Impeller fault failure process modeling and simulation evaluation method

Abstract

The invention provides an impeller fault failure process modeling and simulation evaluation method, which is suitable for the condition that an impeller has a fault during working, and establishes an evaluation-modeling-comparison-analysis systematic solution process. The method mainly comprises the following steps: preliminarily analyzing fault reasons according to turbine unit fault phenomena, including impact of a hub cap on blades, severe vibration of an impeller shaft caused by an eccentric load, collision of an impeller falling on the inner wall of a casing and the like, and establishing explicit dynamic simulation analysis models including external foreign particle impact, hub cap falling impact and collision with the inner wall of the casing; importing LS-DYNA software to carry out SPH granulation processing on an impactor, setting a material model and parameters of the impeller and impact parameters of a simulation model, submitting a simulation file to an operation program, analyzing and processing an impact process, and comparing and analyzing fault data and a simulation result to obtain a fault reason. In the process, relevant parameters are fed back to the simulation model, and the model is continuously optimized and improved to obtain a more accurate simulation model.

Description

Technical Field

[0001] The present invention relates to the technical field related to impeller failure and simulation evaluation, and in particular to an impeller failure process modeling and simulation evaluation method. Background Art

[0002] The structure of a centrifugal compressor assembly includes inlet guide vanes, centrifugal impellers, front hub covers, connecting bolts and impeller shafts. The compressor had a serious failure after one year of operation. After disassembling the equipment, it was found that the impeller blades were severely broken and worn, the guide plate on the inner wall of the casing was cracked and damaged, the impeller shaft was broken, and the two bolts connecting the hub cover and the wheel disc at the front end of the impeller were broken. The hub cover fell off and flew out, and the falling position was about 15 meters away from the impeller. However, after observation, no metallurgical defects and chemical corrosion were found at the fracture of the blades and the impeller shaft.

[0003] After observing and analyzing the fault phenomena, it is found that the failure of impeller blades can be roughly divided into two situations: one is that there is a semicircular fracture notch at the edge of the blade, which is found in a few blades; the other is that severe friction at the edge of the blade causes plastic deformation, which is found in most blades.

[0004] Since there is no real-time record when the failure occurs, and the impact failure occurs in an instant, the time is short and the speed is fast, relevant experimental research cannot be carried out. At present, the possible causes of the failure can only be preliminarily inferred based on the failure phenomenon, including the impact of foreign particles, the impact of the hub cover falling off and the collision with the inner wall of the casing. Finite element simulation technology is used to simulate and verify the impact failure. Therefore, in the modeling and simulation evaluation of the impeller failure process, the impeller and the impact body are modeled, the impact model is meshed using the finite element method, and the impact body is processed by SPH particles. The relevant physical parameters of the simulation model (particle properties and material property parameters, etc.) and impact parameters (impeller rotation speed, impact body speed, incident angle and contact type, etc.) are set to obtain the impact deformation effect diagram and data results such as effective plastic strain ε and paradigm equivalent stress δ. The obtained simulation results are compared and analyzed with the actual failure phenomenon and failure data, and the plastic deformation, wear deformation and fracture notch of the structure are compared. The failure mechanism is analyzed, the cause of the failure is inferred, and a systematic failure solution theory of "evaluation-modeling-comparison-analysis" is formed. In this process, the relevant parameters are fed back to the simulation model, and the model is continuously optimized and improved to obtain a more accurate simulation model. A complete set of explicit dynamics simulation processes is established to achieve accurate simulation and analysis of the fault impact process. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that the cause of the existing impeller failure cannot be speculated, to make a preliminary assessment of the impeller failure phenomenon and to perform explicit dynamic finite element simulation, so a method for modeling and simulating the failure process of the impeller is proposed.

[0006] A method for modeling and simulating the failure process of an impeller, the method comprising the following contents:

[0007] Step (1): The impact type is evaluated according to the actual fault phenomenon and is divided into three types: impact by foreign particles, impact by hub cover falling off, and collision with the inner wall of the casing. A three-dimensional model of the impeller and the impact body is established using modeling software. The impeller can adopt different size parameters, and the impact body includes foreign particles, hub cover, and the inner wall of the casing, so as to realize the construction of different impact models as the basis for subsequent analysis of the cause of the fault;

[0008] Step (2): import the three-dimensional impact model of the impeller and the impact body constructed in step (1) into the LS-DYNA software for pre-processing, perform finite element meshing on the impeller and the impact body respectively, and perform mesh encryption on the impact area. The meshing process is the basis for the subsequent SPH particle processing;

[0009] Step (3): performing SPH particle processing on the foreign matter and hub cover of the impact body model after the gridding processing in step (2), setting parameters such as particle size and distribution density, and setting the EOS state equation;

[0010] The EOS state equation of the particle model in step (3) adopts the Linear Polynomial state equation, and the specific formula is as follows:

[0011] (3.1) In the Linear Polynomial state equation used in the particle model, P is pressure, ρ is density, C0~C6 are constant parameters obtained by fitting experimental data, and E is the current internal energy per unit volume of the material;

[0012] p=C0+C1ρ+C2ρ 2 +C3ρ 3 +(C4+C5ρ+C6ρ 2 )E

[0013] Step (4): The impeller after meshing in step (2) is subjected to the Johnson-Cook constitutive model material to simulate the high-speed impact process. The inner wall of the casing after meshing in step (2) is subjected to the exponential hardening elastic-plastic model to simulate the structural plastic deformation process;

[0014] Step (5): assigning material parameters to the impeller and the inner wall of the casing after the meshing process in step (2) and the impact body after the SPH particle process in step (3), wherein the material parameters include: main material properties such as material density, Poisson's ratio and elastic modulus;

[0015] Step (6): setting impact parameters for the impeller and the inner wall of the casing after the meshing process in step (2) and the foreign matter and hub cover of the impact body model after the SPH particle process in step (3), wherein the impact parameters include: impeller rotation speed n, impact body speed v, incident angle θ and contact type, etc., and assembling the model before simulation analysis;

[0016] Step (7): Submit all processing operations of the above steps (1) to (6) to the software running program, analyze and process the impact process, and obtain the impact deformation effect diagram and data results such as effective plastic strain ε and paradigm equivalent stress δ;

[0017] Step (8): Compare and analyze the simulation results obtained in step (7) with the actual fault phenomenon and fault data, compare the plastic deformation, wear deformation and fracture notch of the structure, analyze the fault mechanism, infer the cause of the fault, and form a systematic fault solution theory of "assessment-modeling-comparison-analysis". In this process, the relevant parameters are fed back to the simulation model, and the model is continuously optimized and improved to obtain a more accurate simulation model, and a complete set of explicit dynamics simulation processes is established to realize accurate simulation and analysis of the fault impact process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A technical flow chart of a method for modeling and simulating the failure process of an impeller;

[0019] Figure 2 This is a schematic diagram of the internal structure of a certain type of centrifugal compressor;

[0020] Figure 3 Meshing diagram for the impact model;

[0021] Figure 4 To extract the unit strain change curve;

[0022] Figure 5 To extract the unit stress variation curve;

[0023] Figure 6 is the velocity variation curve of the impact body;

[0024] Figure 7 This is a comparison diagram of the semicircular fracture notch of the blade in the hub cover shedding impact model;

[0025] Figure 8This is a deformation comparison diagram of the collision model between the impeller and the inner wall of the casing. DETAILED DESCRIPTION

[0026] The technical scheme in the implementation case of the present invention is clearly and completely described below in conjunction with the accompanying drawings and implementation cases. However, the protection scope of the present invention is not limited by the specific implementation methods, and it is obvious that the implementation cases described are only part of the implementation cases of the present invention, not all of the implementation cases.

[0027] like Figure 1 As shown in the figure, it is a technical flow chart for implementation, which specifically includes the following steps:

[0028] Step (1): Figure 2 As shown in the figure, it is the internal structure diagram of a certain type of centrifugal compressor. Based on this, the impact model of the impeller and the impact body is established. The impact type is evaluated according to the actual fault phenomenon and is divided into three situations: impact of foreign particles, impact of hub cover falling off, and collision with the inner wall of the casing. The three-dimensional model of the impeller and the impact body is established using modeling software. The impeller can adopt different size parameters, and the impact body includes foreign particles, hub cover and the inner wall of the casing, so as to realize the construction of different impact models as the basic basis for subsequent analysis of the cause of the fault;

[0029] Step (2): Figure 3 As shown in FIG. 1 , it is a grid division diagram of the impact model. The three-dimensional impact model of the impeller and the impact body constructed in step (1) is imported into the LS-DYNA software for pre-processing. The impeller and the impact body are respectively subjected to finite element grid division processing, and the impact area is subjected to encrypted grid operation. The grid division processing is the basic basis for the subsequent SPH particle processing.

[0030] Step (3): performing SPH particle processing on the foreign matter and hub cover of the impact body model after the gridding processing in step (2), setting parameters such as particle size and distribution density, and setting the EOS state equation;

[0031] The EOS state equation of the particle model in step (3) adopts the Linear Polynomial state equation, and the specific formula is as follows:

[0032] (3.1) In the Linear Polynomial state equation used in the particle model, P is pressure, ρ is density, C0~C6 are constant parameters obtained by fitting experimental data, and E is the current internal energy per unit volume of the material;

[0033] p=C0+C1ρ+C2ρ 2 +C3ρ 3 +(C4+C5ρ+C6ρ 2 )E

[0034] Step (4): The impeller after meshing in step (2) is subjected to the Johnson-Cook constitutive model material to simulate the high-speed impact process. The inner wall of the casing after meshing in step (2) is subjected to the exponential hardening elastic-plastic model to simulate the structural plastic deformation process;

[0035] Step (5): assigning material parameters to the impeller and the inner wall of the casing after the meshing process in step (2) and the impact body after the SPH particle process in step (3), wherein the material parameters include: main material properties such as material density, Poisson's ratio and elastic modulus;

[0036] Step (6): setting impact parameters for the impeller and the inner wall of the casing after the meshing process in step (2) and the foreign matter and hub cover of the impact body model after the SPH particle process in step (3), wherein the impact parameters include: impeller rotation speed n, impact body speed v, incident angle θ and contact type, etc., and assembling the model before simulation analysis;

[0037] Step (7): Submit all processing operations of the above steps (1) to (6) to the software running program to analyze and process the impact process to obtain the impact deformation effect diagram and data results such as effective plastic strain ε and normal equivalent stress δ. Figure 4 , Figure 5 and Figure 6 As shown, the strain change curve of the extraction unit, the stress change curve of the extraction unit and the velocity change curve of the impact body are respectively shown. The impact body has an initial velocity. After hitting the blade, the velocity begins to decrease, but does not drop to 0. Then the velocity shows a gradual upward trend. This shows that the velocity direction of the impact body has a certain angle with the velocity direction of the blade. When it first hits, it is affected by the resistance of the blade. Then, due to the change in the movement direction of the impact body, the blade generates power on the impact body, causing the impact body to increase in velocity and gradually move away from the impeller.

[0038] Step (8): Figure 7 As shown in the figure, it is a comparison of the semicircular fracture notch of the blade in the hub cover falling impact model. Figure 8 As shown, it is a deformation comparison diagram of the collision model between the impeller and the inner wall of the casing. The simulation results obtained in step (7) are compared and analyzed with the actual fault phenomenon and fault data, and the plastic deformation, wear deformation and fracture notch of the structure are compared to analyze the fault mechanism, infer the cause of the fault, and form a systematic fault solution theory of "evaluation-modeling-comparison-analysis". In this process, the relevant parameters are fed back to the simulation model, and the model is continuously optimized and improved to obtain a more accurate simulation model, and a complete set of explicit dynamics simulation processes are established to realize accurate simulation and analysis of the fault impact process.

[0039] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary implementation cases described above, and that some local modifications or changes may be made without departing from the principles and basic features of the present invention, all of which fall within the scope of protection of the present invention. Therefore, no matter from which point of view, the implementation cases should be regarded as exemplary and non-restrictive, and the scope of the present invention is determined by the appended claims. The present invention does not involve parts that are identical to the prior art or can be implemented using the prior art.

Claims

1. A method for modeling and simulating the failure process of an impeller, characterized in that: The method comprises the following steps: Step (1): The impact type is evaluated according to the actual fault phenomenon and is divided into three types: impact by foreign particles, impact by hub cover falling off, and collision with the inner wall of the casing. A three-dimensional model of the impeller and the impact body is established using modeling software. The impeller can adopt different size parameters, and the impact body includes foreign particles, hub cover, and the inner wall of the casing, so as to realize the construction of different impact models as the basis for subsequent analysis of the cause of the fault; Step (2): import the three-dimensional impact model of the impeller and the impact body constructed in step (1) into the LS-DYNA software for pre-processing, perform finite element meshing on the impeller and the impact body respectively, and perform mesh encryption on the impact area. The meshing process is the basis for the subsequent SPH particle processing; Step (3): performing SPH particle processing on the foreign matter and hub cover of the impact body model after the gridding processing in step (2), setting parameters such as particle size and distribution density, and setting the EOS state equation; The EOS state equation of the particle model in step (3) adopts the Linear Polynomial state equation, and the specific formula is as follows: (3.1) In the Linear Polynomial state equation used in the particle model, P is pressure, ρ is density, C0~C6 are constant parameters obtained by fitting experimental data, and E is the current internal energy per unit volume of the material; p=C0+C1ρ+C2ρ 2 +C3p 3 +(C4+C5p+C6p 2 )E Step (4): The impeller after meshing in step (2) is subjected to the Johnson-Cook constitutive model material to simulate the high-speed impact process. The inner wall of the casing after meshing in step (2) is subjected to the exponential hardening elastic-plastic model to simulate the structural plastic deformation process; Step (5): assigning material parameters to the impeller and the inner wall of the casing after the meshing process in step (2) and the impact body after the SPH particle process in step (3), wherein the material parameters include: main material properties such as material density, Poisson's ratio and elastic modulus; Step (6): setting impact parameters for the impeller and the inner wall of the casing after the meshing process in step (2) and the foreign matter and hub cover of the impact body model after the SPH particle process in step (3), wherein the impact parameters include: impeller rotation speed n, impact body speed v, incident angle θ and contact type, etc., and assembling the model before simulation analysis; Step (7): Submit all processing operations of the above steps (1) to (6) to the software running program, analyze and process the impact process, and obtain the impact deformation effect diagram and data results such as effective plastic strain ε and paradigm equivalent stress δ; Step (8): Compare and analyze the simulation results obtained in step (7) with the actual fault phenomenon and fault data, compare the plastic deformation, wear deformation and fracture notch of the structure, analyze the fault mechanism, infer the cause of the fault, and form a systematic fault solution theory of "evaluation-modeling-comparison-analysis". In this process, the relevant parameters are fed back to the simulation model, and the model is continuously optimized and improved to obtain a more accurate simulation model, and a complete set of explicit dynamics simulation processes is established to realize accurate simulation and analysis of the impeller fault impact process.

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