• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.3-5
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• 1993

실내 음향특성의 컴퓨터 씨뮬레이션 기법은 모형실험 기법과 더불어 건축물의 음향설계 분야에서 널리 사용되는 도구이다. 본 연구에서는 건축물의 음향특성을 설계단계에 예측하기 위해 영상법에 기초한 실내음향 해석 소프트웨어를 개발하였다. 개발된 소프트웨어는 건축물의 3차원 형상모델, 벽면등 반사체의 흡음특성, 음원과 수음점의 위치 등의 데이터를 입력하면, 음선의 전파경로, 수음위치에서의 반사음 패턴, 실내 음향 특성의 평가척 (음의 명료도, 잔향시간 등)을 산출하여 출력하는 기능을 지니고 있다. 기존의 씨뮬레이션 기법이 소요 장비나 비용, 시간적 제약으로 널리 실용화되기 어려웠던 점을 고려하여 PC급에서 간편하게 활용할 수 있도록 개발하였고 음선 전차경로의 그래픽 표현, 반사음 패턴의 분석등, 건축물의 음향 설계를 위한 기능을 부여하는데 중점을 두었다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3357-3368
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• 1994

Total pressure losses required to calculate the total-to-total efficiency are estimated by integrating empirical loss coefficients of four loss mechanisms along the mean-line of blades as follows; blade profile loss, secondary flow loss, end wall loss and tip clearance loss. The off-design points are obtained on the basis of Howell's off-design performance of a compressor cascade. Also, inlet-outlet air angles and camber angle are obtained from semi-empirical relations of transonic airfoils' minimum loss incidence and deviation angles. And nominal point is replaced by the design point. It is concluded that relatively simple loss models and Howell's off-design data permit us to calculate the off-design performance with satisfactory accuracy. And this method can be easily extended for off-design performance prediction of multi-stage compressors.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.881-884
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• 2011

Secondary throat supersonic exhaust diffusers were designed by Normal-shock theory and manufactured. Experimental studies of the diffusers were performed using nitrogen gas of room temperature. It showed a difference about 18% between the experimental and theoretical results. The difference was shown by friction loss at the wall of the diffuers.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.4
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• pp.25-35
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• 2002

A calculation procedure for designing LRE regenerative cooling system is introduced. In LRE thrust chamber, heat is transfered from the hot gas to the wall by convection and radiation, then conduction through the wall and finally convection to the liquid coolant. A cooling channel is designed on the basis of heat transfer rate calculated by using criterial method and integral method. The result is compared with existing Russian cooling channel design code. Also a design logic and quantitative effect of various parameters were introduced to help better understanding for those who is not familiar to LRE system.

• Journal of the Korean GEO-environmental Society
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• v.9 no.1
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• pp.11-16
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• 2008

In this paper, vertical earth pressure by CANDE program is compared with that by some equations such as the equation by Janssen, Marston, Spangler, and Handy to calculate vertical earth pressure with respect to several factors acting on a rigid buried-pipe filled cohesionless soil. As a result of comparative analysis of vertical earth pressure with each equation, primary factors are affected by backfill width, backfill depth and wall friction. Moreover, vertical earth pressure is linearly increased with backfill depth and width from results of the finite element method. Handy's Equation is reasonable for finite element method while Marston equation is overestimated in case of the design of buried-pipe and box.

• Tunnel and Underground Space
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• v.27 no.1
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• pp.12-25
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• 2017

In local underground mines heavily depending on the natural ventilation, ducted fan auxiliary ventilation system is strongly recommended instead of the total mine ventilation system requiring large capital and operating costs. Optimizing the installation of ducted fans in series in long large-opening mines is required to assure the economy and efficiency of the ventilation system. The two most critical design parameters for optimization are the wall separation distance and gap length between adjoining ducts. This study aims at deriving the optimal values for those two parameters concerning the economic and environmental aspects through the extensive CFD analysis, which minimizes pressure loss, leakage and entrainment of the contaminated air in the gap space. The ranges of the wall separation distance and gap length for study are selected by taking into consideration the existing recommendations and guidelines. The ultimate goal is to optimize the auxiliary ventilation system using ducted fans in series to provide a reliable and efficient solution to maintain clean and safe workplace environment in local long underground mines.

• Journal of the Korean Society for Railway
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• v.18 no.6
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• pp.522-532
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• 2015

In the present study, a tunnel type soundproof wall with partial opening is proposed to reduce the environmental noise caused by railway vehicles traveling on bridges, which affects residents of high-rise apartment buildings; the study also attempts to minimize load due to wind and the weight of the wall. Applying the principles of computational fluid dynamics and structural mechanics, and the ray tracing method, a reduction in noise as well as of the overall weight of the soundproof walls is estimated. Analysis results show that the proposed soundproof wall with a partial opening weighs less, while reducing the wind loading by up to 30%. To prevent direct propagation of sound through openings in the wall, an acoustic louver, which is a type of silencer, could be considered for the opening. In order to achieve a similar noise effect with existing insulation material, the fluid flow and the insulation effect of the acoustic louver are analyzed. As the considered opening is in the range of 30~40% of the total length of the soundproof wall, the noise effect and wind load are reduced by 10dB and 25% respectively. Consequently, opening some part of tunnel type soundproof walls and installing louvers on the wall openings can have the effects of weight-reduction and reduced wind load. If a partial opening is applied with proper sound material application, a gain of an additional 5~10dB of noise reduction can be achieved.

• The Korean Journal of Rheology
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• v.8 no.3_4
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• pp.187-198
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• 1996

최근에 본 연구자에 의해서 단축 스크류 공정에서 카오스 스크류라고 명명되어진 카오스 혼합장치가 성공적으로 개발되었다. 기하학적 조건이나 공정조건에 대한 설계변수로 카오스 스크류를 설계하기 위하여 체류시간, 포인카레 단면 그리고 혼합패턴등에 대한 계산 과 해석이 이루어져야 하는데 이를 단지 Runge-Kutta 방법에 의해 속도장을 적분한다면 상당한 계산시간이 소비된다. 이러한 수치문제를 극복하기 위하여 본논문에서는 새로운 사 상법을 제안한다. 이 방법으　 사용하면 벽면 근처의 특이점 영역에서도 수치문제가 해결된 다. 본 논문에서 제안하는 수치사상법은 Runge-Kutta 방법에 비하여 수치계산의 효율성과 정확도 면에서, 특히 유안요소법으로 얻은 속도장에 대하여 우수함이 밝혀졌다. 이러한 사상 법은 공간주기 유동장뿐만 아니라 시간주기 유동장에서 적용할수 있다.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.2
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• pp.62-76
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• 1995

The safety analysis becomes very essential in the crash environment with the growth of automobile industry. Recently, an airbag system is required to protect the occupant. The effects of an airbag can be evaluated exactly from the barrier or sled test which is quite expensive. The airbag system in a passenger car is analyzed with the occupant analysis program. The modeling of the passenger car including an airbag is established and the results are verified by comparisons with real crash tests. However, the solution of an airbag design can not be obtained easily with the conventional method such as an optimization due to the nonlinearity and complexity of the problem. An iterative design algorithm using the orthogonal array is proposed to overcome the difficulties. The design trend of an airbag is recommended to minimize the injury of an occupant with the proposed design algorithm and the results are discussed.

• Journal of Energy Engineering
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• v.3 no.1
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• pp.62-69
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• 1994

화염중에 존재하는 이온 및 전자의 전기적 성질을 이용하여 연소실내의 화염전파속도를 파악하기 위해 실린더 헤드에 이온 프로브를 삽입하여 천연가스 및 가솔린의 화염전파속도를 측정하였다. 본 연구에 이용된 이온전류장치 설계에 의한 방법은 광학적 측정 장비에 비해 간단하며 쉽게 측정할 수 있고 가격도 저렴하고 응답성도 우수하였다. 이온 프로브의 제작과 신호처리에 관한 기초적인 지식을 얻었으며 천연가스 및 가솔린의 연소시 연소압력의 상승지점과 이온발생지점이 일관성있게 나타났다. 기관회전수의 증가에 따라서 연소실내의 화염전파속도가 증가했으며 같은 연소조건이라고 할 수 있는 동일 기관회전수, 당량비의 조건에서 점화시간에 대한 화염전파속도를 비교해 보면 메탄의 경우가 이론치보다 6 ms∼9 ms 정도 늦었다. 또한, 메탄가스 및 가솔린에 대해 이온 전류강도 및 화염 도달시간을 측정하였으며 연소실 벽면에서는 열전달에 의한 냉각효과로인해 화염 전파속도 및 이온농도가 감소했다.