• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.402-405
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• 2011

디젤엔진에서 발생되는 PM과 $NO_X$는 강화되는 배기규제의 주요 저감대상으로서 이의 저감을 위한 다양한 후처리장치가 개발되고 있다. 이중 Urea-SCR은 $NO_X$의 전환율이 높고 연비에 미치는 영향이 작기 때문에 $NO_X$저감을 위한 최선의 장치로 인식되고 있다. 하지만, 우레아 수용액의 물성치 특성으로 인하여 동절기 $-20^{\circ}C$이하로 내려가는 지역에서 동결되는 문제점을 해결해야한다. 따라서 이러한 우레아 저장탱크에 해동 시스템을 적용하여 시동초기 우레아를 적정 시간내에 안정적으로 공급가능한 기술의 확보가 필요하다. 본 연구에서는 요소수 저장탱크 내부에 냉각수 순환 가열방식(CH)과 전기 가열방식(EH)을 이용하여 동결된 요소수의 해동현상에 대한 3차원 비정상상태 수치 해석을 수행하였다. 이를 통하여 해동 과정 중 나타난 액상분율, 온도영역 그리고 자연대류를 분석하여 각 가열 방식에 대한 해동특성을 비교하였으며 순수 갈륨 융해 실험 결과값과 수치 해석 결과값를 통하여 수치 해석 방법을 검증하였다. 결론적으로 1,000ml의 우레아 수용액이 확보되기까지의 시간은 CH의 경우, 275s, 그리고 EH의 경우, 230s임을 알 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.3
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• pp.195-203
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• 2019

Since the hypersonic intake is directly related to the overall performance of the engine, it is essential to analyze performance characteristics under various off-design conditions. In this paper, Busemann intake and conical intake with external compression were designed, and numerical simulations were performed at on/off-design conditions. Based on the results, the overall performance characteristics of two types of intake were analyzed in various Mach numbers and angle of attacks. The results showed that performance degradation of Busemann intake with truncation angle of 2 degrees was minimal. Also, the performance of Busemann intake was higher than external compression intake at various Mach numbers, however, the starting characteristics were significantly reduced with an angle of attack.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.8
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• pp.585-592
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• 2007

Good cold start characteristics are essential for satisfactory operation of fuel cell vehicles. In this study, the melting process has been numerically investigated for a water tank used in fuel cell vehicles. The 2-D model of the tank containing ice and plate heaters was assumed and the unsteady melting process of the ice was calculated. The enthalpy method was used for the description of the melting process, and a FVM code was used to solve the problem. The feasibility study compared with other experiment showed that the developed program was able to describe the melting process well. From the numerical analysis carried out for different wall temperatures of the pate heaters, some important design factors could be found such as local overheating and pressurization in the tank.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.4
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• pp.97-102
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• 2008

The vibration of a vehicle, which is caused by and transmitted from the engine, has significant effect on the ride comfort and the dynamic characteristics of the engine mount system have direct influence on the vibration and noise of the vehicle. This paper examines the body shake caused by the engine excitation force on engine key on/off of a medium truck by experiment and simulation. The analysis model consists of the engine, a body including the frame, front and rear suspensions and tires. The force element between the body and the suspension is modeled as a combination of a suspension spring and a damper. The engine shake obtained from the experiment was compared with the result of the computer simulation, and by using the verified computer model, parametric study of the body shake on engine key on/off is performed with changing the stiffness of an engine mount rubber, the engine mount angle, and the position of engine mounts.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.10
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• pp.4665-4671
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• 2013

Engine mounting system is the most responsible system for NVH performance of vehicle. The vibration at idle shake, road shake, Key ON/OFF, gear shift tuned by the engine mount position and stiffness. Previously described Engine mounting system theory investigated and summarized in this paper. Decoupling of the Power train rigid mode and Reducing the angle between Torque-Roll-Axis and Elastic-roll-Axis is starting point of optimization. Multi-optimization analysis was performed because of variety simulation case and FE-model. Eventually, Find the best mount location and the stiffness has improved the performance of the vehicle NVH.

• Journal of Korean Medical classics
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• v.18 no.3 s.30
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• pp.106-115
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• 2005

${\ulcorner}$상한론(傷寒論)${\lrcorner}$시동한시기장기적저작(是東漢時期張機的著作), 시한의학제일부임상의학전저(是韓醫學第一部臨床醫學傳著), 저부서용리법방약어일로(這部書熔理法方藥於一爐), 개변증론치지선하(開辨證論治之先河), 시고대의학이론적존기지작(是古代醫學理論的尊基之作). ${\ulcorner}$상한론(傷寒論)${\lrcorner}$당중사용치자적처방유8종(當中使用梔子的處方有8種). 저사처방당중(這些處方當中), 치자시탕, 치자건강탕(梔子乾薑湯), 치자후박탕(梔子厚朴湯), 치자감초시탕, 치자생강시적하면도유일구' 득토자('得吐者) 지후복(止後服)'. 저개구자가해석위'(복용해탕후(服用該湯后))토자정지계속복용(吐者停止繼續服用)'. 거차가이인위사용치자적이상5개처방구유용토공능. 대우저개관점, 력대의가유사지긍정성태도(歷代醫家有些持肯定性態度), 유사인위시와전(有些認爲是訛傳), 지부정태도(持否定態度). 대차필자근거여하삼개방면, 즉(卽): 제일(第一), ${\ulcorner}$신농본초경(神農本草經)${\lrcorner}$화(和)${\ulcorner}$명의별록(名醫別錄)${\lrcorner}$당중미제도치자구유용토공능(當中未提到梔子具有涌吐功能). 제이(第二), 사용치자적기타삼개방제, 미제도(未提到)‘토(吐)’. 제삼(第三), 종제도저5개처방적조문내용래간, 시불능사용토법적(是不能使用吐法的). 인위(認爲)‘득토자(得吐者), 지후복(止後服)’ 시후인오첨적구자(是後人誤添的句子), 병차인위치자무용토공능(幷且認爲梔子無涌吐功能).

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.39-39
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• 1998

본 연구는 500KW급 수평축 풍력발전기용으로 개발된 회전날개의 시제품 제작에 앞서 축소모델에 대한, 이론적으로 예측된 공력성능과 신축에 의한 공력성능을 비교 검토함으로서, 설계결과를 검증하고, 필요한 경우 설계를 보완하여 개발위험도를 최소화하기 위해 수행되었다. 시험모델의 크기는 실제의 5%로서 직경이 2.1m이며 날개의 시위길이는 0.2r/R에서 0.101m, 날개끝에서 0.043m 이고, 날개단면형 상온 FX-S-03-182이다. 블레이드의 재질은 Glass/Epoxy 복합재료로 제작되었으며, 실제 풍황을 모사하기 위해 자연풍 상태에서 실험하였다. 실험장치의 구성은 15m 높이의 타워에 회전날개와 전자브레이크 및 각종 센서를 장착하였고, 날개가 회전하기 시작하면 제동장치에 의해 부하를 주면서 토크, 회전수, 풍속 등을 각각의 센서로부터 자료획득장치를 통해 자료처리를 할 수 있도록 하였다. 실험하는 동안 풍속은 4m/s-13m/s 정도로서 시동 풍속인 4m/s와 정격풍속인 12m/s를 포함하여 회전날개의 전체적인 특성을 파악하기 용이하였고, 이론적인 예측성능과 측정된 성능을 비교 검토한 결과 비슷한 결과를 얻어 공력설계 및 해석 방법을 검증하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.149-152
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• 2009

A pyrostarter is a sort of gas generator, which supplies the energy to drive turbines by the combustion gas of a solid propellant charged internally. The igniter of the pyrostarter should guarantee the ignition reliability expecially for the solid propellant with a low fame temperature. For the development of the igniter, several closed bomb testes have been performed to decide several design parameters to get a sufficient chamber pressure build-up for the ignition. Moreover, as a result of the firing testes with pyrostarters, the ignition reliability have been verified and the amount of igniter propellants has been reviewed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.6
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• pp.434-440
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• 2007

One of the cold start problems of a FCV is the freezing of the water in the water tank when a FCV is not in operation and the surrounding temperature drops below $0^{\circ}C$. The ice in the tank should be melted as quickly as possible for a satisfactory operation of fuel cell vehicles. In this study, the melting process for the constant heat fluxes of the plate heaters was numerically calculated in the 2-D model of the tank and plate heaters. The enthalpy method and FVM code was used for this analysis. The changes of the temperature with heat fluxes and the heat transfer area could be investigated. The energy balance error was found to increase with the heat flux. From this numerical analysis, the proper heat flux value and some important design factors relating local overheating and pressurization of the water tank could be examined.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.3
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• pp.9-15
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• 2010

Numerical investigation was carried out on axisymmetric over-expanded rocket nozzle to predict flow fields of transitional shock separation patterns. The unsteady, compressible N-S equations with k-$\omega$ SST for turbulence model closure were solved using a fully implicit finite volume scheme. Computed results were in good agreement with previous experimental works. It was found that strong side-loads were generated during the transition of RSS to FSS due to the development of a vortex ring in the inviscid jet core region. Hysteresis phenomenon exhibited by the shock-separation patterns was also found during the start-up and shut-down processes.