scholarly journals Dynamic Characteristics and Experimental Research of Dual-Rotor System with Rub-Impact Fault

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Hongzhi Xu ◽  
Nanfei Wang ◽  
Dongxiang Jiang ◽  
Te Han ◽  
Dewang Li
Keyword(s):  
Dynamic Characteristics ◽  
Element Model ◽  
Rotor System ◽  
Rotor Vibration ◽  
Double Frequency ◽  
Fundamental Frequencies ◽  
Outer Rotor ◽  
Dimensional Finite Element ◽  
Frequency Components ◽  
Collision Force

Rub-impact fault model for dual-rotor system was further developed, in which rubbing board is regarded as elastic sheet. Sheet elastic deformation, contact penetration, and elastic damping support during rubbing of sheet and wheel disk were considered. Collision force and friction were calculated by utilizing Hertz contact theory and Coulomb model and introducing nonlinear spring damping model and friction coefficient. Then kinetic differential equations of rub-impact under dry rubbing condition were established. Based on one-dimensional finite element model of dual-rotor system, dynamic transient response of overall structure under rub-impact existing between rotor wheel and sheet was obtained. Meanwhile, fault dynamic characteristics and impact of rubbing clearance on rotor vibration were analyzed. The results show that, during the process of rub-impact, the spectrums of rotor vibration are complicated and multiple combined frequency components of inner and outer rotor fundamental frequencies are typical characteristic of rub-impact fault for dual-rotor system. It also can be seen from rotor vibration response that the rubbing rotor’s fundamental frequency is modulated by normal rotor double frequency.

scholarly journals Spectrum Analysis of a Coaxial Dual-Rotor System with Coupling Misalignment

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Hongxian Zhang ◽  
Liangpei Huang ◽  
Xuejun Li ◽  
Lingli Jiang ◽  
Dalian Yang ◽  
...  
Keyword(s):  
Spectral Characteristics ◽  
Element Model ◽  
Rotor System ◽  
Harmonic Frequencies ◽  
Coaxial Rotor ◽  
Outer Rotor ◽  
Frequency Components ◽  
Harmonic Resonance ◽  
The Finite Element Model ◽  
Engine Rotor

The finite element model of a dual-rotor system was established by Timoshenko beam element. The dual-rotor system is a coaxial rotor whose supporting structure is similar to that of an aero-engine rotor system. The inner rotor is supported by three bearings, which makes it a redundantly supported rotor. The outer rotor connects the inner rotor by an intershaft bearing. The spectrum characteristics of the dual-rotor system under unbalanced excitation and misalignment excitation were analysed in order to study the influence of coupling misalignment of the inner rotor on the spectral characteristics of the rotor system. The results indicate that the vibration caused by the misaligned coupling of the inner rotor will be transmitted to the outer rotor through the intershaft bearing. Multiple harmonic frequency components, mainly 1x and 2x, will be excited by the coupling misalignment. The amplitudes of all harmonic frequencies increase with the misalignment in both the inner and outer rotors. The vibration level of the outer rotor affected by the misalignment is lower than that of the inner rotor because it is far from the misaligned coupling. Harmonic resonance occurs when any harmonic frequencies of the misalignment response coincide with a natural frequency of the system. In order to verify the theoretical model, experiments are performed on a test rig. Both the experimental and simulation results are in good accordance with each other.

scholarly journals Analysis of Dynamic Characteristics for a Rotor System with Pedestal Looseness

2011 ◽  
Vol 18 (1-2) ◽  
pp. 13-27 ◽  
Author(s):  
Hui Ma ◽  
Xueyan Zhao ◽  
Yunnan Teng ◽  
Bangchun Wen
Keyword(s):  
Finite Element ◽  
Dynamic Characteristics ◽  
Rotational Speed ◽  
Element Model ◽  
Rotor System ◽  
High Order Harmonic ◽  
Bifurcation Phenomenon ◽  
Frequency Components ◽  
Increasing Process ◽  
Harmonic Components

This paper presents a finite element model of a rotor system with pedestal looseness stemming from a loosened bolt and analyzes the effects of the looseness parameters on its dynamic characteristics. When the displacement of the pedestal is less than or equal to the looseness clearance, the motion of the rotor varies from period-one through period-two and period-three to period-five with the decreasing of stiffness of the non-loosened bolts. The similar bifurcation phenomenon can be also observed during the increasing process of the rotational speed. But the rotor motion is from period-six through period-three to period-four with the decreasing of the foundation stiffness. When the stiffness of the foundation is small and the displacement of pedestal is greater than the looseness clearance, the response of the rotor exhibits period-one and high order harmonic components with the decreasing of looseness clearance, such as 2X, 3X etc. However, when the stiffness of the foundation is great, the spectrum of the response of the rotor will be from combined frequency components to the continuous spectrum with the decreasing of the looseness clearance.

Dynamics of Multi-Disk Rotor System with Rub-Impact Fault

2009 ◽  
Vol 16-19 ◽  
pp. 1082-1086
Author(s):  
Ji Shuang Dai ◽  
Hui Ma ◽  
Xue Jun Wang ◽  
Bang Chun Wen
Keyword(s):  
Finite Element ◽  
Contact Region ◽  
Element Model ◽  
Rotor System ◽  
Nonlinear Finite Element Method ◽  
Fractional Frequency ◽  
Theoretical Support ◽  
Frequency Components ◽  
Stage 1 ◽  
The Finite Element Model

In this paper, a multi-disk rotor system is studied. The rotor system is properly simplified and the finite element model is established. Assuming that contact region is an arc when the practical rotor-stator rub-impact fault occurs. Contact analysis and nonlinear finite element method are adopted to carry out numerical simulation of rub-impact. The results show that 1/2 fractional frequency components appear in slight rub-impact stage; 1/3 fractional frequency components appear in moderate rub-impact stage and 1/4 fractional frequency components appear in serious rub-impact stage. The research results will provide theoretical support for fault diagnosis of rub-impact.

Fundamental Frequencies of Turbine Blades With Geometry Mismatch in Fir-Tree Attachments

2006 ◽  
Vol 128 (3) ◽  
pp. 512-516 ◽  
Author(s):  
Fei Qin ◽  
Liming Chen ◽  
Ying Li ◽  
Xiaofeng Zhang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Significant Influence ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Element Model ◽  
Gap Size ◽  
Fundamental Frequencies ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Geometry mismatch in a turbine blade root, which arose in manufacturing process or caused by wearing out during service, leads to contact conditions changed in fir-tree attachments. As a result, shifting of the fundamental frequencies and redistribution of stress in the blade base possibly cause failure of the blade. A three-dimensional finite element model of a blade and its fir-tree attachments have been constructed and analyzed by taking into account contact nonlinearity in the attachments and large deformation effect of the blade. The geometry mismatch was introduced into the finite element model by defining gaps between two contact surfaces in the attachments. The influence of gap configuration and gap size on contact and fundamental frequencies was investigated. Results showed that gap configuration has significant influence on fundamental frequencies of the blade, especially on its bending modes. Gap size has little influence on the frequencies but significant influence on the contact status and thus changes stress distribution in the attachments. The results also suggest that modeling contact behavior in fir-tree attachments is necessary to obtain more accurate fundamental frequencies.

Dynamic Characteristics Analysis of a Seal-Rotor System with Rub-Impact Fault

2021 ◽  
Author(s):  
Yuegang Luo ◽  
Pengfei Wang ◽  
Haifeng Jia ◽  
Fengchao Huang
Keyword(s):  
Dynamic Characteristics ◽  
Element Model ◽  
Rolling Bearing ◽  
Rotor System ◽  
Dynamic Responses ◽  
Force Model ◽  
Nonlinear Phenomena ◽  
Combination Frequency ◽  
Labyrinth Seals ◽  
Frequency Locking

Abstract Labyrinth seals are widely used to prevent fluid leakage in high-low pressure areas of the rotating machinery. However, the rub-impact fault easily occurs in labyrinth seals. Considering the influence of gyroscopic effect, a finite element model of seal-rubbing rotor system is established in this study based on the Muszynska seal force model, the rolling bearing force model and the nonlinear rubbing force model. The vibration characteristics under the coupling faults of airflow excitation and rub-impact are analyzed. Firstly, the response of the system without rub-impact fault is numerically simulated and verified by experiments. Subsequently, the dynamic characteristics of the rotor under the conditions of slight rub-impact and severe rub-impact faults are analyzed. Finally, the influence of the rub-impact parameters is further studied. The results indicate that when the rub-impact fault is absent, airflow excitation occurs at a certain speed, which exhibits the characteristics of frequency locking and combination frequency. The coupling dynamic responses of airflow-induced vibration and rub-impact fault show a rich spectrum of nonlinear phenomena, which is closely related to the degree of rub-impact. This study may provide a theoretical basis for the detection and diagnosis of fluid-induced rub-impact fault in labyrinth seal-rotor systems.

scholarly journals Vibration Responses of a Coaxial Dual-Rotor System with Supporting Misalignment

2021 ◽  
Vol 11 (23) ◽  
pp. 11219
Author(s):  
Hongxian Zhang ◽  
Xuejun Li ◽  
Dalian Yang ◽  
Lingli Jiang
Keyword(s):  
Dynamic Characteristics ◽  
Weight Ratio ◽  
Bending Moment ◽  
Element Model ◽  
Rolling Bearing ◽  
Moment Equation ◽  
Rotor System ◽  
Structural Deformation ◽  
Model Studies ◽  
Bearing Loads

In order to improve the thrust-weight ratio, modern aeroengines generally adopt a coaxial dual-rotor system. Factors such as manufacturing errors, assembly errors, bearing wear, and structural deformation can cause misalignment failures in a dual-rotor system. Supporting misalignment is one of the common types of misalignments in a dual-rotor system. To analyze the vibration characteristics of misalignment faults, in this study, we aim to build a finite element model of a dual-rotor system with supporting misalignment. The bearing loads caused by supporting misalignment are calculated using the three-bending moment equation method. Bearing loads are introduced into the dynamic model of the dual-rotor system. The influence of supporting misalignment at different bearings on the dynamic characteristics of the rotor system is investigated based on the supporting misalignment model. Studies have shown that supporting misalignment at different bearings has similar effects on the dynamic characteristics of the dual-rotor system. The proposed supporting misalignment model is more adaptable than the coupling misalignment model. It indicates that the damping of a rolling bearing should be considered in the dynamic analysis of a dual-rotor system although the value of the damping is not large. An experimental analysis is carried out. The simulation results are in good agreement with the experimental results.

Dynamic Characteristics of Ball Bearing-Coupling-Rotor System with Angular Misalignment Fault

2021 ◽  
Author(s):  
Pengfei Wang ◽  
Hongyang Xu ◽  
Yang Yang ◽  
Hui Ma ◽  
Duo He ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Degrees Of Freedom ◽  
Ball Bearing ◽  
Element Model ◽  
Rolling Bearing ◽  
Rotor System ◽  
Radial Clearance ◽  
Axial Vibration ◽  
Restoring Force ◽  
Misalignment Fault

Abstract The rotor misalignment fault, which occurs only second to unbalance, easily occurs in the practical rotating machinery system. Rotor misalignment can be further divided into coupling misalignment and bearing misalignment. However, most of the existing references only analyze the effect of coupling misalignment on the dynamic characteristics of the rotor system, and ignore the change of bearing excitation caused by misalignment. Based on the above limitations, a five degrees of freedom nonlinear restoring force mathematical model is proposed, considering misalignment of bearing rings and clearance of cage pockets. The finite element model of the rotor is established based on the Timoshenko beam element theory. The coupling misalignment excitation force and rotor unbalance force are introduced. Finally, the dynamic model of the ball bearing-coupling-rotor system is established. The radial and axial vibration responses of the system under misalignment fault are analyzed by simulation. The results show that the bearing misalignment significantly influences the dynamic characteristics of the system in the low-speed range, so bearing misalignment should not be ignored in modeling. With the increase of rotating speed, rotor unbalance and coupling misalignment have a greater impact. Misalignment causes periodic changes in bearing contact angle, radial clearance, and ball rotational speed. It also leads to reciprocating impact and collision between the ball and cage. In addition, misalignment increases the critical speed and the axial vibration of the system. The results can provide a basis for health monitoring and misalignment fault diagnosis of the rolling bearing-rotor system.

scholarly journals The Influence of Ring-Speed Ratio Dynamic Change on Nonlinear Vibration Response of High-Speed Turbocharger Rotor System

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Guangfu Bin ◽  
Liang Zhang ◽  
Feng Yang ◽  
Anhua Chen
Keyword(s):  
Nonlinear Vibration ◽  
High Speed ◽  
Dynamic Change ◽  
Element Model ◽  
Rotor System ◽  
Vibration Response ◽  
Speed Ratio ◽  
Model Parameters ◽  
Rotor Vibration ◽  
Nonlinear Transient

The ring-speed ratio is a comprehensive dynamic index of floating ring bearing structure and operating parameters, which directly affects the dynamic behavior of the turbocharger rotor system. The cross stiffness of ring-speed ratio and floating ring bearing and the work of oil film force are analyzed. The influence of dynamic ring-speed ratio change on the vibration response of floating ring bearing was studied. The finite element model of the rotor-floating ring bearing system is constructed; its model parameters are verified through the measured critical rotor speed. Newmark integral method is used to analyze the nonlinear transient response. The results show that when the ring-speed ratio is between 0.18 and 0.24, the rotor is in a good operating state; when it increases from 0.24 to 0.36, the rotor vibration is dominated by frequency division, and the system will be less stable. The square of the ring-speed ratio is inversely proportional to the rotational speed of the journal where the subfrequency vibration occurs. It helps to know the nonlinear vibration by judging the journal speed when the rotor vibration occurs in subfrequency. The conclusion provides a reference for the mechanical dynamics design and intelligent management and maintenance of this kind of turbine rotors.

The Analysis of Dynamic Characteristics for the Powerhouse Structure of the Riverbed-Hydroelectric Station

2012 ◽  
Vol 226-228 ◽  
pp. 1285-1288
Author(s):  
Xuan Mao Peng ◽  
Zheng Xiang Song ◽  
Lin Jiang
Keyword(s):  
Finite Element ◽  
Dynamic Characteristics ◽  
Dynamic Stress ◽  
Three Dimensional ◽  
Hydroelectric Station ◽  
Element Model ◽  
Calculation Model ◽  
Dimensional Finite Element ◽  
Hanjiang River ◽  
Three Dimensional Finite Element

The paper creates a three-dimensional finite element model with the Xihe Project on the Hanjiang River as a background. The space integrated finite element method is applied to analyze the dynamic characteristics of the spatial structure of the riverbed-hydroelectric station. The aim is to calculate and analyze the free vibration characteristics of the whole structure, the dynamic displacement and the dynamic stress under the two typical conditions. The calculation model is effective to consider the interaction of the upstream dam section, the main and auxiliary powerhouse and the downstream water retaining structure, as well as the foundation. The results obtained will be a valuable reference for optimizing the dynamic characteristics of the powerhouse structure of riverbed-hydroelectric station and improving the engineering design.

scholarly journals Dynamic Behavior Analysis of Intermediate Bearing-Squeeze Film Dampers-Rotor System under Constant Maneuvering Overload

2021 ◽  
Vol 2021 ◽  
pp. 1-24
Author(s):  
Nan Zheng ◽  
Mo-li Chen ◽  
Gui-Huo Luo ◽  
Zhi-Feng Ye
Keyword(s):  
Dynamic Behavior ◽  
Dynamic Characteristics ◽  
Rotor System ◽  
Squeeze Film ◽  
Nonlinear Dynamic Model ◽  
Maneuvering Flight ◽  
Squeeze Film Dampers ◽  
Frequency Components ◽  
Simulation Results ◽  
Rotor Dynamic

Under the flight maneuvering of an aircraft, the maneuvering load on the rotor is generated, which may induce the change of dynamic behavior of aeroengine rotor system. To study the influence on the rotor dynamic behavior of constant maneuvering overload, a nonlinear dynamic model of bearing-rotor system under arbitrary maneuver flight conditions is presented by finite element method. The numerical integral method is used to investigate the dynamic characteristics of the rotor model under constant maneuvering overload, and the simulation results are verified by experimental works. Based on this, the dynamic characteristics of a complex intermediate bearing-squeeze film dampers- (SFD-) rotor system during maneuvering flight are analyzed. The simulation results indicate that the subharmonic components are amplified under constant maneuvering overload. The amplitude of the combined frequency components induced by the coupling of the inner and outer rotors is weakened. The static displacements of the rotor caused by the additional excitation force are observed. Besides, the period stability of the movement of the rotor deteriorates during maneuver flight. The design of counterrotation of the inner and outer rotors can effectively reduce the amplitude of subharmonic under constant maneuvering overload.

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