scholarly journals Multi-Dimensional Harmonic Balance Applied to Rotor Dynamics

2007 ◽  
Author(s):  
Mikhail Guskov ◽  
Jean-Jacques Sinou ◽  
Fabrice Thouverez
Keyword(s):  
Harmonic Balance ◽  
Dynamical Behavior ◽  
Steady State Solution ◽  
Rotor Dynamics ◽  
Radial Clearance ◽  
Rolling Element Bearings ◽  
Arc Length ◽  
Test Rig ◽  
Rolling Element ◽  
Non Linear

A large number of technical systems feature multi-frequency dynamical behavior. Multiple shaft rotating machinery, subject to simultaneous unbalances spinning at different speeds is a particular case of such systems. Common methods of steady state solution are not valid when the addressed systems have non-linear properties. This study presents a generalized version of harmonic balance coupled with arc-length continuation, developed in order to treat the dynamics of a dual shaft test rig provided with an inter-shaft bearing. The non-linearities are brought about by the presence of rolling element bearings with radial clearance. Numerically, the non-linear terms are taken into account via an AFT (alternating frequency-time domain) procedure, involving multi-dimensional FFT. The numerical results show the presence of response peaks corresponding to the rig’s eigenmodes predicted by linear eigensolution and from experiments. The overall behavior is consistent with the counter-rotating character of the machine operation. Non-linear phenomena due to bearings are also observed, especially the stiffening shape of peaks and apparent pedestal anisotropy involving the presence of backward whirling components in the system’s motion.

Experimental investigation on time-domain features in the diagnosis of rolling element bearings by acoustic emission

2021 ◽  
pp. 107754632110161
Author(s):  
Aref Aasi ◽  
Ramtin Tabatabaei ◽  
Erfan Aasi ◽  
Seyed Mohammad Jafari
Keyword(s):  
Acoustic Emission ◽  
Condition Monitoring ◽  
Time Domain ◽  
Central Moment ◽  
Rolling Element Bearings ◽  
Test Rig ◽  
Acoustic Emission Sensor ◽  
Outer Race ◽  
Common Time ◽  
Rolling Element

Inspired by previous achievements, different time-domain features for diagnosis of rolling element bearings are investigated in this study. An experimental test rig is prepared for condition monitoring of angular contact bearing by using an acoustic emission sensor for this purpose. The acoustic emission signals are acquired from defective bearing, and the sensor takes signals from defects on the inner or outer race of the bearing. By studying the literature works, different domains of features are classified, and the most common time-domain features are selected for condition monitoring. The considered features are calculated for obtained signals with different loadings, speeds, and sizes of defects on the inner and outer race of the bearing. Our results indicate that the clearance, sixth central moment, impulse, kurtosis, and crest factors are appropriate features for diagnosis purposes. Moreover, our results show that the clearance factor for small defects and sixth central moment for large defects are promising for defect diagnosis on rolling element bearings.

The Effect of Inlet Grooves and Swirl on the Dynamics of Long Annular Seals in Centrifugal Pumps

1993 ◽  
Author(s):  
Mohamed Ismail ◽  
R. David Brown ◽  
David France
Keyword(s):  
Rolling Element Bearings ◽  
Rigid Rotor ◽  
Centrifugal Pumps ◽  
Test Rig ◽  
Singular Value Decomposition Method ◽  
Forcing Function ◽  
Rolling Element ◽  
The Time Domain ◽  
Value Decomposition ◽  
Annular Seals

Abstract This paper describes additional results from a continuing research program which aims to identify the dynamics of long annular seals in centrifugal pumps. A seal test rig designed to experimentally identify dynamic coefficients using a least-squares technique based on the singular value decomposition method. The analysis is carried out in the time domain using a multifrequency forcing function. The experimental method relies on the forced excitation of a flexibly supported stator by two hydraulic shakers. A rigid rotor supported in rolling element bearings runs through the stator. The only physical connection between shaft and stator is a pair of annular gaps filled with pressurised water discharged axially. The experimental coefficients obtained from the tests are compared with theoretical values.

Stabilizing Effects of Speed Fluctuations on the Dynamic Response of Rolling Element Bearings With Radial Clearances

2005 ◽  
Author(s):  
A. N. Lioulios ◽  
I. A. Antoniadis
Keyword(s):  
Theory Of Elasticity ◽  
Contact Forces ◽  
Radial Clearance ◽  
Rolling Element Bearings ◽  
Governing Parameter ◽  
Frequency Distributions ◽  
Rolling Element ◽  
Stabilization Effect ◽  
Speed Fluctuations ◽  
Varying Compliance

A horizontal balanced rotor supported on ball bearings with radial internal clearance, subjected to rotational speed fluctuations is modeled. The dynamic model takes under consideration contact forces derived by the hertzian theory of elasticity between the balls and the races, the effect of varying compliance, the internal radial clearance and the rotor’s speed fluctuations. The effect of variation in speed fluctuations is examined for periodic, unstable periodic and chaotic responses with the use of frequency distributions, higher order Poincare maps, and Lyapunov exponents. All results presented show a dominant stabilization effect of the speed fluctuations to the system behavior. From the analysis performed, it is concluded that even a minimum fluctuation of the rotor speed may result to major changes of the system dynamics, indicating that speed fluctuations of the rotor are a governing parameter to the dynamic behavior of the system.

Rotor Dynamics in Design of a High Speed Cryogenic Pump for Geo Stationary Launch Vehicles

2014 ◽  
Author(s):  
Srinivasa R. Jammi
Keyword(s):  
High Speed ◽  
Rotor Dynamics ◽  
Rotor System ◽  
Peak Amplitude ◽  
Beam Model ◽  
Rolling Element Bearings ◽  
Launch Vehicles ◽  
Critical Speeds ◽  
Highly Nonlinear ◽  
Rolling Element

On January 5th 2014 the Indian Space Research Organization successfully launched its Geo Stationary Launch Vehicle with an indigenous Cryogenic engine. One of the main design aspects is in its rotor dynamics to predict the peak amplitude unbalance whirl and the speed at which it occurs. This engine has several key technologies, one of them specifically is coupled rotors, viz., Turbine, Hydrogen Pump and Oxidizer supported on seven nonlinear rolling element bearings and several seals all mounted in a flexible casing. The conventional beam model initially adopted failed to predict the speed at which peak unbalance response occurs. The rotor system was first developed in a solid model to determine the critical speeds of the rotor alone considering its 40000 rpm centrifugal loads with bearings treated as linear. Then, unbalance whirl of this rotor system was developed by codes specially developed for this purpose. The rolling element bearings are found to be highly nonlinear with large bearing radial forces at critical speeds. An iterative procedure was developed to match the bearing force and unbalance whirl to determine peak amplitude response speeds. Subsequently, seals and the influence of casing and internal pressures were accounted in the analysis. This paper describes the advanced rotor dynamic design of this pump.

Dynamics of an Improved Inter Shaft Squeeze Film Damper: Theory and Experiment

2007 ◽  
Author(s):  
K. Gupta ◽  
S. Chatterjee
Keyword(s):  
Gas Flow ◽  
Damping Ratio ◽  
Squeeze Film ◽  
Design Parameters ◽  
Radial Clearance ◽  
Rolling Element Bearings ◽  
Squeeze Film Damper ◽  
Wide Range ◽  
Rolling Element ◽  
Theoretical Simulations

Intershaft rolling element bearings are commonly used in aero gas turbine rotors primarily to reduce the length of the engine as well as to avoid obstruction to gas flow path at the turbine end. In order to reduce cross-excitation between the LP and HP shafts of two spool rotor, researchers have proposed introduction of squeeze film in the inter shaft bearing. However, Inter Shaft Squeeze Film Damper (ISSFD) becomes unstable above a threshold operating speeds. In the present work, an improved ISSFD which is inherently stable, is analyzed and tested. It has two rolling element bearings, one each mounted on LP and HP rotor shafts. The two bearings are configured such that the squeeze film is formed between the two non rotating races/surfaces. A centralizing spring between the two races, and a supporting spring between the ground/frame and one of the non rotating races are provided. Two design modifications of this system are analyzed and tested experimentally. Experiments on an improvised two spool rotor setup under unbalance excitation are conducted for all the three designs of ISSFD. In theoretical simulations, various design parameters are varied over a wide range. Theoretical analysis as well as the experiments show that an optimum value of radial clearance exists for a given design to have maximum damping, and a damping ratio of the order of 10% and more is achievable in an ISSFD.

Multi-body simulation and validation of fault vibrations from rolling-element bearings

2020 ◽  
pp. 135065012097797
Author(s):  
Daniel Strömbergsson ◽  
Pär Marklund ◽  
Kim Berglund
Keyword(s):  
Rotational Symmetry ◽  
Roller Bearing ◽  
Rolling Element Bearings ◽  
Test Rig ◽  
Dynamic Simulations ◽  
Optimal Position ◽  
Vibrational Response ◽  
Rolling Element ◽  
Dynamic Simulation Model ◽  
Multi Body

Dynamic simulations are often used to evaluate the vibrational response of rolling-element bearings experiencing defects. Previously, the optimal accelerometer position has been found to be as close as possible to the bearing. However, further details about the influence of rotational symmetry have not been closely investigated. This paper presents a dynamic simulation model of a radially loaded complete spherical roller bearing with a defect in the inner ring and placed in a housing with 72 equally spaced accelerometer positions around the circumference. Surface accelerations have been extracted and transformed into the frequency domain. Thereafter, the vibrational components indicating the defect have been evaluated around the circumference. The results show an optimal position as close as possible to the primary loaded zone and validation test rig experiments show a reasonable qualitative agreement.

Sensitivity Analysis of an Information Maximization Approach to the Blind Separation of the Vibration Responses of Defective Rolling Element Bearings

2005 ◽  
Author(s):  
C. Yiakopoulos ◽  
I. Antoniadis
Keyword(s):  
Neural Network ◽  
Sensitivity Analysis ◽  
Linear Function ◽  
Network Structure ◽  
Vibration Response ◽  
Rolling Element Bearings ◽  
Rolling Element ◽  
Non Linear ◽  
Vibration Responses ◽  
Neural Network Structure

Vibration response of rotating machines is typically mixed and corrupted by a variety of interfering sources and noise, leading to the necessity for the isolation of the useful signal components. A relevant frequently encountered industrial case is the need for the separation of the vibration responses of the same type of bearings inside the same machine. For this purpose, a Blind Source Separation procedure has been successfully applied, based on the maximization of the information transferred in a neural network structure. Thus, a key element for the success of the proposed procedure is the non-linear function used in this single layer Neural Network structure. However, since the vibration response of defective rolling element bearings is characterized by signals with super-Gaussian distributions, a sensitivity analysis of this non-linear function is necessary. First, this analysis is performed in a set of numerical experiments, based on dynamic models of defective bearings. Finally, the same analysis is applied in an experimental test rig.

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