Analytical and Experimental Study of Dynamic Characteristics of Rod Fastened Rotor-Bearing System Under Preload Saturation

2013 ◽  
Author(s):  
Mingjian Lu ◽  
Haipeng Geng ◽  
Guohui Xu ◽  
Lie Yu ◽  
Weimin Wang
Keyword(s):  
Dynamic Characteristics ◽  
Critical Speed ◽  
Contact Stiffness ◽  
Element Model ◽  
Analysis And Design ◽  
Contact Effect ◽  
Rotor Bearing ◽  
Equivalent Bending Stiffness ◽  
Rod Fastening Rotor ◽  
Bearing System

This paper investigates the dynamic characteristics of a composite rotor fastened by rods. Contact stiffness and equivalent bending stiffness between discs with different rod preloads of the rotor are obtained respectively by using the elastic and elastic-plastic contact theory. The finite element model of rotor-bearing system is built with Timoshenko beam elements. Critical speeds are respectively calculated with and without the consideration of contact effect, including the changing bearing dynamic coefficients. A test rig of rod fastening rotor-bearing system has been constructed to verify the numerical model results. The results show that the critical speed increases with rod preload and it keeps almost constant when the rod preload reaches a certain value, called preload saturation. The experiments demonstrate that the rod fastening rotor under preload saturation has the similar dynamic characteristics as integral rotor, such as the critical speed and backward whirl with asymmetric support stiffnesses. This kind of rotors which are under preload saturation can be analyzed and designed as an integral one without considering the contact effect. The study gives referential recommendations for analysis and design of a class of composite rotors which contain discs and rods.

Experimental dynamic analysis of rod-fastening rotor bearing system with a transverse crack

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Nanshan Wang ◽  
Heng Liu ◽  
Qidan Wang ◽  
Shemiao Qi ◽  
Yi Liu
Keyword(s):  
Peer Review ◽  
Dynamic Characteristics ◽  
Vibration Amplitude ◽  
Critical Speed ◽  
Transverse Crack ◽  
Content Type ◽  
Rotor Bearing ◽  
Speed Up ◽  
Rod Fastening Rotor ◽  
Bearing System

Purpose This study aims to obtain the dynamic behaviours of cracked rod-fastening rotor bearing system (RFBS), and experimental investigation was carried out to examine the dynamic characteristics of this kind of assembled rotor bearing system with a transverse crack passing through the critical speed. Design/methodology/approach An experimental test rig of cracked RFBS was established for examining the vibration behaviours between intact and cracked system. The crack on the surface of a fastening rod was simulated by wire-electrode cutting processing method. The comprehensive analysis method of vibration was used to obtain the dynamic characteristics such as vibration amplitude, acceleration and whirling orbits before and after the critical speed as well as the instantaneous response in the process of speed up. Findings Some experimental vibration datum is obtained for cracked RFBS. The appearance of a crack will introduce the initial bending and make the vibration amplitude, acceleration and instant response in the process of speed up increase greatly as well as the change of whirling orbits. Originality/value The actual vibration characteristics for this complex assembled rotor system with a transverse crack are given passing through the critical speed. It can provide some useful help for monitoring the vibration behaviours of this kind of assembled rotor system as well as the detection of the crack fault. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0260/

scholarly journals Dynamic Characteristics and Experimental Research of a Two-Span Rotor-Bearing System with Rub-Impact Fault

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Rui Zhu ◽  
Guang-chao Wang ◽  
Qing-peng Han ◽  
An-lei Zhao ◽  
Jian-xing Ren ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Critical Speed ◽  
Great Influence ◽  
Experimental Platform ◽  
Rotating Machine ◽  
Rotor Bearing ◽  
Before And After ◽  
Analysis System ◽  
The Stability ◽  
Bearing System

Rotor rub-impact has a great influence on the stability and safety of a rotating machine. This study develops a dynamic model of a two-span rotor-bearing system with rubbing faults, and numerical simulation is carried out. Moreover, frictional screws are used to simulate a rubbing state by establishing a set of experimental devices that can simulate rotor-stator friction in the rotor system. Through the experimental platform and its analysis system, the rubbing experiment was conducted, and the vibration of the rotor-bearing system before and after the critical speed is observed. Rotors running under normal condition, local slight rubbing, and severe rubbing throughout the entire cycle are simulated. Dynamic trajectories, frequency spectrum diagrams, chart of axis track, and Poincare maps are used to analyze the features of the rotor-bearing system with rub-impact faults under various parameters. The vibration characteristics of rub impact are obtained. Results show that the dynamic characteristics of the rotor-bearing system are affected by the change in velocity and degree of impact friction. The findings are helpful in further understanding the dynamic characteristics of the rub-impact fault of the two-span rotor-bearing system and provide reference for fault diagnosis.

Effect of a transverse crack on the dynamic behaviours of a 3D rod-fastening rotor bearing system

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Nanshan Wang ◽  
Heng Liu ◽  
Yi Liu ◽  
Qidan Wang ◽  
Shemiao Qi ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Dynamic Model ◽  
Dynamic Characteristics ◽  
3D Finite Element ◽  
Content Type ◽  
Rotor Bearing ◽  
Rod Fastening Rotor ◽  
3D Finite Element Method ◽  
Bearing System

Purpose This paper aims to examine the dynamic behaviours of a three-dimensional (3D) rod-fastening rotor bearing system (RFBS) with a crack in a fastening rod. Design/methodology/approach Based on the 3D finite element method model and stress analysis of a cracked RFBS, a 3D dynamic model of the RFBS with a crack in a fastening rod is established with considering the initial bending and stress redistribution caused by the crack. A combined numerical simulation technology is used to investigate the dynamic behaviours of the system. Findings The distribution of contact stress between the two disks will be not uniform, and the initial bending of the system will occur due to the presence of a crack. This will lead to the change of system stiffness and the dynamic behaviours such as vibration amplitude, and motion orbits will change significantly. Research limitations/implications A 3D finite element method dynamic model is proposed for the study of dynamic characteristics of complex combined rotor bearing system with cracks. Practical implications It is helpful and significant to master the dynamic behaviours of cracked RFBS. It is helpful to detect the presence of a crack of the rotor bearing system. Social implications Some of the losses caused by crack failure may be reduced. Originality/value The proposed 3D method can provide a useful reference for the study of dynamic characteristics of complex combined rotor bearing system with cracks. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2020-0189

Effect of Flexible Damped Bearing-Supports on the Dynamic Stability of High-Speed Turbochargers

2013 ◽  
Author(s):  
A. Alsaeed ◽  
G. Kirk ◽  
S. Bashmal
Keyword(s):  
Dynamic Stability ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Element Model ◽  
Dynamic Coefficients ◽  
Speed Range ◽  
Rotor Bearing ◽  
The Stability ◽  
The Finite Element Model ◽  
Bearing System

The aim of this study is to analytically design flexible damped bearing-supports in order to improve the dynamic characteristics of the rotor-bearing system. The finite-element model of the turbocharger rotor with linearized bearing dynamic coefficients is used to solve for the logarithmic decrements and hence the stability map. The design process attempts to find the optimum dynamic characteristics of the flexible damped bearing-support that would give best dynamic stability of the rotor-bearing system. The method is successful in greatly improving the dynamic stability of the turbocharger and may also lead to a total linear stability throughout the entire speed range when used besides the enhanced-performance hydrodynamic bearings.

Nonlinear dynamic characteristics of a three-dimensional rod-fastening rotor bearing system

2014 ◽  
Vol 229 (5) ◽  
pp. 882-894 ◽  
Author(s):  
Yi Liu ◽  
Heng Liu ◽  
Xin Wang ◽  
Minqing Jing
Keyword(s):  
Dynamic Characteristics ◽  
Nonlinear Dynamic ◽  
Three Dimensional ◽  
Dynamic Features ◽  
Stability Margins ◽  
Mass Eccentricity ◽  
Nonlinear Dynamic Characteristics ◽  
Rotor Bearing ◽  
Rod Fastening Rotor ◽  
Bearing System

The nonlinear dynamic characteristics of three-dimensional rod-fastening rotor bearing system are investigated in this paper. The rod-fastening rotor includes discontinuous shaft, rotating disks, circumferentially distributed rods, and macrointerfaces between disks. The first three parts are discretized by three dimensional elements, and the macrointerfaces are connected by some springs whose stiffness is determined by a proposed linear partition method. For comparison, the three-dimensional dynamic model of a corresponding complete rotor bearing system is also built. After the rod-fastening and complete rotor bearing system are reduced by a component mode synthesis, periodic motions and stability margins are calculated by using the shooting method and path-following technique, and the local stability of system is obtained by using the Floquet theory. Comparative results show the both systems have a resemblance in the bifurcation features when mass eccentricity and rotating speed are changed. The vibration response has the identical frequency components when typical bifurcations occur. The dynamic stress is obtained by regarding the displacements of all nodes as load. Moreover, the unbalanced and insufficient of the pre-tightening forces lead to obvious disadvantageous influence on the stability and vibration of the both systems. Generally, this paper considers the interfacial effect of the rod-fastening rotor bearing system and the relative nonlinear dynamic features are obtained.

Rotor Dynamics Analysis and Testing of a Turbomolecular Pump Rotor-Bearing System

2011 ◽  
Author(s):  
Chih-Neng Hsu ◽  
Hsiao-Wei D. Chiang ◽  
Yu-Meng Huang ◽  
Ying-Chia Fu ◽  
Kuo-Hsun Hsu ◽  
...  
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
Dynamic Characteristics ◽  
Critical Speed ◽  
Experimental Measurements ◽  
Pump System ◽  
Pump Rotor ◽  
Turbomolecular Pump ◽  
Rotor Bearing ◽  
Bearing System

This study is focused on the dynamic characteristics of a vertical turbomolecular pump (TMP) rotor-bearing system. The research methods can be divided into two parts, which are numerical analysis and experimental measurements. In numerical analysis, we use the finite element analysis software DyRoBeS and ANSYS to construct a two- and three-dimensional models of the rotor-bearing system. In the analysis process, by using the pump system assembly testing data, we can verify the rotor-bearing system finite element models under different boundary conditions. Next, we calculate the Campbell diagram to study the dynamic characteristics of the rotor-bearing system, and to compare with the experimental results to verify the models. Finally, we found the relationship between the rotor critical speed and the bearing stiffness in order to study the design of the molecular pump rotor and the bearing system. Experimental measurements were divided into two parts: static modal tests and dynamic measurements. Static modal tests can provide the natural frequencies of the rotor-bearing system. Waterfall diagrams of the dynamic tests can measure the pump system critical speed from zero speed up to the working speed crossing, and to insure that the pump working speed is far from the critical speed of at least 10% in the safe margin. In summary, the results of the experimental measurements and numerical analysis can provide the basis for the design tool for turbomolecular pump rotor-bearing system in order to identify and prevent pump vibrations.

Dynamic Characteristics of Nonlinear Elastics Rotor-Bearing System With Coupling Faults of Pedestal Looseness and Rub-Impact

2009 ◽  
Author(s):  
Yuegang Luo ◽  
Songhe Zhang ◽  
Zhaohui Ren ◽  
Bangchun Wen
Keyword(s):  
Dynamic Model ◽  
Dynamic Characteristics ◽  
Critical Speed ◽  
Dynamic Design ◽  
Coupling Faults ◽  
Nonlinear Motion ◽  
Speed Range ◽  
Rotor Bearing ◽  
Set Up ◽  
Bearing System

A dynamic model of the nonlinear elastics rotor-bearing system with coupling faults of pedestal looseness and rub-impact was set up, taking the linearity and cube item as the physics nonlinear factors. The complex characteristics of the rotor-bearing system were numerically studied. There exists complex nonlinear motion of periodic, quasi-periodic and chaotic in the response of the system. The main motions of the rotor-bearing system with rub-impact fault are periodic-2, periodic-4 and quasi-periodic within the super-critical speed range, but it with coupling faults of pedestal looseness and rub-impact are periodic-3 and chaotic. The influence of oil-film force to the rotor system is weakened by the pedestal looseness fault. The results may bring up theoretical references for fault diagnoses, dynamic design, and security running to rotor-bearing system.

AN ANALYSIS OF THE ELECTRIC SPINDLE'S DYNAMIC CHARACTERISTICS OF HIGH-SPEED GRINDER

2011 ◽  
Vol 10 (01) ◽  
pp. 159-166 ◽  
Author(s):  
C. H. LI ◽  
Y. L. HOU ◽  
C. DU ◽  
Y. C. DING
Keyword(s):  
Dynamic Characteristics ◽  
Performance Optimization ◽  
High Speed ◽  
Critical Speed ◽  
Structural Parameters ◽  
Influential Factors ◽  
Variable Cross ◽  
Tightening Force ◽  
Rotor Bearing ◽  
Bearing System

Structural parameters are important factors that affect the dynamic performance of the electrical spindle of high-speed grinder. In this study, the influences of the electric spindle's major structural parameters on its dynamic characteristics are investigated. Based on the transfer-matrix method and taking into consideration the gyroscopic couple, the shear, the variable cross-section, and other influential factors, a dynamic model is established for the multidisk rotor of the rotor-bearing system of the electric spindle. The critical speeds of first three orders, the modes of variation, and other dynamic characteristic parameters of the electric spindle are programmed and calculated. The influences of the axial pre-tightening force of the bearing, the span of the fulcrum bearing as well as the changes in the front and rear overhangs on the critical speed of the rotor-bearing system on the electric spindle and their pattern of changes are analyzed. The results show that the span of the fulcrum bearing and the overhang have significant influences on the critical speed within a certain range, and the study provide the basis and guidance for the structural design and performance optimization of the electric spindle.

Theoretical and experimental dynamics analysis of rotor-bearing system supported by elliptical bearings

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Zhiming Zhao ◽  
Rui Zhang ◽  
Feng Ji ◽  
Xiaoyang Yuan
Keyword(s):  
Peer Review ◽  
Dynamic Characteristics ◽  
Critical Speed ◽  
Design Method ◽  
Large Diameter ◽  
Rotor System ◽  
Content Type ◽  
Vibration Data ◽  
Rotor Bearing ◽  
Bearing System

Purpose High power and speed are new demands for rotating machinery which needs the journal bearings with high dynamic characteristics. The critical speed of the rotor-bearing system is one of the most significant parameters to evaluate the dynamic characteristics. This paper aims to investigate the theoretical and experimental analysis of a rotor system supported by large diameter elliptical bearings. Design/methodology/approach To obtain the theoretical and experimental support for rotor-bearing system design, dynamic characteristics theoretical analysis based on the finite difference method is given and an experiment focuses on critical speed identification is carried out. Findings The theoretical calculation results indicate that the critical speed is near to 800 rpm and there is no large vibration amplitude round working speed (1,500 rpm). Using the test bench in the factory unit, vibration data including three experimental processes are obtained. According to the vibration data, the critical speed is identified which also indicates that it is stable when working at 1,500 rpm. Originality/value The design method for the rotor system supported by large diameter elliptical bearing can be obtained by the theoretical and experimental results shown in this paper. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2020-0122/

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