Method for evaluating the influence of vertical condenser pump axis inclination on vibration

Abstract

The application discloses a method for evaluating the influence of the shaft line inclination of a vertical condensate pump on vibration, belongs to the technical field of thermal power generation, and solves the problem of how to evaluate the influence of the shaft line inclination of a vertical condensate pump on vibration. The method comprises the following steps: measuring the vibration influence coefficient of an excitation force at different rotating frequencies in a speed-up process through a counterweight test; constructing an identification equation group by using vibration data in the speed-up process and the vibration influence coefficient; and then solving the unbalanced eccentricity and the shaft line inclination excitation force by using a least square method. The accuracy of the identification model is evaluated by comparing the vibration in the speed-up process calculated according to the unbalanced eccentricity and the shaft line inclination excitation force with the vibration in the speed-up process actually measured. The influence of the shaft line inclination of the vertical condensate pump on vibration is evaluated according to the shaft line inclination excitation force and the vibration influence coefficient. Different from the traditional test analysis under a shutdown state, the method can be used for evaluation under a running condition, solves the problem that the influence of the shaft line inclination of the vertical condensate pump on vibration is difficult to evaluate under a running state, and is used for guiding the fault diagnosis of the vertical condensate pump.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal power generation, and relates to a method for evaluating the influence of the inclination of the vertical condensate pump axis on vibration. Background Art

[0002] As Figure 7 shown, the condensate pumps in power plants are arranged vertically, and the motors driving the condensate pumps are located at the top of the condensate pumps. Taking the condensate pump supporting a 600MW steam turbine as an example, the pump weighs about 15t, the top motor weighs about 10t, and the total axis length is about 15 meters. A combined device of guide shoes and thrust bearing is arranged on the pump seat to bear the radial force and axial thrust of the rotor, and multiple water-lubricated rubber bearings are arranged inside the pump to bear the radial force of the rotor. Such a system has the characteristics of a slender rotating shaft and a heavy top and light bottom. If the parallelism of the base plate is incorrect, after the thrust head is installed on the shafting, the working surface is not perpendicular to the center line of the shafting, and after starting the machine, the axis will generate a conical whirling around the vertical center line. The conical whirling of the axis will cause the vibration of the unit, which is prominently manifested at the top of the motor and the bottom of the condensate pump. There are many factors affecting the vibration of the condensate pump, such as imbalance, misalignment, insufficient foundation stiffness, resonance, pipeline restriction, etc., and the axis inclination is only one of the reasons.

[0003] After the vibration fault of the condensate pump occurs, it is necessary to analyze and evaluate the influence of the axis inclination on the vibration according to the vibration characteristics. The methods adopted in the prior art mainly include: 1) Dial indicator method. In the shutdown state, a dial indicator is erected at the exposed shaft section between the motor and the thrust head, the rotor is rotated, and according to the change of the dial indicator reading, the runout at the shaft section can be measured according to the difference between the maximum and minimum readings of the dial indicator. 2) Thrust head level test method. In the shutdown state, a level is erected at the thrust head to test the level of the thrust head, and the inclination of the shaft is judged according to the level. The worse the level, the greater the inclination of the shaft. 3) Ex post facto reasoning method. During equipment maintenance, the guide shoes are opened for inspection, and the axis inclination is analyzed according to the wear conditions of the guide shoes at all levels from top to bottom. 4) Vibration fault diagnosis method. There are many factors affecting the vibration of the condensate pump, including imbalance, misalignment, insufficient foundation stiffness, resonance, pipeline restriction, axis inclination, etc. After the vibration problem occurs, according to the vibration phenomena of the unit, such as the characteristics of spectrum, waveform, phase, etc., the axis inclination is diagnosed. Or, after excluding other fault causes such as imbalance, the remaining is the axis inclination.

[0004] The shortcomings of existing methods are as follows: 1) The dial gauge method and thrust head levelness test method can only be performed in a stopped state, and the measured data only reflects the stopped state. However, the shaft tilt is significantly different in the running state compared to the stopped state. The data obtained by these two methods only shows the shaft tilt and cannot be used to assess the impact of shaft tilt on vibration in the running state. 2) The post-hoc reasoning method requires disassembling the pump and motor, and can only be used for post-hoc analysis, which cannot meet the needs of fault analysis in the running state. 3) The vibration characteristics caused by shaft tilt are very similar to those of imbalance faults, for example, the spectrum is mainly composed of power frequency components, and the waveform is approximately sine wave. Currently, it is still difficult to assess the shaft tilt state and its impact on vibration based on the measured vibration characteristics. After excluding various similar faults other than conical whirl, it can be considered that the fault is caused by shaft tilt. Therefore, vibration fault diagnosis methods require a large number of experiments, which is a huge workload. Summary of the Invention

[0005] The technical problem to be solved by this invention is how to assess the impact of vertical condensate pump shaft tilt on vibration, so as to guide the work of condensate pump vibration fault diagnosis.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0007] A method for assessing the vibration impact of shaft inclination in a vertical condensate pump includes the following steps:

[0008] S1. Establish a calculation model for the total vibration displacement response excited by the unbalanced excitation force and the shaft tilting excitation force at the rotation frequency;

[0009] S2. Select multiple rotation frequency points, construct an identification equation set based on the motor vibration data at different rotation frequencies, and solve the equation set using the least squares method to identify the unbalanced eccentricity vector and the shaft tilt vector.

[0010] S3. Based on the identified unbalanced eccentricity vector and shaft tilt vector, the vibration variation curve during the acceleration process is calculated. The accuracy of the identification model is analyzed based on the overlap between the measured vibration variation curve during the acceleration process and the calculated vibration variation curve during the acceleration process.

[0011] S4. Evaluate the impact of shaft tilt on vibration based on the proportion of the vibration displacement response excited by the shaft tilting excitation force in the total vibration displacement response.

[0012] This invention proposes a method for assessing the vibration impact of vertical condensate pump shaft tilt. It measures the vibration influence coefficient of the excitation force at different rotation frequencies during acceleration through a counterweight test. An identification equation set is constructed from the vibration data and influence coefficients during acceleration, and then the least squares method is used to solve for the unbalanced eccentricity and shaft tilt excitation forces. The accuracy of the identification model is evaluated by comparing the back-calculated vibration during acceleration with the measured vibration during acceleration. The impact of the vertical condensate pump shaft tilt on vibration is assessed based on the identified shaft tilt excitation force and influence coefficients. Unlike traditional testing and analysis under shutdown conditions, this invention's method can be used for assessment under operating conditions, solving the problem of difficulty in assessing the vibration impact of vertical condensate pump shaft tilt during operation, and can be used to guide fault diagnosis of vertical condensate pumps.

[0013] Furthermore, the specific method for establishing the calculation model of the total vibration displacement response excited by the unbalanced excitation force and the shaft tilting excitation force at the rotational frequency in step S1 is as follows:

[0014] S11. Considering the structural characteristics of the electric motor, it is simplified into a single-degree-of-freedom system consisting of mass, springs, and dampers. The electric motor is subjected to an excitation force F from the pump shaft and the motor rotor. This excitation force F is caused by the rotor's unbalanced excitation force F. u and the excitation force F of the tilting shaft r It consists of two parts, and their calculation formulas are as follows:

[0015]

[0016] Where u is the eccentricity of the rotor unbalanced excitation force; ω is the rotation frequency; γ1 is the phase angle of the rotor unbalanced excitation force; r is the amplitude of the shaft tilting excitation force; and γ2 is the phase angle of the shaft tilting excitation force.

[0017] S12. According to vibration theory, the dynamic equation of the electric motor is:

[0018]

[0019] Where m is the vibrating mass of the motor, k is the motor stiffness coefficient, c is the motor damping coefficient, and x, These are the motor's vibration displacement response, velocity response, and acceleration response, respectively.

[0020] S12. The vibration displacement response x(t) is the sum of the vibration displacements excited by the rotor unbalance excitation force and the shaft tilting excitation force:

[0021]

[0022] Among them, A u (ω),A r(ω) represents the amplitude of the vibration displacement response excited by the unbalanced excitation force and the shaft tilting excitation force at the rotation frequency ω, respectively. These are the phases of the vibration displacement responses excited by the unbalanced excitation force and the shaft tilting excitation force at the rotation frequency ω, respectively.

[0023] The calculation formula is as follows:

[0024]

[0025] in, ξ=c / (2mω n ).

[0026] Abbreviated as:

[0027]

[0028] Where α(ω) is the influence coefficient of the excitation force on the vibration at the rotational frequency ω, that is:

[0029]

[0030] S14. Unbalanced excitation force, shaft tilting excitation force, influence coefficient, and vibration displacement response all include amplitude and phase, and are uniformly expressed in complex form:

[0031]

[0032] The arrow above a variable indicates that the variable is a complex number;

[0033] S15, Overall vibration response Complex numbers are represented as:

[0034]

[0035] in, This represents the vibration displacement response excited by the unbalanced excitation force at a rotational frequency ω. The vibration displacement response is the result of the tilting excitation force of the shaft at a rotational frequency ω. These are the unbalanced eccentricity vector and the axis tilt vector, respectively.

[0036] Furthermore, the aforementioned influence coefficient The measurement method is as follows:

[0037] 1) Place vibration sensors horizontally at the top of the motor to test the vibration at the top of the motor;

[0038] 2) Start the motor to its rated speed, and use a vibration sensor to test the vibration of the motor at its rated speed. Record the vibration amplitude and phase as A0 and A1, respectively. In complex form:

[0039]

[0040] 3) A counterweight is added to the motor shaft. The product of the counterweight's weight and the radius of the counterweight is e, and the installation angle is β. The resulting unbalanced excitation force of the counterweight... In complex form:

[0041]

[0042] 4) Use a vibration sensor to test the vibration of the motor after adding a counterweight, and record the amplitude as A1 and the phase as... In complex form:

[0043]

[0044] 5) Influence coefficient of excitation force on vibration The calculation formula is as follows:

[0045]

[0046] Furthermore, the method described in step S2 for selecting multiple rotation frequency points, constructing an identification equation set based on motor vibration data at different rotation frequencies, and solving the equation set using the least squares method to identify the unbalance eccentricity vector and shaft tilt vector is as follows:

[0047] Select n frequency points ω1, ω2, ..., ω to be analyzed n Based on the motor vibration data at different rotation frequencies, the following set of identification equations is constructed:

[0048]

[0049] Equation (13) is solved using the least squares method, thereby identifying the unbalanced eccentricity vector and the shaft tilt vector.

[0050] The advantages of this invention are:

[0051] This invention proposes a method for assessing the vibration impact of vertical condensate pump shaft tilt. It measures the vibration influence coefficient of the excitation force at different rotation frequencies during acceleration through a counterweight test. An identification equation set is constructed from the vibration data and influence coefficients during acceleration, and then the least squares method is used to solve for the unbalanced eccentricity and shaft tilt excitation forces. The accuracy of the identification model is evaluated by comparing the back-calculated vibration during acceleration with the measured vibration during acceleration. The impact of the vertical condensate pump shaft tilt on vibration is assessed based on the identified shaft tilt excitation force and influence coefficients. Unlike traditional testing and analysis under shutdown conditions, this invention's method can be used for assessment under operating conditions, solving the problem of difficulty in assessing the vibration impact of vertical condensate pump shaft tilt during operation, and can be used to guide fault diagnosis of vertical condensate pumps. Attached Figure Description

[0052] Figure 1 This is a flowchart of a method for assessing the impact of shaft inclination on vibration in a vertical condensate pump according to an embodiment of the present invention;

[0053] Figure 2 This is a simplified model for the dynamic analysis of the condensate pump motor in this embodiment of the invention;

[0054] Figure 3 The curves showing the change of amplitude and phase of the influence coefficient with rotational speed during the acceleration process obtained from the counterweight test in this embodiment of the invention are shown.

[0055] Figure 4 The curves showing the measured vibration amplitude and phase changes with rotational speed during the acceleration process according to an embodiment of the present invention are shown.

[0056] Figure 5 This is a comparison of the measured and calculated vibration amplitude and phase curves as a function of rotational speed during the acceleration process in this embodiment of the invention.

[0057] Figure 6 The curves showing the variation of vibration amplitude with rotational speed during the acceleration process of this embodiment of the invention, caused by unbalanced excitation force and shaft tilt.

[0058] Figure 7 The tilting of the vertical condensate pump shaft and the resulting conical vortex. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0061] Example 1

[0062] like Figure 1 As shown, a method for assessing the vibration impact of shaft inclination in a vertical condensate pump includes the following steps:

[0063] 1. Establish a calculation model for the total vibration displacement response excited by the unbalanced excitation force and the shaft tilting excitation force at the rotation frequency;

[0064] like Figure 2 As shown, considering the structural characteristics of the electric motor, it is simplified into a single-degree-of-freedom system consisting of mass, springs, and dampers. The electric motor is subjected to an excitation force F from the pump shaft and the motor rotor. This excitation force F is caused by the rotor's unbalanced excitation force Funbalanced. u and the excitation force F of the tilting shaft r It consists of two parts, and their calculation formulas are as follows:

[0065]

[0066] Where u is the eccentricity of the rotor unbalanced excitation force, in g·m; ω is the rotation frequency, in rad / s; γ1 is the phase angle of the rotor unbalanced excitation force; r is the amplitude of the shaft tilting excitation force, in N; and γ2 is the phase angle of the shaft tilting excitation force.

[0067] According to vibration theory, the dynamic equation of an electric motor can be written as:

[0068]

[0069] Where m is the vibrating mass of the motor, k is the motor stiffness coefficient, c is the motor damping coefficient, and x, These are the motor's vibration displacement response, velocity response, and acceleration response, respectively.

[0070] The vibration displacement response x(t) is the sum of the vibration displacements excited by the rotor unbalance excitation force and the shaft tilting excitation force, and can be written as:

[0071]

[0072] Among them, A u (ω),A r (ω) represents the amplitude of the vibration displacement response excited by the unbalanced excitation force and the shaft tilting excitation force at the rotation frequency ω, respectively. These are the phases of the vibration displacement responses induced by the unbalanced excitation force and the shaft tilting excitation force at the rotation frequency ω, respectively.

[0073] The calculation formula is as follows:

[0074]

[0075] in, ξ=c / (2mω n ).

[0076] It can be abbreviated as:

[0077]

[0078] Where α(ω) is the influence coefficient of the excitation force on the vibration at the rotational frequency ω, that is:

[0079]

[0080] Unbalanced excitation force, shaft tilt excitation force, influence coefficient, and vibration displacement response all include amplitude and phase, and are uniformly expressed in complex form:

[0081]

[0082] The arrow above a variable indicates that the variable is a complex number;

[0083] Overall vibration response Complex numbers are represented as:

[0084]

[0085] in, This represents the vibration displacement response excited by the unbalanced excitation force at a rotational frequency ω. The vibration displacement response is the result of the tilting excitation force of the shaft at a rotational frequency ω. These are the unbalanced eccentricity vector and the axis tilt vector, respectively.

[0086] The influence coefficient The measurement method is as follows:

[0087] (1) Arrange vibration sensors horizontally at the top of the motor to test the vibration at the top of the motor;

[0088] (2) Start the motor to its rated speed, and use a vibration sensor to test the vibration of the motor at its rated speed. Record the vibration amplitude and phase as A0 and A1, respectively. In complex form:

[0089]

[0090] (3) A counterweight is added to the motor shaft. The product of the counterweight weight and the radius of the counterweight is e, and the installation angle is β. The resulting unbalanced excitation force of the counterweight... In complex form:

[0091]

[0092] (4) Use a vibration sensor to test the vibration of the motor after adding a counterweight, and record the amplitude as A1 and the phase as... In complex form:

[0093]

[0094] (5) Influence coefficient of excitation force on vibration The calculation formula is as follows:

[0095]

[0096] Figure 3 The curves showing the amplitude and phase of the influence coefficient as a function of rotational speed during the acceleration process, obtained from the counterweight test, are presented.

[0097] 2. Select multiple rotation frequency points, construct an identification equation set based on the motor vibration data at different rotation frequencies, and solve the equation set using the least squares method to identify the unbalanced eccentricity vector and the shaft tilt vector;

[0098] Select n frequency points ω1, ω2, ..., ω to be analyzed n Based on the motor vibration data at different rotation frequencies, the following set of identification equations is constructed:

[0099]

[0100] Equation (16) is solved using the least squares method, thereby identifying the unbalanced eccentricity vector and the shaft tilt vector. .

[0101] Figure 4 A set of measured vibration amplitude and phase curves as a function of rotational speed during the acceleration process are presented.

[0102] 3. Based on the identified unbalanced eccentricity vector and shaft tilt vector, the vibration variation curve during acceleration is calculated. The accuracy of the identification model is analyzed by comparing the overlap between the measured vibration variation curve during acceleration and the calculated vibration variation curve during acceleration.

[0103] Based on the identified unbalanced eccentricity vector and shaft tilt vector Substituting into formula (8), the vibration change curve with rotational speed during the acceleration process is calculated. Based on the overlap between the measured vibration change curve during the acceleration process and the calculated vibration change curve during the acceleration process, the accuracy of the identification model is analyzed. Figure 5 A set of curves comparing the measured and inversely calculated vibration amplitude and phase with rotational speed during the acceleration process are presented.

[0104] 4. Evaluate the impact of shaft tilt on vibration based on the proportion of the vibration displacement response excited by the shaft tilting excitation force in the total vibration displacement response.

[0105] During the acceleration process, the vibrations of the motor caused by unbalanced excitation force and the vibrations caused by shaft tilting excitation force are respectively:

[0106]

[0107] according to The amplitude and its proportion in the total vibration are used to assess the impact of axis tilt on the vibration. Figure 6 A set of curves showing the variation of vibration amplitude with rotational speed caused by unbalanced excitation force and shaft tilt during acceleration are presented.

[0108] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for assessing the impact of shaft inclination on vibration in a vertical condensate pump, characterized in that, Includes the following steps: S1. Establish a calculation model for the total vibration displacement response excited by the unbalanced excitation force and the shaft tilting excitation force at the rotational frequency. The specific method is as follows: S11. Considering the structural characteristics of the electric motor, it is simplified into a single-degree-of-freedom system consisting of mass, springs, and dampers. The electric motor is subjected to an excitation force F from the pump shaft and the motor rotor. This excitation force F is caused by the unbalanced excitation force of the rotor. and shaft tilting excitation force It consists of two parts, and their calculation formulas are as follows: (1) Where u is the eccentricity of the rotor unbalanced excitation force; The rotational frequency; r is the phase angle of the rotor unbalance excitation force; r is the amplitude of the shaft tilt excitation force. The phase angle of the excitation force when the shaft is tilted; S12. According to vibration theory, the dynamic equation of the electric motor is: (2) Where m is the vibrating mass of the motor, k is the motor stiffness coefficient, and c is the motor damping coefficient. , , These are the motor's vibration displacement response, velocity response, and acceleration response, respectively. S12, Vibration Displacement Response The sum of the vibration displacements excited by the rotor imbalance excitation force and the shaft tilt excitation force is: (3) in, Respectively, rotation frequency The amplitude of the vibration displacement response excited by the unbalanced excitation force and the shaft tilting excitation force. Respectively, rotation frequency The phase of the vibration displacement response excited by the unbalanced excitation force and the shaft tilting excitation force; The calculation formula is as follows: (4) in, , ; Abbreviated as: (5) in, Rotation frequency The influence coefficient of the excitation force on the vibration, i.e.: (6) S14. Unbalanced excitation force, shaft tilting excitation force, influence coefficient, and vibration displacement response all include amplitude and phase, and are uniformly expressed in complex form: (7) The arrow above a variable indicates that the variable is a complex number; S15, Overall vibration response Complex numbers are represented as: (8) in, Rotation frequency The vibration displacement response induced by the unbalanced excitation force. Rotation frequency The vibration displacement response induced by the tilting excitation force of the lower shaft. These are the unbalanced eccentricity vector and the axis tilt vector, respectively. S2. Select multiple rotation frequency points, construct an identification equation set based on the motor vibration data at different rotation frequencies, and solve the equation set using the least squares method to identify the unbalanced eccentricity vector and the shaft tilt vector. S3. Based on the identified unbalanced eccentricity vector and shaft tilt vector, the vibration variation curve during the acceleration process is calculated. The accuracy of the identification model is analyzed based on the overlap between the measured vibration variation curve during the acceleration process and the calculated vibration variation curve during the acceleration process. S4. Evaluate the impact of shaft tilt on vibration based on the proportion of the vibration displacement response excited by the shaft tilting excitation force in the total vibration displacement response.

2. The method for assessing the impact of shaft inclination on vibration of a vertical condensate pump according to claim 1, characterized in that, The influence coefficient The measurement method is as follows: 1) Place vibration sensors horizontally at the top of the motor to test the vibration at the top of the motor; 2) Start the motor to its rated speed, and use a vibration sensor to test the vibration of the motor at its rated speed. Record the vibration amplitude and phase as follows: and It can be expressed in complex form as: (9) 3) Add a counterweight to the motor shaft. The product of the counterweight's weight and the radius of the counterweight is e, and the installation angle is [value missing]. The resulting unbalanced excitation force In complex form: (10) 4) Use a vibration sensor to test the vibration of the motor after adding a counterweight, and record the amplitude value. Phase is It can be expressed in complex form as: (11) 5) Influence coefficient of excitation force on vibration The calculation formula is as follows: (12)。 3. The method for assessing the impact of shaft inclination on vibration of a vertical condensate pump according to claim 1, characterized in that, The method described in step S2, which involves selecting multiple rotation frequency points, constructing a set of identification equations based on motor vibration data at different rotation frequencies, and solving the set of equations using the least squares method to identify the unbalance eccentricity vector and shaft tilt vector, is as follows: Select n frequency points to be analyzed Based on the motor vibration data at different rotation frequencies, the following set of identification equations is constructed: (13) The least squares method is used to solve equation (13), thereby identifying the unbalanced eccentricity vector and the shaft tilt vector. .

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