A numerical model on stress assessment of a defective elliptic gathering tubeused in the heat recovery boiler of a pyrolyzer is built up. The effect of local defects on thecarrying capacity of the tube is analyzed by ...A numerical model on stress assessment of a defective elliptic gathering tubeused in the heat recovery boiler of a pyrolyzer is built up. The effect of local defects on thecarrying capacity of the tube is analyzed by using the MSC/NASTRAN finite element code, and thecritical size of defects is obtained. Then, two numerical models of damaged tube with local andintegral reinforcements, respectively, are also calculated. Stress classification and assessmentsare provided by applying the ASME and JB4732-1995 standard. Some guidance and suggestions about thetube reinforcements and the prediction of the remaining life of the structure for engineeringpractice are discussed.展开更多
The aim of this paper is the formulation of the finite element method in polar coordinates to solve transient heat conduction problems. It is hard to find in the literature a formulation of the finite element method(F...The aim of this paper is the formulation of the finite element method in polar coordinates to solve transient heat conduction problems. It is hard to find in the literature a formulation of the finite element method(FEM) in polar or cylindrical coordinates for the solution of heat transfer problems. This document shows how to apply the most often used boundary conditions. The global equation system is solved by the Crank-Nicolson method. The proposed algorithm is verified in three numerical tests. In the first example, the obtained transient temperature distribution is compared with the temperature obtained from the presented analytical solution. In the second numerical example, the variable boundary condition is assumed. In the last numerical example the component with the shape different than cylindrical is used. All examples show that the introduction of the polar coordinate system gives better results than in the Cartesian coordinate system. The finite element method formulation in polar coordinates is valuable since it provides a higher accuracy of the calculations without compacting the mesh in cylindrical or similar to tubular components. The proposed method can be applied for circular elements such as boiler drums, outlet headers, flux tubes. This algorithm can be useful during the solution of inverse problems, which do not allow for high density grid. This method can calculate the temperature distribution in the bodies of different properties in the circumferential and the radial direction. The presented algorithm can be developed for other coordinate systems. The examples demonstrate a good accuracy and stability of the proposed method.展开更多
基金Foundation of Yangzi Petro-chemical Ltd. and Chinese Academy of Science (No. KJ95-1-201).
文摘A numerical model on stress assessment of a defective elliptic gathering tubeused in the heat recovery boiler of a pyrolyzer is built up. The effect of local defects on thecarrying capacity of the tube is analyzed by using the MSC/NASTRAN finite element code, and thecritical size of defects is obtained. Then, two numerical models of damaged tube with local andintegral reinforcements, respectively, are also calculated. Stress classification and assessmentsare provided by applying the ASME and JB4732-1995 standard. Some guidance and suggestions about thetube reinforcements and the prediction of the remaining life of the structure for engineeringpractice are discussed.
文摘The aim of this paper is the formulation of the finite element method in polar coordinates to solve transient heat conduction problems. It is hard to find in the literature a formulation of the finite element method(FEM) in polar or cylindrical coordinates for the solution of heat transfer problems. This document shows how to apply the most often used boundary conditions. The global equation system is solved by the Crank-Nicolson method. The proposed algorithm is verified in three numerical tests. In the first example, the obtained transient temperature distribution is compared with the temperature obtained from the presented analytical solution. In the second numerical example, the variable boundary condition is assumed. In the last numerical example the component with the shape different than cylindrical is used. All examples show that the introduction of the polar coordinate system gives better results than in the Cartesian coordinate system. The finite element method formulation in polar coordinates is valuable since it provides a higher accuracy of the calculations without compacting the mesh in cylindrical or similar to tubular components. The proposed method can be applied for circular elements such as boiler drums, outlet headers, flux tubes. This algorithm can be useful during the solution of inverse problems, which do not allow for high density grid. This method can calculate the temperature distribution in the bodies of different properties in the circumferential and the radial direction. The presented algorithm can be developed for other coordinate systems. The examples demonstrate a good accuracy and stability of the proposed method.
