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.

Influence on Coupling Vibration of Rotor System with Grouped Blades due to Mistuned Lacing Wire

2011 ◽  
Vol 101-102 ◽  
pp. 1119-1125 ◽  
Author(s):  
Yi Jui Chiu ◽  
Dar Zen Chen ◽  
Chia Hao Yang
Keyword(s):  
Natural Frequencies ◽  
Rotor System ◽  
Numerical Results ◽  
Mode Shapes ◽  
Rotation Effect ◽  
Coupling Vibration ◽  
Coupling Mode ◽  
The Wire ◽  
Grouped Blades

The influence on coupling vibrations among shaft-torsion and blade-bending coupling vibrations of a rotor system with grouped blades was investigated analytically. The natural frequencies and the mode shapes of the system were solved with five- and six-blade cases used as examples. First, numerical results showed how the natural frequencies varied with the wire stiffness and the lacing wire mistuned. The diagrams of the coupling mode shapes were drawn. From the results, it was found that lacing wire did not affect the SB (shaft-blades) coupling modes, but the BB (inter-blades) modes were indeed affected by the lacing wire. At wire stiffness k*=10, the repeated BB modes split into more distinct modes. The BB modes were of (N-1) / 2 and N / 2 multiplicity for odd and even numbered blades. When the system has a mistuned lacing wire, it splits the BB modes and will once more have (N-1) frequencies. In the rotation effect, whatever tuned or mistuned, the lacing wires did not affect the instability. That means the instability preexisted due to rotation and was not induced by lacing wires.

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.

Modal Analysis and Unbalanced Response Analysis of Rotor System

2014 ◽  
Vol 668-669 ◽  
pp. 209-212
Author(s):  
Mei Huang ◽  
Zhao Yang Xing ◽  
Yuan Yuan Zhao ◽  
Jian Nan Tang ◽  
Hao Yuan
Keyword(s):  
Modal Analysis ◽  
Natural Frequency ◽  
Vibration Mode ◽  
Rotor System ◽  
Response Analysis ◽  
Unbalanced Force

In this article, the entity model of the bearing-rotor system is established and meshed in ANSYS. The natural frequency and vibration mode of the rotor system is analyzed in order to avoid the occurrence of resonance. At the same time, the results showed that not only the location of the unbalance incentive of the system should be taken into account, but also consider the size of the unbalanced force.

Vibration Analysis of the Load on Helicopter Swashplate Rod

2012 ◽  
Vol 226-228 ◽  
pp. 119-123
Author(s):  
Fang Wang ◽  
Ming Chen
Keyword(s):  
Mathematical Model ◽  
Control System ◽  
Natural Frequency ◽  
Vibration Analysis ◽  
Vibration Mode ◽  
Rotor Speed ◽  
Helicopter Control ◽  
Flight Experiment ◽  
Control Precision ◽  
Mode Function

The swashplate rod is a key component of helicopter control system. The vibration environment of helicopter is quite complex. The natural frequency of the swashplate rod is generally low. So resonance occurs easily. Resonance could reduce control precision or even damage the whole control system. Established dynamic and mathematical model of swashplate rod. Analyzed the vibration characteristics. Obtained the natural frequency and vibration mode function of the rod. In the compression, tension and free state, the natural frequency of the rod is basically the same. Made flight experiment with a developing helicopter as object. Measured the load of the swashplate rod in flight conditions. Make Fourier analysis to the load. Obtained the frequencies of the load on the rod. The frequencies coincide with 1 and 2 times of the rotor speed.

The Natural Characteristics of Fluid Conveying Pipe under Different Supporting Conditions

2013 ◽  
Vol 372 ◽  
pp. 612-619 ◽  
Author(s):  
Ri Dong Bao
Keyword(s):  
Boundary Conditions ◽  
Natural Frequency ◽  
Vibration Mode ◽  
Fluid Pressure ◽  
Vertical Vibration ◽  
Elastic Coefficient ◽  
Pipe Section ◽  
Mode Function ◽  
Constrained Coefficients ◽  
Natural Characteristics

The natural characteristics of fluid conveying pipe with its ends under different supporting conditions were investigated. The expression of vertical vibration mode-function of pipe beam was derived from the boundary conditions of similarly supported beam. The effect of different supporting elastic coefficient, fluid pressure, flowrate, and axial force of pipe section on its natural characteristics was calculated and analyzed based on the eigenequation of motion. The numerical computation results showed that its natural frequency was proportional to elastic supporting coefficient and axially pressed force of pipe section, but was proportional conversely to fluid flowrate, fluid pressure and axially sectional drawn force of pipe. The natural frequency of different modes can be coupled with each other, the primarily mode and secondly mode would change either. In order to improve the natural frequency of fluid conveying pipe, the elastically constrained coefficients should be extended and the axially pressed force of pipe section should be avoided.

scholarly journals Modeling Cantilever Branch Structure of Aero-Engine Power Turbine and Analyzing Its Influence

2018 ◽  
Vol 36 (4) ◽  
pp. 728-734 ◽  
Author(s):  
Yebao Xia ◽  
Xingmin Ren ◽  
Yongfeng Yang
Keyword(s):  
Critical Speed ◽  
Vibration Mode ◽  
Structural Parameters ◽  
Rotor System ◽  
Unbalance Response ◽  
Power Turbine ◽  
Aero Engine ◽  
Turbine Component ◽  
Calculation Results ◽  
Turbine Disks

In the power turbine component of an aero-engine, there exists a unique cantilever branch structure, on which turbine disks are mounted. Due to the cantilever's characteristics, this structure exhibits a vibration of large amplitude; thus its characteristics need to be studied in detail.In this paper, the motion equations combining the structure and the shaft were deduced; then its vibration mode was given, and the criticl speed was computed; finally the unbalance response of an integrated rotor system was simulated.The calculation results are compared with the simulation results without considering the branch structure.Some key parameters' influences are studied thoroughly, e.g., the branch shaft's length, the flange's offset and the installation orientation. As the results show, the branch structure has a large influence on the vibration mode and critical speed of the rotor system, thus it should not be simplified and ignored in modelling; After adjusting the branch structure's parameters, the characteristics of a vibration mode do not change, and the effects of branch structural parameters on critical speed are closely related to the corresponding vibration mode; the bending stiffness and the critical speed of the rotor system both decreased with increasing branch shaft's length; if reducing the flange's offset and fabricating the branch structure reversely, a sharp increase in the unbalance response of the turbine disc will occur. In conclusion, the dynamical characteristics of the integrated rotor system can be optimized through reasonably designing the branch structure.

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.

Modal Experiment Research on Fluid-Solid Coupling Vibration of Hydraulic Long-Straight Pipeline of Shield Machine

2011 ◽  
Vol 105-107 ◽  
pp. 286-293 ◽  
Author(s):  
Jing Hua Xie ◽  
Ke Tian ◽  
Li He ◽  
Tian Ren Yang ◽  
Xiang Heng Zhu
Keyword(s):  
Natural Frequency ◽  
Natural Frequencies ◽  
Vibration Mode ◽  
Vertical Plane ◽  
Low Frequency ◽  
Pipeline System ◽  
Experiment Research ◽  
Coupling Vibration ◽  
The Difference ◽  
Shield Machine

The hydraulic long-straight pipeline system of the shield machine is to be studied in this paper. Modal parameters of the hydraulic long-straight pipeline whose length is 8m under three kinds of spans (single span, double spans and four spans) were measured and analyzed. Considering the inherent vibration characteristics of the shield machine, we limited the natural frequency of the multi-span long straight pipeline studied within the range of 0~ 200Hz.What the experiment shows is as follows: Firstly, the natural frequency of the hydraulic long-straight pipeline is densely distributed mainly in the low frequency; Secondly, the natural frequencies of vibration in the horizontal plane are slightly higher than those of corresponding orders in the vertical plane, although the difference is little; In addition, by increasing the number of supports, pipeline span can be reduced and the natural frequencies of pipeline can be significantly increased, but this will make the vibration mode change irregularly.

Effect of crack on free vibration of a pre-stressed curved plate

2021 ◽  
pp. 095440622199486
Author(s):  
Can Gonenli ◽  
Hasan Ozturk ◽  
Oguzhan Das
Keyword(s):  
Finite Element ◽  
Free Vibration ◽  
Natural Frequency ◽  
Present Model ◽  
Mode Shapes ◽  
Load Parameter ◽  
Flexible Plate ◽  
Cantilever Plate ◽  
Finite Element Software ◽  
Aspect Ratios

In this study, the effect of crack on free vibration of a large deflected cantilever plate, which forms the case of a pre-stressed curved plate, is investigated. A distributed load is applied at the free edge of a thin cantilever plate. Then, the loading edge of the deflected plate is fixed to obtain a pre-stressed curved plate. The large deflection equation provides the non - linear deflection curve of the large deflected flexible plate. The thin curved plate is modeled by using the finite element method with a four-node quadrilateral element. Three different aspect ratios are used to examine the effect of crack. The effect of crack and its location on the natural frequency parameter is given in tables and graphs. Also, the natural frequency parameters of the present model are compared with the finite element software results to verify the reliability and validity of the present model. This study shows that the different mode shapes are occurred due to the change of load parameter, and these different mode shapes cause a change in the effect of crack.

scholarly journals Impact of Geometrical Imperfections on Estimation of Buckling and Limit Loads in a Silo Segment Using the Vibration Correlation Technique

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 567
Author(s):  
Łukasz Żmuda-Trzebiatowski ◽  
Piotr Iwicki
Keyword(s):  
Natural Frequencies ◽  
Vibration Mode ◽  
Mode Shapes ◽  
Correlation Technique ◽  
Limit Loads ◽  
Linear Buckling ◽  
Geometrical Imperfections ◽  
Linear Problems ◽  
Formed Channel ◽  
Corrugated Wall

The paper examines effectiveness of the vibration correlation technique which allows determining the buckling or limit loads by means of measured natural frequencies of structures. A steel silo segment with a corrugated wall, stiffened with cold-formed channel section columns was analysed. The investigations included numerical analyses of: linear buckling, dynamic eigenvalue and geometrically static non-linear problems. Both perfect and imperfect geometries were considered. Initial geometrical imperfections included first and second buckling and vibration mode shapes with three amplitudes. The vibration correlation technique proved to be useful in estimating limit or buckling loads. It was very efficient in the case of small and medium imperfection magnitudes. The significant deviations between the predicted and calculated buckling and limit loads occurred when large imperfections were considered.

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