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Effect of Propeller-propulsion on Aerodynamic Characteristics of WIG-Craft
박경우(Kyoungwoo Park),이주희(Juhee Lee),홍철호(Chol-Ho Hong),강기준(Kijun Kang),안종관(Jong-Kwan Ahn) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Numerical investigations for the 3-dimensional WIG effect vehicle with DUP (direct underside pressurization) have been performed to analyze aerodynamic characteristics and static height stability. The computational model is consisted of all compartments of a WIG effect vehicle such as propeller, fuselage, air chamber, main wing, and tail. Increased pressure under the fuselage by DUP-device( propeller and air chamber) can considerably reduce the take-off speed and thus minimize the effect of the hump drag which is one of the technical difficulties of the WIG effect vehicle, while the vehicle can be accelerated to take off on water. The accelerated air by the propeller comes into the air chamber through the channel at the middle of the fuselage and it results in an augmentation of the lift by changing its dynamic pressure to static one. Additionally, the DUP-device is not favorable for both stability and aerodynamic performance of the WIG effect vehicle because the accelerated air produces an excessive drag, negative pitching moment and 3-dimensional effects (that is, yawing and rolling moments). The result shows that the effect of yawing and rolling moments is not serious.
박경우(Kyoungwoo Park),김진배(Jin-Bae Kim),이주희(Juhee Lee) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.12
A 3-dimensional numerical investigation of a WIG effect vehicle with DUP (direct underside pressurization) is performed to predict aerodynamic characteristics and the static height stability. DUP can considerably reduce take-off speed and minimize the hump drag while the vehicle accelerates on the water to take off. The DUP of the model vehicle, Aircat, consists of a propeller in the middle of the fuselage and an air chamber under the fuselage. The air accelerated by the propeller comes into the camber through the channel in the middle of fuselage and augments lift by changing its dynamic pressure to static pressure dramatically. However, the air accelerated by a propeller produces excessive drag and reduces static height stability.
실리카 에어로겔/고분자 복합재의 물리적 특성에 관한 연구
박경우(Kyoungwoo Park),이연(Yeon Lee),윤종국(Jong-Kuk Yoon),구경완(Kyung-Wan Koo) 대한전기학회 2013 전기학회논문지 Vol.62 No.9
Thermal insulation material was prepared by cross-linking chemical reaction of silica aerogel and epoxy resin, which has a high porous and vacant properties. The structural, mechanical, and thermal properties were analyzed in order to verify its application for industrial and electrical applications. The thermal conductivities were changed from 115 mW/mK to 75 mW/mK by reducing the contents of nano-porous silica areogel powders. The compressive loading is also decreased by increasing the contents of silica aerogels by 20 wt% in aerogel/epoxy composites. It is concluded that the formulated composite materials can be applied to building materials, electronics parts, and heavy industries.
박경우(Kyoungwoo Park),최동훈(Dong-Hoon Choi),이관수(Kwan-Soo Lee),장규호(Kyu-Ho Chang) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
The design optimization of the plate heat exchanger with staggered pin arrays for a fixed volume is performed<br/> numerically. The flow and thermal fields are assumed to be a streamwise-periodic flow and heat transfer with constant<br/> wall temperature and they are solved by using the finite volume method. The optimization is carried out by using the<br/> sequential linear programming (SLP) method and the weighting method is used for solving the multi-objective problem.<br/> The results show that the optimal design variables for the weighting coefficient of 0.5 are as follows; S = 6.497 mm, P =<br/> 5.496 mm, D1 = 0.689 mm, and D2 = 2.396 mm. The Pareto optimal solutions are also presented.
대형자동차 요소수탱크내 2상 열전달특성에 관한 수치적 연구
박경우(Kyoungwoo Park),문성준(Seong Joon Moon),이호길(Ho Kil Lee) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
The sticker emission standards (Euro 5, 6, and 6C) for commercial diesel vehicles in the European Union have been issued for last two decades. These growing demands on NOx emission reductions require the need of better after treatment methods in the automotive industry. One of the crucial technologies for NOx reduction is by after treatment of the exhausts with a Urea SCR-system (i.e., the selective catalytic reduction using urea as a reducing agent). In Urea SCR-system a mixture of urea and deionized water (urea water solution, UWS, 32.5wt%) injects into a catalytic reactor in which urea converts NOx into nitrogen gas and water. In the present work, flow and heat transfer characteristics in the UWS tank for heavy duty vehicles are investigated numerically. The conservation equations for mass, momentum, and energy including the heat conduction and natural convection with phase change processes are solved by the STAR-CCM+, which is one of the commercial S/W package. The enthalpy porosity method is adopted to obtain the heat transfer characteristics included the melting amount of UWS. In addition to, the effects of shape of tank cover and supplied heat on the melting amount are also investigated. From the above mentioned methodology, many important results can be obtained.
박경우(Kyoungwoo Park),권정태(Jeong-Tae Kwon),박상린(Sangrin Park),한재현(Jae-Hyun Han),이헌(Heon Lee),김광수(Kwang-Soo Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
PECVD process has taken advantages of a fast process of manufacture and low cost of production because it is operated at lower temperature than that of existing process. In CVD process, the wafer quality is mainly dependent on the uniformity of film thickness and the film density may reduce due to a low temperature process. In the present work, numerical analyses are carried out to improve the deposition performance of annealing chamber. To do this, governing equations are solved by CFD and TDMAS ([(CH3)2N]3SiH) is considered as the working fluid. In addition, the effect of inlet velocity of O2 and position and length of nozzle on the deposition rate and uniformity are investigated numerically and the computational results are compared with those of experiments.
박경우(Kyoungwoo Park),임효재(Hyo Jae Lim),권정태(Jeong Tae Kwon),이주희(Juhee Lee),유근열(Keun Yeol Yu) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
An optimal shape for a paper machine headbox can improve the paper quality and increase the production speed, simultaneously. In the present work, the optimization of headbox shape is carried out by integration CFD and optimization algorithm. The shape of the baseline headbox is parameterized and rebuilt with four-Bezier curves. Each Bezier curve is composed of five control points. The range of design variables and their resolutions are two primary keys for the successful optimization. In the paper machine headbox, the optimum values of the design variables can be achieved when the deviation of flow rate at each tube and the amount of return flow at exit are minimized, simultaneously. To complete the optimization, the finite volume method for calculating the objective functions and a multi-objective genetic algorithm for carrying the optimization process are used, respectively. After twenty-five evolutions, the non-dominated Pareto individuals can be obtained.
박경우(Kyoungwoo Park),임효재,김병삼(Byeong-Sam Kim),이주희(Juhee Lee),김광수(Kwang-Soo Kim),박상린(Sang-Lin Park) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
A main function of paper machine headbox is to deliver a uniform dispersion of fibers in water through the manifold to a paper machine wire. The paper quality is mainly influenced by the flow characteristics taking place in a headbox. In the present work, the prediction of transport phenomena and the optimization of shape of headbox are carried out by integration of CFD and optimization technology. The back-wall of headbox is parameterized by a Bezier curve and its 9-control points and the diffuser diameters are adopted as the design variables. Because the optimal solutions can be obtained when the deviation of flow rate at each manifold and the pressure drop in the headbox are minimized, they are considered as the objective functions. To obtain the non-dominated optima, Pareto set, the multi-objective genetic algorithm is used. After twenty-five evolutions, the 6 numbers of non-dominated optima can be obtained.
박경우(Kyoungwoo Park),이주희(Juhee Lee),안종관(Jong-Kwan Ahn),김광수(Kwang-Soo Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
The purpose of this study is to predict the effect of cyclone shape on pressure loss and its efficiency. Generally, the increase of inlet velocity of gas improves the separation efficiency, while it results in increasing in the pressure losses. The standard turbulence model with isotropic assumption cannot predict the flow characteristics with Rankine vortex but the RSM(Reynolds stress model) can estimate them properly. Because of difficulty of the adoption of turbulence model, the validation of CFD model is carried out by comparing with experimental results. It is known that the influence of the contract cone at a dust corrector is significant on pressure loss and separation efficiency. This study focuses on flow characteristics according to shapes of the cone, which is made up by angle of cone. As the results of computation, the increase of cone angle increases the separation efficiency and decreases the pressure loss.