• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.220-226
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• 2002

A general solution method is presented to obtain the unbalance response orbit from the finite element based equations of motion of a gear-coupled two-shaft rotor-bearing system. Particularly, are proposed the analytical solutions of major and minor axis radii of the orbit. The method has been applied to analyze the unbalance response of a 800 refrigeration-ton turbo-chiller rotor-bearing system, having a bull-pinion speed increasing gear. The bumps of unbalance responses have been observed at the first torsional natural frequency due to the coupling of lateral and torsional dynamics by the gear meshing. Further, the proposed analytical solutions have been validated with results obtained by a full numerical approach.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.101-106
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• 1993

A new rotor control scheme, the isotropic control of anisotropic rotor bearing system in complex state space, is proposed, which utilizes the concepts on the eigenstructure of the isotropic rotor system. Then the control scheme is applied to an active magnetic bearing system and the control performance is investigated in relation to control energy, transient response, and unbalance response. In particular, it is shown that the proposed method is efficient for control of unbalance response.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.3 s.96
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• pp.354-363
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• 2005

Squeeze film dampers (SFDs) have been commonly used to effectively enhance the dynamic behavior of the rotating shaft supported by rolling element bearings. However, due to the recent trends of high operating speed, high load capacity and light weight in rotating machinery, it is becoming increasingly important to change the dynamic characteristics of rotating machines in operation so that the excessive vibrations, which may occurparticularly when passing through critical speeds or unstable regions, can be avoided. Semi-active type SFDs using magneto-rheological fluid (MR fluid), which responds to an applied magnetic field with a change in rheological behavior, are introduced in order to find its applications to rotating machinery as an effective device attenuating unbalance responses. In this paper, a semi-active SFD using MR fluid is designed, tested, and identified to investigate the capability of changing its dynamic properties such as damping and stiffness.In order to apply the MR-SFD to the vibration attenuation of a rotor, a systematic approach for determining the damper's optimal location is investigated, and also, a control algorithm that could improve the unbalance response characteristics of a flexible rotor is proposed and its control performance is validated with a numerical example.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1005-1011
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• 2004

Squeeze film dampers (SFDs) have been commonly used to effectively enhance the dynamic behavior of the rotating shaft supported by rolling element bearings. However, due to the recent trends of high operating speed, high load capacity and light weight in rotating machinery, it is becoming increasingly important to change the dynamic characteristics of rotating machines in operation so that the excessive vibrations, which may occur particularly when passing through critical speeds or unstable regions, can be avoided. Semi-active type SFDs using magneto-rheological fluid (MR fluid), which responds to an applied magnetic field with a change in rheoloaical behavior, are introduced in order to find its applications to rotating machinery as an effective device attenuating unbalance responses. In this paper, a semi-active SFD using MR fluid is designed, tested and identified by means of linear analysis to investigate the capability of changing its dynamic properties such as damping and stiffness. Furthermore, the proposed device is applied to a rotor system to investigate its potential capability for vibration attenuation: an efficient method for selecting the optimal location of the proposed damper is introduced and control algorithm that could improve the unbalance response properties of a flexible rotor is also proposed.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.9
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• pp.158-166
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• 2004

A new method to measure residual unbalance of rotor - bearing system was proposed. The method which determine residual unbalance based on polar plot and an analytical method which calculates the residual unbalance of the rotor from the vibration response of the Jeffcott rotor are proposed in this study with respect to a real rotor system of which the residual unbalance is unknown. The unbalance eccentricity of the produced experimental model is 3.78 mil, developing the measurement method of the residual unbalance more convenient than the proposed method of ISO and API standard. The proposed method was experimentally compared with the ISO standard, and the two methods were exactly correspondent to each other within an error of 1%.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.9
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• pp.137-147
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• 1995

The unbalance response analysis is one of the essential area in the forced vibration analysis of rotor-bearing systems. Local bearing parameters in rotor-bearing systems are the major sources which give rise to a difficulty in unbalance response computation due to the complicated dynamic properties such as rotational speed dependency and anisotropy. In the present paper, an efficient method for unbalance responses is proposed so as to easily take into account bearing parameters in computation. An exact matrix condensation procedure is proposed which enables the present method to compute unbalance responses by dealing with condensed, small matrices. The proposed method causes no errors even though the computation procedure is based on the small matrices condensed from the full matrices. The present method is illustrated through a numerical example and compared with the conventional method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04a
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• pp.615-619
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• 1995

The unbalance response analysis is one of the essential area in the forced vibration analysis of rotor-bearing systems. Local bearing parameters in ortor-bearing systems are the major sources which give rise to a difficulty in unbalance response computation due to the complicated dynamic properties such as rotational speed dependency and anisotropy. In the present paper, an exact condensation procedure is introduced to easily take into account bearing parameters in computation of unbalance responses for rotor bearing systems. The present method is illustrated through a numerical example and compared with the conventional method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.667-668
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• 2012

• Journal of Mechanical Science and Technology
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• v.15 no.9
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• pp.1226-1239
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• 2001

Rotating machinery often encounters excessive vibration due to various excitation sources. Among others, the synchronous excitation due to rotating unbalance and initial deformation is acknowledged to be one of the major sources of vibration in rotor-bearing systems. In this paper, a synchronous response analysis method in the presence of the initial deformation is proposed to investigate the peculiar effect of the initial deformation on the response of general flexible rotor-bearing systems with rotational speed dependency and the anisotropy. Experiments are performed and compared with computational results to verify the proposed analysis method. Two numerical examples are also provided to illustrate the characteristics of the synchronous response of general rotor-bearing systems due to the initial deformation.

• The KSFM Journal of Fluid Machinery
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• v.13 no.3
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• pp.18-23
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• 2010

This paper predicts the unbalance and transient (start-up) response of a 5MW industrial gas turbine by using commercial rotordynamic tool, DYNAMICS 4.3. The gas turbine is operated at 12,975rpm on squeeze film dampers or tilting pad bearings. The stiffness and damping coefficients of the squeeze film dampers and tilting pad bearings are estimated. It is seen that the vibration amplitude of the gas turbine rotor is sufficiently small around the critical speeds and at the rated speed.