• The KSFM Journal of Fluid Machinery
• /
• v.13 no.3
• /
• pp.24-29
• /
• 2010

Axial fans for an air-conditioning unit are designed to equip the system with an expected flow-rate and low noise level by applying the blade design method of multi-sectioning and local camber generation. In this study, the distributions of chord length, stagger angle, and camber angle are globally and locally determined for the given specific speed, which is considered to be relatively high. The mock-up fans are observed to satisfy the aerodynamic performance and the noise level for the system simultaneously and discussed in terms of local flow patterns related to the emitted noise.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.141-144
• /
• 1997

This paper presents design automation system using API and parametric modeling of solid modeler, which is applied on axial fans for cooling towers. The design data including chord length and twist angle according to the fan length are given by design program, and API functions are applied to automate the modeling and assembly process of fan blade. The boss to connect fan and motor is designed with parametric design function provided by UG so as to be flexibly changed by the value of design parameters. The process of generating 2-D drafting for parts and an assembly is also automated. With developed system, the modeling time is reduced to 5 minutes even with unskilled operators.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.20 no.12
• /
• pp.1153-1160
• /
• 2010

A circular plate is the main part of a circular saw blade, which is widely used in industrial cutting tools. In experiments using a circular saw containing slots, we observed that a number of natural frequencies are simultaneously emerged in specific frequency regions. The interesting phenomenon is called the frequency convergence. Effects of design parameters such as the number, the length and the width of slots, on the frequency-convergence phenomenon are analyzed by FEM simulations using ALGOR. The frequency-convergence phenomenon will be intensified when the number, length and width of slots increase.

• Microbiology and Biotechnology Letters
• /
• v.20 no.4
• /
• pp.445-450
• /
• 1992

An enhancement of the oxygen transfer rate in a 1$\ell$ bioreactor for mammalian cell culture by using a silicone rubber tubing as an oxygenator was investigated. When the silicone membrane was used to supply oxygen to the culture broth, the oxygen transfer coefficients ($k_{\iota}a$) measured in deionized-distilled water were markedly increased. Effect of surface aeration without the tubing aeration was very low under $1.0hr^{-1}$ of $k_{\iota}a$. The enhancing effects of agitation rates on $k_{\iota}a$ were much more effective than those of aeration rates. The increase of $k_{\iota}a$ with increasing tube length was observed as a result of the large surface area for oxygen supply. However, 2 m of the tube length was adequate for a 1$\ell$ vessel. The larger blade type of impeller was effective to enhance the kLa values because of its high mixing intensity. In culture medium supplemented with 5% serum, kLa values were reduced to approximately 40% probably due to the viscosity. We also obtained the normal cell concentration of $5{\times}10^6$ cells/m$\ell$ of HepG2 on microcarriers, which could be achieved in a typical bioreactor for animal cell culture.

• Journal of the Korean Solar Energy Society
• /
• v.36 no.1
• /
• pp.49-61
• /
• 2016

The power production using hub height wind speed tends to be overestimated than actual power production. It is because the hub height wind speed cannot represent vertical wind shear and blade tip loss that aerodynamics characteristic on the wind turbine. The commercial CFD model WindSim is used to compare and analyze each power production. A classification of atmospheric stability is accomplished by Monin-Obukhov length. The concentric wind speed constantly represents low value than horizontal equivalent wind speed or hub height wind speed, and also relevant to power production. The difference between hub height wind speed and concentric equivalent wind speed is higher in nighttime than daytime. Under the strongly convective state, power production is lower than under the stable state, especially using the concentric equivalent wind speed. Using the concentric equivalent wind speed considering vertical wind shear and blade tip loss is well estimated to decide suitable area for constructing wind farm.

• Fashion & Textile Research Journal
• /
• v.20 no.6
• /
• pp.713-721
• /
• 2018

This study aimed to develop a draping manual for the basic bodice to be available in colleges and industries. For this, draping methods mentioned in six different textbooks were comparatively analyzed. As for the research method, draping methods were compared by using training textbook, and basic bodices designed with muslin were assessed using the 5-point Likert scale. First, the draping methods of basic bodices were comparatively analyzed. The main baselines were set as the center front line, the center back line, the bust line, and the shoulder blade line. The position of dart was suggested based on the princess line, in both the front and the back. The value of dart was classified as a fixed size with any associated excess. The length of dart was set based on the bust point and shoulder blade point or a fixed size. The amount of ease was randomly set based on the fixed size, bust circumference, waist circumference, interscye length, armholes and shoulder lines, or the worker's intuition. Second, according to the appearance evaluation of the patterns, the following patterns obtained the highest scores: A pattern 2.5cm away from the B.P point of the waist dart and shoulder dart in the frontal appearance, a pattern of 0.6~0.7cm ease for the front armhole, a pattern with an ease of 1.2cm in the bust and 0.6cm in the waist. As for back appearance, the pattern in which the point of waist dart is 2~3cm from the bust line received the highest score.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.17 no.3
• /
• pp.167-173
• /
• 2014

In this work, based on the blade element-momentum theory (BEMT), we proposed the geometry of a lab-scale horizontal axis tidal turbine with a diameter of 80cm, which can demonstrate the maximum power coefficient, and investigated the effect of blade pitch angle increase on the power coefficient. For validation of the computed power coefficients by the BEMT, we also computed the power coefficient using the computational fluid dynamics (CFD) for each case. For the CFD, 15 times of the turbine radius was used for the length and diameter of the computational domain, and the open boundary condition was prescribed at the boundary of the computational domain. The maximum power coefficients of the turbine acquired by the BEMT and CFD were about 48%, showing a good agreement. Both of the power coefficients computed by the BEMT and CFD tended to decrease when the blade pitch angle increases. The two power coefficients for a given tip-speed ratio were in good agreement. Through the present study, we have confirmed that we can trust the proposed geometry and the computed power coefficients based on the BEMT.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.6
• /
• pp.2109-2124
• /
• 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 A
• /
• v.24 no.3 s.174
• /
• pp.603-612
• /
• 2000

Corrosion characteristics on the 12Cr alloy steel of turbine blade was electro-chemically investigated in 3.5wt% NaCI and 12.7wt% Na2S04 solution, respectively. Electro-chemical polarization test, Huey test and Oxalic acid etching test were previously conducted to estimate corrosion susceptibility of the material. And, using the horizontal corrosion fatigue tester, corrosion fatigue characteristics of 12Cr alloy steel in distilled water, 3.5wt% NaCI solution, and 12.7wt%(1M) Na2S04 solution were also fracture-mechanically estimated and compared their results. Parameter considered was room temperature, 60'C and 90'C. Corrosion fatigue crack length was measured by DC potential difference method.Obtained results are as follows,1) 12Cr alloy steel showed high corrosion rate in 3.5wt% NaCI solution and Na2S04 solution at high tempratue.2) Intergranular corrosion sensitivity of 12 Cr alloy was smaller than austenitic stainless steel.3) Corrosion fatigue crack growth rate in 3.5wt% NaCI and 12.7wt%(IM) Na2S04 solution is entirely higher than in the distilled water, and also increased with the temperature increase.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.11a
• /
• pp.648-651
• /
• 2010

Propeller shall have high efficiency and improved aerodynamic characteristics to get the thrust to fly at high speed for the FAR25 turboprop aircraft. That is way Clark-Y airfoil which is used to conventional turboprop aircraft propeller is selected as a blade airfoil. Javaprop program based on the Adkins method is used for aerodynamic design and analysis of propeller, Adkins method is based on the vortex-blade element theory which design the propeller to satisfy the condition for minimum energy loss. Slipstream displacement don't change and consider a rigid body. High efficiency propeller geometry is generated by varying chord length and pitch angle at design point of FAR25 turboprop aircraft. The propeller design results indicate that could be applied to the FAR25 turboprop aircraft, through analysis of propeller aerodynamic characteristics using the CFD(Computational Fluid Dynamic).