• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.157-163
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• 2003

A systematic numerical experiment has been conducted to study droplet gasification in high pressure environments with pressure oscillations. The general frame of previous rigorous model[1] is retained but tailored for flash equilibrium calculation of vapor-liquid interfacial thermodynamics. Time-dependent conservation equations of mass, momentum, energy, and species concentrations are formulated in axisymmetric coordinate system for both the droplet interior and ambient gases. In addition, a unified property evaluation scheme based on the fundamental equation of state and empirical methods are used to find fluid thermophysical properties over the entire thermodynamic domain of interest. The governing equations with appropriate physical boundary conditions are numerically time integrated using an implicit finite-difference method with a dual time-stepping technique. A series of calculation have been carried out to investigate the gasification of an isolated n-pentane droplet in a nitrogen gas environment over a wide range of ambient pressures and frequencies. Results show that the mean pressures and frequencies of the ambient gas have strong influences on the characteristics of the droplet gasification. The amplitude of the response increases with increasing pressure, and the magnitude of the vaporization response increases with the frequency.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.139-141
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• 2017

By modulating the flow rate of $N_2O$ into a HR motor assembly, a control valve of a hybrid rocket engine plays a role to increase or decrease the thrust. In this study, the control valve has been designed to meet the requirements which are response speed(${\leq}$ about 1 second) and torque(${\geq}$ about $36N{\cdot}m$). Then, when analog signal 0~10V is applied, the situation where the valve is opened and closed has to be realized. To do this, the data values have to be entered into the actuator. Finally, the performance evaluation of the control valve has been performed to validate this product.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.586-587
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• 2012

자동차 산업에 있어서 반도체 기술발전과 더불어 차량 내 기능들이 효율성, 경제성 및 친환경적인 관심을 고려하여 기계식 방식에서 전력전자식 방식으로 대체되고 있는 실정이다. 엔진의 연비를 향상시키기 위해서는 엔진의 연소효율을 개선하거나, 엔진에서 발생되는 손실을 줄이는 것이 필요한데, VVA(Variable Valve Actuation, 가변 밸브 작동) 기술은 엔진 흡기 유동 강화, 펌핑 손실 저감, 기계적 마찰 손실 저감등을 통해 엔진의 연비를 향상시킬 수 있다. 또한 VVA 엔진을 장착한 차량은 차량의 발진 응답성이 향상되고, 배기가스 배출량을 줄일 수 있어 친환경 저연비 차량을 실현하는데 핵심 차량부품기술이다. 최근까지 차량의 전동기 구동의 경우 DC모터 방식이 많이 적용되어 왔으나 DC모터의 내구성 및 효율 등의 이유로 BLDC모터로 바뀌고 있는 추세이다. 본 논문에서는 이와 같은 VVA 기구의 적용을 위하여 BLDC모터 제어기를 개발하였다.

• Journal of the Korean Institute of Gas
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• v.16 no.6
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• pp.17-22
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• 2012

In this study, characteristics of reforming process of Automotive LPG fuel using plasma reactor are investigated. Because plasma reformer technology has advantages of a fast start-up and wide fuel/oxidizer ratio of operation, and reactor size is smaller and more simple compared to typical combustor and catalytic reactor, plasma reforming is suitable to the on-board vehicle reformer. To evaluate the characteristics of the reforming process, parametric effect of $O_2$/C ratio, reactant flow rate and plasma power on the process were investigated. In the test of varying $O_2$/C ratio from partial oxidation stoichiometry to combustion stoichiometry, conversion of LPG was increased but selectivity of $H_2$ decreased. The optimum condition of $O_2$/C ratio for the highest $H_2$ yield was determined to be 0.8~0.9 for 20~50 lpm. The result can be a guide to map optimal condition of reforming process.

• Proceedings of the Korean Society of Community Living Science Conference
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• 2009.09a
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• pp.100-100
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• 2009

지명(地名)은 그 지역의 역사와 전설, 문화, 풍속은 물론 독특한 자연환경이나 생활 모습을 담고 있어 농업농촌의 지역적 특성을 나타낸다. 본 연구는 지명유래의 활용성 증진의 한 방편으로 브랜드 및 문화관광상품 개발을 위해 강릉시 지역의 자연마을 지명유래, 이미지, 관광자원 등을 조사하였다. 강릉시의 자연마을 유래 233건에 대한 자료는 국토지리정보원, 문화원자료집, 강릉시 홈페이지, 산, 강, 골, 고적, 못 등 그 외 지명자료는 한글학회 지명총람에서 1,147건을 수집하였다. 자연마을지명의 유래 233건을 8개 유형으로 구분하면 자연지리 60건, 인문지리 40건, 생태환경 37건, 산업경제 14건, 역사 14건, 유적유물 5건, 민속 49, 종교 14건이며, 지형(27건), 풍수(19건), 고사(19건)관련 유래가 많았다. 강릉시 지역브랜드 개발을 위한 요구도 조사는 지역민 162명과 방문객 154명 총 316명을 조사하여 SPSS WIN 12.0 프로그램을 이용 분석하였다. 응답자의 일반적인 특성은 남성이 50.6%, 대졸자가 54.1%, 연령은 40대(26.9%), 1500만원-3000만원 미만의 연소득자 32.3%가 가장 많았다. 강릉시의 형용사적 이미지를 기술통계량으로 살펴보면 지역민은 전통적인, 평화로운, 보수적인, 순수한, 따뜻한 순으로, 방문객은 순수한, 평화로운, 활기찬, 전통적인, 정감있는 순으로 평균값이 높게 나타났고, 요인분석에 의한 지역민과 방문객의 인지적 형용사 도출결과는 진취적, 평화적, 보수적인 3가지 요인이다. 또한 강릉의 대표적 상징자원은 지역민은 경포대(60.5%), 선교장(24.7%), 오죽헌(23.5%)순이며, 방문객은 경포대(74.7%), 정동진(22.7%), 오죽헌(18.8%) 순으로 높게 응답하였고, 지명 호감도는 지역민의 경우 송림(51.2%), 몽룡실(32.1%), 연화장터(18.5%)순이며, 방문객의 경우 송림(43.5%), 솔밭말(23.4%), 금단이(18.2%)순으로 높았다. 향후 본 연구에서 제시된 연구를 통하여 강릉시의 지명을 활용한 브랜드개성을 측정할 수 있어 마케팅 관점에서 강릉시의 브랜드를 도출하는데 기여할 수 있을 것이다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.3
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• pp.240-248
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• 2013

Torsional vibrations, such as the gear rattle of the manual transmission in vehicle systems, are correlated with the firing stroke from the engine. These vibro-impacts can be examined based upon linear time-invariant analysis. In order to understand the gear dynamics, a specific manual transmission with a front-engine front-wheel drive configuration is investigated. A method to reduce the degrees of freedom is suggested based upon the eigensolutions and frequency response functions, which will lead to the development of an efficient matrix size. The dynamic characteristics of single- and dual-mass flywheels are then compared. The effect of the dual-mass flywheel is investigated based upon the mobility analysis, which will lead to understanding of the concepts for avoiding vibro-impacts. A linear time-invariant system model is examined by employing the effective clutch stiffness from a two-stage clutch damper. Thus, the relationship between the dynamic characteristics and the clutch damper can be predicted by assuming a combination of different stage stiffness levels.

• Journal of Science Education
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• v.46 no.3
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• pp.237-254
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• 2022

The purpose of this study is to examine the changes in the science teaching professionalism self-perception of pre-service elementary teacher as shown in science education lesson course. The subjects of this study were 25 pre-service elementary teachers enrolled in the second year at G National university of education. And the scale of this study were derived and applied by modifying and supplementing the scale of previous studies. The results of this study are as follows: it was found that science teaching professionalism and self-perception of pre-service elementary teachers are improving. In short, it was found that there are significant changes in all sub-domains such as professionalism development efforts, educational contents, instructional method, educational environment and atmosphere, assessment and science teaching preference. As a result of examining the related contents in detail along with the combustion-related science lesson plan, Padlet, and post-test descriptive question responses, there were some good categories and some categories that needed to be supplemented. Based on these results, a plan for enhancing the science teaching professionalism of pre-service elementary teacher needs to be considered.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.2
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• pp.119-125
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• 2017

Ablative material in a rocket nozzle is exposed to high temperature combustion gas, thus undergoes complicated thermal/chemical change in terms of chemical destruction of surface and thermal decomposition of inner material. Therefore, method for conjugate analysis of thermal response inside carbon/phenolic material including rocket nozzle flow, surface chemical reaction and thermal decomposition is developed in this research. CFD is used to simulate flow field inside nozzle and conduction in the ablative material. A change in material density and a heat absorption caused by the thermal decomposition is considered in solid energy equation. And algebraic equation under boundary layer assumption is used to deduce reaction rate on the surface and resulting destruction of the surface. In order to test the developed method, small rocket nozzle is solved numerically. Although the ablation of nozzle throat is deduced to be higher than the experiment, shape change and temperature distribution inside material is well predicted. Error in temperature with experimental results in rapid heating region is found to be within 100 K.

• Journal of Aerospace System Engineering
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• v.11 no.4
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• pp.48-53
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• 2017

Liquid rocket engines (LREs) are very complex systems that include combustion chambers, turbopumps, gas generators, ducts and tubes, valves and etc. Most components of the LREs require higher than or equal to level 6 IT (ISO Tolerance). The components along with pipe line and/or tubing must dispose not to interfere each other. In addition, effectiveness of maintenance and service after assembling should be considered when the allocation of the components are determined. Especially at the stage of the development, tolerance accumulations or unpredictable errors may result in misalignment and/or mismatches at interfaces of the parts. Namely, it is the engine assembling process that many inherent risks are realized and crises or incidents occur. Therefore, a rapid reaction system should be prepared. In this research, 7 tonf class liquid rocket assembling process was studied and actual building steps were introduced.

• Nuclear Engineering and Technology
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• v.16 no.3
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• pp.141-154
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• 1984

An analysis is presented of key phenomena and scenario which imply some general trends for beyond design-basis-accident in Kori-1 PWR dry containment. The study covers a wide range of severe accident sequences initiated by small break LOCA. The MARCH computer code, with KAERI modifications was used in this analysis. The major emphasis of the paper are two folds, 1) the phenomenologic understanding of severe accident and 2) a study of H2 combustion and debris/ water interactions in a specific small break LOCA for Kori-1 plant. The sensitivity studies for the specific plant data and thermal interaction modelings used in the SASA were performed. The results show that if hydrogen burning does occur at low concentration, the resulting peak pressure does not exceed the design value, while the lower concentration assumption results in repeated burning due to the continuing H$_2$ generation. For debris/water interaction, the particle size has no effect on the magnitude of peak pressure for the amount of water assumed to be in the reactor cavity. But, the occurrence of peak pressure is considerably delayed in case of using the dryout correlation. The peak containment pressure predicted from the hydrogen combustion and steam pressure spite during full core meltdown scenario does not present a severe threat to the containment integrity.