A system and method for evaluating vibration characteristics of a guide bearing bracket of a vertical hydro-generator

Abstract

The present invention discloses a vibration characteristic evaluation system and method for a guide bearing bracket of a vertical hydro-turbine generator. First, a three-dimensional geometric model of the guide bearing bracket is established using three-dimensional modeling software. Based on this model, finite element analysis software is introduced to model the test object, divide the grid, assign boundary conditions, debug, and perform calculations. A modal analysis instrument is used to measure the static natural frequency of the guide bearing bracket, and through field testing, the actual static measured vibration mode, stiffness coefficient, and damping ratio of the actual machine are obtained. Based on the static measured data, the actual machine model parameters are optimized, and the characteristics and vibration patterns of the guide bearing bracket under various parameters are calculated and analyzed. The modal frequencies and vibration modes of each order are extracted to obtain the vibration characteristics of the test object. Finally, the vibration characteristics of the test object are evaluated based on the monitored vibration data. The present invention can detect defects in advance, and the testing content is comprehensive, the accuracy is high, and the evaluation is accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic machinery fault diagnosis, and in particular to a vibration characteristic evaluation system and method for a guide bearing bracket of a vertical hydraulic generator. Background Art

[0002] Hydroelectric generator sets are large rotating mechanical equipment characterized by low speeds and large moments of inertia. The weight of the entire unit and the axial water thrust are transmitted to the foundation through the thrust bearing bracket. Simultaneously, the radial centrifugal force generated by rotation is transmitted to the guide bearing frame through the bearing shell, subjecting the frame to periodic forces and causing varying degrees of vibration and fatigue damage. Excessive guide bearing vibration can easily cause material fatigue damage that is difficult to detect, and in severe cases, can affect the safe and stable operation of the hydroelectric generator set. Therefore, to ensure that the machine does not resonate within the operating speed range and to minimize serious damage to the rotor caused by resonance after certain excitations, it is necessary to fully understand the vibration characteristics of the guide bearing bracket of the hydroelectric generator.

[0003] Currently, understanding the vibration characteristics of the guide bearing bracket of a vertical hydro-turbine generator is primarily achieved through real-time vibration monitoring. This involves placing several vibration measurement points on the bearing bracket, remotely monitoring the data, and analyzing it through axis trajectory, time-domain curves, and spectrograms. This method has several drawbacks: First, due to the limited number of measurement points, only X- or Y-direction data can be monitored, lacking a comprehensive understanding of the vibration characteristics; second, this method is a post-analysis measure. If resonance is detected in the guide bearing bracket during operation, the unit must be shut down for processing, failing to provide early detection and prevention. Third, it fails to provide in-depth analysis of the generator bracket's natural vibration mechanism.

[0004] Therefore, it is necessary to find a comprehensive and reliable vertical hydro-generator guide bearing bracket vibration characteristic evaluation system and method. Summary of the Invention

[0005] In order to overcome the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a vibration characteristic evaluation system and method for a vertical hydro-generator guide bearing bracket, which can detect defects in advance, has comprehensive test content, high precision and accurate evaluation.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A vibration characteristic evaluation system for a guide bearing bracket of a vertical hydro-turbine generator includes three-dimensional modeling software, finite element analysis software, a modal test and analysis unit, and a vibration monitoring unit. The three-dimensional modeling software is responsible for establishing a three-dimensional geometric model of the guide bearing bracket; based on this model, the finite element analysis software is imported to model a test object 1, divide the mesh, set boundary conditions, debug, and perform calculations.

[0008] The modal test and analysis unit includes a test piece 1, a test piece support arm 2, an acceleration sensor 3, an excitation hammer 4, a CRAS vibration and dynamic signal acquisition and analysis instrument 5, a computer including modal analysis software 6, and a data transmission line 7;

[0009] The test piece 1 is placed horizontally and naturally, and a test piece support arm 2 is provided on the test piece 1, and acceleration sensors 3 are evenly arranged on the test piece support arm 2. The acceleration sensor 3 is connected to the input end of the modal analyzer 5 through a data transmission line 7, and the output end of the modal analyzer 5 is connected to the input end of the computer 6. The test piece 1 is struck by a force hammer 4, and a force sensor is provided on the force hammer 4. The force sensor is connected to the input end of the modal analyzer 5 through a data line 7.

[0010] The vibration monitoring unit is used for dynamic vibration monitoring and recording of the guide bearing bracket. The vibration monitoring unit includes: a test probe, a data cable, a computer, monitoring software and a storage device. The test probe is arranged on the measuring point of the guide bearing bracket. The electrical signal of the vibration condition of the measuring point measured by the test probe is transmitted to the computer through the data cable, and is stored in the storage device after being analyzed by the monitoring software.

[0011] A method for evaluating vibration characteristics of a guide bearing bracket of a vertical hydro-generator comprises the following steps:

[0012] 1) Collect data of each unit,

[0013] 2) Construct a real machine model of the guide bearing bracket system and conduct modal analysis and prediction.

[0014] 3) The test obtains the actual measured vibration mode, stiffness coefficient, and damping ratio of the real machine,

[0015] 4) Based on the measured data, optimize the real machine model and extract the modal frequencies and vibration shapes of each order.

[0016] 5) Monitor and record the vibration data of the guide bearing bracket under different conditions,

[0017] 6) Combined with the monitored guide bearing bracket vibration data, a comprehensive evaluation of the vibration characteristics of the turbine generator guide bearing bracket is conducted.

[0018] The specific operation process of step 1) is as follows:

[0019] Collect information on the guide bearing bracket's geometric dimensions, connection method, material, generator speed, and electrical parameters.

[0020] The specific operation process of step 2) is as follows:

[0021] 21) Use 3D modeling software to build a 3D geometric model of the test piece based on the shape of the guide bearing bracket;

[0022] 22) Import finite element analysis software into the 3D model;

[0023] 23) Modeling is done according to the real machine parameters, and the material density and Young's modulus physical parameters of each part are given;

[0024] 24) The guide bearing bracket model is divided into grids according to the material and the gravitational acceleration is given;

[0025] 25) Establish a local coordinate system at the guide bearing section, establish a circular bracket body at the rotation center, and establish bracket arms along several characteristic directions evenly distributed around the periphery. When modeling, select the unit body according to the bracket type, and add rigid fixed features to the bearing base and the end bearing hole of the frame;

[0026] 26) Based on the experience of similar units, select a set of parameters for modal analysis and prediction, and select the excitation response point of this model.

[0027] The step 3) further comprises the following steps:

[0028] 31) Place the test object 1 horizontally and naturally, use auxiliary tools to evenly divide the test object arm 2 and mark the position of the acceleration sensor 3;

[0029] 32) Acceleration sensors 3 are evenly arranged on the support arm 2. The acceleration sensors 3 are connected to the input end of the modal analyzer 5 via a data transmission line 7. The output end of the modal analyzer 5 is connected to the input end of the computer 6. The hammer 4 used to strike the test piece is provided with a force sensor, and the force sensor is connected to the input end of the modal analyzer 5 via a data line 7;

[0030] 33) After the acceleration sensor 3 is in place, an excitation hammer 4 is used to strike one or more positions of the support arm 2. Each acceleration sensor converts the hammer 4 striking signal into an electrical signal and sends the electrical signal to the modal analyzer 5;

[0031] 34) The modal analyzer 5 amplifies, filters and extracts the corresponding modal signal and then sends it to the computer 6;

[0032] 35) The modal analysis software in the computer analyzes the signals and finds that each mode has a specific natural frequency, damping ratio and modal vibration shape, and finally identifies the system modal parameters.

[0033] The step 4) further comprises the following steps:

[0034] 41) Optimize the real machine model parameters based on static measured data processing;

[0035] 42) Calculate and analyze the characteristics and vibration laws of the guide bearing bracket under various parameters, extract the modal frequencies and vibration shapes of each order, and obtain the vibration characteristics of the guide bearing bracket.

[0036] The step 5) further comprises the following steps:

[0037] 51) Monitor and record the vibration of the guide bearing bracket during the speed increase of the turbine generator.

[0038] 52) Monitor and record the vibration of the guide bearing bracket under different load conditions of the turbine generator.

[0039] Beneficial effects of the present invention:

[0040] 1. The detection method described in the present invention is used to test the generator guide bearing before installation, so as to find defects before commissioning and eliminate them early, thereby avoiding resonance phenomena such as tailwater tube vortex, guide vane Karman vortex, main shaft seal self-excited vibration and speed double frequency vibration, thereby avoiding shutdown accidents.

[0041] 2 The present invention adopts a method that combines three-dimensional modeling, finite element analysis and modal analysis to analyze the vibration characteristics of the guide bearing bracket. The analysis parameters include the specific natural frequency, damping ratio and modal vibration shape of each mode, and finally the modal parameters of the system are identified. The analysis results are comprehensive and scientific, and can provide a basis for the vibration characteristic analysis of the bracket system, vibration fault diagnosis and prediction, and optimization design of the structural dynamic characteristics.

[0042] The assessment system described in this invention uses a combination of modal analysis results and operational vibration data to evaluate the vibration of the guide bearing bracket, verifying each other with high accuracy. The assessment results accurately reflect the condition of the guide bearing bracket, providing an accurate basis for stable operation and condition-based maintenance of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Flowchart of the present invention.

[0044] Figure 2 This is a three-dimensional model diagram of the guide bearing bracket of the vertical hydro-generator.

[0045] Figure 3 Schematic diagram of the structure during experimental modal testing.

[0046] Figure 4 Schematic diagram of the acceleration measurement point layout of the guide bearing bracket of the vertical hydro-generator.

[0047] Figure 5 -First-order vibration mode of the guide bearing bracket of the vertical turbine generator.

[0048] Figure 6 -Second-order vibration mode of the guide bearing bracket of the vertical turbine generator.

[0049] in, Figure 3In the middle: 1 is the test object, 2 is the test object support arm, 3 is the acceleration sensor, 4 is the excitation hammer, 5 is the CRAS vibration and dynamic signal acquisition and analysis instrument, 6 is the computer containing the modal analysis software, and 7 is the data transmission line. DETAILED DESCRIPTION

[0050] The present invention will be described in further detail below with reference to the accompanying drawings.

[0051] The vibration characteristics evaluation system for a vertical hydro-turbine generator guide bearing bracket, described in this invention, consists of 3D modeling software, finite element analysis software, a modal testing and analysis unit, a vibration monitoring unit, and the guide bearing bracket (test object). The 3D modeling software creates a 3D geometric model of the guide bearing bracket. Based on this model, the finite element analysis software is then imported to model the test object, create a mesh, assign boundary conditions, perform debugging, and perform calculations.

[0052] refer to Figure 3 The modal test and analysis unit includes a test piece 1, a test piece support arm 2, an acceleration sensor 3, an excitation hammer 4, a CRAS vibration and dynamic signal acquisition and analysis instrument 5, a computer including modal analysis software 6, and a data transmission line 7.

[0053] The vibration monitoring unit is used for dynamic vibration monitoring and wave recording of the guide bearing bracket, including: vibration probe, data cable, computer, monitoring software and storage device.

[0054] refer to Figure 1 , in conjunction with an example, the vibration characteristic evaluation of the guide bearing support of the vertical hydro-generator according to the present invention includes the following steps:

[0055] 1) Collect information,

[0056] 2) Construct a real machine model of the guide bearing bracket system and conduct modal analysis and prediction.

[0057] 3) The test obtains the actual measured vibration mode, stiffness coefficient, and damping ratio of the real machine,

[0058] 4) Based on the measured data, optimize the real machine model and extract the modal frequencies and vibration shapes of each order.

[0059] 5) Monitor and record the vibration data of the guide bearing bracket under different conditions,

[0060] 6) Combined with the monitored guide bearing bracket vibration data, the vibration characteristics of the turbine generator guide bearing bracket are evaluated.

[0061] The specific operation process of step 1) is:

[0062] Collect information on the guide bearing bracket's geometry, connection method, material, generator speed, and electrical parameters. This equipment is a 6-arm guide bearing bracket, and its main parameters are shown in Table 1.

[0063] Table 1 Main parameters of equipment

[0064]

[0065] The specific operation process of step 2) is as follows:

[0066] 21) Use 3D modeling software to build a 3D geometric model of the test piece based on the shape of the guide bearing bracket.

[0067] 22) Import finite element analysis software into the 3D model,

[0068] 23) Modeling is done according to the real machine parameters, and the physical parameters such as material density and Young's modulus of each part are given.

[0069] 24) The guide bearing bracket model is divided into grids according to the material, and the gravity acceleration is given.

[0070] 25) Establish a local coordinate system at the guide bearing section, create a circular support body at the center of rotation, and establish support arms along six feature directions evenly distributed around the periphery. Select unit body 187 for modeling, and add rigid fixed features to the bearing base and the end bearing hole of the frame;

[0071] 26) Based on the experience of similar units, select a set of parameters for modal analysis and prejudgment, and select the excitation response point of the unit;

[0072] The established model can be found in Figure 2 Three-dimensional model diagram of the guide bearing bracket of the vertical turbine generator.

[0073] The specific operation process of step 3) is as follows:

[0074] 31) Place the test object horizontally and naturally, use auxiliary tools to evenly divide the test object's support arm and mark the position of the acceleration sensor.

[0075] 32) Acceleration sensors are evenly arranged on the support arms. The acceleration sensors are connected to the input of the modal analyzer via a data transmission line. The output of the modal analyzer is connected to the input of the computer. A force sensor is provided on the hammer used to strike the test piece. The force sensor is connected to the input of the modal analyzer via a data line.

[0076] 33) After the acceleration sensor is in place, use the excitation hammer to hit one or more positions of the support arm. Each acceleration sensor converts the hammer impact signal into an electrical signal and sends the electrical signal to the modal analyzer.

[0077] 34) The modal analyzer amplifies, filters and extracts the corresponding modal signal and then sends it to the computer.

[0078] 35) The modal analysis software in the computer analyzes the signal and finds that each mode has a specific natural frequency, damping ratio and modal vibration shape, and finally identifies the system modal parameters;

[0079] The acceleration measurement points are arranged as follows Figure 4 Schematic diagram of the acceleration measurement point arrangement of the guide bearing bracket of a vertical hydro-turbine generator.

[0080] The specific operation process of step 4) is as follows:

[0081] 41) Based on the static measured data processing, optimize the real machine model parameters,

[0082] 42) Calculate and analyze the characteristics and vibration laws of the guide bearing bracket under various parameters, extract the modal frequencies and vibration shapes of each order, and obtain the vibration characteristics of the guide bearing bracket;

[0083] The typical spectrum of vibration characteristics of the guide bearing bracket of this unit is as follows Figure 5 First-order vibration mode and vibration mode of guide bearing bracket of vertical turbine generator Figure 6 Second-order vibration mode of the guide bearing bracket of a vertical hydro-generator.

[0084] The specific operation process of step 5) is as follows:

[0085] 51) Monitor and record the vibration of the guide bearing bracket during the speed increase of the turbine generator.

[0086] 52) Monitor and record the vibration of the guide bearing bracket under different load conditions of the turbine generator;

[0087] like Figure 1 As shown in the figure: the method first uses finite element software combined with three-dimensional modeling software to construct a real machine model of the guide bearing bracket system, selects a set of parameters for modal analysis prediction based on the experience of similar units, and selects the excitation response point of the model; further, the static natural frequency of the guide bearing bracket is measured using a modal analysis instrument; according to the differences in the layout of different guide bearing brackets and on-site construction conditions, the positions of appropriate excitation points and response points are reasonably selected, and the static measured vibration mode, stiffness coefficient and damping ratio of the real machine are obtained through field tests; further, based on the static measured data processing, the parameters of the real machine model are optimized, the characteristics and vibration laws of the guide bearing bracket under various parameters are calculated and analyzed, the modal frequencies and vibration modes of each order are extracted, and the vibration characteristics of the guide bearing bracket are obtained; finally, the vibration characteristics of the guide bearing bracket of the hydro-generator are evaluated in combination with the monitored turbine vibration data.

[0088] Before installing the guide bearing bracket, the vibration of the guide bearing bracket was analyzed according to the method shown. The analysis showed that the main vibration characteristics of the first-order vibration mode are: the bracket center body has Z-direction movement, which drives the support arms to produce displacement in the same direction, and the maximum displacement occurs at the bracket center body. The main vibration characteristics of the second-order vibration mode are that the center body is rotated in the X / Y plane with the generator axis as the center, and drives the support arms to produce displacement, and the maximum displacement occurs at the connection between each support arm and the center body. Based on this conclusion, the guide bearing bracket was reinforced and counterweighted in advance to eliminate the defects in advance. During the generator speed-up process and load operation, the vibration data of the guide bearing bracket was observed and recorded, and the bracket vibration condition was good.

[0089] The detection method described in the present invention tests the generator guide bearing before installation, identifying defects before commissioning, allowing them to be eliminated early and avoiding downtime. The present invention analyzes the vibration characteristics of the guide bearing bracket using a combination of three-dimensional modeling, finite element analysis, and modal analysis. The analysis parameters include the specific natural frequency, damping ratio, and modal shape of each mode, ultimately identifying the system modal parameters. The analysis results are comprehensive and scientific, providing a basis for vibration characteristic analysis, vibration fault diagnosis and prediction, and optimized design of structural dynamic characteristics of the bracket system. The evaluation system described in the present invention combines modal analysis results with operational vibration data to evaluate the vibration of the guide bearing bracket, verifying each other with high accuracy. The evaluation results accurately reflect the status of the guide bearing bracket, providing an accurate basis for stable operation and condition-based maintenance of the unit. This method can be extended to the evaluation of guide bearing brackets of various types of vertical hydro-turbine generators and various vertical rotating machinery.

[0090] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for evaluating the vibration characteristics of a guide bearing support of a vertical hydro-turbine generator, characterized in that: The following steps are included: 1) Collect information on the geometric dimensions, connection method, material, generator speed and electrical parameters of the guide bearing bracket; 2) Construct a real machine model of the guide bearing bracket system and conduct modal analysis and prediction; 3) The actual vibration mode, stiffness coefficient and damping ratio of the real machine are obtained through testing; 4) Based on the measured data, optimize the real machine model and extract the modal frequencies and vibration shapes of each order; 5) Monitor and record the vibration data of the guide bearing bracket under different conditions; 6) Combined with the monitored guide bearing bracket vibration data, conduct a comprehensive assessment of the vibration characteristics of the turbine generator guide bearing bracket; The specific steps of step 2) are as follows: 21) Use 3D modeling software to build a 3D geometric model of the test piece based on the shape of the guide bearing bracket; 22) Import finite element analysis software into the 3D model; 23) Modeling is done according to the real machine parameters, and the material density and Young's modulus of each part are given; 24) The guide bearing bracket model is divided into grids according to the material and the gravitational acceleration is given; 25) When modeling, select the unit body according to the bracket type, and add rigid fixed features to the bearing base and the end bearing hole of the frame; 26) Based on the experience of similar units, select a set of parameters for modal analysis and prejudgment, and select the excitation response point of the unit; The step 3) further includes: 31) The test object (1) is placed horizontally and naturally, and a test object support arm (2) is set on the test object (1). The test object support arm (2) is evenly divided using auxiliary tools and the position of the acceleration sensor (3) is marked; 32) Acceleration sensors (3) are evenly arranged on the support arm (2), and the acceleration sensors (3) are connected to the input end of the modal analyzer (5) through the data transmission line (7). The output end of the modal analyzer (5) is connected to the input end of the computer (6). A force sensor is provided on the hammer (4) for striking the test piece, and the force sensor is connected to the input end of the modal analyzer (5) through the data line (7); 33) After the acceleration sensor (3) is placed in place, an excitation hammer (4) is used to strike one or more positions of the support arm (2), and each acceleration sensor converts the striking signal of the hammer (4) into an electrical signal, and sends the electrical signal to the modal analyzer (5); 34) The modal analyzer (5) amplifies, filters and extracts the corresponding modal signal and then sends it to the computer (6); 35) The modal analysis software in the computer analyzes the signals and finds that each mode has a specific natural frequency, damping ratio and modal vibration shape, and finally identifies the system modal parameters; The step 4) further includes the following steps: 41) Optimize the real machine model parameters based on static measured data processing; 42) Calculate and analyze the characteristics and vibration laws of the guide bearing bracket under various parameters, extract the modal frequencies and vibration shapes of each order, and obtain the vibration characteristics of the guide bearing bracket; The step 5) further includes the following steps: 51) Monitor and record the vibration of the guide bearing bracket during the speed increase of the turbine generator. 52) Monitor and record the vibration of the guide bearing bracket under different load conditions of the turbine generator.

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