• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.10 s.115
• /
• pp.1082-1089
• /
• 2006

In this study, advanced computational analysis system has been developed in order to investigate flow-induced vibration(FIV) phenomenon for general stator-rotor cascade configurations. Relative movement of the rotor with respect to stator is reflected by modeling Independent two computational domains. Fluid domains are modeled using the unstructured grid system with dynamic moving and local deforming methods. Unsteady, Reynolds-averaged Wavier-stokes equations with one equation Spalart-Allmaras and two-equation SST ${\kappa}-{\varepsilon}$ turbulence models are solved for unsteady flow problems and also relative moving and vibration effects of the rotor cascade are fully considered. A coupled implicit time marching scheme based on the Newmark integration method is used for computing the governing equations of fluid-structure interaction problems. Detailed vibration responses for different flow conditions are presented and then vibration characteristics are physically investigated in the time domain as computational virtual tests.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.848-854
• /
• 2006

In this study, a computational analysis system has been developed in order to investigate flow-induced vibration(FIV) phenomenon for general stator-rotor cascade configurations. Relative movement of the rotor with respect to stator is reflected by modeling independent two computational domains. Fluid domains are modeled using the unstructured grid system with dynamic moving and local deforming methods. Unsteady, Reynolds-averaged Navier-Stokes equations with one equation Spalart-Allmaras and two-equation SST $k-\omega$ turbulence models are solved for unsteady flow problems. A fully implicit time marching scheme based on the Newmark direct integration method is used flow computing the coupled governing equations of the fluid-structure interaction problem. Detailed FIV responses for different flow conditions are presented with respect to time and vibration characteristics are also physically investigated in the time domain.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.1058-1064
• /
• 2000

The analysis of dynamic behaviour of rotor system for the rolling piston type rotary compressor considering hydrodynamic force between motor rotor and stator is presented. In addition to considering other dynamic, loads such as large unbalance forces, gas force and bearing force, we consider the hydrodynamic force induced by the compressed fluid flow through the air gap between motor rotor and stator, and improve the analysis of vibration in rotary compressor. The Childs' method which based on Bulk-now and Hirs' turbulent lubrication model is used to calculate the rotordynamic coefficients due to hydrodynamic force of annular clearance in motor air gap.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1997.04a
• /
• pp.260-265
• /
• 1997

Large dynamic loads act on the rotor in rotary compressors. There are unbalance forces due to eccentric rotation parts and gas forces induced by the difference in pressure between compression and suction gases6 Rotor-journal bearing system is nonlinear since the stiffness and damping coefficients of the lubricating oil film are not constant in the bearings. In this paper, the program for predicting the behaviors of rotor-journal bearing system of rotary compressor is developed. Finite element modeling is used to analyze the flexible rotor. The numerical results are compared with experimental results. The location of balancer weight are suggested for reducing rotor whiring displacement.

• Journal of Power System Engineering
• /
• v.13 no.6
• /
• pp.88-94
• /
• 2009

In this paper, vibration characteristics after applying variable speed control to fans with a rated speed used in a power plant are studied by performing experiments and analyzing finite element models. Then the campbell diagram is presented to verify the reason of the abnormal vibration measured from fan structure during variable operation of Forced Draft Fan & Induced Draft Fan. According to results, it is found that amplitude of acceleration increases abruptly when a 2X harmonic component meets the natural frequency of fan rotor. Therefore it is very important thing that investigate exactly dynamic characteristics for the rotor at variable speed zone before applying variable speed control to a rotor with a rated speed.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.12
• /
• pp.987-993
• /
• 2013

Korean Utility Helicopter(KUH) is the first korean-developed helicopter. Its first flight was performed in March 2010 and then its development was completed successfully by June 2012. During flight test phase, KUH faced various vibration problems and appropriate vibration-reduction devices were designed and applied to solve the problems. The vibration-reduction devices were applied to main rotor blades, main gear box(MGB) supporting structure, cockpit, cabin and pilot seats to reduce rotor-induced 4/rev vibration. Also, dome-fairing was introduced in order to reduce the tail-shake vibration. This paper shows design technique and flight test results for vibration-reduction devices that have been incorporated into KUH.

• Journal of Advanced Marine Engineering and Technology
• /
• v.23 no.2
• /
• pp.244-251
• /
• 1999

Large dynamic loads act on the rotor in rotary compressors. There are unbalance forces due to eccentric rotation parts and gas forces induced by the pressure difference between compression and suction gases. Rotor-journal bearing system is nonlinear since the stiffness and damping coef-ficients of the lubrication oil film are not constant in the bearings. in this paper the program for predicting the behaviors of rotor-journal bearing system of rotary compressor is developed. Finite element modeling is used to analyze the flexible rotor. The numerical results are compared with experimental results.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.13 no.3
• /
• pp.373-384
• /
• 1989

The motions of a spinning rotor and a fluid enclosed in its cavity are known to have mutual interactions, which change the frequencies of forced vibrations and cause instabilities. These phenomena are of technical importance for fluid-cooled turbines as well as spin-stabilized satellites or rockets containing liquid fuels. In this paper the characteristics of unstable whirling of a rotor containing a partitioned cavity filled with two kinds of liquids are investigated experimentally. It studies the influence of rotational speed and filling ratio of two kinds of liquids on unstable whiring. As a result, it is found that the whirl velocity is approximately equal to, or slightly lower for large masses of trapped fluid than rotor critical speed. In case of a spinning rotor partially filled with two kinds of liquids the boundary surface plays a similar role to the free surface, and cases unstable forward whirl.

• Journal of the Korean Society of Safety
• /
• v.12 no.1
• /
• pp.9-18
• /
• 1997

This paper is a study on the dynamic characteristics of truncated cone type squeeze film damper(SFD) bearing and rotor system. This model can alter the radial oil film gap which Is Important to the performance of rotor-bearing system and manufactured easily to change the shape concept of traditional circular type SFD bearing. In theoretical analysis, the oil film pressure distribution, the oil film force, the film damping coefficient and the eccentricity ratio, etc. were induced with regard to the film inertia effect. The film damping coefficients and optimum design parameters are calculated. When unbalance parameter U is greater than 0.2, the nonlinear vibration such as "Jump" phenomena appears in the vicinity of rotor critical speed. At this time, the increases of bearing parameter U, journal distance S, Reynolds number Re can control this unstable vibration. The experimental results show that SFD hearing and rotor system which are designed according to the design parameters in the stable region are operated stably in rotational speed 9,600rpm without nonsynchronous behavior.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.10a
• /
• pp.52-56
• /
• 2011

Recently, KARI(Korea Aerospace Research Institute) has been developing a modern 11.5m diameter four bladed bearingless main rotor system, and this rotor system can be used for 7,000lb class helicopter. Flexbeam and torque tube can be considered as the key structural components, and large elastic twist of flexbeam induced by pitch control motion of torque tube can influence the nonlinear aeroelastic behavior. In this paper, the dynamic characteristic analysis results of bearingless rotor system were presented. In order to construct a input model and validate the analysis procedures, calculated results using the comprehensive helicopter analysis program CAMRAD II were compared with the measured natural frequencies and lag damping data from small-scale wind tunnel test. Next, the analysis model was extended to a full-scale model, and the dynamic analysis results were presented.