scholarly journals Optimization of the Stability and Reliability of Rotor System by the Methodology of Design Experiments

2021 ◽  
Vol 8 (2) ◽  
pp. 302-314
Author(s):  
Brihmat Mostefa ◽  
Refassi Kaddour ◽  
Younes Mimoun ◽  
Douroum Embarek ◽  
Kouadri Amar
Keyword(s):  
Rotor System ◽  
The Stability ◽  
Design Experiments

An investigation on the instability of a flexible liquid-filled rotor

2019 ◽  
Vol 234 (2) ◽  
pp. 165-172
Author(s):  
Guangding Wang ◽  
Huiqun Yuan ◽  
Hongyun Sun
Keyword(s):  
Stokes Equations ◽  
Fluid Motion ◽  
Coupling Model ◽  
Frequency Equation ◽  
Rotor System ◽  
System Stability ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Continuity Equations ◽  
The Stability

In this paper, the stability of a flexible rotor partially filled with liquid is investigated. On the basis of the Navier-Stokes equations for the incompressible flow, a two-dimensional analytical model is developed for fluid motion. Applying the perturbation method, the linearized Navier-Stokes and continuity equations of fluid particles are obtained. Using the boundary conditions of fluid motion, the fluid forces exerted on the rotor are calculated. According to the established fluid-structure coupling model of the rotor system, the whirling frequency equation, which is applied to determine the stability of the system, is derived. The analysis results of the system stability are compared with the theoretical ones reported in the previous study. Good agreement is shown between the results of the present analysis and the literature results. The influences of the main parameters on the dynamic stability of the rotor system are discussed.

On an Independent Period-1 Motion in a Flexible Rotor System

2019 ◽  
Author(s):  
Yeyin Xu ◽  
Albert C. J. Luo
Keyword(s):  
Numerical Simulations ◽  
Internal Resonance ◽  
Mapping Method ◽  
Rotor System ◽  
Flexible Rotor ◽  
Periodic Motions ◽  
Phase Trajectories ◽  
Stability And Bifurcation ◽  
The Stability ◽  
Nonlinear Rotor System

Abstract This paper investigates stable and unstable period-1 motions in a rotor system through the discrete mapping method. The discrete mapping of a nonlinear rotor system is for stable and unstable period-1 motions. The stability and bifurcation of periodic motions are determined. Numerical simulations of periodic motions are completed and phase trajectories, displacement orbits and velocity plane are illustrated. The period-1 motion near the internal resonance is determined with large vibration in the nonlinear rotor system.

scholarly journals The Influence of a Mistuned Blade’s Staggle Angle on the Vibration and Stability of a Shaft-Disk-Blade Assembly

2008 ◽  
Vol 15 (1) ◽  
pp. 3-17 ◽  
Author(s):  
Yi-Jui Chiu ◽  
Shyh-Chin Huang
Keyword(s):  
Natural Frequencies ◽  
Linear Trend ◽  
Rotor System ◽  
Instability Point ◽  
Blade System ◽  
Blade Assembly ◽  
The Stability

The influence on coupling vibrations and stability among shaft-torsion, disk-transverse and blade-bending of a rotor system with a mistuned blade's staggle angle was investigated analytically. A shaft-disk-blade system has been found existing two types of coupling vibrations, disk-blade (DB), and blade-blade (BB) modes when the shaft was assumed rigid. If the shaft's torsional flexibility was taken into account, an additional type of coupling modes, shaft-disk-blade (SDB), appeared. When an angle-mistuned blade existed, the blades periodicity was destroyed and it was found to change not only the natural frequencies but also the types of modes. Due to blade's mistune, the shaft torsion had to participate to balance such that DB modes vanished and replaced by SDB modes. A mistuned staggle angle was numerically found to alter the natural frequencies in an almost linear trend. At last, the rotational effects were found to merge frequency loci and eventually reached an instability point. Very interestingly, a mistuned blade diminished the possible instability caused by blade-dominating modes, which existed in a perfect and periodic rotor. In words, the rotor might benefit from a mistuned blade from the stability viewpoint. The shaft-dominating mode, yet, was unaffected by the mistune and retained a possible instability.

Stability and Bifurcation of Nonlinear Bearing-Flexible Rotor System with a Single Disk

2010 ◽  
Vol 148-149 ◽  
pp. 141-146
Author(s):  
Di Hei ◽  
Yong Fang Zhang ◽  
Mei Ru Zheng ◽  
Liang Jia ◽  
Yan Jun Lu
Keyword(s):  
Nonlinear Dynamic ◽  
Degrees Of Freedom ◽  
Rotor System ◽  
Dynamic Responses ◽  
Flexible Rotor ◽  
Runge Kutta Method ◽  
Stability And Bifurcation ◽  
Single Disk ◽  
The Stability ◽  
Predictor Corrector

Dynamic model and equation of a nonlinear flexible rotor-bearing system are established based on rotor dynamics. A local iteration method consisting of improved Wilson-θ method, predictor-corrector mechanism and Newton-Raphson method is proposed to calculate nonlinear dynamic responses. By the proposed method, the iterations are only executed on nonlinear degrees of freedom. The proposed method has higher efficiency than Runge-Kutta method, so the proposed method improves calculation efficiency and saves computing cost greatly. Taking the system parameter ‘s’ of flexible rotor as the control parameter, nonlinear dynamic responses of rotor system are obtained by the proposed method. The stability and bifurcation type of periodic responses are determined by Floquet theory and a Poincaré map. The numerical results reveal periodic, quasi-periodic, period-5, jump solutions of rich and complex nonlinear behaviors of the system.

An Experimental Investigation on the Response of a Flexible Rotor Mounted in Pressure Dam Bearings

1980 ◽  
Vol 102 (4) ◽  
pp. 842-850 ◽  
Author(s):  
R. D. Flack ◽  
M. E. Leader ◽  
E. J. Gunter
Keyword(s):  
Experimental Investigation ◽  
Rotor System ◽  
Flexible Rotor ◽  
The Stability

The response of a flexible rotor mounted in six bearing sets has been experimentally determined. One set of axial groove bearings and five sets of pressure dam bearings were tested. Conventional synchronous tracking was used in the analysis and other techniques utilizing an FFT analyzer were developed. The stability of the system was seen to strongly depend on the design of the step bearings. The dam bearings were also noted to lock into subsynchronous whip during deceleration after the system went unstable. The response of the system with varying degrees of unbalance is also analyzed and several structural resonances of the rotor system are discussed.

Stability Margin Sensitivity Analysis of a Multi-Rotor System Geared by Spiral Bevel Gear Pairs

2010 ◽  
Vol 97-101 ◽  
pp. 3215-3218
Author(s):  
Ye Sen Fan ◽  
San Min Wang ◽  
Zhen Yang
Keyword(s):  
Sensitivity Analysis ◽  
Optimization Design ◽  
Stability Margin ◽  
Rotor System ◽  
Bevel Gear ◽  
Dynamic Equations ◽  
Spiral Bevel Gear ◽  
Global Dynamic ◽  
Spiral Bevel ◽  
The Stability

To study the stability margin sensitivity to the parameters of the geared rotor system is prerequisite to carry on structure optimization design and vibration control. The global dynamic equations of the geared two rotor system are set up through the coupled matrix of the spiral bevel gear pairs, and the stability margin is obtained by analyzing the global dynamic equations. To enhance the damping of the bearings and to enhance the module and mesh damping of the gear pairs can improve the stability margin of the geared rotor system. The method for the stability margin sensitivity analysis of the geared multi-rotor system is feasible. The conclusions from the numerical example are useful to improve the stability margin of the geared multi-rotor systems.

Rotordynamic Stability Under Partial Admission Conditions in a Large Power Steam Turbine

2009 ◽  
Author(s):  
Lin Gao ◽  
Yiping Dai ◽  
Zhiqiang Wang ◽  
Yatao Xu ◽  
Qingzhong Ma
Keyword(s):  
Steam Turbine ◽  
Fluid Model ◽  
Rotor System ◽  
System Stability ◽  
Steam Turbines ◽  
Large Power ◽  
Control Stage ◽  
Partial Admission ◽  
The Stability ◽  
Load Conditions

At present, the majority of power steam turbines operate under part-load conditions during most of their working time in accordance with the fluctuation of power supply. The load governing method may cause partial admission in control stage and even some pressure stages, which impacts much on the stability of the rotor system. In this paper, CFD and FEM method were used to analyze the effect of partial admission on rotor system stability. A new approach is proposed to simplify the 3D fluid model for a partial admission control stage. Rotordynamic analysis was carried out to test the stability of the HP rotor of a 600 MW steam turbine under different load conditions. 13 different governing modes on the rotor stability were conducted and data were analyzed. It is found that rotor stability varies significantly with different governing modes and mass flow rates, which is consistent with the operation. Asymmetric fluid forces resulted from partial admission cause a fluctuation of the dynamic characteristics of the HP bearings, which consequently affect the stability of the rotor system. One of the nozzle governing modes in which the diagonal valves open firstly is demonstrated as the optimal mode with the maximum system stability. The optimization has been applied to 16 power generation units in China and result in improved rotor stabilities.

Analytical and Experimental Investigation of the Stability of Intershaft Squeeze Film Dampers—Part 1: Demonstration of Instability

1977 ◽  
Vol 99 (1) ◽  
pp. 47-52 ◽  
Author(s):  
D. H. Hibner ◽  
R. G. Kirk ◽  
D. F. Buono
Keyword(s):  
Analytical Model ◽  
High Speed ◽  
Rotor System ◽  
Dynamics Simulation ◽  
Squeeze Film ◽  
Response Analysis ◽  
Turbine Engine ◽  
Engine Vibration ◽  
Bearing Loads ◽  
The Stability

Modern high-speed multishaft gas tubine engines incorporate viscous damped bearings to decrease overall system vibration and bearing loads. As viscous damper technology is applied to advanced engine design, more sophisticated analytical and experimental techniques are required to prove new concepts. This analysis will present the results of an investigation of the feasibility of damping engine vibration with a viscous damped intershaft bearing on a two-shaft gas turbine engine. Experimental results from a rotor dynamics simulation rig indicate an instability of the rotor system at speeds above a fundamental critical speed. An analytical model of the two-rotor system is presented and the results of both a classical stability analysis and a time transient response analysis verify the experimental data. The analytical model may be used to predict the stability of two-shaft engines which incorporate an intershaft damped bearing.

Improve the Stability of Rotor Subjected to Fluid Leakage by Optimum Diameters Design

1990 ◽  
Vol 112 (1) ◽  
pp. 59-64 ◽  
Author(s):  
J. H. Wang ◽  
F. M. Shih
Keyword(s):  
Total Mass ◽  
High Performance ◽  
Optimization Technique ◽  
Slight Modification ◽  
Labyrinth Seal ◽  
Rotor System ◽  
Fluid Leakage ◽  
Rotor Bearing ◽  
The Stability

For high performance turbomachinery, the fluid leakage in the shroud of the blades and the labyrinth seal may cause instability and limit the output rating. In this work, an optimization technique has been used to find the optimum diameters of shaft elements so that the optimized rotor can sustain maximum fluid leakage excitation. The results show that, even without the increase of total mass of the rotor system, the threshold performance of rotor-bearing systems can be significantly improved by slight modification of the shaft diameters.

scholarly journals Dynamic Analysis on Nonlinear Fluid-Structure Interaction Forces of Rub-Impact Rotor System

2014 ◽  
Vol 8 (1) ◽  
pp. 480-486
Author(s):  
Yuegang Luo ◽  
Songhe Zhang ◽  
Bin Wu ◽  
Wanlei Wang
Keyword(s):  
Numerical Simulation ◽  
Coupling Model ◽  
Rotor System ◽  
Nonlinear Dynamic Model ◽  
Interaction Forces ◽  
Structure Interaction ◽  
Movement Characteristics ◽  
Set Up ◽  
The Stability ◽  
Nonlinear Fluid

Based on the coupling model of nonlinear oil-film force and nonlinear seal fluid force, a nonlinear dynamic model of rotor system with rub-impact fault is set up. The dynamic characteristics of the system were studied with numerical simulation and the effects of airflow excited force, rubbing gap and stiffness parameters on movement characteristics of the rotor were analyzed. The results indicate that the airflow excited force can significantly restrain the stability and amplitude of rubbing rotor. The less rubbing gap and larger rubbing stiffness are in favor of the stability of the system.

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