Nonlinear Analysis of Rotor-Bearing Systems Using Component Mode Synthesis

1983 ◽  
Vol 105 (3) ◽  
pp. 606-614 ◽  
Author(s):  
H. D. Nelson ◽  
W. L. Meacham ◽  
D. P. Fleming ◽  
A. F. Kascak
Keyword(s):  
Forced Response ◽  
Component Mode Synthesis ◽  
Squeeze Film ◽  
System Response ◽  
Reduced Order ◽  
Squeeze Film Dampers ◽  
Rotor Bearing ◽  
System Equations ◽  
Transient System ◽  
Blade Loss

The method of component mode synthesis is developed to determine the forced response of nonlinear, multishaft, rotor-bearing systems. The formulation allows for simulation of system response due to blade loss, distributed unbalance, base shock, maneuver loads, and specified fixed frame forces. The motion of each rotating component of the system is described by superposing constraint modes associated with boundary coordinates and constrained precessional modes associated with internal coordinates. The precessional modes are truncated for each component and the reduced component equations are assembled with the nonlinear supports and interconnections to form a set of nonlinear system equations of reduced order. These equations are then numerically integrated to obtain the system response. A computer program, which is presently restricted to single shaft systems has been written and results are presented for transient system response associated with blade loss dynamics, with squeeze film dampers, and with interference rubs.

Nonlinear Analysis of Rotor-Bearing Systems Using Component Mode Synthesis

1982 ◽  
Author(s):  
H. D. Nelson ◽  
W. L. Meacham ◽  
D. P. Fleming ◽  
A. F. Kascak
Keyword(s):  
Forced Response ◽  
Component Mode Synthesis ◽  
Squeeze Film ◽  
System Response ◽  
Reduced Order ◽  
Squeeze Film Dampers ◽  
Rotor Bearing ◽  
System Equations ◽  
Transient System ◽  
Blade Loss

The method of component mode synthesis is developed to determine the forced response of nonlinear, multishaft, rotor-bearing systems. The formulation allows for simulation of system response due to blade loss, distributed unbalance, base shock, maneuver loads, and specified fixed frame forces. The motion of each rotating component of the system is described by superposing constraint modes associated with boundary coordinates and constrained precessional modes associated with internal coordinates. The precessional modes are truncated for each component and the reduced component equations are assembled with the nonlinear supports and interconnections to form a set of nonlinear system equations of reduced order. These equations are then numerically integrated to obtain the system response. A computer program, which is presently restricted to single shaft systems, has been written and results are presented for transient system response associated with blade loss dynamics with squeeze film dampers, and with interference rubs.

scholarly journals Transient Analysis of Rotor-Bearing Systems Using Component Mode Synthesis

1981 ◽  
Author(s):  
H. D. Nelson ◽  
W. L. Meacham
Keyword(s):  
Transient Analysis ◽  
Forced Response ◽  
Component Mode Synthesis ◽  
System Response ◽  
Reduced Order ◽  
Fixed Frame ◽  
Rotor Bearing ◽  
System Equations ◽  
Comparative Results ◽  
Mode Truncation

A method of component mode synthesis is utilized to determine the forced response of linear multi-shaft rotor-bearing systems. The formulation allows for simulation of system response due to blade loss, base shock, maneuver loads, and specified fixed frame forces. The motion of each rotating component of the system is described by superposing constraint modes associated with boundary coordinates and constrained precessional modes associated with internal coordinates. The precessional modes are truncated for each component and the reduced component equations are assembled to obtain a set of complex system equations of reduced order. The method allows for nonsymmetric effects and comparative results are presented for various levels of mode truncation for two example cases.

scholarly journals Analytical and Experimental Investigation of the Stability of the Rotor-Bearing System of a New Small Turbocharger

1987 ◽  
Author(s):  
H. R. Born
Keyword(s):  
Experimental Investigation ◽  
Dynamic Stability ◽  
Squeeze Film ◽  
Test Results ◽  
Flow Capacity ◽  
Squeeze Film Dampers ◽  
Rotor Bearing ◽  
The Stability ◽  
Turbine Design ◽  
Bearing System

This paper presents an overview of the development of a reliable bearing system for a new line of small turbochargers where the bearing system has to be compatible with a new compressor and turbine design. The first part demonstrates how the increased weight of the turbine, due to a 40 % increase in flow capacity, influences the dynamic stability of the rotor-bearing system. The second part shows how stability can be improved by optimizing important floating ring parameters and by applying different bearing designs, such as profiled bore bearings supported on squeeze film dampers. Test results and stability analyses are included as well as the criteria which led to the decision to choose a squeeze film backed symmetrical 3-lobe bearing for this new turbocharger design.

scholarly journals Imbalance Response of a Test Rotor Supported on Squeeze Film Dampers

1998 ◽  
Vol 120 (2) ◽  
pp. 397-404 ◽  
Author(s):  
L. San Andre´s ◽  
D. Lubell
Keyword(s):  
Chaotic Behavior ◽  
Nonlinear Behavior ◽  
Theoretical Models ◽  
Forced Response ◽  
Analytical Models ◽  
Squeeze Film ◽  
Test Rig ◽  
Critical Speeds ◽  
Highly Nonlinear ◽  
Squeeze Film Dampers

Squeeze film dampers (SFDs) provide vibration attenuation and structural isolation to aircraft gas turbine engines which must be able to tolerate larger imbalances while operating above one or more critical speeds. Rotor-bearing-SFD systems are regarded in theory as highly nonlinear, showing jump phenomena and even chaotic behavior for sufficiently large levels of rotor imbalance. Yet, few experimental results of practical value have verified the analytical predictions. A test rig for measurement of the dynamic forced response of a three-disk rotor (45 kg) supported on two cylindrical SFDs is described. The major objective is to provide a reliable data base to validate and enhance SFD design practice and to allow a direct comparison with analytical models. The open-ends SFD are supported by four-bar centering structures, each with a stiffness of 3.5 MN/m. Measured synchronous responses to 9000 rpm due to various imbalances show the rotor-SFD system to be well damped with amplification factors between 1.6 and 2.1 while traversing cylindrical and conical modes critical speeds. The rotor amplitudes of motion are found to be proportional to the imbalances for the first mode of vibration, and the damping coefficients extracted compare reasonably well to predictions based on the full-film, open-ends SFD. Tight lip (elastomeric) seals contribute greatly to the overall damping of the test rig. Measured dynamic pressures at the squeeze film lands are well above ambient values with no indication of lubricant dynamic cavitation as simple theoretical models dictate. The measurements show absence of nonlinear behavior of the rotor-SFD apparatus for the range of imbalances tested.

Response of a Squeeze Film Damper-Elastic Structure System to Multiple and Consecutive Impact Loads

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Luis San Andrés ◽  
Sung-Hwa Jeung
Keyword(s):  
Transient Response ◽  
Damping Ratio ◽  
Test System ◽  
Elastic Structure ◽  
Squeeze Film ◽  
Radial Clearance ◽  
System Response ◽  
Fluid Inertia ◽  
Squeeze Film Dampers ◽  
Structural Isolation

Squeeze film dampers (SFDs) are common in aircraft gas turbine engines, customized to provide a desired level of damping while also ensuring structural isolation. This paper presents measurements obtained in a test rig composed of a massive cartridge, an elastic structure, and an open-ends SFD with length L = 25.4 mm, diameter D = 127 mm, and radial clearance c = 0.267 mm. ISO VG 2 oil at room temperature lubricates the thin film. The measurements quantify the system transient response to sudden loads for motions departing from various static eccentricity displacements, es/c = 0–0.6. The batch of tests include recording the system response to (a) one single impact, (b) two (and three) impacts with an elapsed time of 30 ms in between, and (c) two or more consecutive impacts, without any delay, each with a load magnitude at 50% of the preceding impact. The load actions intend to reproduce, for example, a hard landing on an uneven surface or plunging motions from sudden contacts in a machine tool. The test system transient responses due to one or more impacts, each 30 ms apart, show the peak amplitude of motion (ZMAX) is proportional to the magnitude of applied load (FMAX). The identified system damping ratio (ξ) is proportional to the peak dynamic displacement as a linear system would show. Predictions of transient response from a physical SFD model accounting for fluid inertia correlate best with the experimental results as they produce greatly reduced peak dynamic motions when compared to predictions from a purely viscous SFD model. For the responses due to consecutive impacts, one after the other with no delay, the system motion does not decay immediately but builds to produce larger motion amplitudes than in the earlier cases. Eventually, as expected, after several oscillations, the system comes to rest. For an identical damper having a smaller clearance cs = 0.213 mm (0.8c), its damping ratio (ξs) is ∼1.3 to ∼1.7 times greater than the damping ratio for the damper with a larger film clearance (ξ). Hence, the experimentally derived (ξs/ξ) scales with (c/cs)2. The finding demonstrates the importance of manufacturing precisely the components in a damper to produce an accurate clearance.

Eccentric Operation and Blade-Loss Simulation of a Rigid Rotor Supported by an Improved Squeeze Film Damper

1995 ◽  
Vol 117 (3) ◽  
pp. 490-497 ◽  
Author(s):  
J. Y. Zhao ◽  
E. J. Hahn
Keyword(s):  
Outer Ring ◽  
Squeeze Film ◽  
Rigid Rotor ◽  
Cavitation Model ◽  
Squeeze Film Damper ◽  
Constant Stiffness ◽  
Flexible Support ◽  
Squeeze Film Dampers ◽  
Stiffness And Damping ◽  
Blade Loss

This paper outlines an improved squeeze film damper which reduces significantly the dependence of the stiffness of conventional squeeze film dampers on the vibration amplitudes. This improved damper consists of a conventional squeeze film damper with a flexibility supported outer ring. This secondary flexible support is considered to be massless, and to have a constant stiffness and damping. Assuming the short bearing approximation and the ‘π’ film cavitation model, the performances of this damper in preventing bistable operation and sub-synchronous and nonsynchronous motions are theoretically demonstrated for a rigid rotor supported on a squeeze film damper. Blade-loss simulations are carried out numerically.

Rotating Mistuned Bladed Disk Assembly Dynamic Response Prediction Using Component Mode Synthesis Methods With Interface Modes

2005 ◽  
Author(s):  
Francois Duvauchelle ◽  
Duc-Minh Tran ◽  
Roger Ohayon
Keyword(s):  
Response Prediction ◽  
Forced Response ◽  
Component Mode Synthesis ◽  
Synthesis Methods ◽  
Cyclic Symmetry ◽  
Reduced Order ◽  
Bladed Disk ◽  
Static Condensation ◽  
Bladed Disk Assembly ◽  
Reduced Order Methods

Finite element-based reduced order methods are presented with application to the prediction of rotating mistuned bladed disk forced response. These methods have already been applied to tuned non-rotating models having cyclic symmetry. The aim is to reduce significantly the number of interface co-ordinates, which can be very important in classical component mode synthesis methods. The approach is based on the use of the interface modes which result from a static condensation of the whole structure on the whole interface. A first implementation of this procedure and numerical results are presented.

Effects of a Cracked Blade on Mistuned Turbine Engine Rotor Vibration

2007 ◽  
Author(s):  
Akira Saito ◽  
Matthew P. Castanier ◽  
Christophe Pierre
Keyword(s):  
Degrees Of Freedom ◽  
Dimensional Space ◽  
Time Integration ◽  
Element Model ◽  
Forced Response ◽  
System Response ◽  
Turbine Engine ◽  
Reduced Order ◽  
Hybrid Interface ◽  
Engine Rotor

An efficient methodology for predicting the nonlinear forced vibration response of a turbine engine rotor with a cracked blade is presented and used to investigate the effects of the damage on the forced response. The effects of small, random blade-to-blade differences (mistuning) and rotation on the forced response are also considered. Starting with a finite element model, a hybrid-interface method of Component Mode Synthesis (CMS) is employed to generate a reduced-order model (ROM). The crack surfaces are retained as physical degrees of freedom in the ROM so that the forces due to contact interaction in three-dimensional space can be properly calculated. The resulting nonlinear equations of steady-state motion are solved by applying an alternating frequency/time-domain method, which is much more computationally efficient than traditional time integration. Using this reduced-order modeling and analysis framework, the effects of the cracked blade on the system response are investigated for various mistuning levels and rotation speeds. First, the advantages of the selected hybrid-interface CMS method are discussed and demonstrated. Then, the resonant frequency shift associated with the stiffness loss due to the crack, as well as vibration localization about the cracked blade are thoroughly investigated. In addition, the results of the nonlinear ROMs are compared to those obtained with linear ROMs as well as blade-alone ROMs. It is shown that several key system vibration characteristics are not captured by the simpler models, but that some insight into the system response can be gained from the blade-alone response predictions. Furthermore, it is demonstrated that while the effects of the crack often appear similar those of mistuning, differences between the effects of mistuning and damage can be discerned by observing and comparing the response across different families of system modes.

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