High-robustness pull rod design method of gas turbine

Abstract

The invention relates to a high-robustness pull rod design method of a gas turbine, which comprises the following steps of: calculating maximum imposable force and minimum imposable force of a pull rod; determining a reasonable range of the neck diameter of the pull rod according to structural limitation and material performance; carrying out structural design of the pull rod and calculating the axial rigidity of the pull rod to ensure that the axial rigidity of the pull rod and the axial rigidity of a rotor wheel disc meet a matching relationship; and carrying out vibration mode analysis on the pull rod and the rotor, and finally determining pull rod design parameters through iterative optimization. Through the systematic design process, the pre-tightening force holding capacity of the center pull rod under the abnormal working condition is remarkably improved, end teeth are effectively prevented from disengaging or sliding, and the robustness and operation safety of a rotor system are enhanced.

Description

Technical Field

[0001] This invention relates to the field of gas turbine technology, and in particular to a highly robust tie rod design method for gas turbines. Background Technology

[0002] A gas turbine is an internal combustion power machine that uses a continuously flowing gas as a working fluid to drive an impeller to rotate at high speed, converting the energy of fuel into useful work. It is a type of rotating impeller thermal engine.

[0003] The target market for gas turbines is global, with high after-sales costs and long cycles. During the demand analysis phase, assemblability and maintainability are the primary customer requirements. Gas turbine rotors with a high market share often employ a structure combining arc-end teeth / Hirth teeth and a central tie rod. The arc-end teeth / Hirth teeth provide centering and torque transmission for the rotor, while the central tie rod provides preload. If the central tie rod fails to provide sufficient preload as designed during operation, it can cause gas turbine vibration or even explosion; therefore, adequate measures must be taken to ensure that the target preload is maintained during operation.

[0004] For example, CN115609267A discloses an assembly method for a threaded center tie rod, ensuring the perpendicularity of the tie rod to each stage of the rotor, preparing for subsequent balancing. CN203432851U discloses an installation measurement device for aero-engine center tie rods, CN102998182A discloses the same device, and CN116361959A discloses a dynamic modeling method for a complex center tie rod rotor system. The aforementioned disclosed technical solutions ensure the rotor's preload under ideal and stable operating conditions from the perspectives of rotor dynamics calculations and assembly. However, in actual gas turbine operation, abnormal conditions such as local overheating, gas backflow, component failures, and transient situations like operating condition transitions can cause the rotor state to deviate from the simulation design state, resulting in situations where preload exceeds tolerances, leading to excessive vibration. Summary of the Invention

[0005] In response to the shortcomings of the existing production technology, the applicant provides a highly robust tie rod design method for gas turbines, thereby meeting the usage requirements of gas turbines.

[0006] The technical solution adopted in this invention is as follows: A method for designing a highly robust tie rod for a gas turbine includes the following operational steps: S1: Calculate the maximum force F1 that can be applied to the tie rod, that is, apply aerodynamic force, centrifugal load and torque in a two-dimensional state, and calculate the stress of each stage of the rotor by applying different axial forces F4i. Continue until the stress on the part exceeds the material limit, and record the axial force F4 in this state. The maximum applied force F1 = the target axial force F4 / the strength reserve coefficient; The yield strength reserve coefficient > 1.25, and the ultimate strength reserve coefficient is greater than 1.5; S2: Calculate the minimum applied force F2 of the tie rod. Under the state of the sector rotor section, apply aerodynamic force, centrifugal load and torque, and try to apply different axial forces F5i until the working surface of the end teeth is not completely disengaged and no slipping movement occurs, and record the axial force F5 in this state; The minimum applied force F2 = the target axial force F5 / the tightness coefficient; The tightness coefficient = 1.15 - 1.25; S3: Determine the structural scheme and the structure to be arranged at the outer diameter of the central tie rod at the compressor end; S4: Calculate the maximum tie rod neck diameter D1 according to the maximum applied force F1 and the material mechanical property parameters; S5: Calculate the minimum tie rod neck diameter D2 according to the minimum applied force F2 and the material mechanical property parameters; S6: Determine the tie rod neck diameter D3 according to the limitation of the radial space of the central tie rod by the structural scheme; S7: Determine the range of the tie rod neck diameter. When D3 >> D2, D2 ≤ D ≤ min(D1, D3); S8: When D3 < D2 or the value is close to D2, coordinate the structural scheme to obtain the value of D3 until D3 >> D2; S9: Initially determine the value of D within the range of D for subsequent iteration; S10: According to the selected value of D and the current structural scheme, carry out the structural design of the central tie rod and calculate the axial stiffness E2 of the tie rod structure; S11: Calculate the axial stiffness E1 of the rotor disk part; S12: When E1 ≥ (2 - 3)E2, carry out the next calculation.

[0007] As a further improvement of the above technical solution: Recalculate the adjusted axial stiffness E2 of the tie rod until the requirements are met; S13: Calculate the vibration mode of the tie rod below the target speed of the gas turbine S14: Calculate the vibration mode of the rotor below the target speed of the gas turbine S15: When the vibration mode and corresponding speed of the tie rod avoid the vibration mode and corresponding speed of the rotor within the margin ratio range and do not increase the excitation force, determine the final tie rod; S16: When the vibration mode and speed of the tie rod increase the sensitivity of the rotor to vibration within the margin ratio range, readjust the value of D or take other measures.

[0008] Its further technical solution lies in: In S1, stress concentration factors are used to replace local small features.

[0009] The localized small features are holes or keyways.

[0010] In S3, the structure is a centrifugal impeller, a front shaft disk, or a journal.

[0011] The maximum applied force F1 is 1150 kN.

[0012] The minimum applied force F2 is 859 kN.

[0013] The maximum tie rod neck diameter D1 is 32mm.

[0014] The minimum tie rod neck diameter D1 is 20mm.

[0015] The diameter D3 of the tie rod neck is 30mm.

[0016] The axial stiffness E1 is 1310 kN / mm.

[0017] The beneficial effects of this invention are as follows: This invention is simple to operate. By comprehensively considering various load conditions such as aerodynamic force, centrifugal load, and torque, the design ensures that the maximum applicable force does not exceed the structural strength limit, while also ensuring that the minimum applied force is sufficient to prevent the end teeth from disengaging or slipping. This allows the central tie rod to maintain effective preload even under abnormal operation of the gas turbine (such as local overheating, transient operating condition transitions, etc.), significantly improving the safety and reliability of the system.

[0018] This invention achieves a coordinated design of the tie rod structure and rotor system by introducing multiple design dimensions for the tie rod neck diameter (maximum diameter D1, minimum diameter D2, and structurally limited diameter D3) and combining axial stiffness matching with vibration modal analysis. This method optimizes tie rod dimensions while meeting strength, stiffness, and vibration performance requirements, avoiding increased vibration sensitivity or structural interference caused by unreasonable dimensions.

[0019] The present invention fully considers the actual assembly space and structural layout (such as the limitation of the compressor end outer diameter arrangement) in the design, ensuring that the tie rod design not only meets the performance requirements, but also facilitates assembly and maintenance, which meets the customer demand of the gas turbine market for high assemblability and high maintainability, and helps to improve the product's market adaptability and competitiveness.

[0020] Through a step-by-step design process, especially the iterative verification of stiffness matching and vibration modes, the design process is equipped with self-correction and optimization capabilities. When the preliminary design does not meet vibration or stiffness requirements, measures such as adjusting the tie rod diameter or adding auxiliary supports can be taken in a timely manner to ensure that the final design scheme achieves the best balance between performance and reliability.

[0021] The present invention provides a design method for a robust central tie rod, which is a design method that can effectively ensure the effective pre-tightening force of the rotor under abnormal conditions. At the same time, the present invention can ensure the stability of the rotor pre-tightening force under complex working conditions, improve the safety and reliability of the gas turbine operation, and also take into account the convenience of assembly and maintenance, having good engineering practical value and application prospects for popularization. Brief Description of the Drawings

[0022] Figure 1 It is a flow chart of the present invention. Detailed Embodiments

[0023] The following will describe the detailed embodiments of the present invention with reference to the accompanying drawings.

[0024] Embodiment 1: As Figure 1 shown, the anti-loosening central tie rod design method for the gas turbine in this embodiment includes the following operation processes: S1: Calculate the maximum force F1 that can be applied to the tie rod, that is, load the aerodynamic force, centrifugal load and torque in the two-dimensional state, and calculate the stresses of each stage of the rotor by loading different axial forces F4i; Until the stress of the part exceeds the material limit, record the axial force F4 in this state; The maximum applied force F1 = the target axial force F4 / the strength reserve coefficient; The yield strength reserve coefficient > 1.25, and the ultimate strength reserve coefficient is greater than 1.5; S2: Calculate the minimum force F2 that can be applied to the tie rod. Load the aerodynamic force, centrifugal load and torque in the sector rotor section state, and try to load different axial forces F5i until the working surface of the end teeth is not completely disengaged and no slip movement occurs, and record the axial force F5 in this state; The minimum applied force F2 = the target axial force F5 / the tightness coefficient; The tightness coefficient = 1.15 - 1.25; S3: Determine the structural scheme and the structure to be arranged at the outer diameter of the central tie rod at the compressor end; S4: Calculate the maximum tie rod neck diameter D1 according to the maximum applied force F1 and the material mechanical property parameters; S5: Calculate the minimum tie rod neck diameter D2 according to the minimum applied force F2 and the material mechanical property parameters; S6: Determine the tie rod neck diameter D3 according to the limitation of the radial space of the central tie rod by the structural scheme; S7: Determine the range of the tie rod neck diameter. When D3 >> D2, D2 ≤ D ≤ min(D1, D3); S8: When D3 < D2 or the value is close to D2, coordinate the structural scheme to obtain the value of D3 until D3 >> D2; S9: Within the range of values ​​for D, initially determine the value of D for subsequent iterations; S10: Based on the selected D value and the current structural scheme, carry out the structural design of the central tie rod and calculate the axial stiffness E2 of the tie rod structure; S11: Calculate the axial stiffness E1 of the rotor disk section; S12: When E1≥(2~3)E2, proceed to the next calculation.

[0025] Recalculate the adjusted axial stiffness E2 of the tie rod until it meets the requirements; S13: Calculate the mode shape of the tie rod below the target speed of the gas turbine. S14: Calculate the rotor vibration modes below the target speed of the gas turbine. S15: When the mode shape and corresponding speed of the tie rod are within the margin ratio range and avoid the rotor array and corresponding speed, and will not increase the excitation force, determine the final tie rod; S16: When the mode shape and speed of the tie rod are within the margin ratio range, the rotor’s sensitivity to vibration will increase. Readjust the D value or take other measures.

[0026] In S1, stress concentration factors are used to replace local small features.

[0027] Localized minor features include holes or keyways.

[0028] In S3, the structure consists of a centrifugal impeller, a front shaft disc, or a journal.

[0029] The maximum applied force F1 is 1150 kN.

[0030] The minimum applied force F2 is 859 kN.

[0031] The maximum tie rod neck diameter D1 is 32mm.

[0032] The minimum tie rod neck diameter D1 is 20mm.

[0033] The diameter D3 of the tie rod neck is 30mm.

[0034] The axial stiffness E1 is 1310 kN / mm.

[0035] Example 2: When a gas turbine with a dual centrifugal structure uses a central tie rod to preload the rotor, the tie rod design method is as follows: (1) Calculate the maximum applicable force F1 of the tie rod: Apply aerodynamic force, centrifugal load, and torque in a two-dimensional state, and calculate the stress of each rotor stage by applying different axial forces F4i. For local small features such as holes and keyways, stress concentration factors are used instead. Until the stress of a certain part exceeds the material limit, record the axial force F4 in this state. Maximum applied force F1 = target axial force F4 / strength reserve factor; Yield strength reserve factor > 1.25, ultimate strength reserve factor > 1.5; In this embodiment, the maximum applied force F1 is 1150 KN, the target axial force F4 is 1500 KN, and the strength reserve coefficient is 1.3. F41=500KN, F42=1000KN, F43=1200KN, F44=1400KN, F45=1600KN (stress yield limit condition occurs), F46=1500KN (stress close to limit), yield strength reserve coefficient is taken as 1.3; (2) Calculate the minimum applied force F2 of the tie rod. Apply aerodynamic force, centrifugal load and torque in the sector rotor section state, and try to apply different axial forces F5i until the end tooth working surface is not completely disengaged and no slippage occurs. Record the axial force F5 in this state.

[0036] Minimum applied force F2 = target axial force F5 / tightness coefficient.

[0037] Tightness coefficient = 1.15-1.25.

[0038] F51=1200KN, F52=1100KN, slippage occurs; F53=1050KN, slippage disappears; F54=1030KN, slippage trend begins.

[0039] In this embodiment, the minimum applied force F2 is 859KN, the target axial force F5 is 1030KN, and the tightness coefficient is 1.2.

[0040] (3) Determine the structural scheme, arrange the steps at the air compressor end of the central tie rod and make an interference fit with the first stage impeller.

[0041] (4) Based on the maximum applied force F1 and the material mechanical property parameters, calculate the maximum neck diameter of the tie rod D1 = 32 mm; (5) Based on the minimum applied force F2 and the material mechanical property parameters, calculate the minimum tie rod neck diameter D2 = 20 mm; (6) Due to the limitations of the aerodynamic flow channel surface and strength, the diameter of the tie rod neck D3 is determined to be 30mm; (7) Determine the range of the neck diameter of the tie rod, D3>>D2, D2≤D≤min(D1, D3); (8) Within the range of D values, initially determine the value of D (D=30mm) for subsequent iterations; (9) Based on the selected D value and the current structural scheme, carry out the structural design of the central tie rod and calculate the axial stiffness of the tie rod structure E2=517.4KN / mm; (10) Calculate the axial stiffness of the rotor disk section E1 = 1310 KN / mm; (11) E1≥(2~3)E2, proceed with the next calculation.

[0042] (12) Calculate the mode shape of the tie rod below the target speed of the gas turbine (24000 rpm); (13) Calculate the mode shape of the rotor below the target speed of the gas turbine (24000 rpm); (14) If the mode shape and speed of the tie rod are within a certain margin (the margin ratio range is 5%-15%), the rotor will become more sensitive to the unbalance. The D (28mm) value is readjusted and auxiliary support is added after the second centrifugation to reduce the rotor’s sensitivity to the unbalance.

[0043] This invention significantly improves the preload retention capability of the central tie rod under abnormal working conditions through a systematic design process, effectively preventing end teeth from disengaging or slipping, and enhancing the robustness and operational safety of the rotor system.

[0044] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A method for designing a highly robust tie rod for a gas turbine, characterized in that: It includes the following operation processes: S1: Calculate the maximum force F1 that can be applied to the tie rod, that is, load the aerodynamic force, centrifugal load and torque in the two-dimensional state, and calculate the stresses of each stage of the rotor by loading different axial forces F4i; Until the part stress exceeds the material limit, record the axial force F4 in this state; The maximum applied force F1 = the target axial force F4 / the strength reserve coefficient; The yield strength reserve coefficient > 1.25, and the ultimate strength reserve coefficient is greater than 1.5; S2: Calculate the minimum force F2 that can be applied to the tie rod. Load the aerodynamic force, centrifugal load and torque in the sector rotor section state, and try to load different axial forces F5i until the working surface of the end teeth is not completely disengaged and no slip movement occurs, and record the axial force F5 in this state; The minimum applied force F2 = the target axial force F5 / the tightness coefficient; The tightness coefficient = 1.15 - 1.25; S3: Determine the structural scheme and the structure to be arranged at the outer diameter of the central tie rod at the compressor end; S4: Calculate the maximum tie rod neck diameter D1 according to the maximum applied force F1 and the material mechanical property parameters; S5: Calculate the minimum tie rod neck diameter D2 according to the minimum applied force F2 and the material mechanical property parameters; S6: Determine the tie rod neck diameter D3 according to the limitation of the radial space of the central tie rod by the structural scheme; S7: Determine the range of the tie rod neck diameter. When D3 >> D2, D2 ≤ D ≤ min(D1, D3); S8: When D3 < D2 or the value is close to D2, coordinate the structural scheme to obtain the value of D3 until D3 >> D2; S9: In the range of D values, initially determine the value of D for subsequent iteration; S10: According to the selected value of D and the current structural scheme, carry out the structural design of the central tie rod and calculate the axial stiffness E2 of the tie rod structure; S11: Calculate the axial stiffness E1 of the rotor disk part; S12: When E1 ≥ (2 - 3)E2, carry out the next calculation. Otherwise, adjust the value of the tie rod D and recalculate the axial stiffness E2 of the adjusted tie rod until the requirements are met; S13: Calculate the vibration mode of the tie rod below the target speed of the gas turbine; S14: Calculate the vibration mode of the rotor below the target speed of the gas turbine; S15: When the vibration mode of the tie rod and the corresponding speed avoid the vibration mode of the rotor and the corresponding speed within the margin ratio range and do not increase the excitation force, determine the final tie rod; S16: When the vibration mode and speed of the tie rod will increase the sensitivity of the rotor to vibration within the margin ratio range, readjust the value of D or take other measures.

2. The high robustness tie rod design method for a gas turbine as described in claim 1, characterized in that: In S1, the stress concentration coefficient is used to replace the local fine features.

3. The high robustness tie rod design method for a gas turbine as described in claim 2, characterized in that: The local fine features are holes or keyways.

4. The high robustness tie rod design method for a gas turbine as described in claim 1, characterized in that: In S3, the structure is a centrifugal impeller, a front shaft disk or a journal.

5. The high robustness tie rod design method for a gas turbine as described in claim 1, characterized in that: The maximum applied force F1 is 1150 KN.

6. The high robustness tie rod design method for a gas turbine as described in claim 1, characterized in that: The minimum applied force F2 is 859 KN.

7. The high robustness tie rod design method for a gas turbine as described in claim 1, characterized in that: The maximum tie rod neck diameter D1 is 32 mm.

8. The high robustness tie rod design method for a gas turbine as described in claim 1, characterized in that: The minimum tie rod neck diameter D1 is 20 mm.

9. The high robustness tie rod design method for a gas turbine as described in claim 1, characterized in that: The tie rod neck diameter D3 is 30 mm.

10. The high robustness tie rod design method for a gas turbine as described in claim 1, characterized in that: The axial stiffness E1 is 1310 KN / mm.

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