scholarly journals A Comprehensive Thermal and Structural Transient Analysis of a Boiler’s Steam Outlet Header by Means of a Dedicated Algorithm and FEM Simulation

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 111 ◽  
Author(s):  
Marcin Pilarczyk ◽  
Bohdan Węglowski ◽  
Lars O. Nord
Keyword(s):  
Finite Element ◽  
Power Unit ◽  
Thermal Power ◽  
High Capacity ◽  
Fem Simulation ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Element Analysis ◽  
Start Up

Increasing the share of renewables in energy markets influences the daily operation of thermal power units. High capacity power units are more frequently operated to balance power grids and, thus, steam boilers are exposed to unfavorable transient states. The aim of this work was to perform thermal and structural analyses of a boiler’s outlet steam header, with a capacity of 650∙103 kg/h (180 kg/s) of live steam. Based on the measured steam pressure and temperatures on the outer surface of the component, transient temperature fields were determined by means of an algorithm that allows determination of transient stress distributions on the internal and external surfaces, as well as at stress concentration regions. In parallel, a finite element method simulation was performed. A comparison of the obtained results to a finite element analysis showed satisfactory agreement. The analyses showed that the start-up time could be reduced because the total stress did not exceed the allowed values during the regular start-up of the analyzed power unit. The algorithm was efficient and easy to implement in the real control systems of the power units. The numerical approach employed in the presented algorithm also allowed for determination of the time- and place-dependent heating rate value, which can be used as input data for the control system of the power unit.

Finite Element Analysis on Directional Solidification of Al-Ni-Co Alloys

2012 ◽  
Vol 472-475 ◽  
pp. 494-498
Author(s):  
Shi Long Tian ◽  
Zhi Li Yang
Keyword(s):  
Finite Element ◽  
Temperature Gradient ◽  
Directional Solidification ◽  
Molten Steel ◽  
Solidification Front ◽  
Solidification Rate ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Element Analysis ◽  
Co Alloys

Transient temperature fields of directional solidification of Al-Ni-Co alloys were studied by employing finite element method. Temperature gradient at solidification front and solidification rate was analyzed under different pouring temperature of molten steel. The results show that with different initial pouring temperatures of molten steel, individual ratio of temperature gradient at solidification front to solidification rate soars up in the initial stage of solidification, then varies within 2000-6000°C•s•cm-2, and finally plunges down and goes together when the solidification thickness reaches 5-6cm. Simulation result is consistent with the production reality. Numerical simulation results can provide an available reference for process optimization of directional solidification of Al-Ni-Co alloys.

Influence of Welding Conditions on Residual Stresses of Multi-Pass Tube Sheet Welds

2012 ◽  
Vol 525-526 ◽  
pp. 349-352
Author(s):  
Hong Li ◽  
Yong Zheng ◽  
Li Li
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Tube Sheet ◽  
Element Analysis ◽  
Time Dynamic ◽  
Welding Sequence ◽  
Welding Line

Residual stresses and residual plastic strains of the welded structures are the products of nonlinear behaviors during welding. The residual stresses will cause errors during the assembly of the structure and injure the beauty of appearance of the structure. Based on an elastic-plastic-model, finite element numerical simulation of a representative tube sheet penetration assembly with loop welding line joined by multi-pass welding is carried out and the influence of welding conditions on residual stresses of the tube sheet welds is studied in this paper. Nonlinear three dimensional transient temperature fields and real-time dynamic stresses field are analyzed by FEM. The heat source is modeled as a moving heat flux following a double ellipsoid distribution and the temperature-dependent properties of materials are considered. The method of birth and death of element in finite element analysis is applied to simulate the gradual growth of weld pass metal. It is shown that welding sequence, size of groove welding and weld toes dressing will obviously change the magnitude of the residual stresses of tube sheet welds.

Determination of collapse moment of different angled pipe bends with initial geometric imperfection subjected to in-plane bending moments

2021 ◽  
pp. 095440622199640
Author(s):  
Manish Kumar ◽  
Pronab Roy ◽  
Kallol Khan
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Circular Cross Section ◽  
Initial Imperfection ◽  
Bend Angle ◽  
Bending Moments ◽  
Element Analysis ◽  
Geometric Imperfection ◽  
Initial Geometric Imperfection

From the recent literature, it is revealed that pipe bend geometry deviates from the circular cross-section due to pipe bending process for any bend angle, and this deviation in the cross-section is defined as the initial geometric imperfection. This paper focuses on the determination of collapse moment of different angled pipe bends incorporated with initial geometric imperfection subjected to in-plane closing and opening bending moments. The three-dimensional finite element analysis is accounted for geometric as well as material nonlinearities. Python scripting is implemented for modeling the pipe bends with initial geometry imperfection. The twice-elastic-slope method is adopted to determine the collapse moments. From the results, it is observed that initial imperfection has significant impact on the collapse moment of pipe bends. It can be concluded that the effect of initial imperfection decreases with the decrease in bend angle from 150∘ to 45∘. Based on the finite element results, a simple collapse moment equation is proposed to predict the collapse moment for more accurate cross-section of the different angled pipe bends.

Determination of Stress Concentration Around an Oblique Hole by a Finite-Element Technique

1983 ◽  
Vol 105 (2) ◽  
pp. 206-212 ◽  
Author(s):  
Hua-Ping Li ◽  
F. Ellyin
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Maximum Stress ◽  
Plate Thickness ◽  
Two Dimensional ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Parametric Studies ◽  
Element Technique

A plate weakened by an oblique penetration of a circular cylindrical hole has been investigated. The stress concentration around the hole is determined by a finite-element method. The results are compared with experimental data and other analytical works. Parametric studies of effects of angle of inclination, plate thickness, and width are performed. The maximum stress concentration factor (SCF) obtained from the finite-element analysis is higher than experimental results, and this deviation increases with the increase of angle of skewness. The major reason for this difference is attributed to the shear-action between layers parallel to the plate surface which cannot be directly included in the two-dimensional elements. An empirical formula is derived which accounts for the shear-action and renders the finite-element predictions in line with experimentally observed data.

scholarly journals Determination of the striking distance of a lightning rod using finite element analysis

2016 ◽  
Vol 24 ◽  
pp. 4083-4097 ◽  
Author(s):  
Ab Halim ABU BAKAR ◽  
Alyaa ZAINAL ABIDIN ◽  
Hazlee Azil ILLIAS ◽  
Hazlie MOKHLIS ◽  
Syahirah ABD HALIM ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Element Analysis

Simulation of Nine-Spacer Nozzle’s Flow Field of Al Roll-Casting Using Coupled Fluid-Thermal Finite Element Analysis

2010 ◽  
Vol 159 ◽  
pp. 697-702
Author(s):  
Ying Zhou ◽  
Ya Xi Tan
Keyword(s):  
Thermal Analysis ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Flow Field ◽  
Three Dimensional ◽  
Fem Simulation ◽  
Cooling Capacity ◽  
Element Analysis ◽  
Roll Casting ◽  
Element Simulation

A three-dimensional coupled fluid-thermal finite element simulation model has been developed to provide analyzing distribution of velocity and temperature of nine-spacer nozzle by using FEM simulation of FLOTRAN module in ANSYS 6.0. To explore fluid-thermal analysis of the flow fields of nine-spacer nozzle of aluminum roll-casting, stricter analysis of postprocessing result was conducted by MATLAB. It was concluded that flow field of nine-spacer nozzle was able to match cooling capacity of cast rollers, but nine-spacer nozzle’s geometric flaw didn’t suit for working in the case of speed increasing of the drawing-sheet and thickness reducing of the aluminium sheet during roll casting.

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