• 한국수소및신에너지학회논문집
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• 제30권6호
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• pp.567-577
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• 2019

Due to the depletion of fossil fuels and environmental pollution, demand for alternative energy is gradually increasing. Among the various methods, a method to convert biomass into alternative fuel has been proposed. The bio-fuel obtained from biomass through pyrolysis process is called pyrolysis oil (PO) or bio-oil. Because PO is difficult to use directly in conventional engines due to its poor fuel properties, various methods have been proposed to upgrade pyrolysis-oil. The simplest approach is to mix it with conventional fossil fuels. However, due to their different polarity of PO and fossil fuel, direct mixing is impossible. To resolve this problem, emulsification of two fuels with a proper surfactant was proposed, but it costs additional time and cost. Alternatively, the use of alcohol fuels as an organic solvent significantly improve the fuel properties such as fuel stability, calorific value and viscosity. In this study, blends of diesel, n-butanol, and coffee ground pyrolysis oil (CGPO) which is one of the promising PO, was applied to diesel generator. Combustion and emissions characteristics of blended fuels were investigated under the entire load range. Experimental results show that ignition delay is similar to that of diesel at high load. Although, hydrocarbon and carbon monoxide emissions are comparable to diesel, significant reduction of nitrogen oxides and particulate matter emissions were observed.

• 한국추진공학회지
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• 제25권3호
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• pp.62-80
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• 2021

차세대 추진기관에 대한 요구조건과 좋은 추진제의 조건을 정리하였다. 국내외에서 주로 관심을 받고 있는 연료인 케로신, 수소, 메탄의 특성과 효용성을 상호비교하였다. 비교 결과 메탄이 신뢰성, 비용, 재사용성, 유지보수, 친환경, 안전성, 수명, 기술적 난이도, 엔진 사이클 선택, 공통격벽, 무분해 조립 납품 등에서 다른 연료보다 더 유리한 것으로 평가되었다. 그리고 성능 면에서도 케로신보다 비추력이 높아서 발사체의 효율을 증가시킬 수 있다. 메탄은 친환경, 낮은 연소온도, 긴수명, 유지보수의 편의성을 가지고 있어서 재사용과 다목적 엔진 개발에 장점이 있다.

• 한국추진공학회지
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• 제26권2호
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• pp.79-95
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• 2022

1950년대 우주 개발이 시작된 이래로, 다양한 목적에 따라 많은 상단 엔진이 개발되어 운용 중에 있다. 본 논문에서는 과거 개발되었거나 현재 개발 중인 해외 상단 엔진의 정보를 분석하여 그 특징과 성능을 요약하여 제시하였다. 최근 발사된 상업용 대형 발사체의 경우 상단으로는 팽창기 사이클을 적용한 수소 엔진 적용 사례가 많았다. 케로신 엔진은 과거 많은 개발이 이루어졌으며, 이러한 경험을 바탕으로 이론상의 최대 성능에 근접한 것으로 보인다. 한편, 최근 이슈화 되고 있는 메탄 추진제 또한 다양한 장점으로 많은 개발이 진행되는 중이다. 뉴스페이스 시대에 발사체 시장에는 민간 기업이 활발하게 참여하고 있으며, 정부와 기업이 합작하여 차기 엔진을 개발하는 사례도 다수 진행되고 있다.

• 한국수소및신에너지학회논문집
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• 제22권2호
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• pp.152-160
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• 2011

The electromagnetic characteristics of FCEVs (fuel cell electric vehicles) are much different from the existing combustion engine cars as well as hybrid, plug-in-hybrid, and pure electric vehicles due to the high voltage/current generated by a fuel cell stack which uses a compressed hydrogen gas reacted with oxygen. To operate fuel cell stack efficiently, BOP (Balance of Plant) which is consisted of many motors in water pump, air blower, and hydrogen recycling pump as well as inverters for these motors is essential. Furthermore, there are also electric systems for entertainment, information, and vehicle control such as navigation, broadcasting, vehicle dynamic control systems, and so on. Since these systems are connected by high voltage or general cables, EMC (Electromagnetic compatibility) analysis for high voltage and general cable of FCEV is the most important element to prevent the possible electric functional safety errors. In this paper, electromagnetic fields by high voltage and general cables for FCEVs is studied. From numerical analysis results, total time harmonic electromagnetic field strength from high voltage and general cables have difference of 13~16 dB due to ground effect by impedance matching. The EMI results of FECV at 10 m distance shows difference of 41 dB at 30 MHz and 54 dB at 230 MHz compared with only general cable routing.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.156-160
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• 2007

Ejector system is a device to transport a low-pressure secondary flow by using a high-pressure primary flow. Ejector system is, in general, composed of a primary nozzle, a mixing section, a casing part for suction of secondary flow and a diffuser. It can induce the secondary flow or affect the secondary chamber pressure by both shear stress and pressure drop which are generated in the primary jet boundary. Ejector system is simple in construction and has no moving parts, so it can not only compress and transport a massive capacity of fluid without trouble, but also has little need for maintenance. Ejectors are widely used in a range of applications such as a turbine-based combined-cycle propulsion system and a high altitude test facility for rocket engine, pressure recovery system, desalination plant and ejector ramjet etc. The primary interest of this study is to set up an applicable model and operating conditions for an ejector in the condition of sonic and subsonic, which can be extended to the hydrogen fuel cell vehicle. Experimental and theoretical investigation on the sonic and subsonic ejectors with a converging-diverging diffuser was carried out. Optimization technique and numerical simulation was adopted for an optimal geometry design and satisfying the required performance at design point of ejector for hydrogen recirculation. Also, some sonic and subsonic ejectors with the function of changing nozzle position were manufactured precisely and tested for the comparison with the calculation results.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.256-259
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• 2008

Ejector system is a device to transport a low-pressure secondary flow by using a high-pressure primary flow. Ejector system is, in general, composed of a primary nozzle, a mixing section, a casing part for suction of secondary flow and a diffuser. It can induce the secondary flow or affect the secondary chamber pressure by both shear stress and pressure drop which are generated in the primary jet boundary. Ejector system is simple in construction and has no moving parts, so it can not only compress and transport a massive capacity of fluid without trouble, but also has little need for maintenance. Ejectors are widely used in a range of applications such as a turbine-based combined-cycle propulsion system and a high altitude test facility for rocket engine, pressure recovery system, desalination plant and ejector ramjet etc. The primary interest of this study is to set up an applicable model and operating conditions for an ejector in the condition of sonic and subsonic, which can be extended to the hydrogen fuel cell vehicle. Experimental and theoretical investigation on the sonic and subsonic ejectors with a converging-diverging diffuser was carried out. Optimization technique and numerical simulation was adopted for an optimal geometry design and satisfying the required performance at design point of ejector for hydrogen recirculation. Also, some ejectors with a various of nozzle throat and mixing chamber diameter were manufactured precisely and tested for the comparison with the calculation results.

• 한국추진공학회지
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• 제13권3호
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• pp.20-26
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• 2009

30톤급 액체로켓엔진용 터보펌프에 대하여 실매질을 사용하여 성능시험이 이루어졌다. 산화제펌프와 연료펌프에는 각각 액체산소, 케로신의 실매질을 사용하고 터빈에는 고압의 상온 수소가스가 사용되었다. 터보펌프는 설계점과 탈설계점의 전 영역에서 안정적으로 작동하였고 요구되는 성능 조건을 만족 시켰으며 이로써 엔진 서브시스템 수준의 터보펌프 개발이 성능 측면에서 검증되었다고 볼 수 있다. 본 논문에서는 단일 운전으로 세 운용점에서 총 75초간 작동된 경우의 시험결과를 소개하였다. 펌프와 터빈의 성능 특성 관점에서 터보펌프 조립체의 실매질 성능시험 결과와 터보펌프 구성품의 상사 성능시험 결과가 양호하게 일치하였다.

• 한국항공우주학회지
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• 제44권8호
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• pp.675-685
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• 2016

액체로켓엔진의 향후 연구 분야를 제안하였다. 가스발생기 사이클 엔진은 고압화를 통한 다운사이징, 가격경쟁력 확보가 중요 이슈가 될 것이다. 다단연소 사이클 엔진 분야에서는 초고압 터보펌프 개발과 내산화성 소재 개발이 필요할 것으로 기대된다. 로켓엔진 시스템 해석기술 분야에서는 해석 시간절감을 위한 통합화 경향이 예상된다. 이외에도 비용절감을 위한 재사용이 가능한 부스터급 메탄엔진, 3D 프린터를 활용한 제작, 내열/내산화성 소재 개발 등이 주요 연구 주제가 될 것으로 판단된다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.359-365
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• 2008

30톤급 액체로켓엔진용 터보펌프에 대하여 실매질을 사용하여 성능시험이 이루어졌다. 산화제펌프와 연료펌프에는 각각 액체산소, 케로신의 실매질을 사용하고 터빈에는 고압의 상온 수소가스가 사용되었다. 터보펌프는 설계점과 탈설계점의 전 영역에서 안정적으로 작동하였고 요구되는 성능 조건을 만족시켰으며 이로써 엔진 서브시스템 수준의 터보펌프 개발이 성능 측면에서 검증되었다고 볼 수 있다. 본 논문에서는 단일 운전으로 세 운용점에서 총 75초간 작동된 경우의 시험결과를 소개하였다. 펌프와 터빈의 성능 특성 관점에서 터보펌프 조립체의 실매질 성능시험 결과와 터보펌프 구성품의 상사 성능 시험 결과가 양호하게 일치하였다.

• 한국수소및신에너지학회논문집
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• 제25권6호
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• pp.643-647
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• 2014

Two types of fuel supply method ar used in CNG vehicles. One is premixed ignition and the other is gas-jet ignition. In premixed ignition, the fuel is introduced with intake air so that homogeneous air-fuel mixture may form. The ignitability of this method depends on the global equivalence ratio. In gas-jet ignition, CNG is introduced directly into the engine combustion chamber. The overall mixture is stratified by retarded fuel injection. In this study, a visualization technique was employed to obtain fundamental properties regarding overall mixture formation of direct injected CNG fuel inside a constant volume chamber. Jet angles, penetrations and projected jet area with respect to ambient pressure are investigated. The penetration decreases apparently and the time reaching the CVC wall was delayed as the chamber pressure increases. This is caused by the higher inertia of the fluid elements that the injected fluid must accelerate and push aside. It is same to liquid fuel such as diesel and gasoline, but this phenomenon is far more prominent for the gaseous fuel.