The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Wen-chang Tsao - One of the best experts on this subject based on the ideXlab platform.
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DETC2011-48818 Study of Start-up vibration response for Oil Whip and dry Whip through Hilbert Huang Transform
2015Co-Authors: Chen-chao Fan, Min-chun Pan, Jhe-wei Syu, Wen-chang TsaoAbstract:Oil Whip induces self-excited vibration in fluid-handling machines, and what is worse, it can cause self-excited reverse precessional full annular rub, known as “dry Whip ” which is a secondary phenomenon resulting from a primary cause and may lead to a catastrophic failure of machines; that is, “coincidence of Oil Whip and dry Whip ” that occurs repeatedly with constant frequency and amplitude in small clearance cases of fluid-handling machines. Early detection of rub malfunction is essential to avoid damage. Hilbert Huang Transform, which included an empirical mode decomposition and Hilbert spectral analysis, is applied. Hilbert Huang Transform is a great method for analyzing non-linear and non-stationary signals, such as rotor startup signals. Hilbert Huang Transform clearly indicates instability at its initiation stage, and energy concentration changes by different stages. Malfunctions like rub can not observe by Hilbert spectrum. Hilbert spectrum combining full spectrum is developed, as know full Hilbert spectrum, to interpret the rub. The coincidence of Oil Whip and dry Whip is observed definitely through FHS. The advantage of the full Hilbert spectrum is to offer a faster, more efficient method to diagnose fluid-induced instability
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Study of Start-Up Vibration Response for Oil Whip and Dry Whip Through Hilbert Huang Transform
Volume 1: 23rd Biennial Conference on Mechanical Vibration and Noise Parts A and B, 2011Co-Authors: Chen-chao Fan, Min-chun Pan, Jhe-wei Syu, Wen-chang TsaoAbstract:Oil Whip induces self-excited vibration in fluid-handling machines, and what is worse, it can cause self-excited reverse precessional full annular rub, known as “dry Whip” which is a secondary phenomenon resulting from a primary cause and may lead to a catastrophic failure of machines; that is, “coincidence of Oil Whip and dry Whip” that occurs repeatedly with constant frequency and amplitude in small clearance cases of fluid-handling machines. Early detection of rub malfunction is essential to avoid damage. Hilbert Huang Transform, which included an empirical mode decomposition and Hilbert spectral analysis, is applied. Hilbert Huang Transform is a great method for analyzing non-linear and non-stationary signals, such as rotor startup signals. Hilbert Huang Transform clearly indicates instability at its initiation stage, and energy concentration changes by different stages. Malfunctions like rub can not observe by Hilbert spectrum. Hilbert spectrum combining full spectrum is developed, as know full Hilbert spectrum, to interpret the rub. The coincidence of Oil Whip and dry Whip is observed definitely through FHS. The advantage of the full Hilbert spectrum is to offer a faster, more efficient method to diagnose fluid-induced instability.Copyright © 2011 by ASME
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Study of start-up vibration response for Oil whirl, Oil Whip and dry Whip
Mechanical Systems and Signal Processing, 2011Co-Authors: Chen-chao Fan, Min-chun Pan, Jhe-wei Syu, Wen-chang TsaoAbstract:Abstract Oil Whip induces self-excited vibration in fluid-handling machines and causes self-excited reverse precessional full annular rub, known as “dry Whip”, which is a secondary phenomenon resulting from a primary cause, that is, “coexistence of Oil Whip and dry Whip”. For predicting these instabilities, the clues are hidden in start-up vibration signals of these kinds of machines. This paper presents a method for predicting these kinds of instabilities. First, a Hilbert spectrum combining a full spectrum, which is named the “full Hilbert spectrum”, is developed to reveal the whole process. Next, the transient position of a shaft centerline combining an acceptance region is introduced to predict instability at an early stage. The results presented in this study amply demonstrate the transition from stability to instability and the behavior of fluid-induced instability and rub in rotor systems. By this finding, bearing designers can completely understand these instability phenomena existing in fluid-handling machines. As a result, the control parameter for designing controllable bearings can be obtained and the instability problems can be resolved. Consequently, these findings are worth noting.
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Active Elimination of Oil Whip and Dry Whip Through the Use of Electromagnetic Exciter
Volume 5: 22nd International Conference on Design Theory and Methodology; Special Conference on Mechanical Vibration and Noise, 2010Co-Authors: Chen-chao Fan, Min-chun Pan, Wen-chang Tsao, Jhe-wei SyuAbstract:Oil Whip induces self-excited vibration in fluid-handling machines, and what is worse, it can cause self-excited reverse precessional full annular rub, known as “dry Whip”, which is a secondary phenomenon resulting from a primary cause, and may lead to a catastrophic failure of machines; that is, “coincidence of Oil Whip and dry Whip” that occurs repeatedly with constant frequency and amplitude in small clearance cases. This paper presents a technique using an electromagnetic exciter (EE), that can raise the threshold of stability of a rotary machine and then eliminate the coincidence of Oil Whip and dry Whip in the normal operational range. In addition, an experimental rotor rig, a general model of a rotor/beating system with an EE and corresponding governing motion equations, computation of stiffness supplied by the EE, design example, stability judged by root locus plots, and criterion for eliminating the coincidence of the Oil Whip and dry Whip are constructed, derived and established. Experimental results demonstrate that the coincidence of Oil Whip and dry Whip of the rotary machine can be removed effectively. These results can be used to diagnose rub and fluid-induced instability in this k ind of rotary machine.Copyright © 2010 by ASME
Aly El-shafei - One of the best experts on this subject based on the ideXlab platform.
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SEMAJIB: A Versatile High Performance Smart Bearing
Mechanisms and Machine Science, 2018Co-Authors: Aly El-shafeiAbstract:The experimental development of the Smart Electro-Magnetic Actuator Journal Integrated Bearing (SEMAJIB) is presented in this paper. The SEMAJIB is a smart high performance integrated bearing that combines a fluid film bearing (FFB) with an electro-magnetic actuator (EMA) in one integrated device. In all cases, the fluid film bearing shall carry the load, whereas the electro-magnetic actuator can be used as a pure controller or both as a controller and a load carrying element. In the latter case the electro-magnetic actuator can be considered as an active magnetic bearing (AMB). This paper summarizes the development of the SEMAJIB as a compact integrated bearing. It is shown that the SEMAJIB can easily transgress the multiple critical speeds of the 2-inch laboratory rotor, as well as suppress not only the first mode Oil Whip, but also the second mode Oil Whip, and additionally can control the rotor unbalance. The use of PD, H∞ and Fuzzy Logic control to control the SEMAJIB is presented and compared. It is shown that the SEMAJIB is a high performance bearing that is versatile and can replace tilting-pad bearings in high performance rotating machinery.
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Oil Whip Elimination Using Fuzzy Logic Controller
Journal of Engineering for Gas Turbines and Power, 2015Co-Authors: A. S. Dimitri, Jarir Mahfoud, Aly El-shafeiAbstract:Oil Whip is a self-excited sub-synchronous vibration which limits the range of operating speed of Journal Bearings (JB). JB have wide range of applications due to their high loading capacity, simple geometry, and lubrication. When the speed of rotation increases, the Oil Whip instability is excited with a frequency corresponding to the rotor critical speed which causes excessive undesirable vibration.A solution for this instability is implemented through this paper. The control action is implemented through a new integrated bearing device. The bearing consists of JB and Electromagnetic Actuator (EMA). The Oil Whip control action is applied through the EMA.A fuzzy logic control algorithm is developed and experimentally applied to a rotor test rig. The fuzzy logic controller is suitable to deal with problems of uncertainties and non-linearity.The experimental results show the ability of the developed fuzzy logic controller to eliminate the Oil Whip instability when applied to a test rig which simulates industrial rotor through an integrated bearing prototype which was designed and manufactured.© 2014 ASME
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Magnetic Actuator Control of Oil Whip Instability in Bearings
IEEE Transactions on Magnetics, 2015Co-Authors: A. S. Dimitri, Aly El-shafei, Amr A. Adly, Jarir MahfoudAbstract:Magnetic actuators are successfully used in the control of rotating machinery using feedback to eliminate the undesired vibration. Control algorithms can be implemented through the magnetic forces applied using the magnetic actuator, which are controlled through the current induced in the cOils. Throughout this paper, we suggest the elimination of the excessive Oil Whip vibration excited due to the rotation of flexible rotor supported on fluid film bearings using the magnetic forces. The fluid film bearings and magnetic actuators are integrated into one unit. An $\text{H}\infty $ controller is designed considering the robustness issues to suit a flexible rotor. The controller performance is successfully tested.
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Developments in Fluid Film Bearing Technology
IUTAM Symposium on Emerging Trends in Rotor Dynamics, 2010Co-Authors: Aly El-shafeiAbstract:This paper presents some new developments in Fluid Film Bearing (FFB) technology. The phenomena of Oil whirl and Oil Whip leading to instability in FFB supported rotors; limit the performance of rotating machinery. This paper presents some new developments that affect the instability threshold, namely the positive effect of angular misalignment on the instability threshold and related design improvements in FFB design. In addition, the concept of an integrated FFB with active magnetic bearing (AMB) is discussed with implications on improving the stability threshold, and actively controlling FFBs.
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Some Experiments on Oil Whirl and Oil Whip
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2004Co-Authors: Aly El-shafei, Sameh H Tawfick, M. S. Raafat, G. M. AzizAbstract:The Oil whirl and Oil Whip phenomena have been well known since the early twentieth century. However, there is a lot of confusion on the parameters that affect the onset of instability. In this study, we investigate the onset of instability on a flexible rotor mounted on two plain cylindrical journal bearings. The rotor is run through the first critical speed, the instability, and the second critical speed. Tests are conducted at various unbalance levels, pressures, and misalignment conditions on the coupling. it is shown that, by far, the misalignment of the coupling is the parameter that is most effective on the onset of instability. In particular angular misalignment resulted in the smoothest rotor response.
Chen-chao Fan - One of the best experts on this subject based on the ideXlab platform.
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DRAFT: ACTIVE SELF-EXCITED VIBRATION ELIMINATION OF ROTATING MACHINE WITH AN ELECTROMAGNETIC EXCITER
2016Co-Authors: Chen-chao Fan, Min-chun PanAbstract:Journal bearings are commonly used in large rotary machineries because they have excellent mechanical and geometric properties as well as large load-carrying capacities. Nevertheless, the Oil whirl and Oil Whip instabilities limit their applications due to their insufficient stiffness at high running speeds. This paper presents a method to increase the stiffness of a rotating machine using an electromagnetic exciter (EE), which can raise the threshold of instability of the rotating machine and eliminate fluid-induced instability. The EE is a controllable auxiliary device that can provide additional stiffness to the bearings to increase the operating ranges of a rotating machine, while the journal bearings act as load-carrying devices. Together, the EE complements the JB to stiffen the rotor system and raise the threshold of instability. A simple control scheme is used to calculate the amount of supplemental stiffness supplied by the EE. The experimental results demonstrate that the Oil whirl and Oil Whip instabilities of the rotating machine can be eliminated effectively, even at higher running speeds. The advantage of the EE is to offer a faster, more stable method to eliminate fluid-induced instability.
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DETC2011-48818 Study of Start-up vibration response for Oil Whip and dry Whip through Hilbert Huang Transform
2015Co-Authors: Chen-chao Fan, Min-chun Pan, Jhe-wei Syu, Wen-chang TsaoAbstract:Oil Whip induces self-excited vibration in fluid-handling machines, and what is worse, it can cause self-excited reverse precessional full annular rub, known as “dry Whip ” which is a secondary phenomenon resulting from a primary cause and may lead to a catastrophic failure of machines; that is, “coincidence of Oil Whip and dry Whip ” that occurs repeatedly with constant frequency and amplitude in small clearance cases of fluid-handling machines. Early detection of rub malfunction is essential to avoid damage. Hilbert Huang Transform, which included an empirical mode decomposition and Hilbert spectral analysis, is applied. Hilbert Huang Transform is a great method for analyzing non-linear and non-stationary signals, such as rotor startup signals. Hilbert Huang Transform clearly indicates instability at its initiation stage, and energy concentration changes by different stages. Malfunctions like rub can not observe by Hilbert spectrum. Hilbert spectrum combining full spectrum is developed, as know full Hilbert spectrum, to interpret the rub. The coincidence of Oil Whip and dry Whip is observed definitely through FHS. The advantage of the full Hilbert spectrum is to offer a faster, more efficient method to diagnose fluid-induced instability
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Study of Start-Up Vibration Response for Oil Whip and Dry Whip Through Hilbert Huang Transform
Volume 1: 23rd Biennial Conference on Mechanical Vibration and Noise Parts A and B, 2011Co-Authors: Chen-chao Fan, Min-chun Pan, Jhe-wei Syu, Wen-chang TsaoAbstract:Oil Whip induces self-excited vibration in fluid-handling machines, and what is worse, it can cause self-excited reverse precessional full annular rub, known as “dry Whip” which is a secondary phenomenon resulting from a primary cause and may lead to a catastrophic failure of machines; that is, “coincidence of Oil Whip and dry Whip” that occurs repeatedly with constant frequency and amplitude in small clearance cases of fluid-handling machines. Early detection of rub malfunction is essential to avoid damage. Hilbert Huang Transform, which included an empirical mode decomposition and Hilbert spectral analysis, is applied. Hilbert Huang Transform is a great method for analyzing non-linear and non-stationary signals, such as rotor startup signals. Hilbert Huang Transform clearly indicates instability at its initiation stage, and energy concentration changes by different stages. Malfunctions like rub can not observe by Hilbert spectrum. Hilbert spectrum combining full spectrum is developed, as know full Hilbert spectrum, to interpret the rub. The coincidence of Oil Whip and dry Whip is observed definitely through FHS. The advantage of the full Hilbert spectrum is to offer a faster, more efficient method to diagnose fluid-induced instability.Copyright © 2011 by ASME
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Study of start-up vibration response for Oil whirl, Oil Whip and dry Whip
Mechanical Systems and Signal Processing, 2011Co-Authors: Chen-chao Fan, Min-chun Pan, Jhe-wei Syu, Wen-chang TsaoAbstract:Abstract Oil Whip induces self-excited vibration in fluid-handling machines and causes self-excited reverse precessional full annular rub, known as “dry Whip”, which is a secondary phenomenon resulting from a primary cause, that is, “coexistence of Oil Whip and dry Whip”. For predicting these instabilities, the clues are hidden in start-up vibration signals of these kinds of machines. This paper presents a method for predicting these kinds of instabilities. First, a Hilbert spectrum combining a full spectrum, which is named the “full Hilbert spectrum”, is developed to reveal the whole process. Next, the transient position of a shaft centerline combining an acceptance region is introduced to predict instability at an early stage. The results presented in this study amply demonstrate the transition from stability to instability and the behavior of fluid-induced instability and rub in rotor systems. By this finding, bearing designers can completely understand these instability phenomena existing in fluid-handling machines. As a result, the control parameter for designing controllable bearings can be obtained and the instability problems can be resolved. Consequently, these findings are worth noting.
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Active Elimination of Oil Whip and Dry Whip Through the Use of Electromagnetic Exciter
Volume 5: 22nd International Conference on Design Theory and Methodology; Special Conference on Mechanical Vibration and Noise, 2010Co-Authors: Chen-chao Fan, Min-chun Pan, Wen-chang Tsao, Jhe-wei SyuAbstract:Oil Whip induces self-excited vibration in fluid-handling machines, and what is worse, it can cause self-excited reverse precessional full annular rub, known as “dry Whip”, which is a secondary phenomenon resulting from a primary cause, and may lead to a catastrophic failure of machines; that is, “coincidence of Oil Whip and dry Whip” that occurs repeatedly with constant frequency and amplitude in small clearance cases. This paper presents a technique using an electromagnetic exciter (EE), that can raise the threshold of stability of a rotary machine and then eliminate the coincidence of Oil Whip and dry Whip in the normal operational range. In addition, an experimental rotor rig, a general model of a rotor/beating system with an EE and corresponding governing motion equations, computation of stiffness supplied by the EE, design example, stability judged by root locus plots, and criterion for eliminating the coincidence of the Oil Whip and dry Whip are constructed, derived and established. Experimental results demonstrate that the coincidence of Oil Whip and dry Whip of the rotary machine can be removed effectively. These results can be used to diagnose rub and fluid-induced instability in this k ind of rotary machine.Copyright © 2010 by ASME
Min-chun Pan - One of the best experts on this subject based on the ideXlab platform.
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DRAFT: ACTIVE SELF-EXCITED VIBRATION ELIMINATION OF ROTATING MACHINE WITH AN ELECTROMAGNETIC EXCITER
2016Co-Authors: Chen-chao Fan, Min-chun PanAbstract:Journal bearings are commonly used in large rotary machineries because they have excellent mechanical and geometric properties as well as large load-carrying capacities. Nevertheless, the Oil whirl and Oil Whip instabilities limit their applications due to their insufficient stiffness at high running speeds. This paper presents a method to increase the stiffness of a rotating machine using an electromagnetic exciter (EE), which can raise the threshold of instability of the rotating machine and eliminate fluid-induced instability. The EE is a controllable auxiliary device that can provide additional stiffness to the bearings to increase the operating ranges of a rotating machine, while the journal bearings act as load-carrying devices. Together, the EE complements the JB to stiffen the rotor system and raise the threshold of instability. A simple control scheme is used to calculate the amount of supplemental stiffness supplied by the EE. The experimental results demonstrate that the Oil whirl and Oil Whip instabilities of the rotating machine can be eliminated effectively, even at higher running speeds. The advantage of the EE is to offer a faster, more stable method to eliminate fluid-induced instability.
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DETC2011-48818 Study of Start-up vibration response for Oil Whip and dry Whip through Hilbert Huang Transform
2015Co-Authors: Chen-chao Fan, Min-chun Pan, Jhe-wei Syu, Wen-chang TsaoAbstract:Oil Whip induces self-excited vibration in fluid-handling machines, and what is worse, it can cause self-excited reverse precessional full annular rub, known as “dry Whip ” which is a secondary phenomenon resulting from a primary cause and may lead to a catastrophic failure of machines; that is, “coincidence of Oil Whip and dry Whip ” that occurs repeatedly with constant frequency and amplitude in small clearance cases of fluid-handling machines. Early detection of rub malfunction is essential to avoid damage. Hilbert Huang Transform, which included an empirical mode decomposition and Hilbert spectral analysis, is applied. Hilbert Huang Transform is a great method for analyzing non-linear and non-stationary signals, such as rotor startup signals. Hilbert Huang Transform clearly indicates instability at its initiation stage, and energy concentration changes by different stages. Malfunctions like rub can not observe by Hilbert spectrum. Hilbert spectrum combining full spectrum is developed, as know full Hilbert spectrum, to interpret the rub. The coincidence of Oil Whip and dry Whip is observed definitely through FHS. The advantage of the full Hilbert spectrum is to offer a faster, more efficient method to diagnose fluid-induced instability
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Study of Start-Up Vibration Response for Oil Whip and Dry Whip Through Hilbert Huang Transform
Volume 1: 23rd Biennial Conference on Mechanical Vibration and Noise Parts A and B, 2011Co-Authors: Chen-chao Fan, Min-chun Pan, Jhe-wei Syu, Wen-chang TsaoAbstract:Oil Whip induces self-excited vibration in fluid-handling machines, and what is worse, it can cause self-excited reverse precessional full annular rub, known as “dry Whip” which is a secondary phenomenon resulting from a primary cause and may lead to a catastrophic failure of machines; that is, “coincidence of Oil Whip and dry Whip” that occurs repeatedly with constant frequency and amplitude in small clearance cases of fluid-handling machines. Early detection of rub malfunction is essential to avoid damage. Hilbert Huang Transform, which included an empirical mode decomposition and Hilbert spectral analysis, is applied. Hilbert Huang Transform is a great method for analyzing non-linear and non-stationary signals, such as rotor startup signals. Hilbert Huang Transform clearly indicates instability at its initiation stage, and energy concentration changes by different stages. Malfunctions like rub can not observe by Hilbert spectrum. Hilbert spectrum combining full spectrum is developed, as know full Hilbert spectrum, to interpret the rub. The coincidence of Oil Whip and dry Whip is observed definitely through FHS. The advantage of the full Hilbert spectrum is to offer a faster, more efficient method to diagnose fluid-induced instability.Copyright © 2011 by ASME
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Study of start-up vibration response for Oil whirl, Oil Whip and dry Whip
Mechanical Systems and Signal Processing, 2011Co-Authors: Chen-chao Fan, Min-chun Pan, Jhe-wei Syu, Wen-chang TsaoAbstract:Abstract Oil Whip induces self-excited vibration in fluid-handling machines and causes self-excited reverse precessional full annular rub, known as “dry Whip”, which is a secondary phenomenon resulting from a primary cause, that is, “coexistence of Oil Whip and dry Whip”. For predicting these instabilities, the clues are hidden in start-up vibration signals of these kinds of machines. This paper presents a method for predicting these kinds of instabilities. First, a Hilbert spectrum combining a full spectrum, which is named the “full Hilbert spectrum”, is developed to reveal the whole process. Next, the transient position of a shaft centerline combining an acceptance region is introduced to predict instability at an early stage. The results presented in this study amply demonstrate the transition from stability to instability and the behavior of fluid-induced instability and rub in rotor systems. By this finding, bearing designers can completely understand these instability phenomena existing in fluid-handling machines. As a result, the control parameter for designing controllable bearings can be obtained and the instability problems can be resolved. Consequently, these findings are worth noting.
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Active Elimination of Oil Whip and Dry Whip Through the Use of Electromagnetic Exciter
Volume 5: 22nd International Conference on Design Theory and Methodology; Special Conference on Mechanical Vibration and Noise, 2010Co-Authors: Chen-chao Fan, Min-chun Pan, Wen-chang Tsao, Jhe-wei SyuAbstract:Oil Whip induces self-excited vibration in fluid-handling machines, and what is worse, it can cause self-excited reverse precessional full annular rub, known as “dry Whip”, which is a secondary phenomenon resulting from a primary cause, and may lead to a catastrophic failure of machines; that is, “coincidence of Oil Whip and dry Whip” that occurs repeatedly with constant frequency and amplitude in small clearance cases. This paper presents a technique using an electromagnetic exciter (EE), that can raise the threshold of stability of a rotary machine and then eliminate the coincidence of Oil Whip and dry Whip in the normal operational range. In addition, an experimental rotor rig, a general model of a rotor/beating system with an EE and corresponding governing motion equations, computation of stiffness supplied by the EE, design example, stability judged by root locus plots, and criterion for eliminating the coincidence of the Oil Whip and dry Whip are constructed, derived and established. Experimental results demonstrate that the coincidence of Oil Whip and dry Whip of the rotary machine can be removed effectively. These results can be used to diagnose rub and fluid-induced instability in this k ind of rotary machine.Copyright © 2010 by ASME
Jhe-wei Syu - One of the best experts on this subject based on the ideXlab platform.
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DETC2011-48818 Study of Start-up vibration response for Oil Whip and dry Whip through Hilbert Huang Transform
2015Co-Authors: Chen-chao Fan, Min-chun Pan, Jhe-wei Syu, Wen-chang TsaoAbstract:Oil Whip induces self-excited vibration in fluid-handling machines, and what is worse, it can cause self-excited reverse precessional full annular rub, known as “dry Whip ” which is a secondary phenomenon resulting from a primary cause and may lead to a catastrophic failure of machines; that is, “coincidence of Oil Whip and dry Whip ” that occurs repeatedly with constant frequency and amplitude in small clearance cases of fluid-handling machines. Early detection of rub malfunction is essential to avoid damage. Hilbert Huang Transform, which included an empirical mode decomposition and Hilbert spectral analysis, is applied. Hilbert Huang Transform is a great method for analyzing non-linear and non-stationary signals, such as rotor startup signals. Hilbert Huang Transform clearly indicates instability at its initiation stage, and energy concentration changes by different stages. Malfunctions like rub can not observe by Hilbert spectrum. Hilbert spectrum combining full spectrum is developed, as know full Hilbert spectrum, to interpret the rub. The coincidence of Oil Whip and dry Whip is observed definitely through FHS. The advantage of the full Hilbert spectrum is to offer a faster, more efficient method to diagnose fluid-induced instability
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Study of Start-Up Vibration Response for Oil Whip and Dry Whip Through Hilbert Huang Transform
Volume 1: 23rd Biennial Conference on Mechanical Vibration and Noise Parts A and B, 2011Co-Authors: Chen-chao Fan, Min-chun Pan, Jhe-wei Syu, Wen-chang TsaoAbstract:Oil Whip induces self-excited vibration in fluid-handling machines, and what is worse, it can cause self-excited reverse precessional full annular rub, known as “dry Whip” which is a secondary phenomenon resulting from a primary cause and may lead to a catastrophic failure of machines; that is, “coincidence of Oil Whip and dry Whip” that occurs repeatedly with constant frequency and amplitude in small clearance cases of fluid-handling machines. Early detection of rub malfunction is essential to avoid damage. Hilbert Huang Transform, which included an empirical mode decomposition and Hilbert spectral analysis, is applied. Hilbert Huang Transform is a great method for analyzing non-linear and non-stationary signals, such as rotor startup signals. Hilbert Huang Transform clearly indicates instability at its initiation stage, and energy concentration changes by different stages. Malfunctions like rub can not observe by Hilbert spectrum. Hilbert spectrum combining full spectrum is developed, as know full Hilbert spectrum, to interpret the rub. The coincidence of Oil Whip and dry Whip is observed definitely through FHS. The advantage of the full Hilbert spectrum is to offer a faster, more efficient method to diagnose fluid-induced instability.Copyright © 2011 by ASME
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Study of start-up vibration response for Oil whirl, Oil Whip and dry Whip
Mechanical Systems and Signal Processing, 2011Co-Authors: Chen-chao Fan, Min-chun Pan, Jhe-wei Syu, Wen-chang TsaoAbstract:Abstract Oil Whip induces self-excited vibration in fluid-handling machines and causes self-excited reverse precessional full annular rub, known as “dry Whip”, which is a secondary phenomenon resulting from a primary cause, that is, “coexistence of Oil Whip and dry Whip”. For predicting these instabilities, the clues are hidden in start-up vibration signals of these kinds of machines. This paper presents a method for predicting these kinds of instabilities. First, a Hilbert spectrum combining a full spectrum, which is named the “full Hilbert spectrum”, is developed to reveal the whole process. Next, the transient position of a shaft centerline combining an acceptance region is introduced to predict instability at an early stage. The results presented in this study amply demonstrate the transition from stability to instability and the behavior of fluid-induced instability and rub in rotor systems. By this finding, bearing designers can completely understand these instability phenomena existing in fluid-handling machines. As a result, the control parameter for designing controllable bearings can be obtained and the instability problems can be resolved. Consequently, these findings are worth noting.
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Active Elimination of Oil Whip and Dry Whip Through the Use of Electromagnetic Exciter
Volume 5: 22nd International Conference on Design Theory and Methodology; Special Conference on Mechanical Vibration and Noise, 2010Co-Authors: Chen-chao Fan, Min-chun Pan, Wen-chang Tsao, Jhe-wei SyuAbstract:Oil Whip induces self-excited vibration in fluid-handling machines, and what is worse, it can cause self-excited reverse precessional full annular rub, known as “dry Whip”, which is a secondary phenomenon resulting from a primary cause, and may lead to a catastrophic failure of machines; that is, “coincidence of Oil Whip and dry Whip” that occurs repeatedly with constant frequency and amplitude in small clearance cases. This paper presents a technique using an electromagnetic exciter (EE), that can raise the threshold of stability of a rotary machine and then eliminate the coincidence of Oil Whip and dry Whip in the normal operational range. In addition, an experimental rotor rig, a general model of a rotor/beating system with an EE and corresponding governing motion equations, computation of stiffness supplied by the EE, design example, stability judged by root locus plots, and criterion for eliminating the coincidence of the Oil Whip and dry Whip are constructed, derived and established. Experimental results demonstrate that the coincidence of Oil Whip and dry Whip of the rotary machine can be removed effectively. These results can be used to diagnose rub and fluid-induced instability in this k ind of rotary machine.Copyright © 2010 by ASME
