and the assembly pin (174) is fixed to the other end of the two ends (171) of each annular sector.

3. The inner ring (17) according to claim 1, characterized in that, At least one of the at least two annular sectors (170) has a cavity (175) at each of its two ends (171), and at least another of the at least two annular sectors (170) has an assembly pin (174) at each of its two ends (171).

4. The inner ring (17) according to any one of claims 1 to 3, characterized in that, The inner ring includes two ring sectors (170) assembled end-to-end to form the inner ring.

5. The inner ring (17) according to any one of claims 1 to 3, characterized in that, The ratio between the coefficient of thermal expansion of the material constituting the assembly pin (174) and the coefficient of thermal expansion of the material constituting the annular sector (170) is greater than or equal to 1.3 and less than 2.

6. The inner ring (17) according to any one of claims 1 to 3, characterized in that, The ratio between the coefficient of thermal expansion of the material constituting the assembly pin (174) and the coefficient of thermal expansion of the material constituting the annular sector (170) is greater than or equal to 2.

7. The inner ring (17) according to any one of claims 1 to 3, characterized in that, The material constituting the assembly pin (174) is selected from aluminum or nickel-based steel, and the material constituting the annular sector (170) is selected from steel or titanium.

8. The inner ring (17) according to any one of claims 1 to 3, characterized in that, The assembly pin (174) is cylindrical, and the cavity (175) for receiving the assembly pin is cylindrical.

9. A stator (12) of an axial-flow compressor for a turbine, the stator comprising a plurality of variable-pitch blades (13) pivotally mounted between a housing (14) for supporting the blades (13) and an inner ring for supporting the blades, characterized in that, The inner ring is the inner ring (17) according to any one of claims 1 to 8.

10. An axial-flow compressor for a turbine (1), characterized in that, The axial compressor includes at least one stator (12) according to claim 9.

11. A turbine, characterized in that, The turbine includes at least one axial compressor as claimed in claim 10.

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