• The KSFM Journal of Fluid Machinery
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• v.7 no.5 s.26
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• pp.13-19
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• 2004

Centrifugal blowers are widely used for air handling units in industry applications. The blower has a centrifugal impeller and a scroll casing including a driving component such as an electric motor. The impeller takes forward or backward blades to induce flows into the blower, Comprehensive investigation according to the two kinds of blades is systematically carried out for a guidance of design for this kind research. It is observed that flow rate of the blower with forward blades is larger than that of the system with backward blades. Otherwise, the system noise is more pronounced in the case of the blower with forward blades. The reason is due to larger velocity from the rotating forward blades that pose obtuse angle with the circumferential direction. The distinguished characteristics are validated by a parallel experiments with a wind tunnel and in an anechoic chamber. Numerical analysis for the system shows detail information inside the blades and the casing. A series of figures to show the flow details offer deep understanding of the performance of a centrifugal blower with different blades.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.113-118
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• 2000

Centrifugal pump are widely used and the noise generated by these machines causes one of the most serious problems. In general, the centrifugal pump noise is often dominated by tones at BPF(blade passage frequency) and its higher harmonics. This is a consequence of the strong interaction between the flow discharged from the impeller and the cutoff in the casing. However, only a few researches have been carried out on predicting the noise because of the difficulty in obtaining detailed information about the flow field and casing effects on noise radiation. The objective of this study is to develop a prediction method for the unsteady flow field and the acoustic pressure field of a centrifugal pump, and to calculate the effects of small vanes that are attached in original impeller-splitter impeller. We assume that the impeller rotates with a constant angular velocity and the flow field around the impeller is incompressible and inviscid. So, a discrete vortex method(DVM) is used to model the centrifugal pump and to calculate the flow field. The force of each element on the blade is calculated by the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. The splitter impeller changes the acoustic characteristics as well as performance. Two-splitter type impeller is good for acoustic characteristics.

• International Journal of Aerospace System Engineering
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• v.8 no.1
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• pp.1-13
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• 2021

Contra-rotating fan is comprised of two rotors which are rotating in the opposite direction. The fan stages are named rotor-1 and rotor-2. Benefits from the use of contra rotation are in terms of better efficiency and improved thrust to weight ratio. Failure of contra-rotating fan stage blade in-service results in safety risks, repair costs, and revenue losses. This paper focuses on the vibration analysis and one way fluid-structure interaction of high aspect ratio, low speed contrarotating fan rotors. Modal analysis and modal pre-stress analysis of contra-rotating fan rotors were carried out to calculate the natural frequencies, One way fluid-structure interaction (FSI) was carried out where the computational analysis of the blades was performed using ANSYS CFX. The boundary conditions for CFD analysis were considered from the actual experimental velocity flow field at the inlet and pressure outlet. Based on the results obtained from the CFD analysis, the structural analysis such as deformation and Von-Misses stresses was carried out by using the finite element method (FEM) with ANSYS. The results provide necessary guidelines for the safe running of the contra-rotating fan. The analysis also will be helpful to understand the change of flow behavior due to a rotor deformation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.12
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• pp.1062-1070
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• 2016

The heat transfer and flow characteristics of gas turbine blade tip were investigated in this paper by using the conjugate heat transfer analysis. The rotor inlet boundary condition profile which was taken from the first stage nozzle outlet was used to analyse. The profile contained the velocity and temperature information. This study presents the influence of tip clearance about aerodynamic loss, heat transfer coefficient and film cooling effectiveness with the squealer tip designed blade model which tip clearance variation range from 1% to 2.5% of span. Results showed that the aerodynamic loss and the heat transfer coefficient were increased when the tip clearance was increased. Especially when the tip clearance was 2% of the span, the average heat transfer coefficient on the tip region was increased obviously. The film cooling effectiveness of tip region was increasing with decreasing of the tip clearance. There was high film cooling effectiveness at cavity and near tip hole region.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.2109-2124
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• 1991

A simulation program is developed to analyse the performance of an axial flow turbine stage based on the meanline prediction method. The gradient projection method is utilized to minimize the aerodynamic losses under the specified constraints on such as flow coefficient, total pressure ratio, stage power and blade loading coefficient. After obtaining the optimum point for minimizing the stage loss, a sensitivity analysis is carried out ground the optimum point to find the effects of the design variables and the design constraints on the stage performance. The result of the senitivity analysis under a constant blade loading coefficient shows that the total loss is more sensitive to the mean diameter, the absolute flow angle at nozzle outlet, the relative flow angle at rotor outlet and the axial mean velocity compared to the chords and the pitches. Moreover, the design constraints on the degree of reaction at root and the blade length-to-diameter ratio are found to be most influencial on the maximization of the overall aerodynamic efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.10
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• pp.795-803
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• 2015

The boundary layer developing over the suction surface of a first-stage turbine blade for power generation has been investigated in this study. For three locations selected in the region where local thermal load changes dramatically, mean velocity, turbulence intensity, and one-dimensional energy spectrum are measured with a hot-wire anemometer. The results show that the suction-surface boundary layer suffers a transition from a laminar flow to a turbulent one. This transition is confirmed to be a "separated-flow transition", which usually occurs in the shear layer over a separation bubble. The local minimum thermal load on the suction surface is found at the initiation point of the transition, whereas the local maximum thermal load is observed at the location of very high near-wall turbulence intensity after the transition process. Frequency characteristics of turbulent kinetic energy before and after the transition are understood clearly from the energy spectrum data.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.3
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• pp.183-191
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• 2022

A design method for a propeller type rim-driven axial-flow turbine for a micro-hydropower system is presented. The turbine consists of pre-stator, impeller and post-stator, where the pre-stator plays a role as a guide vane to provide circumferential velocity to the on-coming flow, and the impeller as a rotational power generator by absorbing angular momentum of the flow. BEM(Blade Element Method), which is based on the turbine Euler equation, is employed to design the pre-stator and impeller blades. NACA 66 thickness form and a=0.8 mean camber line, which is widely accepted as a marine propeller blade section, is used for the pre-stator and turbine blade section. A CFD method, derived from the discretization of the RANS equations, is applied for the analysis of the designed turbine system. The design conditions of the turbine is confirmed by the CFD calculation. Turbine characteristic curve is calculated by the CFD method, in order to provide the performance characteristics at off-design operation conditions. The proposed procedures for the design of a propeller type rim-driven axial-flow turbine are established and confirmed by the CFD analysis.

• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.185-192
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• 2010

Design of velocity-compounded turbine for 75ton class LRE turbopump application and pressure compounded turbine for 30ton class LRE turbopump has been performed. 1D calculation and CFD analysis were conducted in determining blade and flow passage shape of velocity compounded turbine iteratively. Finally, 23.1% improved specific power and 5% reduced weight turbine to the original design was developed. In case of pressure-compounded supersonic turbine design, rotational speed was increased by 50% and the effect of carryover ratio, 2nd nozzle installation angle, leakage flow of 2nd nozzle, and work sharing factor was studied. Final 1D design resulted 36% increased specific power and 51% reduced weight comparing to the original single-row impulse turbine. It is anticipated that nozzle flow path design will be very important for the accomplishment of expected performance of pressure-compounded turbine and nozzle shape optimization will be conducted through the CFD analysis.

• Journal of the Korean Solar Energy Society
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• v.31 no.3
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• pp.116-125
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• 2011

This study examined vertical shafts in high-rise apartments of the old high-rise buildings, reviewed the possibility of using flue ducts, and analyzed airflow patterns according to pressure differences between in and out side of flue ducts through computational fluid dynamics(CFD). The resulting conclusions are as follows: 1) The analysis results of airflow according to the stack effect of flue ducts show that smaller-diameter flue ducts(${\phi}1.2m$) would be morefavorable in increasing downward wind velocity than bigger-diameter ones(${\phi}1.6m$) and that the introduction ducts for outside air should be more than 50% of flue duct diameter to obtain a downward wind velocity higher than $3.0^m/s$ that is the minimum blade wind velocity of a small domestic wind generator. 2) The optimal installation location of a bypass introduction duct is the neutral plane of a flue duct or lower. When the diameter of the upper duct is bigger than that of the lower duct, it will generate more effects on the increase of downward wind velocity in flue ducts.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2C
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• pp.125-131
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• 2008

Ground stiffness(shear wave velocity) is one of the key parameters in geotechnical earthquake engineering. An In-situ seismic technique has its own advantages and disadvantages over the others in stiffness measurements. By combining the crosshole and seismic cone techniques and utilizing favourable features of bender elements, a new hybrid probe has been developed in order to enhance data quality and easiness of testing. The basic structure of the probe, called "MudFork" is a fork composed of two blades, on each of which source and receiver bender elements were mounted respectively. To evaluate the disturbance caused by the penetration of the probe, shear wave velocity measurements were carried out in the Kaolinite slurry in the laboratory. Finally, the probe was penetrated in coastal mud near Incheon, Korea, using SPT(standard penetration test)rods pushed with a routine boring machine and shear wave velocity measurements were carried out. The results were verified with data from laboratory and cone testing. The performance of the probe turns out to be excellent in terms of data quality and testing convenience.