Low-Order Acoustic Modelling for Annular Combustors: Validation and Inclusion of Modal Coupling

2002 ◽  
Author(s):  
Ste´phanie Evesque ◽  
Wolfgang Polifke
Keyword(s):  
Passive Control ◽  
Three Dimensional ◽  
Nonlinear Effects ◽  
Order Model ◽  
Modal Coupling ◽  
Annular Combustor ◽  
Dimensional Finite Element ◽  
The Stability ◽  
Three Dimensional Finite Element ◽  
Low Order

A two-dimensional low-order model of a generic annular premixed combustor, comprising an annular combustion chamber connected to an annular plenum via a finite number of burners, is developed and validated. The shapes and frequencies of the eigenmodes as well as the stability of the combustor against self-excited oscillations can be predicted with such a model. The dynamical characteristics of each burner is described mathematically in terms of its transfer matrix. The case where the transfer matrices of individual burners differ from each other can be handled by the model formulation presented. This is important in situations where non-identical burners are used in an annular combustor as a means of passive control, or where nonlinear effects lead to non-identical burner behaviour. The resulting loss of axisymmetry enhances the coupling between nonplane acoustic modes of different order. This modal coupling is accounted for by the model. The eigenmode shapes and frequencies predicted by the low-order model are validated by comparison with the results of a three-dimensional finite element acoustic model of a generic annular combustor configuration.

Structural Stability Evaluation for Lifting Lug Design of Large Marine Engine by Finite Element Analysis

2007 ◽  
Vol 353-358 ◽  
pp. 2855-2859
Author(s):  
W.C. Lee ◽  
Chae Sil Kim ◽  
J.B. Na ◽  
D.H. Lee ◽  
S.Y. Cho ◽  
...  
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Design Procedure ◽  
Steel Structures ◽  
Stability Evaluation ◽  
Element Analysis ◽  
Marine Engines ◽  
Dimensional Finite Element ◽  
The Stability ◽  
Three Dimensional Finite Element

Since most marine engines are generally very huge and heavy, it is required to keep safety from accidents in dealing them. Several types of lifting lugs have been used to assemble hundred ton–large steel structures and carry the assembled engines. Recently a few crashes have been occurred in carrying engines due to breaking down the lugs. Although the stability evaluation of the lifting lug has therefore been very important for safety, systematic design procedure of the lugs, which includes the structural analysis considering stability, has few reported. This paper describes the three dimensional finite element structural modeling for a lifting lug, the studies for determining the reasonable loading and boundary conditions, and the stability evaluation with the results of structural analyses. It should be very helpful for designing the other types of lifting lugs with safety.

Prediction of the Thermoacoustic Combustion Instabilities in Practical Annular Combustors

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Giovanni Campa ◽  
Sergio Mario Camporeale
Keyword(s):  
Combustion Chamber ◽  
Three Dimensional ◽  
Design Stage ◽  
Combustion Instabilities ◽  
Combustion Chambers ◽  
Stability Maps ◽  
Dimensional Finite Element ◽  
Practical Tool ◽  
The Stability ◽  
Three Dimensional Finite Element

A three-dimensional finite element code is used for the eigenvalue analysis of the thermoacoustic combustion instabilities modeled through the Helmholtz equation. A full annular combustion chamber, equipped with several burners, is examined. Spatial distributions for the heat release intensity and for the time delay are used for the linear flame model. Burners, connecting the plenum and the chamber, are modeled by means of the transfer matrix method. The influence of the parameters characterizing the burners and the flame on the stability levels of each mode of the system is investigated. The obtained results show the influence of the 3D distribution of the flame on the modes. Additionally, the results show what types of modes are most likely to yield humming in an annular combustion chamber. The proposed methodology is intended to be a practical tool for the interpretation of the thermoacoustic phenomenon (in terms of modes, frequencies, and stability maps) both in the design stage and in the check stage of gas turbine combustion chambers.

Assessment of Free Standing Body in Dry and Submerged Condition and Under Seismic Loading

2019 ◽  
Author(s):  
Beniamino Rovagnati ◽  
Phuong H. Hoang
Keyword(s):  
Three Dimensional ◽  
Nuclear Industry ◽  
Spent Fuel ◽  
Free Standing ◽  
Transient Model ◽  
Dimensional Finite Element ◽  
Rocking Motion ◽  
Free Body ◽  
The Stability ◽  
Three Dimensional Finite Element

Abstract A free standing, slender body may experience rocking motion followed by overturning when it is subject to strong seismic motions. When the free body is submerged in water, it will also be subject to lateral forces acting along the side of the free body as a result of water sloshing. This highly non-linear situation is of particular interest to engineers in the nuclear industry in need to assess the stability of transfer casks containing spent fuel and submerged in a confined pit or pool. In this work, a three-dimensional finite element dynamic transient model of a free standing cask is developed and analyzed using ANSYS. Both dry and submerged conditions are considered. Cask to floor friction, buoyancy force, and sloshing are accounted for in the assessment. The model is validated against well-accepted contributions on sloshing and rocking provided by G.W. Housner.

A Method for Reducing the Order of Nonlinear Dynamic Systems

1984 ◽  
Vol 51 (2) ◽  
pp. 391-398 ◽  
Author(s):  
S. F. Masri ◽  
R. K. Miller ◽  
H. Sassi ◽  
T. K. Caughey
Keyword(s):  
Dynamic Systems ◽  
Three Dimensional ◽  
Element Model ◽  
Random Excitation ◽  
Reduced Order Model ◽  
Order Model ◽  
Reduced Order ◽  
Dimensional Finite Element ◽  
Restoring Forces ◽  
Three Dimensional Finite Element

An approximate method that uses conventional condensation techniques for linear systems together with the nonparametric identification of the reduced-order model generalized nonlinear restoring forces is presented for reducing the order of discrete multidegree-of-freedom dynamic systems that possess arbitrary nonlinear characteristics. The utility of the proposed method is demonstrated by considering a redundant three-dimensional finite-element model half of whose elements incorporate hysteretic properties. A nonlinear reduced-order model, of one-third the order of the original model, is developed on the basis of wideband stationary random excitation and the validity of the reduced-order model is subsequently demonstrated by its ability to predict with adequate accuracy the transient response of the original nonlinear model under a different nonstationary random excitation.

Stability of Vertically Bent Pipelines Buried in Sand

2004 ◽  
Vol 126 (3) ◽  
pp. 382-390 ◽  
Author(s):  
Sahel N. Abduljauwad ◽  
Hamdan N. Al-Ghamedy ◽  
Junaid A. Siddiqui ◽  
Ibrahim M. Asi ◽  
Naser A. Al-Shayea
Keyword(s):  
Internal Pressure ◽  
Three Dimensional ◽  
Computer Software ◽  
Specific Weight ◽  
Bend Angle ◽  
Element Analysis ◽  
Minimum Cover ◽  
Dimensional Finite Element ◽  
The Stability ◽  
Three Dimensional Finite Element

This paper discusses the stability of underground pipelines with preformed vertical bends buried in sandy soil. More specifically, the minimum cover height required to prevent the pipe from bowing under the action of forces due to temperature change and internal pressure is estimated. The variables considered include the pipe and soil materials, diameter, thickness, overburden height, bend radius, bend angle, internal pressure, fluid specific weight, and temperature variation. A comprehensive three-dimensional finite element analysis is carried out. The results are extracted from the output obtained. These results are put in a database which is used to develop general regression models to determine the relationships among the different variables. Different buckling modes are also considered. All of these results and models are entered into a computer software program for ready access.

A Three-Dimensional Finite Element Method for Large Elastic Deformations of Ventricular Myocardium: II—Prolate Spheroidal Coordinates

1996 ◽  
Vol 118 (4) ◽  
pp. 464-472 ◽  
Author(s):  
K. D. Costa ◽  
P. J. Hunter ◽  
J. S. Wayne ◽  
L. K. Waldman ◽  
J. M. Guccione ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Three Dimensional ◽  
Solution Time ◽  
Order Model ◽  
Prolate Spheroidal ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Prolate Spheroidal Coordinates ◽  
Spheroidal Coordinates

A three-dimensional finite element method for nonlinear finite elasticity is presented using prolate spheroidal coordinates. For a thick-walled ellipsoidal model of passive anisotropic left ventricle, a high-order (cubic Hermite) mesh with 3 elements gave accurate continuous stresses and strains, with a 69 percent savings in degrees of freedom (dof) versus a 70-element standard low-order model. A custom mixed-order model offered 55 percent savings in dof and 39 percent savings in solution time compared with the low-order model. A nonsymmetric 3D model of the passive canine LV was solved using 16 high-order elements. Continuous nonhomogeneous stresses and strains were obtained within 1 hour on a laboratory workstation, with an estimated solution time of less than 4 hours to model end-systole. This method represents the first practical opportunity to solve large-scale anatomically detailed models for cardiac stress analysis.

Closure of a Nuclear Waste Repository Deeply Imbedded in a Stratified Salt Bed

1994 ◽  
Vol 116 (4) ◽  
pp. 567-573 ◽  
Author(s):  
Wei Xu ◽  
Joseph Genin
Keyword(s):  
Triaxial Compression ◽  
Three Dimensional ◽  
Element Model ◽  
Nuclear Waste Repository ◽  
Relaxation Functions ◽  
Dimensional Finite Element ◽  
Set Up ◽  
The Stability ◽  
Three Dimensional Finite Element

The Waste Isolation Pilot Plant (WIPP) is a repository vault, mined deep into a salt strata. It eventually closes in on itself, encapsulating its contents. At room temperature salt may be regarded as a linear, isotropic, viscoelastic material. In this study, using triaxial compression test results on salt, we determine the relaxation functions and set up the boundary value problem for the encapsulation mechanism of a salt vault. Closure of the repository as a function of time is determined using a three-dimensional finite element model. The Tresca failure criterion is used to predict the stability of the repository. Finally, the study is validated by comparing our results to in-situ measured data.

scholarly journals Stability Analysis of High-Pile and high-pier Considering Initial Pier Deviation

2021 ◽  
Vol 261 ◽  
pp. 02050
Author(s):  
Mei-Liang Zhu ◽  
Li-Qing Zhang ◽  
Ye Ma ◽  
Shun-Kun Jiang
Keyword(s):  
Three Dimensional ◽  
Horizontal Displacement ◽  
Nonlinear Buckling ◽  
Buckling Loads ◽  
Dimensional Finite Element ◽  
Calculation Results ◽  
High Pier ◽  
The Stability ◽  
Three Dimensional Finite Element ◽  
Better Than

Based on the high-pile and high-pier bridge of Qianhuang Expressway, eigenvalue buckling analysis is carried out by establishing three-dimensional finite element models of three different bridge types and high-pier types, and the corresponding structural nonlinear buckling loads under different initial pier deviations are calculated. The calculation results show that the nonlinear buckling loads of three high-pier types are less than elastic buckling loads. The stability of column high-pile and high-pier of continuous bridge is better than that of simple supported bridge, and the stability of plate high-pier is better than that of other two high-piers. In addition, the corresponding buckling load decreases with the increase of the initial horizontal displacement, indicating that the pier top offset of the high-pile and high-pier bridge is not conducive to the stability of the structure.

Buckling Analysis of Pile during Hammer Placement

2012 ◽  
Vol 256-259 ◽  
pp. 467-470
Author(s):  
Shao Zeng Guo ◽  
Run Liu
Keyword(s):  
Finite Element ◽  
Geometric Nonlinearity ◽  
Large Diameter ◽  
Three Dimensional ◽  
Element Model ◽  
Offshore Engineering ◽  
Dimensional Finite Element ◽  
The Stability ◽  
Three Dimensional Finite Element

Large diameter and thin thickness are the main characteristics of the steel pipe piles in offshore engineering. Before piling a pile, heavy hammer will be placed on the top of it, which may emerge a serious risk in pile buckling. A three dimensional finite element model of pile and soil was established for a case study. The modified Riks method which can automatically search a suitable increment factor of loads is adopted to assess the stability of the pile, and the geometric nonlinearity and pile-soil interaction were both considered. The practical example shows that the critical load considering pile-soil interaction is much smaller than that in a fixed constraint.

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