Analysis of Hua Power Plant Beckles Stress Simulation Analysis

The thermal pipeline is important to play an important role in the operation of thermal power plant equipment, and the safe and stable operation of the body and accessories is very important. The elbow, as an indispensable part of the thermal pipeline, directly affects the safety of the unit. On the basis of the GB/T 16507-2013 “Water Pipe Boiler” standard, this article uses the simulation simulation software to analyze the stress of 90 ° elbow under different bending radius. Distribution status. The calculation results show that: under the same wall thickness, the maximum stress is concentrated in the inner arc. As the curved radius R increases, the maximum stress of the inner arc gradually decreases. At the same time Instead, it gradually increased. Under different wall thickness, the maximum stress occurs at the outer arc.


Introduction
As an important energy supply base for the country, the safety operation is important.However, in the long -term operation and high temperature and high pressure environment, it is difficult to avoid equipment loss and wear.Among them, the elbow is one of the key components of pipeline connection, and its performance and service life directly affects the safe operation of the entire pipeline.Therefore, in the daily maintenance of thermal power plant, it is very important to repair and replace the elbow [1][2] .In order to ensure the quality and safety of the elbow of the thermal power plants, it is required to strictly abide by national standards and industry specifications, comprehensively supervise the manufacturing, quality inspection and installation of the elbow, and conduct regular spot inspection and maintenance.For the elbows of new equipment, suppliers are required to provide certification documents and quality assurances that meet national standards and industry specifications [3][4][5] .When maintaining and replacing the elbow, it is necessary to ensure that the operator has rich experience and professional skills, conduct a comprehensive inspection of pipelines and accessories, discover problems in time, and maintain its normal operation [6] .At the same time, we must regularly maintain the pipeline and its accessories, detect the degree of wear of the elbow, and take measures to repair or replace them in time [7][8] .In short, the elbow is a very critical part of the pipeline, and its failure may cause serious losses to the operation of the thermal power plant.Therefore, it must fully strengthen its inspection and maintenance work to ensure its safe operation and ensure the normal operation of the thermal power plant.Thermal power generation is my country's energy chimney and one of the main energy supply methods in the world.The key to thermal power is to ensure its combustion efficiency and operation safety.In the firepower station, the pipeline system is a key component of the transportation fuel and cooling water, and the elbow is one of the very important part of them.However, in the environment of high temperature and high pressure and complexity, the elbow of the fire power plant is easily affected by many factors, including pressure corrosion, wear, and flow of flow.These reasons have accelerated the loss and degeneration of the elbow, which leads to the failure of the elbow.Once it fails, it will not only affect the production of crafts, but also cause more serious safety accidents.Therefore, in order to ensure the operational safety and production efficiency of the thermal power plants, more stringent requirements are put on the design, manufacturing and maintenance of the elbow.Therefore, this thesis aims to study the safety of the elbow of the thermal power plant, and explore its operating principles, structural characteristics and maintenance and maintenance through simulation and simulation data under different pipe diameters.Through the research and analysis of relevant national standards and specifications, the design and manufacturing of the elbow of the thermal power plants were discussed in detail, and corresponding improvement measures and suggestions were put forward to provide a reference for ensuring the safe operation of the thermal power plant [9] .

Analysis of operating conditions of the elbow operation
As an important part of the pipeline system, the Hua Power Plant's elbow is directly affecting the stability and safety of the entire pipeline system under high temperature, high pressure and complex conditions.The following is the analysis of the operating conditions of the elbow of the thermal power plant [10][11] : (1) Temperature: In the high temperature and high pressure environment of the thermal power plant, the elbow is usually affected by high surface temperature and ambient temperature.This makes it prone to temperature expansion in long -term operation, which will cause fatigue breaks of elbow materials.
(2) Pressure: The elbow of the thermal power plant is usually affected by high pressure.These pressures often come from the flow of liquid or gas in the pipeline.Affected by continuous pressure and pressure changes, the materials and structures of the elbow will deform and fatigue, which will affect its operating stability.
(3) Flow: During the process of transporting medium, the hemo -power plant elbows often suffer from flow resistance and the interference of vortex.These factors will not only affect the elbow itself, but also may have a second negative impact on the pipeline system that connect to it.(4) Corrosion: Affected by the medium, the elbow and pipeline system often cause corrosion.Corrosion may occur anywhere in the elbow and directly affect its life and performance.
(5) wear: During long -term operation, the elbow and pipeline systems are easily worn by the environment and medium.The wear may come from a variety of factors such as environmental corrosion, ruling of particulate matter, or the shear force of liquid, which causes its surface wear, cracks and even failure.Based on the above points, we can see that the working factors suffered during the operation of the heb power plant are very complicated.Therefore, when designing, manufacturing and maintaining the elbow of the thermal power plant, the interaction of different factors is needed to ensure its safe operation and reliability.

Evaluate parameter calculation
The excellent performance of P91 Steel has been recognized by my country's power industry.It has been widely used in sub -critical 600MW, ultra -critical 600MW unit main steam pipeline, and hightemperature re -steam steam pipelines.The P91 bending process mainly adopts inductive heating bending method.According to the standard requirements of DL/T 515-2018 "Power Pipe" standard, the curved radius of the alloy tube and the Ausides stainless steel tube When the inductive heating, the length L0 of the straight tube section at both ends of the bending pipe must meet Table 1 recommendation requirements [12][13] .(1) Calculation thickness formula for the curved or elbow arc calculation is: (2) Calculation thickness formula for the inner arc calculation of the curved tube or elbow is: (3) Calculating thickness formula of straight sections and medium arc calculation of bends or elbows are: In the formula: Δt -calculation thickness, mm; K0 -The shape coefficient of the bending pipe outdoor; P -Calculate the pressure, MPa; D0 -outer diameter, mm; Ψw -weld weakening coefficient; [σ] -My use stress, MPa; R -Rest on the center line of the bending pipe, mm; Ki -The shape coefficient of the inner arc in the curved pipe; Δmin -minimum thickness, mm.Supercritical pressure boiler refers to a boiler with the main steam pressure exceeding the critical pressure 22.12 mp.Generally, the main steam pressure of the large -capacity supercritical pressure boiler is set at about 24.5 MPa, and the temperature is 566°C/566°C.P91 (10cr9mo1vnbn) The corresponding allowable stress at 566 °C is 81 mPa.At this pressure and temperature, the minimum wall thickness corresponding to the curved radius of different elbows is shown in Table 2.

Simulation simulation analysis
This article uses SolidWorks 3D modeling software to carry out three -dimensional models of 90 °elbow of φ431.8mm, and divide the elbow grid through the COMSOL simulation software to perform stress analysis of the curved tube by applying border load.Φ431.The three -dimensional model of the 90 °elbow of 8mm is shown in Figure 1: At the same time, the minimum stress at the inner arc is increased with the curved radius R, but it gradually increases.And as the curved radius increases, the maximum stress of the inner arc is reduced, while the length of the tube is increased and the manufacturing cost increases.In the actual scene, the inner arc of the 90 °elbow is inconsistent with the thickness of the outer arc, and the thickness of the outer arc should be smaller than the thickness of the inner arc.The simulation results diagram is shown in 9.

Figure 9.The stress distribution of different wall thickness
It can be seen from Figure 9 that the internal arc and the thickness of the outer arc are inconsistent with the 90 °elbow under a certain load, the maximum stress occurs at the outer arc, and the position of the maximum stress of the equal wall thickness is different in the inner arc position.In summary, in the actual testing test and failure analysis work, the preliminary judgment is first made based on the actual inside of the inside and outside arcs on the scene, and then the modeling analysis is performed through the simulation software to find the maximum stress distribution position in order to carry out effective validity Test the test work, and at the same time, further discussion and research can be discussed according to the simulation results.

Conclusion
This Weili formula calculation obtains various parameters of the bending tubes of different bending radius, and analyzed the same wall-thick bending radius from 3.0D0-8.0D0to the maximum stress status characteristics of the maximum stress status characteristics of different wall thickness through the COMSOL simulation ,Concluded as follow: 1) Under the same wall thickness, as the curved radius R increases, the maximum stress of the inner arc gradually decreases.At the same time, the minimum stress at the inner arc is increased with the curved radius R, but it gradually increases.And as the curved radius increases, the maximum stress of the inner arc is reduced, and the length of the tube is increased.
2) The thickness of the inner arc and the outer arc is inconsistent with the 90 °elbow under a certain load, the maximum stress occurs at the outer arc, and the position of the maximum stress of the equal wall thickness is different in the inner arc position.
3) The feasibility analysis of the operation of the bending pipe through the simulation simulation provides an important theoretical basis for bending tube detection and judgment and material process improvement.

Figure 1 .Figure 2 .Figure 3 .Figure 4 .Figure 5 . 5 Figure 6 .Figure 7 .Figure 8 .
Figure 1.Model of three -dimensional construction of bending pipesIn order to meet the thickness of the inner arc at the same time, after calculating the thickness of the direct tube segment, the comprehensive consideration is comprehensively considered to use the minimum wall thickness 61 mm for the stress simulation analysis under different bending radius.The mechanical performance of the material is shown in Table3.The simulation conditions are: internal pressure 24.2 MPa, the simulation results are shown in Figure2-8: Table 3. Material Mechanical Properties Parameters Material Elastic modulus/Pa Poisson's ratio density/(kg/m 3 ) P91 200×10 9 0.30 7.85×10 3

Table 1 .
Direct tube length L0 recommended value unit at both ends of the bending pipe unit: mm Water Pipe Boiler" curved pipe or elbow strength school verification formula, calculate the minimum thickness under different curved radius:

Table 2 .
Different curved radius, bending tube wall thickness unit: mm