Dissertations / Theses on the topic 'Rotor system- Vibrational characteristics'
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1
Mat, Isa Ahmad A. "An investigation of the dynamic characteristics of a bolted-rotor system." Thesis, Aston University, 2001. http://publications.aston.ac.uk/11837/.
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A Jeffcott rotor consists of a disc at the centre of an axle supported at its end by bearings. A bolted Jeffcott rotor is formed by two discs, each with a shaft on one side. The discs are held together by spring loaded bolts near the outer edge. When the rotor turns there is tendency for the discs to separate on one side. This effect is more marked if the rotor is unbalanced, especially at resonance speeds. The equations of motion of the system have been developed with four degrees of freedom to include the rotor and bearing movements in the respective axes. These equations which include non-linear terms caused by the rotor opening, are subjected to external force such from rotor imbalance. A simulation model based on these equations was created using SIMULINK. An experimental test rig was used to characterise the dynamic features. Rotor discs open at a lateral displacement of the rotor of 0.8 mm. This is the threshold value used to show the change of stiffness from high stiffness to low stiffness. The experimental results, which measure the vibration amplitude of the rotor, show the dynamic behaviour of the bolted rotor due to imbalance. Close agreement of the experimental and theoretical results from time histories, waterfall plots, pseudo-phase plots and rotor orbit plot, indicated the validity of the model and existence of the non-linear jump phenomenon.
2
Біденко, І. Г. "Імовірнісний підхід до визначення основних характеристик системи "ротор-шпаринні ущільнення" відцентрового насоса. Вплив імовірнісного характеру параметрів системи "ротор-шпаринні ущільнення" на вібраційні характеристики відцентрового насоса." Master's thesis, Сумський державний університет, 2018. http://essuir.sumdu.edu.ua/handle/123456789/71068.
Full textAbstract:
Робота присвячена дослідженню силових гідродинамічних факторів, що
виникають під час течії рідини в циліндричних дроселюючих каналах
ущільнень відцентрових машин. Ротор і ущільнення розглядаються при цьому
як замкннена гідромеханічна система, у якій роль зв’язуючої ланки виконує
перекачуване середовище, його інерційні і гідродинамічні характеристики.
Вплив середовища особливо істотний при наявності великих градієнтів
швидкостей і тисків. Такі умови саме і характерні для малих зазорів шпаринних
ущільнень, на яких дроселюються великі перепади тиску, а одна зі стінок
належить ротору, що обертається і вібрує. Таким чином, ротор і ущільнення
являють собою складну гідромеханічну систему, характеристики якої мають
визначальний вплив на надійність та герметичність відцентрових машин.
Ускладнює ситуацію той факт, що зазвичай на практиці через встановлені
допуски на виготовлення геометричні параметри ущільнень мають випадковий
характер, крім того, вони можуть змінюватися в процесі експлуатації через знос
поверхонь, і таким чином, динамічні навантаження, що діють на ротор, також
будуть мати випадковий характер. Тому в роботі проведено ймовірнісний
розрахунок динамічних характеристик ротора, в якому відповідні параметри
описуються випадковими величинами або функціями.Вероятностный подход к определению основных характеристик системы "ротор - щелевые уплотнения" центробежного насоса. Влияние вероятностного характера параметров системы «ротор - щелевые уплотнения» на вибрационные характеристики центробежного насоса.
Probabilistic approach to determination of basic characteristics of the system “rotor – annual seals” of the centrifugal pump. Influence of the probabilistic nature of the system "rotor - annual seals" parameters on the vibration characteristics of centrifugal pump.
3
Mokhtar, Md Asjad. "Rotordynamic studies on the rotor-stator contact interaction." Thesis, 2018. http://eprint.iitd.ac.in:80//handle/2074/7957.
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4
Huang, Yu-Meng, and 黃裕盟. "Vibration Characteristics Analysis and Modal Testing of a Turbo Molecular Pump Rotor-Bearing System." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/50303943730299618843.
Full textAbstract:
碩士國立清華大學
動力機械工程學系
98
This study is focused on the dynamic characteristics of a vertical turbo molecular pump 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 ANSYS and DyRoBeS to construct a two-dimensional and three-dimensional model of the rotor-bearing system. In the analysis process, by constantly changing the pump system assembly methods we can correct and verify the rotor-bearing system finite element model under different boundary conditions. Next, we calculate the Campbell diagram to understand the dynamic characteristics of the rotor-bearing system, and to compare with the experimental results to verify the model. Finally, we found the relationship between the rotor critical speed and the bearing stiffness in order to provide the design of the molecular pump rotor and the bearing system. Experimental measurements were divided into two parts: static percussion tests and dynamic measurements. Static test can provide the natural frequencies of the rotor-bearing system. Waterfall diagram of the dynamic test can measure the pump system’s 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 10% in the safe range. In summary, the results of the experimental measurements and numerical analysis can be the basis for the design of the turbo molecular vacuum pump rotor-bearing system analysis techniques in order to identify and prevent pump vibrations.
5
Chi, Hsing-Tsan, and 吉星燦. "Prediction of the torsional vibration characteristics ofa damped rotor-shaft system from those of its scale model." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/31402777399044292085.
Full textAbstract:
碩士國立高雄海洋科技大學
輪機工程研究所
99
This paper presents the scaling laws that provide the geometry and dynamic similitude conditions between the damped rotor-shaft system and its scale model, so that the torsional vibration characteristics of the full-size rotor-shaft system can be predicted from those of its scale model. The last scaling laws are determined from the equations of motion of the full-size rotor-shaft system and its scale model. Then, the scaling factors, that establish the relationship between the last two systems, involved in the preceding scaling laws (i.e., explicit scaling factors) are determined according to the fundamental physical properties of each scalable parameter of the system, while those not involved in the scaling laws (i.e., the implicit scaling factors) are determined based on the theory of dimensional analysis. Both the free and forced torsional vibration characteristics of the full-size rotor-shaft system and those of its scale model are used to validate the presented scaling laws and scaling factors.
6
Chen, Hui-Shan, and 陳慧珊. "Prediction of the lateral vibration characteristics of a full-size rotor-bearing system from those of its scale model." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/04093532359052749919.
Full textAbstract:
碩士國立高雄海洋科技大學
輪機工程研究所
96
The object of this paper is to study how to predict the lateral vibration characteristics of the full-size rotor-bearing system by using the scale rotor-bearing model and the associated scaling laws, such that one may significantly reduce the time and money required by the experiments. To this end, the scaling laws for all the relevant parameters regarding the full-size rotor-bearing system and its scale model (such as, sizes of the constituent members, spring constants and damping coefficients of the supports, natural frequencies (of free vibration) and forced-vibration displacements, etc.) are derived first from the equations of motion of the last two systems. Next, the scaling factors for all relevant parameters of the above-mentioned two systems are determined with the theory of dimensional analysis. Now, based on all of the above-mentioned relevant parameters of the full-size rotor-bearing system, one may determine the corresponding parameters of the scale rotor-bearing model by using the associated scaling factors and predict the vibration characteristics of the full-size rotor-bearing system by using the corresponding ones of the scale rotor-bearing model. Finally, the influence of constituent-member sizes on the similarity of natural frequencies (of free vibrations) and the influence of spring constants, damping coefficients and external loads on the similarity of dynamic responses (of forced vibrations) are investigated. Because the literature concerning the use of scaling laws and scale rotor-bearing model for predicting free and forced vibration characteristics of full-size rotor-bearing system is rare, this paper provides a complete and systematic theory and technique in this aspect. Keywords: full-size rotor-bearing system, scale rotor-bearing model, scaling laws, scaling factors, lateral vibration characteristics
7
傅英嘉. "Blade Design and Vibration Characteristic Testing of a Turbo Molecular Pump(TMP) Rotor-Bearing System." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/sue67v.
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8
Kushwaha, Vishwajeet. "Analysis of torsional vibration characteristics for multi-rotor and gear-branched systems using finite element method." Thesis, 2012. http://ethesis.nitrkl.ac.in/3454/1/ethesis_vishwajeet(108me038).pdf.
Full textAbstract:
Torsional vibrations occur due torelative oscillatory motions superposed on the mean rotation. Rotating systems at running speed near the natural frequencies are prone to excessive angular deflections and hence large stresses which can cause rotating components failure or premature fatigue failures. The objective of the present work is to study the torsional vibration characteristics of multi-rotor and gear-branched systems suing finite element method. Finite element method (FEM) is a numerical technique based on principle of discretization to find approximate solutions to engineering problems. The information about the natural frequencies for rotating systems can help to avoid system failure by giving the safe operating speed range. In the present work, finite element method has been used to find these natural frequencies for different possible cases of multi-rotor and gear-branched systems. The various mode shapes for several cases are also shown to illustrate the state of the system at natural frequencies. The results obtained have been compared with Holzer’s method and transfer matrix method to establish the effectiveness of finite element method for such systems.
9
Chun-LinChen and 陳春霖. "Dynamic Characteristics Analysis on Rotor System with Soft Supports." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/38104538988149551398.
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10
Chang, Jer-Rong, and 張哲榮. "A Study on Dynamic Characteristics of Geared Rotor-Bearing System." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/83738202872182721874.
Full textAbstract:
博士國立成功大學
航空太空工程學系
85
This thesis is concerned with the dynamic analysis of a geared rotor-bearing system. A finite element model of the geared rotor-bearing system is developed by taking account of the lateral-torsional coupling effect to obtain the natural frequencies, mode shapes, and the steady-state responses. From the response time histories, the FFT spectra can be obtained to investigate the effects of dynamic coupling terms under different grades of balance quality and spin speeds. In addition, the lateral response due to short circuit torque is examined to be substantial for the turbo-generator set. The nonlinear dynamic behavior of a geared system supported bysqueeze-film dampers is also investigated. The FFT spectra, Poincare maps and bifurcation maps are made to classify the responses whichinclude sub-harmonic, superharmonic, quasi- periodic, and chaotic responses. The hybrid technique of the Harmonic Balance Method and Time Collocation is employed to obtain the stability of the first variation equations with periodic coefficients, which is generatedby the perturbation technique.
11
Lo, Wu-Jen, and 羅武仁. "Dynamic Characteristics Analysis and Testing of a Microturbine Rotor-Bearing System." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/61932283777594980230.
Full textAbstract:
碩士國立清華大學
動力機械工程學系
91
This paper can be divided into two parts, which are numerical analysis and experimental equipment construction and testing. In numerical analysis, we mainly use the finite element method as our basis and MATLAB program design software as our tool, to write the numerical analysis program for a rotor-bearing system. This rotor-bearing system consists of rigid disks, distributed parameter finite rotor elements, and discrete bearings. During modeling of the system, the finite element model includes the effects of translation inertia, rotatory inertia, gyroscopic moments, and shear deformations. In order to verify the numerical analysis program, we choose to analyze the simple uniform rotor. We calculate and compare its natural frequencies, mode shapes, and critical speeds in bending with the theoretical results. After that, we further analyze a more complex system, which contains three disks and two bearings. The influences of the element number, the whirl frequency, the Campbell diagram, and the critical speed versus bearing stiffness diagram were studied. In experimental equipment construction and testing, we continue to progress on the RGT-3600 micro turbine and completed the related works of the equipment construction and testing. It includes the assembly of the hardware, the build of the measurement equipments, the construction of the sub-systems and the test of the sensor elements, the fuel supply, the fuel atomization, the fuel ignition, and the starting motor. We were able to get the micro turbine started properly and shut down safely. In addition, we accumulated many valuable experiences as well as test data.
12
Hong, Fu-Ji, and 洪福基. "The Effect of Temperature on Vibrational Characteristics of a Shaft-Disk System." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/46902597522521273002.
Full textAbstract:
碩士國立高雄第一科技大學
機械與自動化工程所
92
A lot of rotors of rotary machine running under the high-temperature environment, even temperature of rotors does increase progressively or decrease progressively. Because of the change of the temperature and load, the dynamic characteristics of the shaft and disk is also influenced. This paper discusses the effect of dynamic characteristics of the rotor various temperature. For understand relationship of different temperature to vibration amplitude or phase by way of theory and experiment at the same time, It used energy method derive motion equation of rotor and disk that under different temperature, and heat the rotor under various temperature with the heating device, set up the proximitor and keyphaser to measure vibration amplitude and phase. We learns the following from the result. The vibrational amplitude hasn’t increase or decrease obviously due to temperature change, but phase has obvious changes. the system operates below the critical speed, the phase increases with the rising of temperature obviously, reduce with the drop of temperature obviously; Instead, the system operating over critical speed, the phase decreases with the rising of temperature obviously , increases with the drop of temperature obviously, with operate under the critical rotational speed just the oppositly; And it is near to the critical speed, the phase is the greater in change. Consequently, if we use the phase to do relevant application, it need to pay attention to the variation of the shaft temperature to avoid making the wrong judgement and cause unnecessary losses .
13
Huang, Chun-Jung, and 黃俊榮. "A STUDY ON DYNAMIC CHARACTERISTICS OF GEARED ROTOR-BEARING SYSTEM WITH CRACK." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/58896036507200956668.
Full textAbstract:
博士國立成功大學
航空太空工程學系碩博士班
91
In this thesis, the dynamic analysis of a geared rotor-bearing system with an open crack or a breathing crack is discussed. A simple analytic model of a geared rotor system is developed by taking into account the effect of an open transverse surface crack for determination of natural frequencies, critical speeds, and stability of the system. The existing crack results in a local flexibility of the shaft and it is replaced by a set of springs based on the balance of energy. The effect of the crack results in a periodic time-varying system. From the response time histories, the FFT spectra can be obtained for investigating the effects of crack. The Floquet theory is used to examine the stability of the first variation equations with periodic coefficients. Finite element models are developed for geared rotor-bearing system with an open transverse surface crack and with a breathing transverse surface crack for determination of natural frequencies, critical speeds, dynamic response and stability. The results show that additional instability regions of the shaft’s spin speed are observed when a crack occurs on the shaft. The influences of the crack on the stability of the system are significant as the depth increases to an evident value.
14
Yang, Ding-Wen, and 楊丁文. "The Studies of Static/Dynamic Characteristics and Stability in Rotor-aerostatic Bearing System." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/44533345787232415616.
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博士中原大學
機械工程研究所
97
Abstract This project has dealt with the integrated research of the spindles with aerostatic bearings. The contents include studies in load capacity, stiffness, damping ratio, critical inertial force, critical whirl ratio for aerostatic-bearing spindle, analysis for simulating the influences of design parameters in operation performances and characteristics and optimal design for aerobearing-spindle system. The Reynolds equation is solved by the finite difference method and numerical integration to yield static and dynamic characteristics of air film. The motion equation of the rotor-bearing system is obtained by using the perturbation method and the eigensolution method is used to determine the stability threshold. The eccentricity, spindle speed, and restriction parameter are considered in the analysis of the whirl instability of the rotor-aerostatic bearing system for the different comparisons between various designs in the number and location of entry holes of aerostatic bearings.
15
Guan, Zhi-Pin, and 官志彬. "Dynamic Characteristics Analysis and Testing of a Turbo Molecular Pump Rotor-Bearing System." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/43607223254418828101.
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Chou, Yu-Wei, and 周有偉. "A Study on the Dynamic Characteristics of Geared Rotor-Bearing System with Hybrid Method." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/00618026860554916231.
Full textAbstract:
碩士國立成功大學
航空太空工程學系
81
A new technique called Hybrid Method is proposed in the analysis of the geared rotor-bearing system. This technique combines the Finite Element Method and the Generalized Polynomial Expansion Method to formulate the system equations of motion. The compliance and shear deformation of the shaft element, flexibility and damping of the bearings, stiffness and damping and pressure angle of the gear mesh are considered. The coupling between the torsional and lateral vibrations of the gears and the effect of the location of the gear mesh are also considered in the model. The whirl speed analyses and the steady state responses due to mass unbalance and displacement transmission error excitation are then calculated. Finally, the accuracy and the efficiency of the proposed method are demonstrated. The torsional-lateral coupled modes of the system are greatly affected by the gear mesh. It is shown that the stiffness, damping, and pressure angle of the gear mesh have significant influence on these modes. The steady state responses due to the transmission error, at tooth passing frequency during gears meshing, are of high values. The proposed Hybrid Method with application to geared rotor-bearing system, multi-stepped single shaft rotor system, and dual rotor system leads to better efficiency than the Finite Element Method without losing the accuracy.
17
Chang, Chia-Lun, and 張家綸. "The Characteristics Study of Bilateral Oil Magnetic Hybrid Hydrodynamic Bearings Rotor System in Low Speed." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/bx78pc.
Full textAbstract:
碩士中原大學
機械工程研究所
102
The spindles need to use the bearings to suspense the rotor in the rotating machines. In these bearing systems, the fluid hydrodynamic bearings with low noise, high precision, low vibration, long lifetime, and suitable running in the long time operation are more commonly be used in the heavy load system or the long time operation systems.The load capacity of the fluid hydrodynamic bearings as starting or operating at low speed are very small. The phenomenon of dry rub in the bearing and journal will occur and would damage the rotor system. Therefore, in this study, we wish to propose a passive magnetic bearing to combine with the fluid hydrodynamic bearings to improve the drawback to make the magnet-fluid hybrid hydrodynamic bearings could maintain better characteristics as the rotor system is starting or operating at low speed. In this study, the goal is to improve the load capacity of the fluid hydrodynamic bearings by an auxiliary magnetic force from the permanent magnets to promote the lifetime of bearings. Several combination types of the permanent magnets were proposed. By simulation analysis of the magnetic field, the relationship of magnetic forces and positions of magnets can be calculated. Then we can design a suitable passive magnetic bearing on hydrodynamic bearing to be a hybrid bearing to support the rotor. The hybrid bearing can provide magnetic forces to support the spindle suspending in the hydrodynamic bearing with a little gapes. It will make the rotor and the stator would not contact as they are not running or at a low running speed. Thus there have no dry friction in the bearing and the lifetime of the bearing will be promoted. Keywords: Fluid Hydrodynamic Bearings, Passive Magnetic Bearing, Magnet-Fluid Hybrid Hydrodynamic Bearings.
18
Chiou, Chao-Chih, and 邱昭智. "The Investigation of System Characteristics and Identification of Air Bearing Parameters for a High Speed Spindle Modeled with a Single-Rotor System." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/07386264905938784506.
Full textAbstract:
碩士元智大學
機械工程學系
91
The high speed air spindle system has been used popularly in some of the manufacturing machines in electronics industry. Such as those applications in the printed circuit board drilling and wafer saw cutting machines…etc. The study investigates the dynamic characteristics and identifies some of the parameters for the air spindle system by using both the experimental and finite element analysis (FEA) methods. It includes measuring the air bearing stiffness and damping for both cases of with thrust bearing and without thrust bearing. Also, the tests conducted including the spindle placed horizontally in the free-free boundary conditions, and the case where the spindle is supported by the pressurized air when with and without the thrust bearings respectively. The testing is aimed to study the influence of dynamic characteristics and boundary conditions on the air spindle system. The results of the steel ball impact testing for the identification of the bearing stiffness show that the stiffness in radial direction increases for the case with thrust bearing when compare with the case without thrust bearing. Moreover, increasing air pressure will also increase radial stiffness. There’s no observed difference for the stiffness measured with steel balls of different weights in the impact test. From the frequency response function(FRF) measurement for the spindle mandrel itself, it shows that under 20kHz bandwidth, there are four natural frequencies exist when at free boundary conditions. These data are verified further in FEA by adjusting the material constants in the model. These verified material constants together with the measured data of the spring and stiffness constants from ball impact test, are employed later for the analysis in the real case of air bearing supported spindle. The first four frequencies of the real case are not very clear in the FRF test. However, they are checked again in the FEA model. It is found that the results from both of them are very close each other and all are located within the working frequencies of the spindle system. Hence, these frequencies will have key effects in the performance of the spindle system. It is believed that the dynamic characteristics, stiffness and damping obtained in the study will contribute as a critical reference for the high spindle system design.