A method for calculating and evaluating the endurance life of a high-temperature component of a marine combustion engine turbine

Abstract

The application aims to provide a method for calculating and evaluating the durable life of a high-temperature component of a marine engine turbine, which adopts the following steps: performing a mechanical property test on the material of the high-temperature component of the turbine to obtain stress-strain curves under different temperature conditions, and converting the test curves into stress-plastic strain curves under different temperature conditions required for strength calculation and applying the material properties to a strength calculation model. After analyzing the temperature field, flow field and pressure field of the high-temperature component of the turbine, the determined temperature and pressure data are applied to the static strength analysis of the high-temperature component as external load conditions, and detailed temperature and stress data of the high-temperature component under actual working conditions are calculated. The durable life of the high-temperature component is evaluated by using the durable limit data of the material. The application can accurately simulate the stress distribution of all parts of the high-temperature component of the marine engine, and quickly and comprehensively calculate the durable life margin of the high-temperature component.

Description

TECHNICAL FIELD

[0001] The present application relates to a gas turbine life assessment method, in particular, a turbine high-temperature component life assessment method. BACKGROUND

[0002] The gas turbine is a kind of rotary mechanical device which converts the heat energy of high-temperature and high-pressure combustion gas into mechanical energy. In the working process, the combustion chamber, turbine structure and other components work in a harsh environment of high temperature and high speed, and the maximum working temperature can reach about 1000℃. Due to the harsh working conditions, the service life of these high-temperature components is much shorter than that of the cold end components. The endurance service life of the gas turbine high-temperature components is a key indicator for the overall life assessment of the gas turbine. At present, the durability and endurance life assessment process of the gas turbine is to determine the overhaul period time interval and the overall endurance service life of the marine gas turbine by using the endurance service life of the high-temperature components.

[0003] The marine gas turbine engine is usually used for ship power devices and ship internal power generation devices. The marine gas turbine has the characteristics of few operating conditions, long maintenance interval and long service life. Compared with the aero-engine, the service life of the aero-engine is several thousand hours, while the service life of the marine gas turbine engine is more than 100,000 hours. Therefore, the endurance service life assessment of the marine gas turbine requires more material strength parameter data, and the calculation workload and difficulty of the assessment are higher.

[0004] The traditional endurance life calculation and assessment process of the gas turbine high-temperature components is as follows: the stress distribution of the components under the working conditions is calculated, the most dangerous stress area is found, and the endurance life margin of the components is assessed according to the stress value of the dangerous area. The accuracy of the assessment using this method is related to the engineering experience of the user. Because the judgment process of the dangerous area is complex. First, the structure of the turbine high-temperature component is very complex, such as the high-pressure turbine blade, the low-pressure turbine blade, the high-pressure turbine guide vane and the low-pressure turbine guide vane, and the internal design of the component has an air cooling channel. Second, the temperature and stress distribution of each part of the high-temperature component are not the same. The part with the largest stress may not have the highest temperature, and the part with the highest temperature may not have the largest stress. Therefore, it is necessary to determine several dangerous areas according to experience and calculate the endurance life margin. Finally, the part with the lowest endurance life margin is the dangerous area. The accuracy of the whole life assessment depends not only on the engineering experience of the calculator, but also on the complex and tedious calculation process. Therefore, a calculation method is needed to accurately assess the endurance life margin of each part of the high-temperature component to ensure the comprehensiveness and accuracy of the endurance life calculation and assessment of the gas turbine high-temperature component. Therefore, it is necessary to study a kind of endurance life calculation method of the marine gas turbine high-temperature component. This has important engineering value for the in-depth development of the research and development of the new type of marine gas turbine. SUMMARY

[0005] The application aims to provide a marine engine turbine high-temperature component endurance life calculation and evaluation method which improves comprehensiveness, accuracy and efficiency.

[0006] The application is achieved as follows:

[0007] The application is characterized in that:

[0008] (1) The three-dimensional geometric model of the evaluated marine engine high-temperature component is simplified, and a finite element calculation grid is divided;

[0009] (2) The elastic modulus, linear expansion coefficient, thermal conductivity coefficient and material stress-plastic strain curve under different temperature conditions are applied to the high-temperature component calculation model.

[0010] (3) The temperature and aerodynamic external force load are applied to the component calculation model, and the displacement constraint condition is applied: the flow field calculation of the high-temperature component is performed, the temperature value and local aerodynamic pressure data of the high-temperature component model node are calculated, the temperature and aerodynamic pressure data of the model node obtained by the flow field calculation are calculated by difference and applied to the corresponding node of the static strength calculation model, other external force loads are applied to the calculation model, including centrifugal force and torque, the displacement constraint is applied to the calculation model, and the cyclic symmetry boundary constraint is applied to the cyclically symmetric model, and the contact constraint is applied to the contact part;

[0011] (4) The static strength calculation of the high-temperature component model is completed by using the finite element calculation software;

[0012] (5) The static strength stress and strain calculation values of each node in the high-temperature component model are read by using the secondary development post-processing program;

[0013] (6) The high-temperature endurance life margin value of the component is calculated by using the material L-M endurance strength curve, and the calculation formula is:

[0014] P=f(σ)=T A (logt+C)

[0015] Wherein, P is a calculation parameter, σ is stress, T A is a test temperature, t is a test time, and C is a constant;

[0016] (7) The high-temperature endurance life margin value color cloud of the component is displayed: the life margin value of each node of the component model calculated in step (6) is written into the finite element static strength calculation result file; the static strength result file containing the node life margin value is read into the calculation software post-processing platform; and the high-temperature component endurance life margin cloud of the component is displayed by using the post-processing platform.

[0017] The application can also include:

[0018] 1、 Step (2) is specifically:

[0019] The stress-strain curve of the material in the range of 20-950°C is measured by mechanical experiment; the elastic modulus data at different temperatures is calculated by using the stress-strain data at different temperatures; the stress-strain curve experimental data in the range of 20-950°C is converted into real stress-strain data for calculation, and then the stress-plastic strain data at the corresponding temperature is converted; the following formulas are used for material data processing and conversion, wherein the formula ε true = ln (1 + ε nom ), σ true = σ nom (1 + ε nom ) is used for converting the experimental data of the material into real data for calculation, and the formula is used for converting the plastic strain data for calculation,

[0020] Wherein: ε true and σ true are real strain and real stress, ε nom and σ nom are the strain and stress measured by experiment, ε pl is the elastic strain, and E is the elastic modulus of the material;

[0021] The elastic modulus, stress-plastic strain data at different temperature conditions, and the related data of thermal conductivity and thermal expansion coefficient after processing are set to the material properties of the calculation model.

[0022] 2、 Step (6) is specifically:

[0023] The design service life of the high-temperature component is determined; the endurance limit stress of the high-temperature component material at different temperature conditions for the design life is calculated by using the L-M endurance strength curve of the material; the endurance limit stress data of the high-temperature component material at different temperature conditions is read by using the secondary development software; the endurance limit stress value corresponding to the temperature of each node is calculated according to the temperature value of each node of the calculation model; the endurance life margin value of each node in the calculation model of the high-temperature component is calculated by using the life margin calculation formula, and the life margin calculation formula is:

[0024]

[0025] Wherein: n τ is the high-temperature endurance life margin, is the endurance limit stress of the design life hours under the working temperature condition, is the local maximum stress value under the working temperature condition calculated by the component.

[0026] The advantages of the present application are that the present application can simulate the stress distribution of all parts of the high-temperature components of the marine engine in detail and accurately, quickly and comprehensively calculate the endurance life margin of the high-temperature components, and the calculation results can be displayed in the form of color cloud map, and the endurance life margin of each node in the calculation model can be extracted. This has important engineering application value for the static strength calculation and endurance life evaluation of the long-life high-temperature components of the marine engine turbine. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The flow chart for the stress calculation and high-temperature endurance life evaluation of the high-temperature components of the marine engine of the present application;

[0028] Figure 2 The flow chart of the secondary development program for completing the life evaluation calculation of the high-temperature components;

[0029] Figure 3 The stress-strain curves at different temperatures measured by experiments;

[0030] Figure 4 The life margin cloud map of the high-pressure turbine blade calculated by the present application. DETAILED DESCRIPTION

[0031] The present application will be described in more detail below with examples combined with the drawings:

[0032] Combined Figures 1-4 , the present application takes the calculation of the high-pressure turbine moving blade as the object, and completes the endurance life calculation and evaluation of the high-pressure turbine moving blade. The specific process is realized by the following steps:

[0033] Step 1: Simplify the three-dimensional geometric model of the evaluated high-temperature components of the engine, and divide the finite element calculation grid.

[0034] Step 2: Apply the material properties of the high-temperature components calculation model, such as the density, the elastic modulus under different temperature conditions, the linear expansion coefficient, the thermal conductivity coefficient, and the stress-plastic strain curve of the material under different temperatures. ① First, the stress-strain curve of the material in the range of 20℃-950℃ is measured by mechanical experiment. ② The elastic modulus data at different temperatures are calculated by using the stress-strain data under different temperature conditions. ③ The stress-strain curve experimental data in the range of 20℃-950℃ is converted into real stress-strain data for calculation, and then the stress-plastic strain data at the corresponding temperature is converted. The following formulas are used for the material data processing and conversion. Formulas (1) and (2) are used to convert the material experimental data into real data for calculation. Formula (3) is used to convert the plastic strain data for calculation:

[0035] ε true = ln(1+ε nom ) ⑴

[0036] σtrue = σ nom (1+ε nom ) ⑵

[0037]

[0038] where: ε true and σ true are true strain and true stress, ε nom and σ nom are measured strain and measured stress. ε pl is elastic strain, E is modulus of elasticity of material.④ Set the processed modulus of elasticity, stress-plastic strain data and thermal conductivity, thermal expansion coefficient related data under different temperature conditions to the material properties of the calculation model.

[0039] Step 3: Apply temperature, aerodynamic and other external loads to the component calculation model, and apply displacement constraints.①First, calculate the flow field of the calculation component to obtain the temperature value and local aerodynamic pressure data of the calculation model nodes.②Apply the temperature and aerodynamic pressure data of the model nodes calculated by the flow field calculation to the corresponding nodes of the static strength calculation model by difference calculation.③Apply other external loads to the calculation model, such as centrifugal force, torque, etc.④Apply displacement constraints to the calculation model, and apply cyclic symmetry boundary constraints to the cyclically symmetric model, and apply contact constraints to the contact parts, etc.

[0040] Step 4: Use finite element calculation software to calculate the static strength of the component model.

[0041] Step 5: Use the secondary development post-processing program to read the static strength stress and strain calculation values of each node in the high-temperature component model.

[0042] Step 6: Calculate the high-temperature endurance life margin value of the component using the L-M endurance strength curve of the material, and the calculation formula is:

[0043] P = f (σ) = T A (logt + C) ⑷

[0044] Where: P is the calculation parameter, σ is the stress, T A is the test temperature, t is the test time, and C is a constant (determined by test).

[0045] ①Firstly, determine the design life hours of high-temperature components. ②Using the material L-M endurance strength curve, calculate the endurance limit stress of high-temperature component materials under different temperature conditions for the design life hours. (Endurance limit values of materials at different temperatures in 20℃-950℃ range, with 100℃ interval or 50℃ interval.) ③Read the endurance limit stress data of high-temperature component materials at different temperatures using secondary development software. ④According to the temperature value of each node of the calculation model, calculate the endurance limit stress value corresponding to the temperature of each node by difference. ⑤Calculate the endurance life margin value of each node in the high-temperature component calculation model using the life margin calculation formula, and the life margin calculation formula is:

[0046]

[0047] Where: n τ is the high-temperature endurance life margin, is the endurance limit stress for the design life hours under working temperature conditions, is the local maximum stress value of the component under working temperature conditions.

[0048] Step 7: Display the high-temperature endurance life margin value color cloud map of the component. ①Firstly, write the life margin value of each node of the component model calculated in step 6 into the finite element static strength calculation result file. ②Read the static strength result file containing the node life margin value using the post-processing platform of the calculation software. ③Use the post-processing platform to display the high-temperature component endurance life margin cloud map.

[0049] Step 1: Use three-dimensional solid modeling software UG to establish a three-dimensional geometric model of the calculation component. The geometric model is meshed in the finite element calculation software ABAQUS, and second-order solid elements are selected for meshing. Local mesh is encrypted for holes, chamfers, etc. to establish a component calculation mesh model.

[0050] As described in step 3, the temperature and aerodynamic load data of the component calculation model are calculated using the fluid calculation software CFX. After difference calculation using the finite element calculation software ABAQUS, they are applied to the component calculation model.

[0051] As described in step 6, the calculation process of reading the endurance limit data of the component material under different temperature conditions and calculating the endurance stress value corresponding to each node of the calculation model is completed by using Python language to write secondary development program.

[0052] As described in step 7, the display of the high-temperature endurance life margin value color cloud map of the component is achieved by writing the node high-temperature endurance life margin value into the calculation result file of the finite element calculation software ABAQOS using secondary development program, and displaying the life margin cloud map using the post-processing platform of the software ABAQOS.

Claims

1. A method for evaluating the long-term life of a high-temperature component of a marine gas turbine engine, characterized by: (1) simplifying the three-dimensional geometric model of the evaluated high-temperature component of the gas turbine engine and dividing the finite element calculation grid; (2) applying the density, elastic modulus under different temperature conditions, linear expansion coefficient, thermal conductivity coefficient, and stress-plastic strain curve of the material under different temperatures to the calculation model of the high-temperature component; (3) applying temperature, aerodynamic external force load, and displacement constraint conditions to the component calculation model: performing flow field calculation on the calculated high-temperature component to calculate the temperature value and local aerodynamic pressure data of the model nodes; applying the temperature and aerodynamic pressure data of the model nodes obtained by flow field calculation to the corresponding nodes of the static strength calculation model through difference calculation; applying other external force loads to the calculation model, including centrifugal force and torque; applying displacement constraints to the calculation model, and applying cyclic symmetry boundary constraints to the cyclically symmetric model and contact constraints to the contact parts; (4) using finite element calculation software to complete the static strength calculation of the high-temperature component model; (5) using a secondary development post-processing program to read the static strength stress and strain calculation values of each node in the high-temperature component model; (6) calculating the high-temperature endurance life margin value of the component using the L-M endurance strength curve of the material, with the calculation formula being: P = f(σ) = T A (logt + C) where: P is a calculation parameter, σ is stress, T A is the test temperature, t is the test time, and C is a constant. (7) displaying the high-temperature endurance life margin value color cloud map of the component: writing the life margin value of each node of the component model calculated in step (6) into the static strength calculation result file; reading the static strength result file containing the node life margin value using the post-processing platform of the calculation software; and displaying the high-temperature component endurance life margin cloud map of the component using the post-processing platform.

2. A method for calculating and evaluating the endurance lifetime of a high-temperature component of a marine engine turbine according to claim 1, characterized in that: Step (2) is specifically: The stress-strain curve of the material in the range of 20-950 ℃ is measured by mechanical experiment; the elastic modulus data at different temperatures are calculated by using the stress-strain data at different temperatures; the experimental data of the stress-strain curve in the range of 20-950 ℃ is converted into the real stress-strain data for calculation, and then the stress-plastic strain data at the corresponding temperature is converted; the following formulas are used for the conversion of the material data processing, wherein the formulas ε true = ln(1+ε nom ), σ true = σ nom (1+ε nom ) are used for converting the experimental data of the material into the real data for calculation, and the formula is used for converting the plastic strain data for calculation, where: ε true and σ true are the true strain and true stress, ε nom and σ nom are the experimentally measured strain and experimentally measured stress, ε pl is the elastic strain, and E is the modulus of elasticity of the material. setting the processed elastic modulus, stress-plastic strain data, and thermal conductivity, thermal expansion coefficient-related data under different temperature conditions to the material properties of the calculation model.

3. A method of calculating and evaluating the endurance life of a high-temperature component of a marine engine turbine according to claim 1, characterized in that: Step (6) is specifically: determining the design service life of the high-temperature component in hours; using the L-M endurance strength curve of the material to calculate the endurance limit stress of the high-temperature component material under different temperature conditions for the design life duration; reading the endurance limit stress data of the high-temperature component material under different temperature conditions using the secondary development software; differentially calculating the endurance limit stress value corresponding to the temperature of each node according to the temperature value of each node of the calculation model; calculating the endurance life margin value of each node of the high-temperature component calculation model using the life margin calculation formula, which is: where: n τ is the high temperature endurance life margin, is the endurance limit stress for the design life hours at the operating temperature condition, is the calculated local maximum stress value for the component at the operating temperature condition.

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