• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.966-977
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• 2003

This paper investigates how intentional mistuning of bladed disks reduces their sensitivity to unintentional random mistuning. The class of intentionally mistuned disks considered here is limited, for cost reasons, to arrangements of two types of blades (A and B, say). A two-step procedure is then described to optimize the arrangement of these blades around the disk to reduce the effects of unintentional random mistuning. First, a pure optimization effort is undertaken to obtain the pattern (s) of the A and B blades that yields small/the smallest value of the largest amplitude of response to a given excitation in the absence of unintentional random mistuning using Genetic Algorithm. Then, in the second step, a qualitative/quantitative estimate of the sensitivity for the optimized intentionally mistuned bladed disks with respect to unintentional random mistuning is performed by analyzing their amplification factor, probability density function and passband/stopband structures. Examples of application with simple bladed disk models demonstrate the significant benefits of using this class of intentionally mistuned disks.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.538-541
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• 2004

In turbomachinery rotor, there are small differences in the structural and/or geometrical properties of individual blades, which are referred to as blade mistuning. Mistuning effects of the forced response of bladed disks can be extremely large as often reported in many studies. In this paper, the pattern optimization of intentional mistuning for bladed disks considering with damping and coupling effect is the focus of the present investigation. More specifically, the class of intentionally mistuned disks considered here is limited, for cost reasons, to arrangements of two types of blades (A and B, say) and Genetic Algorithm is used to optimize the arrangement of these blades around the disk to reduce the forced response of blade with different damping and coupling stiffness.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.8
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• pp.77-84
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• 2003

Structural analyses of a turbine bladed-disk for a liquid rocket turbopump are peformed to investigate the safety level of strength and vibration at design point. Due to the high rotational speed of the turbopump, effects of centrifugal forces are carefully considered in the structural analysis. Thermal load caused by extreme temperature distribution is also considered as an external force applied to turbine bladed-disk. A three dimensional finite element method (FEM) is used for cyclic symmetry structural analyses with the MSC/NASTRAN DMAP Alter. Interblade phase angles are considered to investigate structural dynamic characteristics as a function of rotational speed. Through the numerical analysis, effects of centrifugal and thermal loads on the turbine bladed-disk are examined.

• Journal of Environmental Science International
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• v.20 no.8
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• pp.929-942
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• 2011

A novel conductivity technique was developed to detect penetration depth of the vessel fluid into the feedpipe. For a given reactor geometry, critical agitator speeds were experimentally determined at the onset of feedpipe backmixing using Rushton 6 bladed disk turbine (6BD) and high efficiency axial flow type 3 bladed (HE-3) impellers. The ratio of the feedpipe velocity to the critical agitator speed ($v_f/v_t$) was constant for either laminar or turbulent feedpipe flow regimes. Compared to the results of fast competitive reaction, feedpipe backmixing had to penetrate at least one feedpipe diameter into the feedpipe to significantly influence the yield of the side product. However, higher $v_f/v_t$ than that for L/d = 0 (position at the feedpipe end) of the conductivity technique is recommended to completely eliminate feedpipe backmixing in conservative design criteria. The conductivity technique was successful in all feedpipe flow conditions of laminar, transitional and turbulent flow regimes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.253-253
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• 2008

The main purpose of this study is to identify the vibrational characteristics for the LP blades of Korean standard fossil power plants. Modal tests for the 6 stage blade with boundary condition in which the root of blades are constrained with the disk were conducted, and FE analysis was also did with the same boundary condition. The steady-stress and modal analyses for the coupled bladed-disk system of LP turbine stages were completed. The dynamic analysis and fatigue analysis were followed to diagnose the integrity of LP turbine blades.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.3
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• pp.58-65
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• 2004

Thermal and structural finite element analyses were performed for the turbopump turbine bladed disk model with shroud of a liquid rocket engine. The only 1/80 part model was analyzed which consists of 3D eight node isoparametric solid elements. The applied loading history consists of a startup condition with a thermal spike and a steady state. Heat transfer coefficient on the blade was predicted using the commercial Navier-Stokes solver, Fluent. Transient thermal responses during startup and steady states were calculated using a 3D finite element code developed. Maximum stress and shroud tip displacement under the influence of centrifugal and thermal loading were also determined.

• The KSFM Journal of Fluid Machinery
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• v.7 no.5 s.26
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• pp.20-28
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• 2004

Static and dynamic structural analyses of a turbine bladed-disk for a liquid rocket turbopump are performed to investigate the safety level of strength and vibration at design point. During operation, turbopump is exposed to various external loads. Therefore, the effects of them should be carefully considered and properly modeled. First, due to the high rotational speed of the turbopump, effects of centrifugal forces are considered in the structural analysis. Thermal load caused by severe temperature differences is also considered. A three dimensional finite element method (FEM) is used for linear and nonlinear structural analyses with modified Newton-Raphson iteration method. After the nonlinear solution is obtained from the structural analysis, dynamic characteristics are obtained as a function of rotational speed from the linearized eigenvalue analysis at an equilibrium position. From the analysis results, characteristics of stress distribution and vibration were thoroughly examined and investigated.