• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.884-891
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• 2016

A secondary injection system in a diesel engine has benefits: it can be controlled independently without interrupting engine control, it can be adapted to various layouts for exhaust systems, and it pose no reductant dilution problems compared to post injection systems in the combustion chamber or other supplemental reductant injections. In a secondary injection system, the efficiency of the catalyst depends on the method of reducing the supply. The reductant needs to be maintained and optimized with constant pressure, the positions and angles of injector is a very important factor. The concentration and amount of reductant can be changed by adjusting secondary injection conditions. However, secondary injection is highly dependent upon the type of injector, injection pressure, atomization, spray technology, etc. Therefore, it is necessary to establish injection conditions the spray characteristics must be well-understood, such as spray penetration, sauter mean diameter, spray angle, injection quantity, etc. Uniform distribution of the reductant corresponding to the maximum NOx reduction in the DeNOx catalyst system must also assured. With this goal in mind, the spray characteristics and impingement plate types of a secondary injector were analyzed using visualization and digital image processing techniques.

• Journal of ILASS-Korea
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• v.7 no.1
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• pp.14-20
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• 2002

It is well known that the flow and spray characteristics is critical factor on the performance and emission of a direct injection diesel engine. So this study aims to investigate the interaction of flow and spray characteristics. At first, in cylinder flow distributions in swirl adaptor for 4-valve cylinder head of DI Diesel engine were investigated under steady conditions for different SCV angles mounted on the cylinder head with steady rig test and 2-D LDV. And the in-cylinder flow was quantified in terms of mean flow coefficient and swirl ratio/tumble ratio. It was found that the swirl ratio is controlled between 2.3 and 3.8. Then spray characteristics of the intermittent injection were investigated. PDA system was utilized for measurement of a droplet size and velocity. The analyses of the PDA results are carried out with Time Dividing Method. It was found that there is a correlation between the swirl flow and SMD. The droplet size and the velocity were nearly constant value with each SCV angle. And the swirl ratio is higher, SMD smaller. The swirl ratio was helpful factor to the atomization of droplet.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2000.11a
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• pp.22-22
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• 2000

DRAM의 고접적화에 따라 기존의 반도체 공정에서 사용중인 여러 가지 기술들이 대부분 그 한계를 보이고 었으며, 대표적인 것이 캐퍼시터 형성기술이다. 따라서 1G DRAM급 이상의 초고집적 회로를 실용화하기 위해서 유전율이 높은 BST ($BrSrTiO_3$) 박막을 이용하여 캐패시터를 제조하려는 기술도 반드시 해결되어야 현재 활발히 실용화 연구가 진행중에 있다. BST 박막을 제조하는 방법은 RF magnetron sputtering, Ion beam reactive co-evaporation, LSM (Liquid Source Misted) CVD, MOCVD 등의 법으로 제조되고 있다. 본 연구에서는 전기-수력 학적 분무(Electro-Hydrodynamic Spray)현상을 이용한 MOCVD에 BaO, SrO, $TiO_2$ 박막을 증착 하여 전기장세기, 기판온도, 시간 등에 따른 특성을 조사하였다. 전기수력학적 분무를 이용한 증착법은 원료를 함유하는 용액을 이용함으로써 이송관의 가열이 필요 없이 장치를 간단하게 할 수 있고, 용액의 유량과 전기장의 세기에 따라 초미세 입자제어도 가능하며, 박막의 조성을 출발 용액으로 부터 조절하는 등의 특징을 가지고 있다. 증착한 박막의 표면, 단면 형상 및 조성을 분석하였고 결정화 여부 및 우선 배향성을 조사하였다. 현재는 개별 박막의 표현 형상과 조성에 대한 연구 결과를 얻었으며, 계속해서 박 막의 여러 특성에 대하 연구할 계획이다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.41.1-41.1
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• 2011

초소수성 표면은 $150^{\circ}$ 이상의 높은 접촉각을 가지며 표면에 오염물질이 묻지 않게 하는 anti-contamination, anti-fingerprint, self-cleaning 기능을 갖고 있는 것이 특징이다. 재료표면의 친/소수성을 제어하기 위해서는 고체 표면의 화학적인 요인과 물리적인 요인 두 가지를 조절함으로써 이루어지는데 즉 물질의 표면에너지와 표면 거칠기를 변화시켜 친/소수성을 부여할 수 있다. 초소수성 표면을 구현하기 위해서는 고체 표면의 에너지를 낮춰야 하며 이는 일반적으로 불소화합물을 사용한다. 불소는 지구상의 원소 중 가장 낮은 표면에너지를 가지고 있어 주로 후라이팬이나 치아 표면에 코팅되며 오염을 방지하는 특성을 지닌다. 실리카는 박막소재로 이용하기 위한 우수한 특성을 가진 물질로서 자연계에서 매우 풍부하게 존재하고 있으며, 생체무해하며 내구성과 내마모성, 화학적 안정성, 고온 안정성 등을 지니고 있어 여러 가지 종류의 전자기기 및 부품의 내외장 코팅에 적용이 적극 검토되고 있다. 이러한 실리카 코팅소재를 바탕으로 초소수성 코팅층을 구현하는 하나의 방법으로서 본 연구에서는 전기분무법을 사용하여 실리카 코팅층을 형성하였으며, 표면에너지를 제어하기 위해 플루오린 처리를 하여 초소수성 실리카 코팅층을 제조하였다. 합성된 실리카 코팅층은 물 뿐만이 아니라 표면장력이 낮은 다른 용액에서도 초소유성을 나타내었다. 이러한 코팅층에 대한 고온 안정성과 UV 저항성, 내구성(durability) 등을 조사하여 실제 응용 가능성을 타진하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.11
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• pp.1530-1537
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• 1998

Mixture formation is one of the significant factors to improve combustion performance of an spark ignition engine. This is affected by spray and atomization characteristics of injector. In the case of EGI system, air-fuel mixing period is so short that a lot of fuel-film and liquid-fuel flow into cylinder. Since this fuel-film is not burnt perfectly in cylinder, it is exhausted in the form of HC emission. In this paper, three measurement techniques were utilized to measure spray characteristics and the amount of fuel-film in the cylinder. At first, PMAS was used to measure the spray characteristics such as size distributions, SMD, and spray angle. Secondly the amount and distribution of fuel-film which flow into through intake valve could be measured quantitatively using the fuel-film measuring device. And lastly, by optical fiber type spark plug used to detect the diffusion flame, the amount of unburned HC was measured. As the result of these experiments, the information of optimal spray characteristics and injection condition to minimize fuel-film could be built up.

• Journal of ILASS-Korea
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• v.24 no.4
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• pp.163-170
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• 2019

In this study, feedback logic using dual O₂ sensor values were developed to increase the purification capability of a three-way catalyst (TWC) in a compressed natural gas (CNG) engine. A heavy-duty inline 6-cylinder engine was used and the CNG was supplied to the engine through a mixer. This study consists of two main parts, namely, the proportional integral (PI) control with a front O₂ sensor and the feedback control with dual O₂ sensors. In the PI control experiment, effects of various parameters, such as P gain, I gain, and lean delay, on the TWC capability were identified. Based on the results of the PI control experiment, the feedback logic using dual O₂ sensor values were developed. In both cases, the nitrogen oxides (NO_X) emissions were nearly zero. However, the carbon monoxide (CO) emissions were reduced significant in the feedback logic with dual O₂ sensors than in the PI control with the front O₂ sensor.

• Journal of ILASS-Korea
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• v.9 no.2
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• pp.9-17
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• 2004

The performance characteristics of lean burn system in gasoline engine are mainly affected by the air-fuel mixture in cylinder, gas exchange process of manifold system, exhaust emission of engine, and the electronic engine control system. In order to obtain the effect of performance factors on the optimum conditions of lean burn engine, this study deal with the behavior of mixture formation, gas flow characteristics of air, flow and evaporation analysis of spray droplet in cylinder, vaporization and burning characteristics of lean mixture in the engine, and the control performance of electronic engine control system. The optimum flow conditions were investigated with the swirl and tumble flows in the combustion chamber with swirl control valve. The performance characteristics and optimum condition of flow field in intake system were analyzed by the investigation of inlet flow of air and combustion stabilization on cylinder.

• Journal of ILASS-Korea
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• v.26 no.3
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• pp.135-141
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• 2021

High-efficient HEV Engine cooling systems reflects variable coolant temperature because it can decrease the hydrodynamic frictional losses of lubricated engine parts in light duty conditions. In order to safely raise the operating temperature of passenger cars to a constant higher level, and thus optimize combustion and all accompanying factors, a new thermostat technology was developed : the electronically map-controlled thermostat. In this work, various crystalline plastics such as polyphthalamide (PPA) and polyphenylenesulfide (PPS) mixed with various glass fiber amounts were introduced into plastic fittings of automotive electronic controlled thermostat for the purpose of suppressing influx of coolant into the element and undesirable opening during hot soaking. Skirt was installed around element frame of automotive electronic controlled thermostat for improving thermal sensitivity in terms of response time, hysteresis and melting temperature. To validate the effectiveness and optimum shape of skirt, thermal sensitivity test and three-dimensional CFD simulation have been performed. As a consequence, important improvement in thermal sensitivity with less than 3℃ of maximum coolant temperature between opening and engine inlet was obtained.

• Journal of ILASS-Korea
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• v.26 no.2
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• pp.57-66
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• 2021

The reactivity controlled compression ignition (RCCI) is the technology that provides two different types of fuel to the combustion chamber with the advantage of significantly reducing particulate matter and nitrogen oxides emissions. However, due to the characteristics of lean combustion, combustion efficiency is worsened. The conventional type of pistons for conventional diesel combustion (CDC) has mostly been used in the researches on RCCI. Because the pistons for CDC are optimized to enhance flow and target spray, the pistons are unsuitable for RCCI. In this study, a piston that is suitable for RCCI is designed to improve combustion efficiency. The new piston was designed by considering the factors such as squish geometry, bowl depth, and surface area. The experiment was carried out by fixing the energy supply to 0.9kJ/cycle and 1.5kJ/cycle respectively. The two pistons were quantitatively compared in terms of thermal efficiency and combustion efficiency.

• Journal of Bio-Environment Control
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• v.6 no.4
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• pp.284-291
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• 1997

This study was conducted to evaluate the optimum hydroponic system and nutrient solution for shortening the early growth period and quality improvement of dendrobium ( Dendrobium Phalaenopsis) seedlings. Dendrobium seedlings with 3 to 4 leaves were transplanted in the deep flow technique(DFT) system, aeroponic system, and ebb and flow system with different concentration of balanced nutrient solutions recommended by the Japanese Horticultural Experiment Station. Growth characteristics of shoot and root were recorded and evaulated among treatments. For autumn cultivation, plant height was the longest at the DFT system with quarter concentration of nutrient solution, where aeroponic system with half concentration of nutrient solution. Aeroponic system stimulated the root growth but fresh weight was observed in the plots of DFT system. For spring cultivation, pH values increased up 7.5 at the DFT and aeroponic system, where EC values did not fluctuate regardless of cultural system. Ebb and flow system showed the best result in the growth of plant followed by BFT system and aeroponic system. Higher concentration of nutrient solution within this range of treatment was recommended for the growth promotion of leaf length and width in DFT system. In conclusion, growth responses differed depending on the cultural system, concentrations of nutrient solutions and duration of cltivation.