Computational Studies of the Unbalance Response of a Whole Aero-Engine Model With Squeeze-Film Bearings

2009 ◽  
Vol 132 (3) ◽  
Author(s):  
Philip Bonello ◽  
Pham Minh Hai
Keyword(s):  
Harmonic Balance ◽  
Linear Part ◽  
Harmonic Balance Method ◽  
Vibration Response ◽  
Squeeze Film ◽  
Engine Model ◽  
Nonlinear Solvers ◽  
Aero Engine ◽  
Receptance Method ◽  
First Time

The computation of the unbalance vibration response of aero-engine assemblies fitted with nonlinear bearings requires the retention of a very large number of modes for reliable results. This renders most previously proposed nonlinear solvers unsuitable for this application. This paper presents three methods for the efficient solution of the problem. The first method is the recently developed impulsive receptance method (IRM). The second method is a reformulation of the Newmark-beta method. In addition to these two time-domain methods, a whole-engine receptance harmonic balance method (RHBM) is introduced that allows, for the first time, the frequency domain calculation of the periodic vibration response of a real engine. All three methods use modal data calculated from a one-off analysis of the linear part of the engine at zero speed. Simulations on a realistically-sized representative twin-spool engine model with squeeze-film damper bearings provide evidence that the popular Newmark-beta method can be unreliable for large-order nonlinear systems. The excellent correlation between the IRM and RHBM results demonstrates the efficacy of these two complementary tools in the computational analysis of realistic whole-engine models.

Computational Studies of the Unbalance Response of a Whole Aero-Engine Model With Squeeze-Film Bearings

2009 ◽  
Author(s):  
Philip Bonello ◽  
Pham Minh Hai
Keyword(s):  
Harmonic Balance ◽  
Linear Part ◽  
Harmonic Balance Method ◽  
Vibration Response ◽  
Squeeze Film ◽  
Engine Model ◽  
Nonlinear Solvers ◽  
Aero Engine ◽  
Receptance Method ◽  
First Time

The computation of the unbalance vibration response of aero-engine assemblies fitted with nonlinear bearings requires the retention of a very large number of modes for reliable results. This renders most previously proposed nonlinear solvers unsuitable for this application. This paper presents three methods for the efficient solution of the problem. The first method is the recently developed impulsive receptance method (IRM). The second method is a reformulation of the Newmark-Beta method. In addition to these two time-domain methods, a whole-engine receptance harmonic balance method (RHBM) is introduced that allows, for the first time, the frequency domain calculation of the periodic vibration response of a real engine. All three methods use modal data calculated from a one-off analysis of the linear part of the engine at zero speed. Simulations on a realistically-sized representative twin-spool engine model with squeeze-film damper bearings provide evidence that the popular Newmark-Beta method can be unreliable for large order nonlinear systems. The excellent correlation between the IRM and RHBM results demonstrates the efficacy of these two complementary tools in the computational analysis of realistic whole-engine models.

A theoretical and experimental investigation into the vibration response of a flexible rotor and squeeze-film damper assembly

2001 ◽  
Vol 215 (10) ◽  
pp. 1251-1269 ◽  
Author(s):  
C-C Siew ◽  
M Hill ◽  
R Holmes ◽  
M Brennan
Keyword(s):  
Harmonic Balance ◽  
Three Dimensional ◽  
Harmonic Balance Method ◽  
Vibration Response ◽  
Mode Shapes ◽  
Squeeze Film ◽  
Flexible Rotor ◽  
Linear Vibration ◽  
Squeeze Film Damper ◽  
Good Agreement

This paper presents two efficient methods to calculate the unbalance vibration response of a flexible rotor provided with a squeeze-film damper (SFD) with retainer springs. Both methods are iterative and combine the harmonic balance and receptance approaches. The first method, called the modified iteration method (MIM), is suitable for predicting the three-dimensional mode shapes of a concentric SFD-rotor system. The second method, called the modified harmonic balance method (MHBM), is developed to calculate the non-linear vibration response of a flexible shaft provided with either a concentric or eccentric SFD. The system is also investigated experimentally under different conditions. The predictions computed by these methods are compared with experimental measurements and reasonably good agreement is obtained.

The Efficient Computation of the Vibration Response of an Aero-Engine Rotor-Damper Assembly

1994 ◽  
Vol 208 (1) ◽  
pp. 41-51 ◽  
Author(s):  
M C Levesley ◽  
R Holmes
Keyword(s):  
Harmonic Balance ◽  
Harmonic Balance Method ◽  
Vibration Response ◽  
Efficient Computation ◽  
Linear Vibration ◽  
Film Rupture ◽  
Aero Engine ◽  
Rupture Pressure ◽  
The Subject ◽  
Engine Rotor

This paper deals with the application of the so-called Harmonic Balance method to the problem of determining the non-linear vibration response of a rotating assembly comprising a rotor, flexible bearing housing and oil film damper. For the latter, due consideration is given to the effects of oil supply pressure, film rupture pressure and end sealing. The paper concludes with some comments on the subject of optimizing a damper to fulfil a given purpose.

A Study of the Nonlinear Interaction Between an Eccentric Squeeze Film Damper and an Unbalanced Flexible Rotor

2004 ◽  
Vol 126 (4) ◽  
pp. 855-866 ◽  
Author(s):  
Philip Bonello ◽  
Michael J. Brennan ◽  
Roy Holmes
Keyword(s):  
Periodic Solutions ◽  
Nonlinear Interaction ◽  
Harmonic Balance ◽  
Linear Part ◽  
Harmonic Balance Method ◽  
Squeeze Film ◽  
Flexible Rotor ◽  
Test Rig ◽  
Squeeze Film Damper ◽  
Static Eccentricity

In this paper, the nonlinear interaction between an eccentric squeeze film damper and an unbalanced flexible rotor is investigated, paying particular attention to the effect of cavitation in the damper. A harmonic balance method that uses the receptance functions of the rotating linear part of the system to determine periodic solutions to the nonlinear problem is used to predict vibration levels in a test rig. By comparing predictions obtained respectively with, and without, lower pressure limits for the squeeze film damper model, it is concluded that cavitation is promoted by increasing static eccentricity and/or unbalance level. This, in turn, is found to have a profound effect on the predictions for the critical vibration levels, which such dampers are designed to attenuate. Experimental results are presented to support the findings.

Experimental Investigation into the Vibration Response of an Aero-Engine Rotor-Damper Assembly

1994 ◽  
Vol 208 (1) ◽  
pp. 52-66 ◽  
Author(s):  
M C Levesley ◽  
R Holmes
Keyword(s):  
Experimental Investigation ◽  
Harmonic Balance ◽  
Vibration Response ◽  
Linear Vibration ◽  
Film Rupture ◽  
Supply Pressure ◽  
Balance Principle ◽  
Aero Engine ◽  
Rupture Pressure ◽  
Engine Rotor

This paper presents experimental results on the non-linear vibration response of a rotating assembly comprising a rotor, flexible bearing housing and oil film damper. For the latter, due consideration is given to the effects of oil-supply pressure, film-rupture pressure and end sealing. The results are compared with predictions based on the Harmonic Balance principle described in a complementary paper (1).

Use of the Harmonic Balance Method for Flexible Aircraft Engine Rotors With Nonlinear Squeeze Film Dampers

2014 ◽  
Author(s):  
Feng He ◽  
Paul Allaire ◽  
Timothy Dimond
Keyword(s):  
Harmonic Balance ◽  
Harmonic Balance Method ◽  
Aircraft Engine ◽  
Balance Method ◽  
Squeeze Film ◽  
Spring Stiffness ◽  
Squeeze Film Damper ◽  
Flexible Rotors ◽  
Squeeze Film Dampers ◽  
Nonlinear Transient

Squeeze film dampers in flexible rotors such as those in compressors, steam turbines, aircraft engines and other rotating machines are often modeled as linear devices. This linearization is valid only for a specified orbit where appropriate equivalent stiffness and damping coefficients can be found. However, squeeze film dampers are inherently nonlinear devices which complicates the analysis. This paper develops the harmonic balance method with a direct force model of the SFDs. This model is used for flexible rotors with squeeze film dampers where the rotor is treated as linear and the squeeze film damper is treated as nonlinear. The predictor-corrector method is employed to obtain the system forced response in the frequency domain after separating the nonlinear components from the linear components of the equations of motion. This approach is much more efficient than conventional full nonlinear transient analysis. The application considered in this paper is the low pressure (LP) compressor of an aircraft engine. The LP compressor rotor has two roller bearings with squeeze film dampers and one ball bearing without a squeeze film damper. Orbits at the fan end dampers and the turbine end dampers for both the harmonic balance and nonlinear transient modeling are compared for accuracy and calculation time. The HB method is shown to be 5 to 12 times faster computationally for similar results. Fast Fourier transform results were obtained for various shaft operating speeds. Results were also obtained for the unbalance response at different locations with gravity loading. Finally, unbalance response of the rotor with varying centering spring stiffness values were obtained. The results show that the centering spring stiffness for the turbine end damper is less sensitive than the fan end damper.

scholarly journals The Effects of Crack on the Transmission Matrix of Rotor Systems

2011 ◽  
Vol 18 (1-2) ◽  
pp. 91-103 ◽  
Author(s):  
Z.K. Peng ◽  
Z.Q. Lang ◽  
G. Meng ◽  
F.L. Chu
Keyword(s):  
Harmonic Balance ◽  
Crack Detection ◽  
Harmonic Balance Method ◽  
Detection Methods ◽  
Rotor Systems ◽  
Crack Location ◽  
Frequency Components ◽  
Harmonic Components ◽  
First Time ◽  
Method Analysis

The dynamic behavior of rotor containing crack is a subject of particular interest and has been extensively investigated by researchers. The effects of crack on the natural frequencies and modal shapes and motion orbits of rotor systems have already been well explored by researchers. In the present study, the infl uence of crack on the transmission matrices of the rotor systems is investigated by using the FEM (finite element method) analysis and the HBM (harmonic balance method) technique. It is for the first time revealed that there are differences between the transmission matrices for the fundamental frequency components and the transmission matrices for the super-harmonic components, and the differences are mainly determined by the crack location. The results are validated by numerical experiments where the system responses of a rotor system are obtained usingRunge-Kuttamethod. The results are of significance for the development of effective crack detection methods in practice.

A Study of the Influence of Static Eccentricity and Unbalance on Cavitation Effects in a Squeeze Film Damped Flexible Rotor

2002 ◽  
Author(s):  
Philip Bonello ◽  
Michael J. Brennan ◽  
Roy Holmes
Keyword(s):  
Dynamic Systems ◽  
Harmonic Balance ◽  
Harmonic Balance Method ◽  
Squeeze Film ◽  
Flexible Rotor ◽  
Test Rig ◽  
Squeeze Film Damper ◽  
Static Eccentricity ◽  
Rotor Dynamic ◽  
Rigid Rotors

The study of eccentric squeeze film damped rotor dynamic systems has largely concentrated on rigid rotors. In this paper, a newly developed receptance harmonic balance method is used to efficiently analyze a squeeze film damped flexible rotor test rig. The aim of the study is to investigate the influence of damper static eccentricity and unbalance level on cavitation and its resulting effect on the vibration level. By comparing predictions for the rotor vibration levels obtained respectively with, and without, lower pressure limits for the eccentric squeeze film damper model, it is demonstrated that cavitation is promoted by increasing static eccentricity and/or unbalance level. This, in turn, is found to have a profound effect on the predictions for the critical vibration levels, which such dampers are designed to attenuate. The reported findings are backed by experimental evidence from the test rig.

scholarly journals Application of Generalized Polynomial Expansion Method to Nonlinear Rotor Bearing Systems

1991 ◽  
Author(s):  
Jon Li Hwang ◽  
Ting Nung Shiau
Keyword(s):  
Hybrid Method ◽  
Harmonic Balance ◽  
Harmonic Balance Method ◽  
Expansion Method ◽  
Polynomial Expansion ◽  
Squeeze Film ◽  
Generalized Polynomial ◽  
Polynomial Expansion Method ◽  
Rotor Dynamic ◽  
Modal Coordinates

Abstract The Generalized Polynomial Expansion Method (GPEM) is utilized to model a large-order flexible-rotor system with nonlinear supports. With the application of GPEM, a set of nonlinear ordinary differential equations are obtained. A hybrid method which combines the merits of the Harmonic Balance Method (HBM) and the Trigonometric Collocation Method (TCM) is used to solve for the nonlinear response of the system. This hybrid method together with reduction techniques can efficiently solve for the motion of the system. The overall algorithm presented provides a very efficient technique for investigating the periodic response of large-order nonlinear rotor systems. Two examples are used to illustrate the merits of the method. One is the simple Jeffcott rotor which is used to check the accuracy of the present numerical algorithms. The other is a flexible shaft with multiple disks, supported by multiple bearings. It is used to show the advantages of the linkage between GPEM and the presented hybrid numerical algorithm. Some of the support bearings are modeled as a squeeze-film damper associated with a center spring. The center spring is considered to be linear and the squeeze-film damper is nonlinear. The nonlinear hydrodynamic forces are obtained using short-bearing theory. Based on the example results, the conclusions can be summarized as follows: (l) For a nonlinear flexible-rotor system, the number of equations needed for the system described by the Generalized Polynomial Expansion Method are always smaller than the number required by the finite element method before applying the condensation technique. This is also true for the linear case which has been discussed by Shiau and Hwang (1989, 1990). (2) A technique of component mode synthesis has been developed based on the modeling approach of the Generalized Polynomial Expansion Method. It is applied to decouple the nonlinear independent and dependent modal coordinates. With this technique, the number of non-zero elements in the generalized modal-forces vector is equal to the number of nonlinear, dependent modal coordinates. The results indicate that the use of GPEM together with component mode synthesis not only retains its merits in solving a linear rotor-dynamic problem, but also provides attainable solutions for the nonlinear rotor-dynamic problem. (3) The hybrid numerical algorithm developed in the present study combines both the advantages of the harmonic-balance method and the collocation method. The use of this hybrid method with condensation technique can significantly save computing time. Furthermore, it can be used to predict the periodic response, including the sub-harmonic response and the super-harmonic response, of a nonlinear system. (4) The time required for the initial formulation processing with this method may be a little more than that required by the finite-element approach. However, it is very small compared to the overall time savings that are accrued.

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