Method and Device for Large Rotor Bearing Force Measurement

2019 ◽  
Author(s):  
Risto Viitala ◽  
Raine Viitala ◽  
Petri Kuosmanen
Keyword(s):  
Force Measurement ◽  
Rotor Bearing ◽  
Bearing Force ◽  
Large Rotor

Nonlinear Dynamics of Flexible Rotors Supported on Journal Bearings—Part I: Analytical Bearing Model

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Mohammad Miraskari ◽  
Farzad Hemmati ◽  
Mohamed S. Gadala
Keyword(s):  
Journal Bearing ◽  
Nonlinear Coefficient ◽  
Journal Bearings ◽  
Flexible Rotor ◽  
Dynamic Coefficients ◽  
Flexible Rotors ◽  
Rotor Bearing ◽  
Bearing Force ◽  
Derivatives Of ◽  
Bearing System

To determine the bifurcation types in a rotor-bearing system, it is required to find higher order derivatives of the bearing forces with respect to journal velocity and position. As closed-form expressions for journal bearing force are not generally available, Hopf bifurcation studies of rotor-bearing systems have been limited to simple geometries and cavitation models. To solve this problem, an alternative nonlinear coefficient-based method for representing the bearing force is presented in this study. A flexible rotor-bearing system is presented for which bearing force is modeled with linear and nonlinear dynamic coefficients. The proposed nonlinear coefficient-based model was found to be successful in predicting the bifurcation types of the system as well as predicting the system dynamics and trajectories at spin speeds below and above the threshold speed of instability.

scholarly journals Simulation of Subcritical Vibrations of a Large Flexible Rotor with Varying Spherical Roller Bearing Clearance and Roundness Profiles

Machines ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 28
Author(s):  
Emil Kurvinen ◽  
Raine Viitala ◽  
Tuhin Choudhury ◽  
Janne Heikkinen ◽  
Jussi Sopanen
Keyword(s):  
Simulation Model ◽  
Roller Bearing ◽  
Major Effect ◽  
Bearing Clearance ◽  
Vibration Excitation ◽  
Resonance Response ◽  
Rolling Element ◽  
Rotor Bearing ◽  
Harmonic Resonance ◽  
Large Rotor

In large rotor-bearing systems, the rolling element bearings act as a considerable source of subcritical vibration excitation. Simulation of such rotor bearing systems contains major sources of uncertainty contributing to the excitation, namely the roundness profile of the bearing inner ring and the clearance of the bearing. In the present study, a simulation approach was prepared to investigate carefully the effect of varying roundness profile and clearance on the subcritical vibration excitation. The FEM-based rotor-bearing system simulation model included a detailed description of the bearings and asymmetricity of the rotor. The simulation results were compared to measured responses for validation. The results suggest that the simulation model was able to capture the response of the rotor within a reasonable accuracy compared to the measured responses. The bearing clearance was observed to have a major effect on the subcritical resonance response amplitudes. In addition, the simulation model confirmed that the resonances of the 3rd and 4th harmonic vibration components in addition to the well-known 2nd harmonic resonance (half-critical resonance) can be significantly high and should thus be taken into account already in the design phase of large subcritical rotors.

Nonlinear Vibration Analysis of a Flexible Rotor Supported by a Journal Bearing Considering Journal Angular Motion

2019 ◽  
Author(s):  
Nuntaphong Koondilogpiboon ◽  
Tsuyoshi Inoue
Keyword(s):  
Nonlinear Vibration ◽  
Ball Bearing ◽  
Journal Bearing ◽  
Angular Motion ◽  
Experimental Result ◽  
Flexible Rotor ◽  
Large Disk ◽  
Rotor Bearing ◽  
Bearing Force ◽  
Bearing System

Abstract The effect of bearing length to diameter (L/D) ratio and large disk position on nonlinear vibration (limit cycle and bifurcation type) of a flexible rotor-bearing system is investigated. The rotor consists of a shaft modeled by 1-D finite elements (FE), two small disks and a large disk. It is supported by a self-aligning ball bearing and an axial-groove journal bearing with L/D ratio of 0.4 and 0.6. Two large disk positions: 340 and 575 mm measured from the ball bearing are investigated. The journal angular motion, which is essential for the highly flexible rotor but typically not considered in the previous nonlinear vibration literature; is considered in nonlinear bearing force calculation. The degrees of freedom (DOF) of the rotor-bearing system are reduced to those of the node that the nonlinear journal bearing force and moment act on by real mode component mode synthesis (CMS) that retains only the 1st forward and backward modes. Shooting method and Floquet multiplier analysis are applied to the reduced rotor-bearing system to obtain limit cycles and their stability of each bearing L/D ratio and large disk position case. Numerical results indicate that supercritical Hopf bifurcation only occurs in the case of L/D = 0.4 and large disk position 575 mm, otherwise subcritical occurs. However, if the typical bearing model that does not consider journal angular motion is used, the bifurcation type for the case of L/D = 0.6 with large disk position 575 mm will change to supercritical. Lastly, the experiments with the same L/D ratio and large disk position investigated in the calculation are performed as a validation. The experimental result of each case shows the same bifurcation type as the calculation result using the bearing model that considers the journal angular motion.

The Effect of Cavitation on the Vibration Behaviour of Nonlinear Rotor Bearing Systems

2006 ◽  
Author(s):  
Duc Pham ◽  
Ningsheng Feng ◽  
Eric Hahn
Keyword(s):  
Dynamic Properties ◽  
Fluid Film ◽  
Stable Operation ◽  
Rotor Bearing ◽  
Reaction Forces ◽  
Bearing Stiffness ◽  
Operation Stability ◽  
Bearing Force ◽  
Air Ingress ◽  
Stiffness And Damping

Rotor bearing systems frequently utilise hydrodynamic bearings whose dynamic properties are generally influenced by the bearing reaction forces (which determine the bearing stiffness and damping coefficients). These reaction forces are frequently unknown and are generally determined from the solution of the Reynolds equation using rotor motion measurements as input. Of interest is the attainable accuracy of such bearing force determinations, and for experimental evaluation, a test rig was fabricated, the design specification of which required that the rotor system run stably over its operating speed range. This paper describes the commissioning of this rig for stability purposes with the aid of natural frequency analyses, noting the required design modifications to ensure stable operation. Stability was found to be significantly influenced by the extent of the continuous fluid film in the hydrodynamic circumferentially grooved bearings. It was concluded that the assumption of a 180 degree film extent was totally inappropriate even though the bearing ends were open to the atmosphere, whereas the assumption of fluid film break up at the lubricant saturation vapour pressure proved appropriate for stability predictions provided one ensured that the bearings were flooded. Preliminary bearing force evaluations proved inconclusive, primarily because the self aligning bearings nevertheless experienced angular misalignment; and because there was uncertainty as to how much air was entrained in the bearings, in spite of attempts to prevent air ingress.

Air Bearing Force Measurement of Pico Negative Pressure Sliders During Dynamic Unload

1999 ◽  
Vol 122 (4) ◽  
pp. 771-775 ◽  
Author(s):  
M. Chapin ◽  
D. B. Bogy
Keyword(s):  
Negative Pressure ◽  
High Speed ◽  
Force Measurement ◽  
Force Transducer ◽  
Experimental Results ◽  
Air Bearing ◽  
Load Beam ◽  
Bearing Force ◽  
Lift Off ◽  
Force Displacement

The air bearing forces of “pico negative pressure” (1.25 × 1.0 mm subambient pressure) sliders during the unload process were investigated experimentally. A high speed vertical load/unload mechanism with a sensitive force transducer was developed to measure the air bearing forces. Force histories were measured at various disk rpm and unload velocities. The force histories showed that the suspension load dimple separated from the load beam during the lifting. This separation was held to an acceptable amount by flexure limitors built into the suspension. Force-displacement curves show the need for control of the gap between the limitor and load beam. A technique was developed to determine critical suspension parameters for use in the CML Dynamic Load/Unload Simulator. Simulation of the force history was then in excellent agreement with experimental results. Both simulation and experimental results showed that the lift-off force decreases with increasing disk rpm. Experimental results also showed that higher unload speeds lead to larger lift-off forces. By selecting the correct disk rpm and unload speed, the lift-off force could be minimized. [S0742-4787(00)00103-X]

scholarly journals Vibration Response Analysis of a Gear-rotor-bearing System Considering Steady-state Temperature

2021 ◽  
Author(s):  
Zhou Sun ◽  
Siyu Chen ◽  
Zehua Hu ◽  
Duncai Lei
Keyword(s):  
Steady State ◽  
Material Properties ◽  
Temperature Fields ◽  
Response Analysis ◽  
Nodal Method ◽  
Steady State Temperature ◽  
Rotor Bearing ◽  
Influence Of Temperature On ◽  
Bearing Force ◽  
Bearing System

Abstract As an important factor leading to the failure of gear system, the study of thermal effect is insufficiently deep. Based on the finite element nodal method, a more comprehensive dynamic model of gear-rotor-bearing system is established, which considers the thermal related material properties, time-varying meshing stiffness (TVMS), backlash and friction, gyroscopic effect. The constitutive relation of beam element considering steady-state temperature is reconstructed, and thermal node load is formulated. Considering the influence of temperature on the material properties of flexible shaft and gear, the thermal related TVMS and thermal backlash are obtained. The dynamic response of the system under different steady-state temperature fields is compared, and the influence of hot backlash is studied, then the thermal related vibration characteristics are obtained. Besides, the influence of bearing type on bearing force and axial trajectory is studied. The results show that the system motion changes from period to chaos with the temperature increase in part of the speed range. The appropriate backlash is helpful to restrain the chaotic motion caused by temperature rise. Moreover, the temperature can significantly increase the axial bearing force, and the appropriate bearing can reduce the axial displacement.

Disturbance Accommodating Controllers for Rotating Mechanical Systems

1986 ◽  
Vol 108 (1) ◽  
pp. 24-31 ◽  
Author(s):  
K. D. Reinig ◽  
A. A. Desrochers
Keyword(s):  
Active Control ◽  
Center Of Mass ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Rotor Shaft ◽  
Mass Imbalance ◽  
Shaft System ◽  
Control Schemes ◽  
Bearing Force ◽  
Large Rotor

The use of magnetic bearings for supporting a rotor-shaft system has led to increasing interest in active control schemes. In this work, two disturbance accommodating controllers are developed which minimize the vibration of the system due to the mass imbalance of the rotor. The first controller generates an estimate of the disturbance force arising from this mass imbalance and then cancels its effect through the magnetic bearings. This keeps the rotor displacement at zero but often at the expense of high bearing forces. The second controller remedies this by estimating the eccentricity and then applying a force to the controlled shaft end to offset the effect of the eccentricity. This requires the controlled shaft end to follow a path so that the rotor shaft pivots about the center of mass. Thus, the center of mass of the system does not translate and so a disturbance force never occurs. Therefore, a small magnetic bearing force can be used to control the vibration of a large rotor. Both methods are compared to conventional bearing strategies.

Dynamic analysis of a double-helical geared rotor system with oil-film bearing

2020 ◽  
Vol 92 (4) ◽  
pp. 653-662
Author(s):  
Ying-Chung Chen ◽  
Tsung-Hsien Yang ◽  
Siu-Tong Choi
Keyword(s):  
Dynamic Analysis ◽  
Rotor System ◽  
Content Type ◽  
Oil Film ◽  
Lateral Response ◽  
Helical Angle ◽  
Rotor Bearing ◽  
Bearing Stiffness ◽  
Bearing Force ◽  
Bearing System

Purpose This paper aims to study a dynamic analysis of a double-helical geared rotor system with oil-film bearing. Design/methodology/approach A finite element model of a double-helical geared rotor system with oil-film bearing is developed, in which a rigid mass is used to represent the gear and the Timoshenko beam finite element represents the shaft; the equations of motion are obtained by applying Lagrange’s equation. Natural frequencies, Campbell diagram, lateral responses, axial responses, bearing stiffness coefficients, bearing damping coefficients and bearing force are investigated. Findings Natural frequencies and Campbell diagram of a double-helical geared rotor system with oil-film bearing are investigated. An increased helical angle enhanced the axial response of the system and reduced its lateral response. The distance between the node and bearing affected the lateral response magnitude on the node. The farther away the gear pair was from the central part of the shaft, the higher the system’s resonance frequency became. The different gear pair position has a significant influence on the bearing stiffness coefficient and bearing force, but it just has a little effect on the bearing damping coefficient. Practical implications The model of a double-helical geared rotor system with oil-film bearing is established in this paper. The dynamic characteristics of a double-helical geared rotor system with oil-film bearing are investigated. The numerical results of this study can be used as a reference for subsequent personnel research. Originality/value Although the dynamics characteristics of geared rotor bearing system have been reported in some literature, the dynamic analysis of a double-helical geared rotor-bearing system is still rarely investigated. This paper showed some novel results that lateral and axial response results are obtained by the different helical angle and different gear positions. In the future, it makes valuable contributions for further development of dynamic analysis of a double-helical geared rotor-bearing system.

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