Wiring method for strain gauges of low-pressure turbine shaft of complete aero-engine

Abstract

The invention belongs to the technical field of high-temperature dynamic stress testing of a low-pressure turbine shaft of an aero-engine, and provides a strain gauge routing method for the low-pressure turbine shaft of the aero-engine in order to solve the technical problems that a low-pressure turbine shaft cannot be detached in an assembly state of the aero-engine, a lead cannot be fixed through spot welding and a signal is difficult to lead out reliably due to the fact that a bearing is installed. The method comprises the following steps: spot-welding a plurality of titanium alloy skins with semicircular openings on a wiring path on the inner surface of the fan shaft in advance in a single-piece stage of the fan shaft; during wiring of the whole machine, silk-covered wires led out of a low-pressure turbine shaft sequentially penetrate through the preset skin channel, and vibration-resistant, wear-resistant and glue-free reliable fixing is achieved. Finally, the signal is led out to a telemetering system through a prefabricated through hole of the fan disc. According to the method, the rotor assembly does not need to be disassembled, the strain gauge lead switching and fixing problems under the whole machine condition are effectively solved, the dynamic stress signal can be stably obtained under the full-rotating-speed working condition, and key technical support is provided for strength evaluation and service life prediction of the low-pressure turbine shaft.

Description

Technical Field

[0001] This invention belongs to the technical field of high-temperature dynamic stress testing of low-pressure turbine shafts of aero-engines, and relates to a method for routing strain gauges on low-pressure turbine shafts of aero-engines. Background Technology

[0002] As aero engines develop towards higher temperatures, higher pressures, and higher speeds, the thrust-to-weight ratio of engines continues to increase, placing higher demands on the structural strength of the low-pressure turbine shaft under overall engine conditions. This has led to a growing number of low-pressure turbine shaft-related failures. To accurately obtain its vibration and stress response under operating conditions, strain gauges are typically attached to the surface of the low-pressure turbine shaft, and leads are connected to a telemetry system or a lead-transmitter signal transmission device to effectively extract and measure dynamic strain signals.

[0003] However, under the conditions of an aero-engine, the routing of strain gauges on the low-pressure turbine shaft faces significant challenges. On the one hand, the engine structure is highly compact, and telemetry modules can usually only be installed inside the fan disk cavity. The limited space at the turbine end means that the strain signal lines led from the low-pressure turbine shaft cannot be directly connected to the telemetry module and must be connected through an intermediate adapter. On the other hand, to ensure signal integrity under high-speed rotation and strong vibration environments, the strain leads must be reliably fixed and protected throughout their entire length.

[0004] More importantly, under the constraints of engine assembly sequence and bearing operating environment, traditional fixing processes such as spot welding along the bearing are difficult to implement when the engine is assembled, and conventional wiring methods can no longer meet testing requirements. Furthermore, there are currently no unified technical standards or specifications in this field in China, and the wiring of low-pressure turbine shaft strain gauges under engine assembly conditions remains a technical challenge. Summary of the Invention

[0005] This invention solves the technical challenges of strain gauge lead wire transfer and the inability to spot weld and fix the leads wires when the bearing is already installed, achieving the goal of bonding and reliably routing strain gauges on the low-pressure turbine shaft of an aero-engine in the overall state. The invention discloses a method for routing strain gauges on the low-pressure turbine shaft of an aero-engine. This method is implemented entirely in the assembled state of the aero-engine, without the need to disassemble the low-pressure turbine rotor, fan disk, or main bearing assembly, thus meeting the in-situ dynamic strain monitoring requirements during ground testing of the entire aero-engine.

[0006] Specifically, the method is used to lay strain gauge leads on a non-removable low-pressure turbine shaft in the assembled state of an aero-engine, and includes the following steps:

[0007] S1. Attach strain gauges to the outer surface of the low-pressure turbine shaft, transfer wire to the pins of the strain gauges and introduce it into the inner cavity of the low-pressure turbine shaft through the radial through hole, and lead it forward along the inner wall of the low-pressure turbine shaft to the front end face of the low-pressure turbine shaft. S2. After the wire is passed out from the front end face of the low-pressure turbine shaft, it is introduced into the inner cavity of the fan shaft. Before the fan shaft is assembled, multiple titanium alloy skins are pre-spot welded on the wiring path on the inner surface of the fan shaft. Each titanium alloy skin is provided with a semi-circular hole for the wire to pass through. When routing the wire, the wire is passed through the semi-circular holes of each titanium alloy skin in sequence to achieve fixation and protection. S3. Lead the wire from the end of the fan shaft to the fan disk, and pass it through the pre-made through hole on the fan disk to the outside. Make an electrical connection with the telemetry system lead at the preset transition position on the outside of the fan disk, and lead the strain gauge signal to the telemetry system.

[0008] Further, in step S1, the wire coil is connected to the pins of the strain gauge in any of the following ways: Remove the original lead wires from the strain gauge, solder the wire to the strain gauge lead pads, and perform insulating encapsulation. A length of the original lead wire of the strain gauge is retained, and at a predetermined position on the outer surface of the low-pressure turbine shaft and outside the strain gauge bonding area along the axial direction, the original lead wire is overlapped and soldered to the temperature-controlled wire, and then insulated and encapsulated.

[0009] Furthermore, in step S1, the wire is locally fixed at the front end face of the low-pressure turbine shaft using a skin spot welding method.

[0010] Furthermore, in step S2, the titanium alloy skin is a rectangular thin sheet, and multiple titanium alloy skins are arranged axially at intervals along the wiring path on the inner surface of the fan shaft, and the centers of the semi-circular holes of all the titanium alloy skins are located on the same generatrix.

[0011] Furthermore, in step S3, the position of the pre-made radial through hole on the fan disk avoids the high stress area and the cooling air passage; the preset transition position is located in the annular area outside the rear end face of the fan disk, and the annular area reserves operating space and is far away from the rotating interference component.

[0012] Further, in step S3, the electrical connection includes: After the silk-covered wire is wound around the corresponding polarity end of the telemetry system terminal lead, it is welded together, and the positive and negative connection points are arranged in a staggered manner along the circumference. Each connection point is individually wrapped with polyimide tape and then covered with heat shrink tubing to form double insulation protection.

[0013] In an optional embodiment of the above-mentioned method for routing strain gauges on the low-pressure turbine shaft of an aero-engine, the method further includes an emergency routing path. When it is impossible to open a radial through hole on the fan disk due to structural strength limitations, the following steps are performed: The wire from the low-pressure turbine shaft is led along the inner surface of the fan disk to the front end face of the fan disk by spot welding with a skin. The telemetry system lead wire is routed from the outside to the outer side of the front face of the fan disc; Electrically connect the wire to the telemetry system terminal lead in the non-interference area on the outer side of the front face of the fan disk.

[0014] Furthermore, in step S1, the strain gauge is within the operating temperature range. A foil strain gauge with a temperature range of 120℃ to 250℃, wherein the wire is a single-core copper wire with an outer silicone rubber insulation layer.

[0015] The strain gauge wiring method of the present invention involves pre-welding multiple titanium alloy skins with semi-circular openings onto the wiring path on the inner surface of the fan shaft before assembly; after the entire machine is assembled, the wires led from the low-pressure turbine shaft are sequentially threaded into the pre-set skin channels to achieve reliable fixation without glue, vibration, or interference; finally, the signal is led out to the telemetry system through the pre-fabricated through holes in the fan disc to complete the transmission of dynamic strain signals in the overall machine state.

[0016] Compared to existing technologies, this method effectively solves the difficulties in strain gauge lead transfer under whole-machine conditions and the inability to perform spot welding fixation after bearing installation, successfully achieving reliable strain gauge wiring on the low-pressure turbine shaft in a non-removable state. This allows for stable acquisition of dynamic stress signals across the entire engine operating speed range, significantly improving the survival rate and signal integrity of strain gauges under high-speed, strong vibration, and high-temperature environments, laying a solid technical foundation for structural strength assessment, fault diagnosis, and life prediction of the low-pressure turbine shaft. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the method for routing strain gauges on the low-pressure turbine shaft of an aero-engine according to the present invention; Figure 2 This is a schematic diagram of the wiring of the strain gauges on the low-pressure turbine shaft of the engine. Among them, 1. Low-pressure turbine shaft; 2. Strain gauge; 3. Wire wrapped; 4. Pre-drilled hole for low-pressure turbine shaft; 5. Fan shaft; 6. Bearing; 9. Fan disk; 10. Pre-drilled radial through hole; 11. Telemetry system; 12. Wire wrapped at the end of telemetry system; 14. Front end of fan disk. Detailed Implementation

[0019] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0020] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features of the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] To address the problems of unreliable wiring, easy breakage, and signal interruption caused by non-removable, high-speed rotation, and space constraints in existing technologies, this invention discloses a method for wiring strain gauges on the low-pressure turbine shaft of an aero-engine. This method is implemented entirely in the assembled state of the aero-engine and does not require disassembly of the low-pressure turbine rotor, fan disk, or main bearing assembly, thus meeting the in-situ dynamic strain monitoring requirements during ground testing of the entire engine.

[0022] Specifically, see Figure 1 and Figure 2 As shown, the method is used to lay strain gauge leads on a non-removable low-pressure turbine shaft in the assembled state of an aero-engine, and includes the following steps: S1. Attach strain gauges to the outer surface of the low-pressure turbine shaft, transfer wire to the pins of the strain gauges and introduce it into the inner cavity of the low-pressure turbine shaft through the radial through hole, and lead it forward along the inner wall of the low-pressure turbine shaft to the front end face of the low-pressure turbine shaft. S2. After the wire is passed out from the front end face of the low-pressure turbine shaft, it is introduced into the inner cavity of the fan shaft. Before the fan shaft is assembled, multiple titanium alloy skins are pre-spot welded on the wiring path on the inner surface of the fan shaft. Each titanium alloy skin is provided with a semi-circular hole for the wire to pass through. When routing the wire, the wire is passed through the semi-circular holes of each titanium alloy skin in sequence to achieve fixation and protection. S3. Lead the wire from the end of the fan shaft to the fan disk, and pass it through the pre-made through hole on the fan disk to the outside. Make an electrical connection with the telemetry system lead at the preset transition position on the outside of the fan disk, and lead the strain gauge signal to the telemetry system.

[0023] The principle of the strain gauge wiring method of the present invention is as follows: Before assembly, multiple titanium alloy skins with semi-circular openings are pre-welded on the wiring path on the inner surface of the fan shaft; after the whole machine is assembled, the wires led out from the low-pressure turbine shaft are sequentially passed into the pre-set skin channels to achieve reliable fixation without glue, vibration, and interference; finally, the signal is led out to the telemetry system through the pre-made through hole of the fan disk to complete the dynamic strain signal transmission in the whole machine state.

[0024] In some embodiments of step S1 above, such as Figure 2 As shown, strain gauges 2 are attached to the test positions on the outer surface of the low-pressure turbine shaft 1, and wire-wrapped wires 3 are connected to the strain gauge leads. The wire-wrapped wire 3 is introduced into the inner surface of the low-pressure turbine shaft 1 through a radial through-hole (i.e., the pre-fabricated hole 4 on the low-pressure turbine shaft). The wire-wrapped wire 3 is fixed to both the outer and inner surfaces of the low-pressure turbine shaft 1 using resin adhesive. The wire-wrapped wire 3 is then led forward along the inner wall to the front end of the low-pressure turbine shaft 1 using resin adhesive. Finally, the wire-wrapped wire 3 is fixed to the front end of the low-pressure turbine shaft 1 using spot welding with a skin.

[0025] When taking the lead wire, the pre-drilled hole 4 of the low-pressure turbine shaft is preferably machined 8-10mm forward of the strain gauge bonding position, and the diameter of the hole is about 2mm.

[0026] When taking leads, there are two ways to connect the wrapped wire 3 to the pins of the strain gauge 2: One method is to remove the original lead wires from the strain gauge, solder the wire to the lead pads of the strain gauge, and then perform insulating encapsulation. Another method involves retaining a 3-5mm length of the original strain gauge lead wire and, at a predetermined position approximately 3-5mm outside the strain gauge bonding area on the outer surface of the low-pressure turbine shaft along the axial direction, lap-welding the original lead wire to the temperature-controlled wire and then performing an insulating encapsulation process.

[0027] Optionally, the wire is locally fixed at the front end face of the low-pressure turbine shaft by spot welding.

[0028] Typically, the wire is routed along the low-pressure turbine shaft 1 to the inner surface of the fan shaft 5. During the routing of the wire 3 along the fan shaft 5, it needs to be secured using resin adhesive or spot welding. However, since the bearing 6 corresponding to the fan shaft 5 has already been installed, and due to the special working nature of the bearing 6, the test piece with the bearing 6 cannot be further cured in the furnace with resin adhesive. Furthermore, assessments indicate that spot welding at the corresponding position directly below the fan shaft 5 could potentially cause pitting corrosion in the bearing 6, leading to damage. Therefore, spot welding is not permitted on the inner surface of the fan shaft directly below the bearing 6.

[0029] Based on this, to ensure the effective fixation of the wire 3, in step S2, when the fan shaft 5 is in a single-piece state, multiple titanium alloy skins are pre-spot-welded to the inner surface of the fan shaft directly below the bearing 6. When the wire 3 is led to the inner surface of the fan shaft directly below the bearing 6, the wire is led into the pre-spot-welded titanium alloy skins to achieve fixation and protection of the wire 3. After the wire has passed the inner surface of the fan shaft directly below the bearing 6, the wire is then spot-welded again using the skins to ensure reliable fixation and lead-out of the wire.

[0030] Optionally, the titanium alloy skin is a rectangular thin sheet with a length of 4 cm ± 0.5 cm and a width of 2 cm ± 0.2 cm. During spot welding, a 3 mm edge is reserved on each side in the width direction as a spot welding area, and the middle part is machined into the semi-circular hole. Multiple titanium alloy skins are arranged axially at intervals along the wiring path on the inner surface of the fan shaft, and the spacing between adjacent skins can be set to 1 cm ± 2 mm. The centers of the semi-circular holes of all the titanium alloy skins are located on the same generatrix, that is, multiple skins need to be on a straight line to ensure that the wire 3 is routed along the wiring direction without causing damage to the wire 3. This effectively fixes the wire 3 and ensures reliable lead-out of the wire 3.

[0031] In addition, the semi-circular diameter of the semi-circular hole here is about 2-3 mm larger than the diameter of the silk-covered wire 3 that passes through, which not only ensures the passage of the silk-covered wire 3 but also serves to fix and protect it.

[0032] When leading the wire, after the wire is led out from the fan shaft 5 and then from the end of the fan shaft 5 to the inner surface of the fan disk 9, it can be fixed by spot welding. At this time, the wire 3 can be passed through the pre-made radial through hole 10 on the fan disk and out to the outside of the fan disk 9. The telemetry system 11 is installed at the disk cavity position of the fan disk 9 and the booster stage. One end of the wire 12 at the telemetry system end is fixed at the corresponding position of the telemetry system 11, and the other end of the wire 12 at the telemetry system end passes through the pre-made through hole from the back of the fan disk 9 and out to the outside of the fan disk. It meets the wire 3 of the strain gauge at the corresponding transition position 13 on the outside of the fan disk, and the transition between the wire 3 of the strain gauge and the wire 12 at the telemetry system end is realized at the corresponding transition position on the outside of the fan disk. Using the above method, the strain gauge 2 was attached and its lead wires to the telemetry system 11 were protected. This application realizes the dynamic stress test and analysis of the low-pressure turbine shaft under the whole engine conditions of the aero-engine, laying a technical foundation for the prediction of the life of the low-pressure turbine shaft.

[0033] Optionally, in step S3, after the wire 3 is led to the inner surface of the fan disk 9, a pre-made radial through hole 10 from the inner surface to the outer surface can be pre-made on the fan disk 9. The position of the pre-made radial through hole 10 avoids the high stress area and the cooling air passage, and the hole diameter is about 2mm.

[0034] Furthermore, since the alignment and transition position 13 on the outer side of the fan disk is better when it is closer to the rear end face of the fan disk, but the transition process between the wire-wrapped wire 3 and the wire-wrapped wire 12 at the telemetry system end requires space to complete, the preset transition position is located in the annular area on the outer side of the rear end face of the fan disk. This annular area reserves operating space and is far away from the rotating interference components. More specifically, the alignment and transition position on the outer side of the fan disk is 15-20mm away from the rear end face of the fan disk 9.

[0035] Optionally, in step S3, the electrical connection includes: winding the silk-covered wire around the corresponding polarity end of the telemetry system lead (e.g., 2-3 turns) and then welding it, and arranging the positive and negative connection points circumferentially staggered by 3-5mm to ensure that the signals do not interfere with each other, wrapping each connection position with polyimide tape separately, and covering it with heat shrink tubing to form double insulation protection.

[0036] In an optional embodiment of the above-mentioned method for routing strain gauges on the low-pressure turbine shaft of an aero-engine, if the structural strength of the fan disk 9 is insufficient, making it impossible to machine the pre-fabricated radial through-hole 10 from the inner surface of the fan disk 9 to the outer surface of the fan disk, an emergency routing path can be implemented by performing the following steps: The wire from the low-pressure turbine shaft is led along the inner surface of the fan disk to the front end face of the fan disk by spot welding with a skin; the telemetry system end lead is routed from the outside to the outside of the front end face of the fan disk; the wire and the telemetry system end lead are electrically connected in the non-interference area on the outside of the front end face of the fan disk.

[0037] Specifically, the wire 3 can be spot-welded along the inner surface of the fan disk 9 to the front end of the fan disk 9. At the same time, the wire 12 of the telemetry system end is passed through the pre-made radial through hole 10 to the outside of the fan disk, and then runs along the outside of the fan disk 9 to the front end 14 of the fan disk to meet the wire 3. The connection between the wire 3 and the wire 12 of the telemetry system end is realized at the front end 14 of the fan disk.

[0038] Furthermore, in step S1, the strain gauge is a foil strain gauge with an operating temperature range of -120℃ to 250℃, and the wire is a single-core copper wire with an outer silicone rubber insulation layer, with a wire diameter of 0.3 mm. Its temperature resistance matches that of the strain gauge and is compatible with the telemetry system interface.

[0039] Compared with the prior art, the method of the invention has at least the following technical effects: 1. No need to disassemble the entire engine: Suitable for already assembled aero engines, meeting the requirements for in-situ testing; 2. Vibration and wear resistance: Physical channels are formed by pre-installed titanium alloy skin to avoid direct friction between the wires and the metal wall; 3. Strong process compatibility: The skin is spot-welded at the single-piece stage, which does not interfere with subsequent bearing assembly; 4. High signal stability: Fixed wiring path and reliable insulation reduce electromagnetic interference and the risk of open circuit; 5. Emergency solution: When the fan plate cannot be drilled, the front face adapter solution can be switched to improve the adaptability of the project.

[0040] Obviously, those skilled in the art should understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Various modifications and variations of the embodiments of the present invention are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for routing strain gauge leads on a low-pressure turbine shaft of an aero-engine, used for laying strain gauge leads on a non-removable low-pressure turbine shaft in the assembled state of an aero-engine, characterized in that... The method includes: Strain gauges are attached to the outer surface of the low-pressure turbine shaft. Wires are then transferred to the pins of the strain gauges and introduced into the inner cavity of the low-pressure turbine shaft through radial through holes. The wires are then led forward along the inner wall of the low-pressure turbine shaft to the front end face of the low-pressure turbine shaft. After the wire is passed out from the front end face of the low-pressure turbine shaft, it is introduced into the inner cavity of the fan shaft. Before the fan shaft is assembled, multiple titanium alloy skins are pre-spot welded on the wiring path on the inner surface of the fan shaft. Each titanium alloy skin has a semi-circular hole for the wire to pass through. When routing the wire, the wire is passed through the semi-circular holes of each titanium alloy skin in sequence to achieve fixation and protection. The wire is led from the end of the fan shaft to the fan disk, and then through a pre-made through hole on the fan disk to the outside. It is electrically connected to the lead wire of the telemetry system at a preset transition position on the outside of the fan disk, so that the signal of the strain gauge is led out to the telemetry system.

2. The method for routing strain gauges on the low-pressure turbine shaft of an aero-engine according to claim 1, characterized in that, Adapter wires are attached to the pins of the strain gauge, including any of the following methods: Remove the original lead wires from the strain gauge, solder the wire to the strain gauge lead pads, and perform insulating encapsulation. A length of the original lead wire of the strain gauge is retained, and at a predetermined position on the outer surface of the low-pressure turbine shaft and outside the strain gauge bonding area along the axial direction, the original lead wire is overlapped and soldered to the temperature-controlled wire, and then insulated and encapsulated.

3. The method for routing strain gauges on the low-pressure turbine shaft of an aero-engine according to claim 1 or 2, characterized in that, The wire is locally fixed at the front end face of the low-pressure turbine shaft using a skin spot welding method.

4. The method for routing strain gauges on the low-pressure turbine shaft of an aero-engine according to claim 1, characterized in that, The titanium alloy skin is a rectangular thin sheet, and multiple titanium alloy skins are arranged axially at intervals along the wiring path on the inner surface of the fan shaft, and the centers of the semi-circular holes of all the titanium alloy skins are located on the same generatrix.

5. The method for routing strain gauges on the low-pressure turbine shaft of an aero-engine according to claim 1, characterized in that, The pre-fabricated radial through holes on the fan disk are positioned to avoid high-stress areas and cooling air passages; the preset transition position is located in the annular area outside the rear end face of the fan disk, and this annular area reserves operating space and is far away from rotating interference components.

6. The method for routing strain gauges on the low-pressure turbine shaft of an aero-engine according to claim 1, characterized in that, The electrical connection includes: After the silk-covered wire is wound around the corresponding polarity end of the telemetry system terminal lead, it is welded together, and the positive and negative connection points are arranged in a staggered manner along the circumference. Each connection point is individually wrapped with polyimide tape and then covered with heat shrink tubing to form double insulation protection.

7. The method for routing strain gauges on the low-pressure turbine shaft of an aero-engine according to claim 1, characterized in that, The method also includes an emergency wiring path. When it is impossible to open a radial through hole on the fan disk due to structural strength limitations, the wire from the low-pressure turbine shaft is led along the inner surface of the fan disk to the front end face of the fan disk by skin spot welding. The telemetry system end lead is routed from the outside to the outside of the front end face of the fan disk. The wire and the telemetry system end lead are electrically connected in the non-interference area outside the front end face of the fan disk.

8. The method for routing strain gauges on the low-pressure turbine shaft of an aero-engine according to claim 1, characterized in that, The strain gauge is within the operating temperature range. A foil strain gauge with a temperature range of 120℃ to 250℃, wherein the wire is a single-core copper wire with an outer silicone rubber insulation layer.

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