Component Mode Synthesis of Large Rotor Systems

1982 ◽  
Vol 104 (3) ◽  
pp. 552-560 ◽  
Author(s):  
D. F. Li ◽  
E. J. Gunter
Keyword(s):  
Space Shuttle ◽  
Synthesis Method ◽  
Component Mode Synthesis ◽  
Squeeze Film ◽  
Response Analysis ◽  
Turbine Engine ◽  
Modal Expansion ◽  
Rotor Systems ◽  
Mode Method ◽  
Modal Equation

A scheme is presented for calculating the vibrations of large multi-component flexible rotor systems based on the component mode synthesis method. It is shown that, by a modal expansion of the elastic interconnecting elements, the system modal equation can be conveniently constructed from the undamped eigen representations of the component subsystems. The capability of the component mode method is demonstrated in two examples: a transient simulation of a two-spool gas turbine engine equipped with a squeeze-film damper; and an unbalance response analysis of the Space Shuttle Main Engine oxygen turbopump in which the dynamics of the rotor and the housing are both considered.

Investigation of the Transient Response of a Dual-Rotor System With Intershaft Squeeze Film Damper

1985 ◽  
Author(s):  
Qihan Li ◽  
James F. Hamilton
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Transient Response ◽  
Synthesis Method ◽  
Gas Turbine Engine ◽  
Rotor System ◽  
Squeeze Film ◽  
High Pressure Turbine ◽  
Turbine Engine ◽  
Squeeze Film Damper

A method is presented for calculating the dynamics of a dual-rotor gas turbine engine equipped with a flexible intershaft squeeze-film damper. The method is based on the functional expansion component synthesis method. The transient response of the rotor due to a suddenly applied unbalance in the high-pressure turbine under different steady-speed operations is calculated. The damping effects of the intershaft damper and stability of the rotor system are investigated.

Analytical and Experimental Investigation of the Stability of Intershaft Squeeze Film Dampers—Part 1: Demonstration of Instability

1977 ◽  
Vol 99 (1) ◽  
pp. 47-52 ◽  
Author(s):  
D. H. Hibner ◽  
R. G. Kirk ◽  
D. F. Buono
Keyword(s):  
Analytical Model ◽  
High Speed ◽  
Rotor System ◽  
Dynamics Simulation ◽  
Squeeze Film ◽  
Response Analysis ◽  
Turbine Engine ◽  
Engine Vibration ◽  
Bearing Loads ◽  
The Stability

Modern high-speed multishaft gas tubine engines incorporate viscous damped bearings to decrease overall system vibration and bearing loads. As viscous damper technology is applied to advanced engine design, more sophisticated analytical and experimental techniques are required to prove new concepts. This analysis will present the results of an investigation of the feasibility of damping engine vibration with a viscous damped intershaft bearing on a two-shaft gas turbine engine. Experimental results from a rotor dynamics simulation rig indicate an instability of the rotor system at speeds above a fundamental critical speed. An analytical model of the two-rotor system is presented and the results of both a classical stability analysis and a time transient response analysis verify the experimental data. The analytical model may be used to predict the stability of two-shaft engines which incorporate an intershaft damped bearing.

Vibration Response Analysis on Spindle System of Milling Machine

2015 ◽  
Vol 741 ◽  
pp. 435-440
Author(s):  
Ting Qiang Yao ◽  
Yang Tan ◽  
Ya Yu Huang
Keyword(s):  
Vibration Response ◽  
Response Analysis ◽  
Vibration Test ◽  
Rolling Bearings ◽  
Spindle System ◽  
Rotor Systems ◽  
Multibody Model ◽  
Mode Method ◽  
Fixed Interface ◽  
Spindle Body

The dynamic characteristics and dynamics parameters of rolling bearings is very important to dynamics and vibration response of rotate machine such as rotor systems, gear systems and Spindle systems. The frequencies of rotate machine are affected by dynamics parameters of rolling bearings at different places. The purpose in the work presented is to research a new approach and multibody model of Spindle systems with equivalent dynamics parameters of rolling bearings. The flexible Spindle body has been constructed by the fixed interface component mode method. The four different models of rolling bearings for Spindle systems have been developed using equivalent spring and damper elements. The experiments of Spindle body and Spindle system have been carried out. Experimental modal frequencies have been got by impulse vibration test and sweep frequency vibration test. The frequencies and vibration response of Spindle systems have been calculated by adjusting equivalent spring and damper elements to minimizing errors between the calculated and experiment frequencies. The results show the errors of frequencies of linear equal and unequal spring and damper models are large except the first frequency. However, the errors of nonlinear equal and unequal spring and damper models are small. The predicted frequencies of nonlinear unequal spring and damper model are the most accurate and agree well with the experiment results. The presented method can be applied to calculate the nonlinear equivalent stiffness parameters accurately for rolling bearings in multibody systems.

Investigation of the Transient Response of a Dual-Rotor System With Intershaft Squeeze-Film Damper

1986 ◽  
Vol 108 (4) ◽  
pp. 613-618 ◽  
Author(s):  
Qihan Li ◽  
J. F. Hamilton
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Transient Response ◽  
Synthesis Method ◽  
Gas Turbine Engine ◽  
Rotor System ◽  
Squeeze Film ◽  
High Pressure Turbine ◽  
Turbine Engine ◽  
Squeeze Film Damper

A method is presented for calculating the dynamics of a dual-rotor gas turbine engine equipped with a flexible intershaft squeeze-film damper. The method is based on the functional expansion component synthesis method. The transient response of the rotor due to a suddenly applied imbalance in the high-pressure turbine under different steady-speed operations is calculated. The damping effects of the intershaft damper and stability of the rotor system are investigated.

Component Mode Synthesis of a Vehicle System Model Using the Fictitious Mass Method

2006 ◽  
Vol 129 (1) ◽  
pp. 73-83 ◽  
Author(s):  
M. Karpel ◽  
B. Moulin ◽  
V. Feldgun
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Structural Model ◽  
Synthesis Method ◽  
Normal Modes ◽  
Low Frequency ◽  
Component Mode Synthesis ◽  
Response Analysis ◽  
Element Analysis ◽  
Local Boundary

A new procedure for dynamic analysis of complex structures, based on the fictitious-mass component mode synthesis method, is presented. Normal modes of separate components are calculated by finite-element analysis with the interface coordinates loaded with fictitious masses that generate local boundary deformations in the low-frequency modes. The original fictitious-mass method is extended to include three types of component interconnections: displacement constraints, connection elements, and structural links. The connection elements allow the introduction of springs and dampers between the interface points without adding structural degrees of freedom. The structural links facilitate the inclusion the discrete finite-element representation of typically small components in the coupling equations. This allows a convenient treatment of loose elements and the introduction of nonlinear effects and parametric studies in subsequent analyses. The new procedure is demonstrated with the structural model of a typical vehicle with four major substructures and a relatively large number of interface coordinates. High accuracy is obtained in calculating the natural frequencies and modes of the assembled structure and the separate components with the fictitious masses removed. Dynamic response analysis of the vehicle travelling over a rough road, performed by modal coupling, is in excellent agreement with that performed for the full model.

Dynamic Analysis of Cage Stress in Tapered Roller Bearings Using Component-Mode-Synthesis Method

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Tomoya Sakaguchi ◽  
Kazuyoshi Harada
Keyword(s):  
Rigid Body ◽  
Dynamic Analysis ◽  
Boundary Point ◽  
Axial Load ◽  
Synthesis Method ◽  
Load Condition ◽  
Component Mode Synthesis ◽  
Analysis Model ◽  
Tapered Roller ◽  
Tapered Roller Bearings

In order to investigate cage stress in tapered roller bearings, a dynamic analysis tool considering both the six degrees of freedom of motion of the rollers and cage and the elastic deformation of the cage was developed. Cage elastic deformation is equipped using a component-mode-synthesis (CMS) method. Contact forces on the elastically deforming surfaces of the cage pocket are calculated at all node points of finite-elements on it. The location and pattern of the boundary points required for the component-mode-synthesis method were examined by comparing cage stresses in a static condition of pocket forces and constraints calculated by using the finite-element and the CMS methods. These results indicated that one boundary point lying at the center on each bar is appropriate for the effective dynamic analysis model focusing on the cage stress, especially at the pocket corners of the cages, which are actually broken. A behavior measurement of a polyamide cage in a tapered roller bearing was conducted for validating the analysis model. It was confirmed in both the experiment and analysis that the cage whirled under a large axial load condition and the cage center oscillated in a small amplitude under a small axial load condition. In the analysis, the authors discussed the four models including elastic bodies having a normal eigenmode of 0, 8 or 22, and rigid-body. There were small differences among the cage center loci of the four models. These two cages having normal eigenmodes of 0 and rigid-body whirled with imperceptible fluctuations. At least approximately 8 normal eigenmodes of cages should be introduced to conduct a more accurate dynamic analysis although the effect of the number of normal eigenmodes on the stresses at the pocket corners was insignificant. From the above, it was concluded to be appropriate to introduce one boundary point lying at the center on each pocket bar of cages and approximately 8 normal eigenmodes to effectively introduce the cage elastic deformations into a dynamic analysis model.

A Transfer Matrix Technique for Evaluating the Natural Frequencies and Critical Speeds of a Rotor With Multiple Flexible Disks

1991 ◽  
Author(s):  
Fangsheng Wu ◽  
George T. Flowers
Keyword(s):  
Differential Equation ◽  
Partial Differential Equation ◽  
Transfer Matrix ◽  
Natural Frequencies ◽  
Space Shuttle ◽  
Rotor System ◽  
Partial Differential ◽  
Rotor Systems ◽  
Inertial Moment ◽  
Main Engine

Abstract Modern turbomachinery is used to provide power for a wide range of applications, from steam turbines for electrical power plants to the turbopumps used in the Space Shuttle Main Engine. Such devices are subject to a variety of dynamical problems, including vibration, rotordynamical instability, and shaft whirl. In order to properly design and evaluate the performance and stability of turbomachinery, It is important that appropriate analytical tools be available that allow for the study of potentially important dynamical effects. This research effort is concerned with developing a procedure to account for disk flexibility which can readily be used for investigating how such effects might influence the natural frequencies and critical speeds of practical rotor systems. In the present work, a transfer matrix procedure is developed in which the disk flexibility effects are accounted for by means of additional terms included in the transfer matrix formulation. In this development, the shaft is treated as a discrete system while the disk is modelled as a continuous system using the governing partial differential equation. Based on this governing equation, an equivalent inertial moment Mk*, which is the generalized dynamic force coupling between shaft and disk, is then derived. Analysis shows that only the disk modes of one nodal diameter contribute to the inertial moment, Mk*, and thus influence the natural frequencies of the rotor system. To determine the Mk*, the modal expansion method is employed and the governing partial differential equation of the disk is transformed to a set of decoupled forced vibration equations in the generalized coordinates. The Mk* are then calculated in terms of modal shapes, natural frequencies, and material and geometric parameters which can be found in the literature or can be obtained from experiments. Finally the Mk* are incorporated into the point transfer matrix. By so doing, the properties of quick computational speed and ease of use are retained and the complexity of solving partial differential equations is avoided. This allows the present procedure to be easily applied to practical engineering problems. This is especially true for multiple flexible disk rotor systems. As an example, three different cases for a simplified model of the Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbo-Pump (HPOTP) rotor have been studied using this procedure. Some of the more interesting results obtained in this example study are enumerated below. 1.) Disk flexibility can introduce additional natural frequency(s) to a rotor system. 2.) Disk flexibility can cause shifting of some of the natural frequencies. 3.) As disk flexibility is increased, lower natural frequencies of the rotor system will be influenced. 4.) At certain rotor speeds, disk flexibility may cause the disappearance of a natural frequency. 5.) The axial position of the disk on the rotor shaft has a significant effect on the degree of this influence.

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