Critical Speed Analysis of Sliding Bearing Rotor System Based On ANSYS

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.

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Influence of roundness error screw on running characteristics of sliding bearing based on SDT

MATEC Web of Conferences ◽

10.1051/matecconf/202235501021 ◽

2022 ◽

Vol 355 ◽

pp. 01021

Author(s):

Zhenyu Chen ◽

Wubin Xu ◽

Bing Li

Keyword(s):

Critical Speed ◽

Journal Bearing ◽

Rotor System ◽

Small Displacement ◽

Promoting Effect ◽

Sliding Bearing ◽

Roundness Error ◽

System A ◽

Film Characteristics ◽

Generalized Roundness

In order to study the influence of roundness error on the oil film characteristics of journal bearing rotor system, a dynamic model of journal bearing rotor system with roundness error was established, and a new generalized roundness error equation is derived based on the small displacement screw (SDT) theory. And the influence of roundness error screw parameter dx represented by SDT on critical speed and stability of sliding bearing is analyzed emphatically. The results show that the existence of journal roundness error is beneficial to the bearing capacity and stability of sliding bearing rotor system to a certain extent, and with the increase of roundness error screw parameter, its promoting effect is more obvious; At the same time, the critical speed of the system will increase with the increase of screw parameter, especially when eccentricity ε>0.6; And when Sommerfeld number S>0.6, the roundness error of journal has little influence on stability.

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Feasibility investigation of a compressor rotor supported by gas foil bearings with inhomogeneous bump foils

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1177/13506501211004668 ◽

2021 ◽

pp. 135065012110046

Author(s):

Hao Li ◽

Haipeng Geng ◽

Bo Wang ◽

Wei Zheng

Keyword(s):

Critical Speed ◽

Rotor System ◽

Experimental Result ◽

Test Results ◽

Rotating Speed ◽

Foil Bearings ◽

Dynamic Coefficients ◽

High Order Harmonic ◽

Compressor Rotor ◽

Operating Points

In this paper, a rotordynamic experiment on a compressor rotor system is presented and the feasibility of gas foil bearings with inhomogeneous bump foils is verified. A push–pull device is designed to obtain the stiffness curve and the nominal clearance of foil bearings. Operating points and dynamic coefficients of the rotor system at each rotating speed are predicted. In rotordynamic analysis, an alternative model of the impeller is proposed and the critical speed is predicted by employing the finite element method, in which the dynamic coefficients of inhomogeneous foil bearings are taken into account. Compared with the experimental result, the accuracy of the prediction for the critical speed is verified to be about 14% error. Two sets of foil bearings with 22 and 41 μm nominal clearance are manufactured and tested. Test results indicate that the vibration amplitude can be greatly reduced by diminishing the bearing clearance. When foil bearings with 22 μm clearance are used, the high-order harmonic frequencies of rotor vibration are significantly inhibited, and the amplitude of the rotating frequency is obviously restricted. Thus, the foil bearing with inhomogeneous bump foils tested in this paper can meet the speed requirement of the compressor when the nominal clearance is set at 22 μm.

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Multi Objective Optimisation of an Aero Engine Rotor System Using Nondominated Sorting Genetic Algorithm (NSGA)

Volume 2: Structures and Dynamics; Renewable Energy (Solar, Wind); Inlets and Exhausts; Emerging Technologies (Hybrid Electric Propulsion, UAV, ...); GT Operation and Maintenance; Materials and Manufacturing (Including Coatings, Composites, CMCs, Additive Manufacturing); Analytics and Digital Solutions for Gas Turbines/Rotating Machinery ◽

10.1115/gtindia2017-4681 ◽

2017 ◽

Cited By ~ 1

Author(s):

Joseph Shibu Kalloor ◽

Ch. Kanna Babu ◽

Girish K. Degaonkar ◽

K. Shankar

Keyword(s):

Genetic Algorithm ◽

Critical Speed ◽

Rotor System ◽

Pareto Optimal ◽

Multi Objective ◽

Rayleigh Beam ◽

Unbalance Response ◽

Aero Engine ◽

Nondominated Sorting ◽

Engine Rotor

A comprehensive multi-objective optimisation methodology is presented and applied to a practical aero engine rotor system. A variant of Nondominated Sorting Genetic Algorithm (NSGA) is employed to simultaneously minimise the weight and unbalance response of the rotor system with restriction imposed on critical speed. Rayleigh beam is used in Finite Element Method (FEM) implemented in-house developed MATLAB code for analysis. The results of practical interest are achieved through bearing-pedestal model and eigenvalue based Rayleigh damping model. Pareto optimal solutions generated and best solution selected with the help of response surface approximation of the Pareto optimal front. The outcome of the paper is a minimum weight and minimum unbalance response rotor system which satisfied the critical speed constraints.

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Internal Rotor Friction Induced Instability in High-Speed Rotating Machinery

14th Biennial Conference on Mechanical Vibration and Noise: Vibration of Rotating Systems ◽

10.1115/detc1993-0205 ◽

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.

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Dynamical analysis of hollow-shaft dual-rotor system with circular cracks

Journal of Low Frequency Noise Vibration and Active Control ◽

10.1177/1461348420948287 ◽

2020 ◽

pp. 146134842094828

Author(s):

Yang Yongfeng ◽

Wang Jianjun ◽

Wang Yanlin ◽

Fu Chao ◽

Zheng Qingyang ◽

...

Keyword(s):

Critical Speed ◽

Equations Of Motion ◽

Harmonic Balance Method ◽

Circular Crack ◽

Rotor System ◽

Resonance Phenomenon ◽

Dynamical Analysis ◽

Dynamical Response ◽

Critical Speeds ◽

Hollow Shaft

In this paper, we considered a dual-rotor system with crack in shaft. The influence of circular crack in hollow shaft on dynamical response was studied. The equations of motion of 12 elements dual-rotor system model were derived. Harmonic balance method was employed to solve the equations. The critical speed and sub-critical speed responses were investigated. It was found that the circular crack in hollow shaft had greater influence on the first-backward critical speed than the first-forward critical speed. Owing to the influence of crack, the vibration peaks occurred at the 1/2, 1/3 and 1/4 critical speeds of the rotor system, along with a reduction in sub-critical speeds and critical speeds. The deeper crack away from the bearing affected the rotor more significantly. The whirling orbits, the time-domain responses and the spectra were obtained to show the super-harmonic resonance phenomenon in hollow-shaft cracked rotor system.

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Dynamic Analysis of Flexible Rotor Based on Transfer Symplectic Matrix

Shock and Vibration ◽

10.1155/2019/9154272 ◽

2019 ◽

Vol 2019 ◽

pp. 1-11

Author(s):

Hao Deng ◽

Xi Fang ◽

Huachun Wu ◽

Yiming Ding ◽

Jinghu Yu ◽

...

Keyword(s):

Transfer Matrix ◽

Matrix Method ◽

Critical Speed ◽

Reference Method ◽

Rotor System ◽

High Order ◽

Symplectic Matrix ◽

Hamilton System ◽

System A ◽

Relative Errors

In view of the numerical instability and low accuracy of the traditional transfer matrix method in solving the high-order critical speed of the rotor system, a new idea of incorporating the finite element method into the transfer matrix is proposed. Based on the variational principle, the transfer symplectic matrix of gyro rotors suitable for all kinds of boundary conditions and supporting conditions under the Hamilton system is derived by introducing dual variables. To verify the proposed method in rotor critical speed, a numerical analysis is adopted. The simulation experiment results show that, in the calculation of high-order critical speed, especially when exceeding the sixth critical speed, the numerical accuracy of the transfer symplectic matrix method is obviously better than that of the reference method. The relative errors between the numerical solution and the exact solution are 0.0347% and 0.2228%, respectively, at the sixth critical speed. The numerical example indicates the feasibility and superiority of the method, which provides the basis for the optimal design of the rotor system.

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Investigation on Lubrication State of Sliding Bearings in Low-Speed Rotor System Subjected to Torque Load

International Journal of Rotating Machinery ◽

10.1155/2019/1791830 ◽

2019 ◽

Vol 2019 ◽

pp. 1-11

Author(s):

Xinyu Pang ◽

Wangwang Jiang ◽

Xiaowu Jin

Keyword(s):

Wear Rate ◽

Film Thickness ◽

Rotor System ◽

Thickness Ratio ◽

Sliding Bearing ◽

Film Pressure ◽

Low Speed ◽

Torque Load ◽

Torque Values ◽

Oil Film Pressure

In order to study the influence of torque load on the lubrication and wear of the sliding bearing of the rigid rotor system, the theoretical and experimental researches on the single-span rotor system with low speed were carried out. A special force sensor was used to measure the bearing load under different torque excitations, and the oil film pressure was calculated. The oil film pressure and thickness of sliding bearing under low speed (210r/min) were simulated by combining the lubrication theory. Based on the film thickness ratio theory, the corresponding relationship between the lubrication state and the torque load value was deduced. In addition, the wear rate and abrasive grain morphology of sliding bearing with different torque values were analyzed by means of oil sample preparation to verify this correspondence. The results show that the film thickness ratio has a logarithmic function relationship with the constant torque load, and the film thickness ratio curve can be used to determine the corresponding torque values under different lubrication states. The wear rate under mixed lubrication state increases exponentially with the torque load, and the main wear mechanism is adhesive wear and abrasive wear. The research results have certain guiding significance to the adjustment of the actual running condition of sliding bearing and its life prediction.

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Active Vibration Control of a Non-collocated AMBs Flexible Rotor System to Pass the First Bending Critical Speed

2019 22nd International Conference on Electrical Machines and Systems (ICEMS) ◽

10.1109/icems.2019.8922473 ◽

2019 ◽

Author(s):

Peipei Wang ◽

Changsheng Zhu

Keyword(s):

Vibration Control ◽

Critical Speed ◽

Active Vibration Control ◽

Rotor System ◽

Flexible Rotor ◽

Active Vibration

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Active Elastic Support/Dry Friction Damper with Piezoelectric Ceramic Actuator

Shock and Vibration ◽

10.1155/2014/712426 ◽

2014 ◽

Vol 2014 ◽

pp. 1-10 ◽

Cited By ~ 3

Author(s):

Liao Mingfu ◽

Song Mingbo ◽

Wang Siji

Keyword(s):

Dry Friction ◽

Piezoelectric Ceramic ◽

Vibration Amplitude ◽

Critical Speed ◽

Rotor System ◽

Elastic Support ◽

Basic Operation ◽

Friction Damper ◽

Rotor Vibration ◽

Active Damper

The basic operation principle of elastic support/dry friction damper in rotor system was introduced and the unbalance response of the rotor with elastic support/dry friction damper was analyzed theoretically. Based on the previous structure using an electromagnet as actuator, an active elastic support/dry friction damper using piezoelectric ceramic actuator was designed and its effectiveness of reducing rotor vibration when rotor traverses its critical speed and blade-out event happened was experimentally verified. The experimental results show that the active elastic support/dry friction damper with piezoelectric ceramic actuator can significantly reduce vibration in rotor system; the vibration amplitude of the rotor in critical speed region decreased more than 2 times, and the active damper can protect the rotor when a blade-out event happened, so the rotor can traverse the critical speed and shut down smoothly. In addition, the structure is much simpler than the previous, the weight was reduced by half and the power consumption was only 5 W.

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