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박철웅,김창기,최영,이선엽 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.4
Mixtures of hydrogen and natural gas are promising for improving efficiency and reducing harmful emissions in spark ignition engines,since limits of flammability can be extended while stable combustion is secured. In this research, the combustion characteristics of longelectrode spark plugs were evaluated in a hydrogen blended with natural gas (HCNG) engine. Decreases in the flame propagation distancethrough the use of spark plugs can lead to increased burning rates and further improvement of fuel economy in HCNG engines. An11-liter heavy duty lean burn engine was employed and performance characteristics including emissions were assessed according to thespark timing of the minimum advance for best torque (MBT) for each operating condition. Retarded MBT spark advance timing withlong electrode spark plugs due to increased burning speed supported increases in engine efficiency and reductions of nitrogen oxide(NOx) emissions. The lower positions of initial flame kernels due to the use of long electrode spark plugs were preferable to improvementsof cyclic variability due to reduced flame front quenching, and carbon monoxide (CO) emissions at the flammability limit werealso improved.
박철웅 한국지형학회 2004 한국지형학회지 Vol.11 No.2
Fieldwork is considered an important component that makes students enthusiastic about geography. In addition, fieldwork is recognized as an excellent instruction tool in education of physical geography. Unfortunately, fieldwork has not been practiced due to a lot of reasons, such as fundamental problems in the college entrance examination system, time, costs, safety, and organizational issues. However, the constructivistic education system emphasizes the practical experience learning process that requires students to choose the context and learning course in their own learning process. A long-term field survey for landform analysis enabled us to identify the fieldwork elements that are appropriate ! for geography education. Thus, here we report on the elements of landform that conforms to the contextual system of the 7th curriculum educational process. In addition, teaching methods are proposed for the students to determining and exploring the fieldwork sites according to the fieldwork elements provided. In the future, further geographical research for regional units should be performed to better implement the proposed fieldwork elements, and it is recommended to substantiate the fieldwork as a required course in geography education. 야외학습(Fieldwork)은 지리라는 학문에 대한 열정을 갖게 해주는 주요 구성요소이다. 또한 야외학습은 자연 지리교육의 훌륭한 수업 도구로 인정되고 있다. 하지만 입시제도, 시간과 비용, 안전, 조직 문제 등으로 실질적 으론 거의 이루어지지 못하고 있다. 학습자가 내용의 선정이나 학습과정에 능동적으로 참여하는 구성주의적 교육 과정에서는 현장체험학습이 강조되고 있다. 이에 본 연구는 오랜 답사 경험과 지형 연구를 통하여 밝혀진 지형요소 들 중 제 7차 교육과정 내용체계의 분석을 통하여, 지리교육에 적합한 야외학습의 요소를 추출하였다. 그리고 이 학습요소(해안단구)를 중심으로 학생들이 직접 야외에서 관찰하고 탐구할 수 있는 야외학습 장소의 탐색과 거기에 맞는 지도 방안을 제시했다. 앞으로의 과제는 지역단위의 세밀한 지리 연구가 뒷받침되어야 한다. 아울러 지리과 교육과정에서 야외학습의 실행이 뒷받침되면 지리과 야외학습은 더욱 효율적으로 운영될 수 있을 것이다.
DEVELOPMENT OF HYDROGEN-COMPRESSED NATURAL GAS BLEND ENGINE FOR HEAVY DUTY VEHICLES
박철웅,김창기,최영,이선엽,이성운,이우형,이장희,김태민,김덕상 한국자동차공학회 2017 International journal of automotive technology Vol.18 No.6
Natural gas fuel, as an alternative energy source of transportation, has been used widely since it has an advantage of low emission levels. However, new technologies are required in order to meet the reinforced emission regulations. For this purpose, research into the development of hydrogen-compressed natural gas (HCNG) blend engine was carried out to evaluate its feasibility and emission characteristics. The Engine Research Department at the Korea Institute of Machinery and Materials carried out a large number of tests based on various parameter changes that could affect the performance and emission of HCNG engine in different operating conditions. An earlier stage of the research project focused on the lean combustion of a HCNG engine for heavy duty vehicles to meet the EURO-VI standards. An 11-L/6-cylinder CNG engine was used for the test. The effects of the excess air ratio change were assessed based on various content ratios of hydrogen in the natural gas fuel. In the later part of the HCNG research, a stoichiometric mixture operation was suggested to meet reinforced emission regulation without requiring a De-NOx system. Additionally, an exhaust gas recirculation (EGR) system was introduced for the purpose of improving thermal efficiency and durability. The optimal operating conditions were selected to achieve the best thermal efficiency to meet the required emission levels. In this paper, we demonstrate that a HCNG engine can achieve a significant decrease in NOx emissions, as compared to that of a CNG engine, while meeting the requirements of the EURO-VI standards during a transient mode cycle test. EGR can suppress the weakness of stoichiometric mixture combustion strategy, such as the deterioration of the durability and thermal efficiency, while the emission level can be lowered with the use of a three-way catalyst. The possibility of further reduction of emissions and CO2 with EGR was evaluated to access practical application of a HCNG engine in the field. From that evaluation, the HCNG engine with stoichiometric mixture operation for heavy duty vehicles was developed. The emission levels of HCNG engine were 50 % lower when compared to the EURO-VI standards with a greater than 10 % decrease in CO2 compared to that of a natural gas engine.