Double Overhung Disk and Parameter Effect on Rotordynamic Synchronous Instability—Morton Effect—Part II: Occurrence and Prevention

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Xiaomeng Tong ◽  
Alan Palazzolo
Keyword(s):  
Transient Analysis ◽  
Operating Parameters ◽  
Flow Ratio ◽  
The Finite Element Method ◽  
Oil Viscosity ◽  
Testing Conditions ◽  
Bending Mode ◽  
Morton Effect ◽  
Nonlinear Transient ◽  
Parametric Studies

This paper performs the parametric studies corresponding with the theoretical Morton effect (ME) model explained in Part I of this paper, where the fully nonlinear transient analysis based on the finite element method is introduced. Operating parameters, such as oil supply temperature, bearing clearance, oil viscosity, etc., are perturbed from the testing conditions to investigate the shifting of critical speeds and ME instability onset speed (IOS). The ME is significantly affected by the rotor bending mode with large overhung deflections, and operating parameters should be adjusted to increase the separation margin between the operating speed and the corresponding critical speed for ME mitigation. Reducing the carryover flow ratio and using the asymmetric bearing pivot offset are capable to suppress the ME by reducing both the average and differential journal temperature. The heat barrier sleeve with air or ceramic isolation is designed to prevent the heat flux into the journal and can successfully mitigate the ME based on the simulations.

Three-Dimensional Thermohydrodynamic Morton Effect Simulation—Part I: Theoretical Model

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Junho Suh ◽  
Alan Palazzolo
Keyword(s):  
Heat Flux ◽  
Theoretical Model ◽  
Transient Analysis ◽  
Three Dimensional ◽  
Fluid Film ◽  
Integration Scheme ◽  
Morton Effect ◽  
Rotor Bearing ◽  
Nonlinear Transient ◽  
Bearing System

The present study is focused on accurate prediction of the Morton effect problem including journal asymmetric heating and the corresponding long period amplitude oscillations using a nonlinear time transient rotor-dynamic simulation. This paper presents a theoretical model of thermal induced synchronous instability problems in a nonlinear rotor–bearing system, and suggests a new computational algorithm for the nonlinear transient analysis of the Morton effect where the dynamic and thermal problems are combined. For the analysis of the Morton effect problem, a variable viscosity Reynolds equation and a 3D energy equation are coupled via temperature and viscosity, and solved simultaneously. Three-dimensional heat transfer equations of bearing and shaft are modeled by a finite element method, and thermally coupled with the fluid film via a heat flux boundary condition. Asymmetric heat flux into the synchronously whirling rotor is solved by the orbit time averaged heat flux from fluid film to the spinning shaft surface. The journal orbit is calculated by the nonlinear transient dynamic analysis of a rotor–bearing system with a variable time step numerical integration scheme. For the computation time reduction, modal coordinate transformation is adopted in dynamic and thermal transient analysis. Thermal bow effect makes a significant change to the dynamic behavior of a rotor–bearing system, and a thermal hysteresis bode plot, that is one of the characteristics of the Morton effect problem, is presented with time varying spin speed.

scholarly journals Dynamic Analysis of Honeycomb Sandwich Beam with Multiple Debonds

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
B. Saraswathy ◽  
R. Ramesh Kumar ◽  
Lalu Mangal
Keyword(s):  
Analytical Solution ◽  
Transient Analysis ◽  
Sandwich Beam ◽  
Beam Theory ◽  
Beam Length ◽  
Honeycomb Core ◽  
Element Analysis ◽  
Fast Fourier Transform Analysis ◽  
Honeycomb Sandwich ◽  
Nonlinear Transient

Analytical formulation for the evaluation of frequency of CFRP sandwich beam with debond, following the split beam theory, generally underestimates the stiffness, as the contact between the honeycomb core and the skin during vibration is not considered in the region of debond. The validation of the present analytical solution for multiple-debond size is established through 3D finite element analysis, wherein geometry of honeycomb core is modeled as it is, with contact element introduced in the debond region. Nonlinear transient analysis is followed by fast Fourier transform analysis to obtain the frequency response functions. Frequencies are obtained for two types of model having single debond and double debond, at different spacing between them, with debond size up to 40% of beam length. The analytical solution is validated for a debond length of 15% of the beam length, and with the presence of two debonds of same size, the reduction in frequency with respect to that of an intact beam is the same as that of a single-debond case, when the debonds are well separated by three times the size of debond. It is also observed that a single long debond can result in significant reduction in the frequencies of the beam than multiple debond of comparable length.

Coupled Electromagnetic-Thermal Field Investigation in Induction Heating Device

2009 ◽  
Vol 152-153 ◽  
pp. 407-410
Author(s):  
Ilona Ilieva Iatcheva ◽  
Rumena Stancheva ◽  
Hristofor Tahrilov ◽  
Ilonka Lilianova
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Induction Heating ◽  
Heating System ◽  
Field Investigation ◽  
Field Analysis ◽  
The Finite Element Method ◽  
Nonlinear Transient ◽  
Induction Heating System ◽  
Element Method

The aim of the work is precise coupled –electromagnetic and temperature field analysis of an induction heating system by finite element method. Presented example is referred to real induction heating system. The problem was solved as nonlinear, transient and axisymmetrical. The numerical model of the coupled fields is based on the finite element method and electromagnetic and temperature distributions have been obtained using COMSOL 3.3 software package.

Nonlinear Transient Analysis of Aircraft Landing Gear Brake Whirl and Squeal

1995 ◽  
Author(s):  
Matt H. Travis
Keyword(s):  
Finite Element ◽  
Transient Analysis ◽  
Landing Gear ◽  
Friction Modeling ◽  
Explicit Integration ◽  
Aircraft Landing ◽  
Aircraft Landing Gear ◽  
Nonlinear Transient ◽  
Element Approach ◽  
Stiffness And Damping

Abstract The feasibility of computing non-linear transient finite element simulations of aircraft landing gear brake whirl and squeal is demonstrated and discussed. Methodology to conduct the high frequency brake transient analysis is developed using an explicit integration finite element approach. Results indicate the approach has the capability to simulate brake dynamic behavior in dynamometer and aircraft landing gear installations — thus enabling evaluation of modifications to braking systems that lead to more stable and robust designs. A simple multi-disk brake model is developed and described. Modeling techniques for including the dynamometer road wheel and runway in the simulations are given. Issues such as piston housing hydraulic fluid stiffness and damping effects, and parametric friction modeling are discussed.

Simulation of Mold Filling for Non-Newtonian Fluids - Part 2

2006 ◽  
Vol 3 (2) ◽  
pp. 52-60
Author(s):  
Venkatesh M. Kulkarni ◽  
Chu Wee Liang ◽  
C.W. Tan ◽  
P.A. Aswatha Narayana ◽  
K.N. Seetharamu
Keyword(s):  
Stokes Equations ◽  
Navier Stokes ◽  
The Finite Element Method ◽  
Molding Process ◽  
Algebraic Form ◽  
Design Guideline ◽  
Navier Stokes Equations ◽  
Transfer Molding ◽  
Encapsulation Process ◽  
Parametric Studies

This paper deals with the flow in the resin transfer molding process commonly used for IC chip encapsulation in the electronic packaging industry. A solution algorithm is presented for modeling the flow of a non-Newtonian fluid obeying a Power-Law model and the algorithm is used to conduct parametric studies in transfer molding. The flow model uses the Hele-Shaw approximation to solve the Navier-Stokes Equations and a pseudo-concentration algorithm for tracking the interface between the resin and the air. The Finite Element Method is employed to reduce the governing partial differential equations to algebraic form. The model is used to study the flow from the transfer ram into the cavity for different dimensions of transfer molding tools. Parametric studies are carried out to obtain balanced filling for transfer molding configuration. Parametric studies could provide a design guideline to optimize the encapsulation process prior to the setting up of an actual manufacturing set.

Comparison Between Linear and Nonlinear Transient Analysis Techniques to Find the Stability of a Rigid Rotor

1999 ◽  
Vol 121 (1) ◽  
pp. 198-201 ◽  
Author(s):  
Ram Turaga ◽  
A. S. Sekhar ◽  
B. C. Majumdar
Keyword(s):  
Transient Analysis ◽  
Stability Limit ◽  
Journal Bearings ◽  
Quantitative Comparison ◽  
Rigid Rotor ◽  
Analysis Techniques ◽  
Analysis Technique ◽  
Nonlinear Transient ◽  
Nonlinear Transient Analysis ◽  
The Stability

The subsynchronous whirl stability limit of a rigid rotor supported on two symmetrical finite journal bearings has been studied using the linearised perturbation method and the nonlinear transient analysis technique. A quantitative comparison for journal bearings with different l/d ratios has been provided.

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