Vibration Analysis and Transformation of Hyper Compressor Pipeline for LDPE Plants

2013 ◽  
Author(s):  
W. J. Bai ◽  
Y. Q. Li ◽  
Q. Duan
Keyword(s):  
Finite Element ◽  
Wave Theory ◽  
The Finite Element Method ◽  
Ultra High Pressure ◽  
Process Gas ◽  
Acoustical Analysis ◽  
Compressor Pipe ◽  
Pipeline Vibration ◽  
Element Theory ◽  
Pipe Vibration

Excessive pipe vibration brings a series of serious problems, especially for hyper compressors used by LDPE production. Therefore, the pipeline vibration issues should be handled with care as the process gas reaches pressures up to 350 MPa (50,000 psi). This paper focuses on how to analyze the hyper compressor pipe vibration during operation and maintenance. Taking the outlet pipe vibration of an ultra-high pressure ethylene compressor for example, firstly the vibration level was assessed by the site measurement and signal processing. Then the acoustical analysis was executed based on the plane wave theory and the finite element theory. After that, the modal analysis of pipelines was made with the finite element method. Finally the analyses of all the obtained results made it possible to identify the true reason for pipeline vibration — gas pulsation with large amplitude instead of gas column resonance and structure resonance. Based on the integrated analyses of the results, the retrofit measures were proposed and verified.

On Finite Difference Schemes for Elliptic Equations with Discontinuous Coefficients

2013 ◽  
Vol 13 (3) ◽  
pp. 281-289
Author(s):  
Manfred Dobrowolski
Keyword(s):  
Finite Element ◽  
Finite Difference ◽  
Elliptic Equations ◽  
Approximation Error ◽  
Discontinuous Coefficients ◽  
Difference Schemes ◽  
Finite Difference Schemes ◽  
The Finite Element Method ◽  
Order Four ◽  
Element Theory

Abstract. We study the convergence of finite difference schemes for approximating elliptic equations of second order with discontinuous coefficients. Two of these finite difference schemes arise from the discretization by the finite element method using bilinear shape functions. We prove an convergence for the gradient, if the solution is locally in H3. Thus, in contrast to the first order convergence for the gradient obtained by the finite element theory we show that the gradient is superclose. From the Bramble–Hilbert Lemma we derive a higher order compact (HOC) difference scheme that gives an approximation error of order four for the gradient. A numerical example is given.

Dynamic Analysis of Axially Non-Uniform Thin Cylindrical Shells

1972 ◽  
Vol 14 (1) ◽  
pp. 49-71 ◽  
Author(s):  
A. A. Lakis ◽  
M. P. Paidoussis
Keyword(s):  
Finite Element ◽  
Cylindrical Shells ◽  
Flexural Vibration ◽  
Convergence Criteria ◽  
The Finite Element Method ◽  
Stiffened Shells ◽  
Hybrid Finite Element ◽  
Stress Resultant ◽  
Nodal Displacements ◽  
Element Theory

Part 1 of this paper presents a new theory for the dynamic and static analysis of axially non-uniform, thin cylindrical shells. It is a hybrid of finite element and classical shell theories: the shell is subdivided into cylindrical finite elements, and the displacements within each (expressed in terms of nodal displacements), i.e., the displacement functions, are obtained using Sanders' equations for thin cylindrical shells in full. Sanders' theory gives zero strains for small rigid-body motions, so that displacement functions based on it satisfy the convergence criteria of the finite-element method. Expressions for the mass, stiffness and stress-resultant matrices are obtained, and the method for constructing the equivalent global matrices is given. This paper is supported by Part 2, where the eigenvalues of a number of shells are calculated and compared with other theories and experiments. In Part 2, the free flexural vibration characteristics of thin cylindrical shells are studied by this new, hybrid finite-element theory, where the displacement functions are determined by solution of the cylindrical thin-shell equations. Uniform shells with simply-supported, clamped and free ends are studied, as well as ring-stiffened shells and shells with thickness discontinuities. The frequencies of vibration are compared with those obtained by other theories and with the experiments of others. Agreement with other theories is good and, in the majority of cases, is even better with the experiments.

Simulation of tuning graphene plasmonic behaviors by ferroelectric domains for self-driven infrared photodetector applications

Nanoscale ◽  
2019 ◽  
Vol 11 (43) ◽  
pp. 20868-20875 ◽  
Author(s):  
Junxiong Guo ◽  
Yu Liu ◽  
Yuan Lin ◽  
Yu Tian ◽  
Jinxing Zhang ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Interfacial Effect ◽  
Infrared Photodetector ◽  
The Finite Element Method ◽  
Ferroelectric Domains ◽  
Element Method

We propose a graphene plasmonic infrared photodetector tuned by ferroelectric domains and investigate the interfacial effect using the finite element method.

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