Investigation of Stresses in Coal Gasifier Hearth under Thermal Loading using Finite Element Analysis

2014 ◽  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Loading ◽  
Element Analysis ◽  
Coal Gasifier

Finite Element Analysis of Local Inelastic Strain Based on Stress Redistribution Locus

2008 ◽  
Author(s):  
Shunji Kataoka ◽  
Takuya Sato
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Loading ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
Pressure Vessels ◽  
Stress Redistribution ◽  
Strain Diagram ◽  
Element Analysis ◽  
Inelastic Analysis

Creep-fatigue damage is one of the dominant failure modes for pressure vessels and piping used at elevated temperatures. In the design of these components the inelastic behavior should be estimated accurately. An inelastic finite element analysis is sometimes employed to predict the creep behavior. However, this analysis needs complicated procedures and many data that depend on the material. Therefore the design is often based on a simplified inelastic analysis based on the elastic analysis result, as described in current design codes. A new, simplified method, named, Stress Redistribution Locus (SRL) method, was proposed in order to simplify the analysis procedure and obtain reasonable results. This method utilizes a unique estimation curve in a normalized stress-strain diagram which can be drawn regardless of the magnitude of thermal loading and constitutive equations of the materials. However, the mechanism of SRL has not been fully investigated. This paper presents results of the parametric inelastic finite element analyses performed in order to investigate the mechanism of SRL around a structural discontinuity, like a shell-skirt intersection, subjected to combined secondary bending stress and peak stress. This investigation showed that SRL comprises a redistribution of the peak and secondary stress components and that although these two components exhibit independent redistribution behavior, they are related to each other.

Thermo-Mechanical Stress near Apex of a Bi-Material Wedge by a Novel Finite Element Analysis

2012 ◽  
Vol 525-526 ◽  
pp. 93-96
Author(s):  
Xue Cheng Ping ◽  
Lin Leng ◽  
Si Hai Wu
Keyword(s):  
Finite Element Method ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Finite Elements ◽  
Mechanical Stress ◽  
Displacement Field ◽  
Thermal Loading ◽  
Numerical Solutions ◽  
Asymptotic Solutions ◽  
Element Analysis

A super wedge tip element for application to a bi-material wedge is develop utilizing the thermo-mechanical stress and displacement field solutions in which the singular parts are numerical solutions. Singular stresses near apex of an arbitrary bi-material wedge under mechanical and thermal loading can be obtained from the coupling between the super wedge tip element and conventional finite elements. The validity of this novel finite element method is established through existing asymptotic solutions and conventional detailed finite element analysis.

An Analytical and Finite Element Analysis Study of Multilayered Pressure Vessels Under Thermal Conditions

2005 ◽  
Author(s):  
Soheir A. R. Naga ◽  
M. O. A. Mokhtar
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Wall Thickness ◽  
Thermal Loading ◽  
Thermal Conditions ◽  
Pressure Vessels ◽  
Element Analysis ◽  
Linear Temperature ◽  
Vessel Wall Thickness ◽  
Shell Geometry

The present paper is an endeavor towards assessing the stresses which may be induced in multi-layer pressure vessels subjected to the combined effects of pressure and temperature gradients across the vessel wall thickness. Assuming different geometries of membrane shells; namely cylindrical and spherical shells, a solution based on prescribed model with radial linear temperature distribution has been attained. The solution relates the induced stresses to the shell geometry, layers properties, number of layers, wall thickness and the working conditions of pressure and temperature gradient. In the analysis each layer composing the vessel thickness is treated as a membrane shell of revolution (thin lamina). By the aid of finite element analysis (FEA) technique, different cases of pressure vessels under thermal loading are investigated.

Three-Dimensional Modeling of Creep Damage in Airfoils for Advanced Turbine Systems

2008 ◽  
Author(s):  
Ventzislav G. Karaivanov ◽  
Danny W. Mazzotta ◽  
Minking K. Chyu ◽  
William S. Slaughter ◽  
Mary Anne Alvin
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Gas Turbines ◽  
Damage Mechanics ◽  
Thermal Loading ◽  
Three Dimensional ◽  
Creep Damage ◽  
Creep Model ◽  
Working Fluid ◽  
Element Analysis

Future oxy-fuel and hydrogen-fired turbines promise increased efficiency and low emissions. However, this comes at the expense of increased thermal load from higher inlet temperatures and a change in the working fluid in the gas path, leading to aero-thermal characteristics that are significantly different than those in traditional gas turbines. A computational methodology, based on three-dimensional finite element analysis (FEA) and damage mechanics is presented for predicting the evolution of creep in airfoils in these advanced turbine systems. Information revealed from three-dimensional computational fluid dynamics (CFD) simulations of external heat transfer and thermal loading over a generic airfoil provides detailed local distributions of pressure, surface temperature, and heat flux penetrating through the thermal barrier coated layer. There is an additional mechanical loading due to the centrifugal acceleration of the airfoil. Finite element analysis is then used to predict temperature and stress fields over the domain of the airfoil. The damage mechanics-based creep model uses a scalar damage parameter. This creep model is coupled with finite element analysis to predict the evolution of stress and creep damage over the entire airfoil. Visualization of the creep damage evolution over the airfoil shows the regions that are most susceptible to failure by creep.

A Case Study Evaluating the Effects of High Cycle Thermal Loading Within a Pressurised Water Reactor Mixing Tee Using Conjugate CFD/FE Methods

2016 ◽  
Author(s):  
James Wilson ◽  
Chris Currie ◽  
Michael Jones ◽  
Lewis Davenport
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Loading ◽  
Branch Pipe ◽  
Metal Temperature ◽  
Local Geometry ◽  
Operational Experience ◽  
Element Analysis ◽  
Water Reactor

In nuclear plant piping systems thermal fatigue damage can arise at locations where there is turbulent mixing of different temperature flows. The severity of this phenomenon is difficult to assess via plant instrumentation due to the high frequencies involved. NESC report EUR 22763 EN, published in 2007, defines the “Level 1” screening criterion for the design of austenitic stainless steel mixing tees, based on recorded incidents of fatigue cracking in civil power plants. The experimental data indicates that damage due to High Cycle Thermal Loading (HCTL) is unlikely to occur if the temperature difference between the hot and cold inlet streams is less than 80°C. The “Level 2” approach outlined by NESC provides a methodology for the calculation of a fatigue usage factor based on the assumption of a sinusoidal thermal loading at the most damaging frequency for a given ΔT. Advice is given on selection of heat transfer coefficient, fatigue curves, fatigue strength reduction factors and plasticity correction factors. Experience shows that these methods can be overly pessimistic when compared with plant operational experience. This paper describes a case study using the more detailed NESC “Level 3” evaluation of HCTL at a Pressurised Water Reactor (PWR) mixing tee using a coupled Computational Fluid Dynamics and Finite Element Analysis (CFD/FE) analysis to evaluate the complete load spectra together with the ASME 2010 fatigue S-N curve. The CFD model used is “conjugate”, ie it calculates temperatures in both the fluid and the metal. Large Eddy Simulation (LES) was used to investigate HCTL effects using an appropriate mesh size to accurately predict the rapid fluctuations in metal temperature local to the surface. Metal temperature predictions using conjugate CFD analyses provided the input to finite element analysis, utilising rain-flow techniques, in order to derive fatigue usage factors in the areas of interest. This study found that the severity of HCTL is influenced by various factors such as flow conditions, local geometry including bore match features, integral conical reducers that allow progressive change in pipe radius as well as branch pipe swirl penetration.

Sign in / Sign up

Export Citation Format

Share Document