Method for estimating fatigue life of transmission mechanism of axial-flow unit under AGC (Automatic Gain Control) operation

Abstract

The invention relates to the technical field of impulse turbines, in particular to an axial-flow unit transmission mechanism fatigue life estimation method under AGC operation, which comprises the following steps of: determining a part of which the fatigue life needs to be calculated in a transmission mechanism, establishing a corresponding finite element model, and setting reasonable boundary conditions and load conditions; calculating to obtain tension and compression stress of the most dangerous position of each component under different oil pressures, making a stress and oil pressure corresponding curve, obtaining accurate operation times and oil pressure of the transmission mechanism through a rain flow method according to actual operation data of a power station, obtaining stress change amplitude of the transmission mechanism through the stress and oil pressure curve, and obtaining a fatigue life curve of the transmission mechanism according to a fatigue life curve in an ASME standard. And obtaining the fatigue life of the corresponding position. Through the method, the fatigue life of the transmission mechanism can be estimated more accurately, and the problem that a traditional method only considers starting and stopping and neglects the influence of frequent operation on the structural life under AGC operation is solved.

Description

Technical Field

[0001] The invention relates to the field of water turbines, and in particular to a method for estimating fatigue life of a transmission mechanism of an axial flow unit under AGC operation. Background Art

[0002] The transmission mechanism of the turbine unit in a hydropower station is the guarantee for the unit to maintain normal operation and regulation. According to the requirements of the power grid, large and medium-sized axial-flow propeller units in my country all adopt the AGC operation mode to play the role of peak load and frequency regulation. However, under the AGC operation mode, the operation of the unit becomes abnormally frequent. The traditional transmission mechanism fatigue life prediction method only calculates the fatigue under the start-up and shutdown conditions, and the consideration of the situation is too single. Therefore, it is not suitable for the fatigue calculation of the transmission mechanism under the AGC operation mode, which seriously endangers the safe operation of the unit. Therefore, it is urgent to invent a method for predicting the fatigue life of the transmission mechanism of the axial-flow unit under AGC operation. Summary of the invention

[0003] In order to solve the above technical problems, the present invention proposes a method for estimating the fatigue life of the transmission mechanism of an axial-flow unit under AGC operation, which can more accurately calculate the fatigue life of the transmission mechanism according to the actual operation conditions of the power station, and solves the problem that the transmission mechanism of the axial-flow unit only considered start-up and shutdown in the past, while ignoring the impact of frequent unit operations under AGC operation on the structural life.

[0004] The present invention is achieved by adopting the following technical solutions:

[0005] A method for estimating fatigue life of a transmission mechanism of an axial flow unit under AGC operation comprises the following steps:

[0006] Step S1, determining the components in the transmission mechanism whose fatigue life needs to be calculated;

[0007] Step S2, establishing a finite element model of each component, setting corresponding reasonable boundary conditions and load conditions under different oil pressure conditions, and calculating the stress of each component of the transmission mechanism by a finite element calculation method;

[0008] Step S3, extracting the maximum tensile stress and the maximum compressive stress of the most dangerous position of each component of the transmission mechanism in step S2 under different oil pressures in the opening and closing working conditions;

[0009] Step S4, according to the stress value obtained in step S3, making a corresponding curve between stress and oil pressure at the most dangerous position of each component of the transmission mechanism under two working conditions: opening and closing;

[0010] Step S5, according to the oil pressure change data during the actual operation of the power station, the accurate number of transmission mechanism operations and the corresponding oil pressure are obtained by the rain flow method, and then the corresponding curve between the stress and the oil pressure obtained in step S4 is used to obtain the stress at the most dangerous position of each component corresponding to each operation of the transmission mechanism;

[0011] Step S6: According to the calculation result obtained in step S5, the stress change amplitude of the most dangerous position of each component of the transmission mechanism is obtained, and the fatigue life of the corresponding position is obtained by using the fatigue life curve in the ASME standard.

[0012] As a preferred implementation, in S1, the components for which fatigue life needs to be estimated are determined based on the composition of the transmission mechanism, specifically including the piston rod, the operating frame, the ear handle, the connecting rod, the swing arm, and the connecting rod pin.

[0013] As a preferred implementation, in S2, according to the components determined in S1, their respective structural characteristics and connection relationship with other components are analyzed, an accurate finite element model is established, reasonable boundary conditions are set, contact is set in the connection between the transmission mechanism components, a reasonable friction coefficient is given, and the influence of the contact gap is considered; the transmission mechanism is realized by oil pressure regulation, and the load condition sets multiple oil pressures, which are distributed in an arithmetic progression, and the respective results are calculated respectively for subsequent curve production;

[0014] As a preferred implementation, in S3, based on the structural characteristics of each component in the transmission mechanism and the calculation results in S2, the position where fatigue failure of each component is most likely to occur is determined and set as a dangerous position, and then the maximum tensile stress and maximum compressive stress corresponding to the position under the opening and closing conditions are respectively extracted, and the corresponding data points are extracted according to the oil pressure number set in S2;

[0015] As a preferred implementation, in S4, based on the data extracted in S3, the corresponding curves of oil pressure and stress at multiple dangerous positions of different components are produced, and for the same dangerous position, the curve should be approximately a straight line;

[0016] As a preferred implementation, in S5, according to the oil pressure change data during the actual operation of the power station, a corresponding program is written, and the number of effective transmission mechanism operations and the corresponding oil pressure that affect the fatigue life are obtained by the rain flow method. Then, by using the corresponding curve between the stress and the oil pressure obtained in S4, the stress at the most dangerous position of each component corresponding to each operation of the transmission mechanism can be obtained;

[0017] As a preferred implementation, in S6, based on the data obtained in S5, the stress amplitude change of the set dangerous position at each adjustment is obtained, and then the fatigue life curve in the ASME standard is used to obtain the allowable number of cycles at the position, and then the fatigue life of the component is obtained by the cumulative damage theory.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. Through the present invention, according to the structural characteristics and actual operation of the transmission mechanism, the most suitable finite element model, reasonable boundary conditions and loading methods of each component are established.

[0020] 2. Through the present invention, a rain flow method program is compiled to innovatively convert the oil pressure data of the actual operation of the power station into oil pressure data that can be used to calculate the fatigue life of each component of the transmission mechanism.

[0021] 3. Through the present invention, an innovative curve corresponding to the oil pressure and working stress of different components is obtained, and the stress amplitude of the components is extracted in a programmed manner, thereby calculating the fatigue life.

[0022] 4. Through the present invention, when calculating the fatigue life of each component of the transmission mechanism, the influence of each operation of the transmission mechanism under AGC operation on the fatigue life is fully and accurately considered, and the calculated fatigue life is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart of the fatigue life estimation method for the transmission mechanism of the axial flow unit under AGC operation;

[0024] Figure 2 It is a cross-sectional view of the components of the transmission mechanism of the axial flow unit;

[0025] Figure 3 It is the ASME fatigue curve diagram;

[0026] Figure 4 It is a schematic diagram of the corresponding curve between stress and oil pressure;

[0027] Component identification in the figure: 1. piston rod; 2. operating frame; 3. ear handle; 4. connecting rod; 5. connecting rod pin; 6. rotating arm; 7. blade. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The fatigue life prediction method of the transmission mechanism of the axial flow unit under AGC operation is as follows: Figure 1 As shown, the first specific implementation mode includes the following steps:

[0030] Step S1, determining the components in the transmission mechanism whose fatigue life needs to be calculated, which may specifically include the piston rod 1, the operating frame 2, the ear handle 3, the connecting rod 4, the connecting rod pin 5, the rotating arm 6 and other components;

[0031] Step S2, establishing a finite element model of each component, setting corresponding reasonable boundary conditions and load conditions under different oil pressure conditions, and calculating the stress of each component of the transmission mechanism by a finite element calculation method;

[0032] Step S3, extracting the maximum tensile stress and the maximum compressive stress of the most dangerous position of each component of the transmission mechanism in step S2 under different oil pressures in the opening and closing working conditions;

[0033] Step S4, according to the stress value obtained in step S3, making a corresponding curve between stress and oil pressure at the most dangerous position of each component of the transmission mechanism under two working conditions: opening and closing;

[0034] Step S5, according to the oil pressure change data during the actual operation of the power station, the accurate number of transmission mechanism operations and the corresponding oil pressure are obtained by the rain flow method, and then the corresponding curve between the stress and the oil pressure obtained in step S4 is used to obtain the stress at the most dangerous position of each component corresponding to each operation of the transmission mechanism;

[0035] Step S6: According to the calculation result obtained in step S5, the stress change amplitude of the most dangerous position of each component of the transmission mechanism is obtained, and the fatigue life of the corresponding position is obtained using the fatigue life curve in the ASME standard.

[0036] In this embodiment, the fatigue life estimation method of the axial flow unit transmission mechanism under AGC operation can more accurately calculate the fatigue life of the transmission mechanism according to the actual operation conditions of the power station, solving the problem that the axial flow unit transmission mechanism only considered start and shutdown in the past, while ignoring the impact of frequent unit operations under AGC operation on the structural life.

[0037] Specific implementation method 2: Figure 1 As shown, this embodiment further limits S1 belonging to the specific embodiment 1. In this embodiment, in S1, according to the composition of the transmission mechanism, specifically including the piston rod, the operating frame, the ear handle, the connecting rod, the swing arm, and the connecting rod pin, the components whose fatigue life needs to be estimated are determined.

[0038] In this implementation, the components for which fatigue life estimation is required are determined based on the functional differences of the components of the transmission mechanism, which provides a basic target for subsequent fatigue life estimation.

[0039] Specific implementation method three: Figure 1 As shown, this embodiment further limits S2 belonging to the specific embodiment one. In this embodiment, in S2, according to the components determined by S1, their respective structural characteristics and connection relationships with other components are analyzed, an accurate finite element model is established, and reasonable boundary conditions are set. Since it is a transmission mechanism, contact must be set in the connection between the components, a reasonable friction coefficient is given, and the influence of the contact gap is considered; since the transmission mechanism is realized by oil pressure regulation, multiple oil pressures are set as load conditions, distributed in an arithmetic progression, and their respective results are calculated separately for subsequent curve production.

[0040] In this embodiment, according to the structural characteristics of different components, an accurate finite element model is established, reasonable boundary conditions are set, and multiple oil pressure load conditions are loaded to provide a model basis for subsequent fatigue life estimation.

[0041] Specific implementation method four: Figure 1 As shown, this embodiment further limits S3 belonging to the specific embodiment one. In this embodiment, in S3, based on the structural characteristics of each component in the transmission mechanism and the calculation results in S2, the position where fatigue failure of each component is most likely to occur is determined and set as a dangerous position. Then, the maximum tensile stress and maximum compressive stress corresponding to the position under the opening and closing conditions are extracted respectively, and the corresponding data points are extracted according to the oil pressure number set in S2.

[0042] In this embodiment, according to the structural characteristics of different components and their working conditions, the dangerous position prone to fatigue failure is determined, and the tensile and compressive stresses of the position under different working conditions are extracted for the subsequent preparation of the corresponding curve of oil pressure and stress.

[0043] Specific implementation method five: Figure 1 As shown, this embodiment further limits S4 belonging to the specific embodiment one. In this embodiment, in S4, based on the data extracted by S3, corresponding curves of oil pressure and stress at multiple dangerous positions of different components are produced. For the same dangerous position, the curve should be approximately a straight line.

[0044] In this implementation, the tensile and compressive stresses at various dangerous locations are extracted, and a corresponding curve is established between the oil pressure and the stress for subsequent fatigue life estimation, which greatly reduces the workload of conventional methods.

[0045] Specific implementation method six: Figure 1As shown, this embodiment further limits S5 belonging to the specific embodiment one. In this embodiment, in S5, a corresponding program is written according to the oil pressure change data during the actual operation of the power station, and the effective number of transmission mechanism operations and the corresponding oil pressure that affect the fatigue life are obtained by the rain flow method. Then, the corresponding curve between the stress and the oil pressure obtained in S4 is used to obtain the stress at the most dangerous position of each component corresponding to each operation of the transmission mechanism.

[0046] In this implementation, based on the actual operation data of the power plant, a program is written to convert it into data that can be used to calculate fatigue life. This method has strong practicality and scalability.

[0047] Specific implementation method seven: Figure 1 As shown, this implementation mode further limits S6 belonging to the specific implementation mode 1. In this implementation mode, in S6, the stress amplitude change of the set dangerous position at each adjustment is obtained according to the data obtained in S5, and then the fatigue life curve in the ASME standard is used to obtain the allowable number of cycles of the position, and then the fatigue life of the component is obtained by the cumulative damage theory.

[0048] In this implementation, based on the industry standard fatigue life curve, the fatigue life of the corresponding components can be estimated using the obtained stress amplitude change.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, it should be clear to those skilled in the art that the technical solutions described in the above embodiments may be modified, or some or all of the technical features therein may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for estimating the fatigue life of the transmission mechanism of an axial flow unit under AGC operation, characterized in that The following steps are involved: S1. Determine the components in the transmission mechanism whose fatigue life needs to be calculated; S2. Establish finite element models of various components, set corresponding reasonable boundary conditions and load conditions under different oil pressure conditions, and calculate the stress of various components of the transmission mechanism by finite element calculation method; S3, extracting the maximum tensile stress and maximum compressive stress at the most dangerous position of each component of the transmission mechanism in S2 under different oil pressures in the opening and closing conditions; S4. Based on the stress values ​​obtained in S3, a corresponding curve between stress and oil pressure at the most dangerous position of each component of the transmission mechanism under the two working conditions of opening and closing is produced; S5. According to the oil pressure change data during the actual operation of the power station, the accurate number of transmission mechanism operations and the corresponding oil pressure are obtained by the rain flow method. Then, the corresponding curve between the stress and the oil pressure obtained in S4 is used to obtain the stress at the most dangerous position of each component corresponding to each operation of the transmission mechanism. S6. According to the calculation results obtained in S5, the stress change amplitude of the most dangerous position of each component of the transmission mechanism is obtained, and the fatigue life of the corresponding position is obtained using the fatigue life curve in the ASME standard.

2. The method for estimating fatigue life of a transmission mechanism of an axial flow unit under AGC operation according to claim 1, characterized in that: In S1, the components for which fatigue life needs to be estimated are determined based on the composition of the transmission mechanism, which specifically includes a piston rod, an operating frame, a lug handle, a connecting rod, a rotating arm, and a connecting rod pin.

3. The method for predicting fatigue life of a transmission mechanism of an axial flow unit under AGC operation according to claim 1, characterized in that: In S2, according to the components determined in S1, their respective structural characteristics and connection relationship with other components are analyzed, an accurate finite element model is established, reasonable boundary conditions are set, contact is set in the connection between the transmission mechanism components, a reasonable friction coefficient is given, and the influence of the contact gap is considered; The transmission mechanism is realized through oil pressure regulation. Multiple oil pressures are set as load conditions and distributed in an arithmetic progression. The respective results are calculated and used for subsequent curve production.

4. The method for estimating fatigue life of a transmission mechanism of an axial flow unit under AGC operation according to claim 1, characterized in that: In S3, based on the structural characteristics of each component in the transmission mechanism and the calculation results in S2, the position where fatigue failure of each component is most likely to occur is determined and set as a dangerous position. Then, the maximum tensile stress and maximum compressive stress corresponding to the position under the opening and closing conditions are extracted respectively, and the corresponding data points are extracted according to the oil pressure number set in S2.

5. The method for estimating fatigue life of a transmission mechanism of an axial flow unit under AGC operation according to claim 1, characterized in that: In S4, based on the data extracted in S3, the corresponding curves of oil pressure and stress at multiple dangerous positions of different components are produced. For the same dangerous position, the curve should be approximately a straight line.

6. The method for predicting fatigue life of a transmission mechanism of an axial flow unit under AGC operation according to claim 1, characterized in that: In S5, a corresponding program is written according to the oil pressure change data during the actual operation of the power station, and the effective transmission mechanism operation times and the corresponding oil pressure that affect the fatigue life are obtained by the rain flow method. Then, the corresponding curve between the stress and the oil pressure obtained in S4 is used to obtain the stress at the most dangerous position of each component corresponding to each operation of the transmission mechanism.

7. The method for predicting fatigue life of a transmission mechanism of an axial flow unit under AGC operation according to claim 1, characterized in that: In S6, based on the data obtained in S5, the stress amplitude change of the set dangerous position during each adjustment is obtained, and then the fatigue life curve in the ASME standard is used to obtain the allowable number of cycles at the position, and then the fatigue life of the component is obtained by the cumulative damage theory.

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