Dynamic Instability of a High-Speed Rotor Containing a Partitioned Cavity Filled With Two Kinds of Liquids

1989 ◽  
Vol 111 (4) ◽  
pp. 450-456 ◽  
Author(s):  
Y. Jinnouchi ◽  
Y. Araki ◽  
J. Inoue ◽  
S. Kubo
Keyword(s):  
Natural Frequency ◽  
Cylindrical Cavity ◽  
High Speed ◽  
Critical Speed ◽  
Dynamic Instability ◽  
Rotor System ◽  
Rotor Speed ◽  
Unstable Region ◽  
System Parameters ◽  
Unstable Behavior

This paper is concerned with the dynamic instability of a high-speed rotor containing a partitioned cavity filled with two kinds of liquids of different density. The system considered simulates a centrifuge of two liquids type, in which the cylindrical cavity is divided into fan-shaped compartments in order to suppress asynchronous whirling motions induced by waves in the liquids traveling around the cavity. Assuming rotor vibrations to be small, liquids inviscid, and external damping negligible, perturbed motions of the liquid-rotor system are analyzed. The theory shows that the rotor containing a partitioned cavity can still exhibit unstable behavior, similar to that observed for a rotor system equipped with centrifugal pendula, in the region where the rotor speed is nearly equal to the sum of the critical speed of the system and the natural frequency of the liquids. The theory has been verified by the experiments. The dependence of the unstable region on the main system parameters is also discussed.

Internal Rotor Friction Induced Instability in High-Speed Rotating Machinery

1993 ◽  
Author(s):  
James F. Walton ◽  
Michael R. Martin
Keyword(s):  
Internal Friction ◽  
Natural Frequency ◽  
High Speed ◽  
Critical Speed ◽  
Rotating Machinery ◽  
Rotor System ◽  
Analytical Models ◽  
Interference Fit ◽  
Internal Rotor

Abstract Results of a program to investigate internal rotor friction destabilizing effects are presented. Internal-friction-producing joints were shown to excite the rotor system first natural frequency, when operating either below or above the first critical speed. The analytical models used to predict the subsynchronous instability were also confirmed. The axial spline joint demonstrated the most severe subsynchronous instability. The interference fit joint also caused subsynchronous vibrations at the first natural frequency but these were bounded and generally smaller than the synchronous vibrations. Comparison of data from the two test joints showed that supersynchronous vibration amplitudes at the first natural frequency were generally larger for the interference fit joint than for the axial spline joint. The effects of changes in imbalance levels and side loads were not distinguishable during testing because amplitude-limiting bumpers were required to restrict orbits.

Analysis of Stiffness of Viscoelastic-Friction Damper for High-Speed Rotor System

2012 ◽  
Vol 538-541 ◽  
pp. 768-772
Author(s):  
Wen Zhong Li ◽  
Fu Xiang Zhang
Keyword(s):  
Friction Coefficient ◽  
High Speed ◽  
Critical Speed ◽  
Cone Angle ◽  
Rotor System ◽  
Outer Ring ◽  
Axial Stiffness ◽  
Friction Damper ◽  
Damping Material

To reduce the excessive vibration of a high-speed rotor system as it passes its critical speed, a viscoelastic-friction damper(VEFD) are introduced into the support. Its stiffness factor is analyzed. Results show, the stiffness factor decreases with the cone angle increasing among 55-80 degrees monotonically. And it is the same trend when the stiffness of the damping material ring decreases. In the case of friction coefficient among 0.1-0.5, the stiffness factor increases monotonically. So adopted a proper structure, suitably chosen the above parameters and the axial stiffness of the outer-ring, the damper can present appropriate stiffness.

Optimization Design and Experimental Study of a Two-disk Rotor System Based on Multi-Island Genetic Algorithm

2019 ◽  
Vol 36 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Jingjing Huang ◽  
Longxi Zheng ◽  
Chris K Mechefske ◽  
Bingbing Han
Keyword(s):  
Genetic Algorithm ◽  
Vibration Amplitude ◽  
High Speed ◽  
Optimization Design ◽  
Critical Speed ◽  
Optimization Method ◽  
Rotor System ◽  
Flexible Rotor ◽  
Optimum Position ◽  
Transient Experiments

Abstract Based on rotor dynamics theory, a two-disk flexible rotor system representing an aero-engine with freely supported structure was established with commercial software ANSYS. The physical model of the two-disk rotor system was then integrated to the multidisciplinary design optimization software ISIGHT and the maximum vibration amplitudes experienced by the two disks when crossing the first critical speed were optimized using a multi-island genetic algorithm (MIGA). The optimization objective was to minimize the vibration amplitudes of the two disks when crossing the first critical speed. The position of disk 1 was selected as the optimization variable. The optimum position of disk 1 was obtained at the specified constraint that the variation of the first critical speed could not exceed the range of ±10 %. In order to validate the performance of the optimization design, the proof-of-transient experiments were conducted based on a high-speed flexible two-disk rotor system. Experimental results indicated that the maximum vibration amplitude of disk 1 when crossing the first critical speed declined by 60.9 % and the maximum vibration amplitude of disk 2 fell by 63.48 % after optimization. The optimization method found the optimum rotor positions of the flexible rotor system which resulted in minimum vibration amplitudes.

The Dynamic Analysis of SFD-Sliding Bearing Flexible Rotor System Based on Optimization Design

2012 ◽  
Vol 159 ◽  
pp. 355-360
Author(s):  
Ji Yan Wang ◽  
Rong Chun Guo ◽  
Xu Fei Si
Keyword(s):  
High Speed ◽  
Optimization Design ◽  
Critical Speed ◽  
Structural Parameters ◽  
Rotor System ◽  
Flexible Rotor ◽  
Optimization Analysis ◽  
Sliding Bearing ◽  
Critical Speeds ◽  
Design Variables

The paper establishes the mechanical model of SFD-sliding bearing flexible rotor system, adopting Runge-Kutta method to solve nonlinear differential equation, thus acquiring the unbalanced response curve and then gaining the first two critical speeds of the system. Meanwhile, the paper analyzes the sensitivity of the system on the first two critical speeds towards structural parameters, offering design variables to optimization analysis. Based on sensitivity analysis, genetic algorithm is employed to give an optimization analysis on critical speed, which aims to remove critical speed from working speed as much as possible. The critical speed ameliorates after the optimization which supplies theoretical basis as well as theoretical analysis towards the dynamic stability of high-speed rotor system and provides reference for the design of such rotor system.

Numerical Analysis for the Stability of Cylinder Gas Film Seal

2013 ◽  
Vol 655-657 ◽  
pp. 526-530
Author(s):  
Gang Ma ◽  
Jun He ◽  
Xin Min Shen
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Reynolds Equation ◽  
Working Condition ◽  
Critical Mass ◽  
System Stability ◽  
Dynamics Analysis ◽  
Rotor Speed ◽  
Analysis Model ◽  
The Stability

Non-contacting gas film seal applies to the high speed working condition and a numerical method was presented for analyzing the effect of speed on the stability of cylinder gas film seal. The dynamics analysis model was established, solving the time-dependent Reynolds equation coupling with the dynamic equations. Through numerical simulation, the critical speed of cylinder gas film seal system and the diagram of critical mass versus rotor speed were obtained. The influence of the speed on dynamic stability was studied. The results show that the system stability becomes worse as rotor speed increases.

The Influence of Internal Damping on the Rotordynamic Stability of a Flywheel Rotor With Flexible Hub

2005 ◽  
Author(s):  
Alfonso Moreira ◽  
George Flowers ◽  
Alex Matras ◽  
Mark Balas ◽  
Jerry Fausz
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Experimental Testing ◽  
Research Effort ◽  
Simulation Studies ◽  
Internal Damping ◽  
System Parameters ◽  
Carbon Fiber Epoxy ◽  
Testing And Evaluation ◽  
Flywheel Rotor

An investigation about the influence of internal damping on the rotordynamic stability of high-speed flywheel energy storage systems made from carbon fiber epoxy is presented. The research effort consists of simulation studies coupled with experimental testing and evaluation. Damping values obtained from composite beam samples and a composite rotor hub design are shown. The effect of vibration frequency on damping is examined and discussed. These parameters are then used in a series of simulation studies that examine the effects of internal damping on rotordynamic behavior. An experimental model has been developed to verify the conclusions made from the simulations. The experimental testing consisted of creating a prototype rig, characterizing the system parameters, applying these parameters to determine the expected critical speed and experimentally determine the actual critical speed. These results are presented and their implications for flexible hub flywheel designs discussed.

Vibration of a Misaligned Rotor System with Asymmetric Shaft Stiffness

2012 ◽  
Vol 503-504 ◽  
pp. 813-818
Author(s):  
Sheng Feng ◽  
Hai Peng Geng ◽  
She Miao Qi ◽  
Lie Yu
Keyword(s):  
Natural Frequency ◽  
Vibration Amplitude ◽  
Rotor System ◽  
Lateral Vibration ◽  
Rotor Speed ◽  
Flexible Coupling ◽  
Parallel Misalignment ◽  
Rigid Disks ◽  
Simulation Results ◽  
Speed Simulation

Vibration characteristics of a misaligned rotor with asymmetric shaft stiffness are studied. The system consists of two shafts connected by a flexible coupling with parallel misalignment, two rigid disks attached at the middle of each shaft and one of the shafts has asymmetric stiffness. The governing ordinary differential equations are derived using Lagrange dynamics and integrated through numerical methods. The effects of asymmetry, eccentricity and misalignment are studied through the peak-to-peak lateral vibration amplitude at different rotor speed. Simulation results show that the amplitude peaks at the natural frequency associated with unbalance and parallel misalignment, while half the natural frequency associated with the asymmetric shaft stiffness. This study may contribute to enrich understanding of the vibration of a rotor system under the cases of eccentricity, parallel misalignment and asymmetric shaft stiffness.

The Dynamic Analysis of High-Speed Energy Storage Flywheel Rotor System

2013 ◽  
Vol 770 ◽  
pp. 78-83
Author(s):  
Xiu Hua Zhang ◽  
Guang Xi Li ◽  
Long Nie
Keyword(s):  
Steady State ◽  
Energy Storage ◽  
High Speed ◽  
Transient Analysis ◽  
Critical Speed ◽  
Large Scale ◽  
Simulation Analysis ◽  
Rotor System ◽  
Analysis Method ◽  
Flywheel Rotor

This article aims at large-scale energy storage flywheel rotor system, obtaining the dynamic characteristics. Through theoretical analysis, and after doing a simulation analysis for a given flywheel rotor on the 0-20000 RPM, getting the flywheel rotor critical speed, the transient analysis and imbalance response. The system is in steady state at runtime according to the analysis results. Providing also certain theory basis for study of flywheel rotor system according to the analysis method .

scholarly journals The Influence of Shaft’s Bending on the Coupling Vibration of a Flexible Blade-Rotor System

2017 ◽  
Vol 2017 ◽  
pp. 1-19 ◽  
Author(s):  
Chao-feng Li ◽  
Hou-xin She ◽  
Wen Liu ◽  
Bang-chun Wen
Keyword(s):  
Natural Frequency ◽  
Critical Speed ◽  
Vibration Mode ◽  
Rotor System ◽  
Rotor Blades ◽  
Mode Shapes ◽  
Coupling Vibration ◽  
Mode Function ◽  
Coupling Mode ◽  
Supporting Condition

The influence of shaft bending on the coupling vibration of rotor-blades system is nonignorable. Therefore, this paper analyzed the influence of shaft bending on the coupling vibration of rotor-blades system. The vibration mode function of shaft under elastic supporting condition was also derived to ensure accuracy of the model as well. The influence of the number of blades, the position of disk, and the support stiffness of shaft on critical speed of system was analyzed. The numerical results show that there were two categories of coupling mode shapes which belong to a set where the blade’s first two modes predominate in the system: shaft-blade (SB) mode and interblade (BB) mode due to the coupling between blade and shaft. The BB mode was of repeated frequencies of (Nb-2) multiplicity for number blades, and the SB mode was of repeated frequencies of (2) multiplicity for number blades. What is more, with the increase of the number of blades, natural frequency of rotor was decreasing linearly, that of BB mode was constant, and that of SB mode was increasing linearly. Natural frequency of BB mode was not affected while that of rotor and SB mode was affected (changed symmetrically with the center of shaft) by the position of disk. In the end, vibration characteristics of coupling mode shapes were analyzed.

Sign in / Sign up

Export Citation Format

Share Document