Simplified calculation method for tightening torque of connecting screw of gas turbine

Abstract

The invention relates to a gas turbine connecting screw tightening torque simplified calculation method which comprises the following steps: determining the function of a gas turbine connecting part, and calculating a functional target clamping force; calculating the allowable clamping force of the screw based on the strength of the screw, wherein the range of the safety coefficient K is as follows; comparing the allowable clamping force of the screw with the functional target clamping force to carry out strength check so as to determine the final clamping force; and calculating the equivalent tightening torque. Complex torque calculation is decomposed into four steps with clear targets, and the recommended tightening torque can be calculated only by selecting formulas and parameters according to the steps.

Description

Technical Field

[0001] This application relates to the fields of gas turbine manufacturing, assembly and maintenance technology, and in particular to a simplified calculation method for the tightening torque of gas turbine connecting screws. Background Technology

[0002] For critical components such as the gas turbine's load-bearing frame, pipeline flanges, and bearing housings, the accuracy of the tightening torque is paramount. Insufficient torque may lead to loose connections and gas leaks; excessive torque may cause screws to elongate, threads to strip, or even break.

[0003] Current methods have significant shortcomings: the lookup table method is coarse, relying on standard torque tables without considering the actual stress state of the screw under specific operating conditions such as high temperature and vibration in a gas turbine, resulting in poor accuracy and difficulty in ensuring safety. The classic formula method is complex. In the formula, the value of the torque coefficient K depends on experience and fluctuates greatly. The calculation of the target preload F is itself a complex problem, requiring high skill from engineers and involving a tedious process. While finite element analysis and other methods rely on specialized software and are accurate, they involve complex modeling and time-consuming calculations, making them unsuitable for rapid on-site decision-making and batch applications.

[0004] Therefore, we propose a simplified calculation method for the tightening torque of gas turbine connecting screws. Summary of the Invention

[0005] To address the shortcomings of existing production technologies, this applicant provides a simplified calculation method for the tightening torque of gas turbine connecting screws. This method breaks down the complex torque calculation into four clearly defined steps. Engineers only need to select the formula and parameters according to the steps to calculate the recommended tightening torque. No advanced theoretical foundation is required; the logic is clear and easy to implement.

[0006] The technical solution adopted in this application is as follows: A simplified calculation method for the tightening torque of gas turbine connecting bolts includes the following steps: S1, determine the function of the gas turbine connection parts and calculate the functional target clamping force. ; S2, Calculate the allowable clamping force of the screw based on the screw strength. , ,in, This represents the yield strength of the screw material at the operating temperature. Let be the stress cross-sectional area of ​​the screw; For the safety factor, the range of K is: ; S3, Compare the allowable clamping force of the screw. Clamping force with functional target Perform a strength check to determine the final clamping force. ; S4, calculate the equivalent tightening torque T using a simplified formula. Where d is the nominal diameter of the screw.

[0007] Its further features are: In step S1, when the function of the connection part is gas sealing, the functional target clamping force is... The determining principle is ; Where P is the maximum working pressure. For the sealing area, denoted as the friction coefficient of the mating surface.

[0008] In step S1, when the function of the connection part is structural load-bearing, the functional target clamping force is... The determining principle is ; Where M is the maximum working bending moment or shear force, n is the number of screws, and r is the screw distribution radius. denoted as the friction coefficient of the mating surface.

[0009] In step S1, when the function of the connection part is to prevent loosening and vibration, the functional target clamping force is... The determining principle is ; in, The expected maximum axial alternating load. denoted as the friction coefficient of the mating surface.

[0010] In step S3, when Then take .

[0011] In step S3, when Upgrade the screw specifications and materials, and recalculate the allowable clamping force of the screw through step S2. .

[0012] In step S2, the safety factor K is set to 0.7 for parts that bear alternating loads, have slight stress concentrations, or are of extremely high importance.

[0013] In step S2, the safety factor K for the parts that bear static loads and are in stable working conditions is set to 0.8.

[0014] The beneficial effects of this application are as follows: This application features a compact and reasonable structure that is easy to operate. By decomposing the complex torque calculation into four clearly defined steps, engineers only need to select the formulas and parameters according to the steps. No advanced theoretical foundation is required. The logic is clear and easy to implement. Through the principle of strength matching, it avoids screw failure caused by over-tightening and can achieve lightweight connection structure, and achieve a balance between safety and economy by making full use of screw strength.

[0015] In addition, this application also has the following advantages: (1) The high temperature and vibration characteristics of the gas turbine are fully considered. By selecting high temperature yield strength and targeted functional target force, the calculation results are more in line with the actual working conditions and the working conditions are highly targeted.

[0016] (2) Compared with finite element analysis and complex theoretical derivation, this application has a very fast calculation speed, which is particularly suitable for multi-scheme comparison in the design stage and rapid decision-making in on-site maintenance, greatly improving efficiency.

[0017] (3) The whole method is logically rigorous and forms a closed loop. It is simple and easy to implement, and ensures the reliability and security of the calculation results.

[0018] (4) By standardizing and streamlining complex engineering problems through the security system K, a unity of simplicity and reliability is achieved, which has strong practicality and patentability. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the process of this application. Detailed Implementation

[0020] The specific embodiments of this application are described below with reference to the accompanying drawings.

[0021] A simplified calculation method for the tightening torque of gas turbine connecting bolts includes the following steps: S1, determine the function of the gas turbine connection parts and calculate the functional target clamping force. ; When the connection part functions as a gas seal, the functional target clamping force The determining principle is Where P is the maximum working pressure. For the sealing area, denoted as the friction coefficient of the mating surface.

[0022] When the function of the connection is structural load-bearing, the functional target clamping force is... The determining principle is Where M is the maximum working bending moment or shear force, n is the number of screws, and r is the screw distribution radius. denoted as the friction coefficient of the mating surface.

[0023] When the function of the connection part is to prevent loosening and resist vibration, the functional target clamping force is... The determining principle is ;in, The expected maximum axial alternating load. denoted as the friction coefficient of the mating surface.

[0024] S2, Calculate the allowable clamping force of the screw based on the screw strength. , ,in, This represents the yield strength of the screw material at the operating temperature. Let be the stress cross-sectional area of ​​the screw; For the safety factor, the range of K is: ; S3, Compare the allowable clamping force of the screw. Clamping force with functional target To perform a strength check, the final clamping force will be determined. ; when Then take .

[0025] when Upgrade the screw specifications and materials, and recalculate the allowable clamping force of the screw through step S2. .

[0026] S4, calculate the equivalent tightening torque T using a simplified formula. Where d is the nominal diameter of the screw.

[0027] In step S2, the safety factor K is within its range The selection logic is as follows: for parts that bear alternating loads, have slight stress concentrations, or are of extremely high importance, the safety factor K is set to 0.7; for parts that bear static loads and have stable operating conditions, the safety factor K is set to 0.8.

[0028] In step S4, the selection logic for 0.2 is as follows: 0.2 is an empirical average value for common steel screws coated with standard lubricant (such as molybdenum disulfide). It takes into account the influence of thread friction and bearing surface friction, and achieves great simplification while ensuring accuracy.

[0029] Step S1 begins by identifying the specific functions of the screw connection (sealing, load-bearing, and anti-loosening) to ensure that the calculation objective is clear; In step S3, by comparison and Strength verification is performed, which is part of the design feedback process: if the strength is sufficient, the process continues. If the strength is insufficient, feedback is sent to the design team, requesting the screws to be upgraded until the requirements are met, thus fundamentally ensuring the safety of the connection.

[0030] In step S4, a simplified empirical formula is used. Calculate the tightening torque.

[0031] The complex torque calculation is broken down into four clearly defined steps. Engineers only need to select formulas and parameters according to the steps. No advanced theoretical foundation is required. The logic is clear and easy to implement. By applying the strength matching principle in step S2, we can avoid screw failure caused by over-tightening, and by making full use of the screw strength, we can achieve a balance between lightweight connection structure, safety and economy.

[0032] The calculation results are more closely aligned with actual working conditions by taking into full account the characteristics of gas turbines such as high temperature and vibration, and by selecting high temperature yield strength and targeted functional target forces.

[0033] Compared to finite element analysis and complex theoretical derivations, this application has an extremely fast calculation speed, making it particularly suitable for comparing multiple schemes during the design phase and for rapid decision-making in on-site maintenance, thus greatly improving efficiency.

[0034] The entire method is logically rigorous, forming a closed loop. It is simple and easy to implement, while ensuring the reliability and security of the calculation results.

[0035] By standardizing and streamlining complex engineering problems through the security system K, a balance between simplicity and accuracy is achieved, resulting in strong practicality and patentability.

[0036] Example 1 Gas turbine outlet flange M20*1.5 (8.8 grade) screw connection, working temperature 200℃, sealing gas pressure 2MPa, sealing surface inner diameter 180mm, outer diameter 220mm.

[0037] A simplified calculation method for the tightening torque of gas turbine connecting bolts includes the following steps: S1, the function of the gas turbine connection is gas sealing, and the calculation function is to determine the clamping force. , Where P is the maximum working pressure. For the sealing area, The coefficient of friction of the mating surfaces; ; Pick ; but, ; S2, Calculate the allowable clamping force of the screw based on the screw strength. , ,in, This represents the yield strength of the screw material at the operating temperature. Let be the stress cross-sectional area of ​​the screw; For safety factor; The safety factor K is set to 0.7; 8.8 grade screws were found to be suitable for use at 200℃. M20 screws ; but, ; S3, Compare the allowable clamping force of the screw. Clamping force with functional target To perform a strength check, the final clamping force will be determined. ; The original M20 8.8 grade screws do not meet the requirements and need to be upgraded; Assuming an upgrade to M24 10.9 grade screws, M24 screws Grade 10.9 screws at 200℃ Recalculate ; at this time ,Pick ; S4, calculate the equivalent tightening torque T using a simplified formula. Where d is the nominal diameter of the screw; .

[0038] That is, the recommended tightening torque for the M24 10.9 grade screw at this location is 804. .

[0039] The above description is an explanation of this application and not a limitation thereof. The scope of this application is defined by the claims. Within the scope of protection of this application, any form of modification may be made.

Claims

1. A method for simplified calculation of a tightening torque of a gas turbine connecting screw, characterized in that, Comprising the following steps: S1, determine gas turbine connection site function and calculate functional target clamping force ; S2, calculating the screw allowable clamping force based on the screw strength , wherein, is the yield strength of the screw material at the working temperature; is the stress cross-sectional area of the screw; is the safety factor, K ranges from ; S3, compare with screw allowable clamping force with functional target clamping force strength check to determine the final clamping force ; S4, calculate the equivalent tightening torque T, using the simplified formula where d is the nominal diameter of the screw.

2. A simplified calculation method of a gas turbine connection screw tightening torque according to claim 1, characterized in that: In step S1, when the connection site functions as a gas seal, the functional target clamping force is determined according to the principle ; where P is the maximum working pressure, is the sealing area, is the coefficient of friction of the joint surface.

3. A simplified method of calculating the tightening torque of a gas turbine connecting screw as claimed in claim 1, characterized in that: In step S1, when the connection site functions as a structural load bearing, the functional target clamping force is determined according to the principle ; where M is the maximum working bending moment or shear force, n is the number of screws, and r is the radius of distribution of the screws, is the coefficient of friction of the joint surface.

4. A simplified method of calculating the tightening torque of a gas turbine connecting screw as claimed in claim 1, characterized in that: In step S1, when the connection site functions as an anti-loosening and anti-vibration, the functional target clamping force is determined according to the principle of ; wherein, is the expected maximum axial alternating load, is the coefficient of friction of the joint surface.

5. A simplified method of calculating the tightening torque of a gas turbine connecting screw as claimed in claim 1, characterized in that: In step S3, when then take .

6. A simplified method of calculating the tightening torque of a gas turbine connecting screw as claimed in claim 1, characterized in that: In step S3, when , the screw gauge, the material is upgraded, and the screw allowable clamping force is recalculated through step S2 .

7. A simplified method of calculating the tightening torque of a gas turbine connecting screw as claimed in claim 1, characterized in that: In step S2, for the parts that bear alternating load, have slight stress concentration or are of great importance, the safety factor K is biased to 0.

7.

8. A simplified method of calculating the tightening torque of a gas turbine connecting screw as claimed in claim 1, characterized in that: In step S2, for the parts that bear static load and are stable in working condition, the safety factor K is biased to 0.8.

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