• 대한기계학회논문집
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• 제15권3호
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• pp.1030-1043
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• 1991

본 연구에서는 모델링오차나 외란 등의 불확실성에도 강인한 슬라이딩 모드 제어방법을 이용하여 새로운 연료분사 제어기를 설계하였다. 그리고 8253 타이머와 A/D 변환기, 인터페이스회로 등으로 MPI가솔린 엔진용 전자 제어장치를 실제 엔진에 적용시킴으로써 새로이 설계된 연료분사 제어시스템의 성능을 파악하였다.엔진의 운전상태를 여러가지 제어 모드로 분류할 수 있으나 엔진회전수가 2000rpm, 부하가 20N의 일정한 부하 조건에서 엔진회전수를 1500rpm에서 2000rpm으로 변화시켰을 때의 과도상태 응답을 파악하였다. 이와 같이 새로운 슬라이딩 모드 연료분사 제어시스템 을 개발하여 3원촉매 변환기의 변환효율을 극대화함으로써 배기가스의 유해물질을 최 소화하는 것을 본 연구의 목적으로 하였다.

• 기계저널
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• 제28권1호
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• pp.5-11
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• 1988

고부가가치의 산업은 적극 육성하여 국부를 급속히 확장하면서 국제경쟁력이 아주 뒤지는 저임 금공산품은 과감히 수입을 확대하는 과감한 경제정책의 변환이 필요한 때가 되었다. 이 정책의 변환에 대비한 필자의 의견을 요약하면 다음과 같다. (1) 세계적인 기술혁신은 가속될 것이며 한국의 대기업들은 종합등급 8을 조속히 소화하고 종합등급의 고도기술분야에서 선진국과 경쟁 하여야 한다. (2) 앞으로 적극 육성할 국제분업산업의 주체는 종합등급 5∼7의 중기업이며 적 절한 기술혁신과 기술인력의 고급화 노력이 조직적으로 경주되어야 한다. (3) 국제분업유망공 업을 육성하는 방안의 기본은 필요한 수준의 고급기술인력을 필요한 기업에 공급하는 것이다. 지금과 같이 대기업의 고급기술인력독점은 지양되어야 한다. (4) 공업기술의 3 기본기술중 가장 낙후된 신뢰성 확보기술은 정부의 적극적인 육성책 없이는 발전시킬 수 없다. 정부의 강력한 육성정책을 기대해 본다.

• 월간 기계설비
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• 2호통권199호
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• pp.81-81
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• 2007

행정자치부(장관 박명재)가 지역예산을 집행하는 계약과정에서 발생하는 문제의 해결을 돕기 위해 마포구 공덕동에 소재한 한국지방재정회관에서「지방계약민원 종합상담센타」를 개설, 지난 1월 22일부터 민원상담서비스에 들어갔다. 이 센타는 2006년‘지방자치단체를 당사자로 하는 계약에 관한 법령’시행 이후 폭발적으로 증가하는 민원상담을 소화하는 한편, 서비스의 질을 높여 체계적·능동적인 민원서비스를 위해 개설 됐으며 △상담신청 → 1차상담서비스 → 진행상황 파악 → 미진한부분에 대한 사후 서비스 → 수범사례 전파의 순으로 서비스가 진행된다.「지방계약민원 종합상담센타」는 앞으로 자치단체, 교육행정기관, 건설업체 등에 대한 신속하고 품질 높은 민원상담서를 제공, 고객만족을 확대하고 제도적 건의사항이나 문제점을 즉시 파악해 정책에 반영할 계획이다. 한편 이날 현판 제막식에는 김경회 대한설비건설협회 상임이사를 비롯한 건설단체 임원 및 지방자치단체 시·도 계약담당 사무관, 시·도 교육청 계약담당 사무관, 행자부 산하기관 임원 등이 참석했다.

• 한국수소및신에너지학회논문집
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• 제34권2호
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• pp.122-131
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• 2023

Currently, major foreign countries such as Europe, the United States, Japan, and China have established policy and technology goals by 2050 to achieve the hydrogen economy. In line with this, Korea is also preparing to leap forward as a leading country in the world's best hydrogen economy by establishing a technology development target by 2050. In this paper, by examining and analyzing domestic and foreign policy and technology trends to date, implications for domestic hydrogen policy and technology trends are discussed, and major issues and future contents are summarized.

• 대한기계학회논문집B
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• 제29권9호
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• pp.997-1005
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• 2005

The extinction characteristics of low strain rate normal gravity (1-g) nonpremixed methane-air flames were studied numerically and experimentally. A time-dependent axisymmetric two-dimensional (2D) model considering buoyancy effects and radiative heat transfer was developed to capture the structure and extinction limits of 1-g flames. One-dimensional (1D) computations were also conducted to provide information on 0-g flames. A 3-step global reaction mechanism was used in both the 1D and 2D computations to predict the measured extinction limit and flame temperature. A specific maximum heat release rate was introduced to quantify the local flame strength and to elucidate the extinction mechanism. Overall fractional contribution by each term in the energy equation to the heat release was evaluated to investigate the multi-dimensional structure and radiative extinction of 1-g flames. Images of flames were taken for comparison with the model calculation undergoing extinction. The two-dimensional numerical model was validated by comparing flame temperature profiles and extinction limits with experiments and ID computation results. The 2D computations yielded insight into the extinction mode and flame structure of 1-g flames. Two combustion regimes depending on the extinction mode were identified. Lateral heat loss effects and multi-dimensional flame structure were also found. At low strain rates of 1-g flame ('Regime A'), the flame is extinguished from the weak outer flame edge, which is attributed to multi-dimensional flame structure and flow field. At high strain rates, ('Regime B'), the flame extinction initiates near the flame centerline due to an increased diluent concentration in reaction zone, which is the same as the extinction mode of 1D flame. These two extinction modes could be clearly explained with the specific maximum heat release rate.

• 대한기계학회논문집B
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• 제29권9호
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• pp.988-996
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• 2005

Flame structure and extinction mechanism of counterflow methane/air non-premixed flame diluted with nitrogen are studied by NASA 2.2 s drop tower experiments and two-dimensional numerical simulations with finite rate chemistry and transport properties. Extinction mechanism at low strain rate is examined through the comparison among results of microgravity experiment, 1D and 2D simulations with a finite burner diameter. A two-dimensional simulation in counterflow flame especially with a finite burner diameter is shown to be very important in explaining the importance of multidimensional effects and lateral heat loss in flame extinction, effects that cannot be understood using a one-dimensional flamelet model. Extinction mechanism at low strain rate is quite different from that at high strain rate. Low strain rate flame is extinguished initially at the outer flame edge, the flame shrinks inward, and finally is extinguished at the center. It is clarified from the overall fractional contribution by each term in energy equation to heat release rate that the contribution of radiation fraction with 1D and 2D simulations does not change so much and the overall fractional contribution is decisively attributed to radial conduction ('lateral heat loss'). The experiments by Maruta et at. can be only completely understood if multi-dimensional heat loss effects are considered. It is, as a result, verified that the turning point, which is caused only by pure radiation heat loss, has to be shifted towards much lower global strain rate in microgravity flame.

• 대한기계학회논문집B
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• 제35권6호
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• pp.625-632
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• 2011

[ $CH_4$ ]고온공기 대향류 확산화염의 점화특성을 화염제어 연속계산법을 이용하여 수치해석적으로 검토하였다. 화학반응의 계산에는 GRI-v1.2 반응기구를 이용하였으며, 화염 최고온도를 총괄 스트레인율의 역수에 대해 나타내어 점화 및 소화특성에 관한 화염 최고온도의 S-곡선을 얻을 수 있었다. 총괄 스트레인율 변화에 따른 화염구조를 고찰하기 위해 S-곡선에서 Upper Branch와 Middle Branch의 화염 온도 분포와 속도구배를 비교하였다. 총괄 스트레인율값은 화염면과 혼합층의 연료과 공기측 경계에서 정의되는 국소 스트레인율값과도 비교하였다. 연료측과 공기측의 국소 스트레인율은 총괄 스트레인율과의 좋은 상관관계에 있음을 알 수 있었다. 화염제어 연속계산법이 확산화염의 점화, 소화특성을 검토하는 데 매우 유용한 방법임을 확인하였다.

• 대한기계학회논문집B
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• 제25권4호
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• pp.540-545
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• 2001

Many previous researches on the premixed flame in a tube have treated the unsteady flame behaviors in which the shape, position and intensity of the flame varied, but more detail and fundamental research has been necessary. The flame stabilization condition in a tube, a unique steady state, and the unsteady behaviors, using the stabilization condition as an initial condition, were carried out in recent years. In this paper, propane-air premixed flame was stabilized in a tube and the flame behavior was observed when the mean velocity variation was imposed into the opposite direction of the initial mean velocity. The velocity variation is larger than the burning velocity and longer than the reaction time scale. During the period of the velocity variation flame is not extinguished. But after the period of the mean velocity variation the flame could be re-stabilized or be extinguished depending on the experimental conditions: equivalence ratio, period of velocity variation and magnitude of velocity variation. The extinction mechanisms were classified into the two cases, one is caused by the flame stretch in the shear layer near the wall, and the other is caused by the vortices and vortexes, which are generted by the acoustic waves.

• 대한기계학회논문집B
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• 제28권12호
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• pp.1557-1566
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• 2004

A flame extinction phenomenon is a typical unsteady process in combustion. Flame extinction is characterized by various physical phenomena, such as convection, diffusion, and the production of heat and mass. Flame extinction can be achieved by either increasing the strain rate or curvature, by diluting an inert gas or inhibitor, or by increasing the thermal or radiant energy loss. Though the extinction is an inherently transient process, steady and quasi-steady approaches have been used as useful tools for understanding the flame extinction phenomenon. Recently, unsteady characteristics of flames have been studied by many researchers, and various attempts have been made to understand unsteady flame behavior, by using various extinction processes. Representative parameters for describing flame, such as flame temperature, important species related to reactions, and chemi-luminescence of the flame have been used as criterions of flame extinction. In these works, verification of each parameter and establishing the proper criterions of the extinction has been very important. In this study, a time-dependent flame temperature and an OH radical concentration were measured using optical methods, and the instantaneous change of the flame luminosity was also measured using a high-speed ICCD (HICCD) camera. We compare the unsteady extinction points obtained by three different methods, and we discuss transient characteristics of maximum flame temperature and OH radical distribution near the extinction limit.

• 대한기계학회논문집B
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• 제29권3호
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• pp.390-401
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• 2005

In this study, extinction limit extension of unsteady $(CH_{4}+N_{2})$/air diffusion flames was investigated experimentally. A spatially locked flame in an opposing jet burner was perturbed by linear velocity variation, and time-dependent flame luminosity, transient maximum flame temperature and OH radical were measured over time with the high speed camera, Rayleigh scattering method and OH laser-induced fluorescence, respectively. Unsteady flames survive at strain rates that are much higher than the extinction limit of steady flames, and unsteady extinction limits extend as the slope of the strain rate increases or the initial strain rate decreases. We verified the validity of the equivalent strain rate concept by comparing the course of unsteady extinction process and steady extinction process, and it was found that the equivalent strain rate concept represents well the unsteady effect of a convective-diffusive zone. To investigate the reason of the unsteady extinction limit extension, we subtracted the time lag of the convective-diffusive zone by using the equivalent strain concept. Then the modified unsteady extinction limits become smaller than the original unsteady extinction limits, however, the modified unsteady extinction limits are still larger than the steady extinction limits. These results suggest that there exist the unsteady behavior of a diffusive-reactive zone near the extinction limit due to the chemical non-equilibrium states associated with unsteady flames.