• Journal of the Korean Institute of Gas
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• v.20 no.1
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• pp.52-61
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• 2016

Liquefied petroleum gas is regarded as a promising alternative fuel as it is eco-friendly, has good energy efficiency and output performance, practically and has high cost competitiveness over competing fuels. In spark-ignition engine, direct injection technology improves engine volumetric efficiency apparently and operates engine using the stratified charge that has relatively higher combustion efficiency. This study designed a combustion chamber equipped with visualization system by applying gasoline direct injection engine principle. In doing so, the study recorded and analyzed ignition probability and flame propagation process of spark-ignited direct injection LPG in a digital way. The result can contribute as a basic resource widespread for spark-ignited direct injection LPG engine design and optimization extensively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.544-549
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• 2017

This paper aims to examine the effect of rotational fluid motion about the efficiency of the gas - liquid ejector, which is a core unit in a ship equilibrium water treatment system. The ejector is a device for injecting ozone into ship equilibrium by the negative pressure generated by exchange of momentum between water and ozone. The existing ejector ejects the driving fluid with a simple form. In this paper, however, a rotation induction device is applied to the driving nozzle so that the driving fluid can be rotated and injected. To investigate the flow characteristics by the rotational movement of the driving fluid, CFD was used. The pressure and flow rate of the driving fluid, the negative pressure and suction flow rate of the suction fluid in the suction part, and the discharge pressure were predicted. On the basis of the results, the efficiency of the ejector using the rotation induction system was 22.25%, which was about 1.7% better than that of the existing ejector. Finally, to verify the feasibility of the CFD, an experiment was conducted on the ejector using the rotation induction device and the results were similar to those of the CFD.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.5
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• pp.136-144
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• 2010

Exhaust gas recirculation (EGR) is an emission control technology allowing significant NOx emission reduction from light-and heavy duty diesel engines. The future EGR type, dual loop EGR, combining features of high pressure loop EGR and low pressure loop EGR, was developed and optimized by using a commercial engine simulation program, GT-POWER. Some variables were selected to control dual loop EGR system such as VGT (Variable Geometry Turbocharger)performance, especially turbo speed, flap valve opening diameter at the exhaust tail pipe, and EGR valve opening diameter. Applying the dual loop EGR system in the light-duty diesel engine might cause some problems, such as decrease of engine performance and increase of brake specific fuel consumption (BSFC). So proper EGR rate (or mass flow) control would be needed because there are trade-offs of two types of the EGR (HPL and LPL) features. In this study, a diesel engine under dual loop EGR system was optimized by using design of experiment (DoE). Some dominant variables were determined which had effects on torque, BSFC, NOx, and EGR rate. As a result, optimization was performed to compensate the torque and BSFC by controlling start of injection (SOI), injection mass and EGR valves, etc.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.482-482
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• 2013

반도체 소자의 미세화와 더불어 세정공정의 중요성이 차지하는 비중이 점점 커지고, 이에 따라 세정 기술 개발에 대한 요구가 증대되고 있다. 기존 세정 기술은 화학약품 위주의 습식 세정 방식으로 표면 손상, 화학 반응, 부산물, 세정 효율 등 여러 가지 어려움이 있다. 따라서 건식세정 방식이 활발하게 도입되고 있으며 대표적인 것이 에어로졸 세정이다. 에어로졸 세정은 기체상의 작동기체를 이용하여 에어로졸을 형성하고 표면 오염물질과 직접 물리적 충돌을 함으로써 세정한다. 하지만 이 또한 생성되는 에어로졸 내 발생 입자로 인해 패턴 손상이 발생하며 이러한 문제점을 극복하기 위하여 본 연구에서는 가스클러스터 장치를 이용한 세정 특성 평가에 관한 연구를 수행하였다. 가스 클러스터란 작동기체의 분자가 수십에서 수백 개 뭉쳐 있는 형태를 뜻하며 이렇게 형성된 클러스터는 수 nm 크기를 형성하게 된다. 그리고 짧은 시간의 응축에 의해 수십 nm 크기까지 성장하게 된다. 에어로졸 세정과 다르게 클러스터가 성장할 환경과 시간을 형성하지 않음으로써 작은 클러스터를 형성하게 되며 이로 인해 패턴 손상을 최소화 하고 상대적으로 높은 효율로 오염입자를 제거하게 된다. 클러스터 세정 장비를 이용한 표면 처리는 충돌에 의한 제거에 기반한다. 따라서 생성 및 가속되는 클러스터로부터 대상으로 전달되는 운동량의 정도가 세정 특성에 영향을 미치며 이는 생성되는 클러스터의 크기에 종속적이다. 생성 클러스터의 크기 분포는 분사 거리, 유량, 분사 각도, 노즐 냉각 온도 등의 변수에 관한 함수이다. 따라서 본 연구에서는 $CO_2$ 클러스터를 이용한 세정 특성을 평가하기 위하여 이러한 변수에 따라서 오염 입자의 종류, 크기에 따른 PRE (particle removal efficiency)를 평가하고 다양한 선폭의 패턴을 이용하여 손상 실험을 수행하였다. 제거 효율에 사용된 입자는 $CeO_2$와 $SiO_2$이며, 각각 30, 50, 100, 300 nm 크기를 정량적으로 오염시킨 쿠폰 웨이퍼를 제조하여 세정 효율을 평가하였다. 정량적 오염에는 SMPS (scanning mobility particle sizer)를 이용한 크기 분류와 정전기적 입자 부착 시스템이 사용되었다. 또한 패턴 붕괴 평가에는 35~180 nm 선폭을 가지는 Poly-Si 패턴을 이용하였다. 실험 결과 클러스터 형성 조건에 따라 상대적으로 낮은 패턴 붕괴에서 95% 이상의 높은 오염입자 제거효율을 전반적으로 보이는 것을 확인할 수 있었다. 따라서 이론적 계산에 기반하여 세정에 요구되는 클러스터 크기를 가정하고, 이를 통하여 세정에 적용할 경우 높은 기존 세정 방법의 단점을 보완하면서 높은 세정 효율을 가지는 대체 세정 방안으로 이용할 수 있음을 확인하였다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2019.01a
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• pp.53-56
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• 2019

본 논문에서는 화력을 이용하는 대형 파워 플랜트 설비의 미세먼지 발생량을 저감시키고 능동적으로 제어 할 수 있는 효율적인 시스템을 제안한다. 이 시스템은 기존의 고정형으로 설계된 집진기 방식의 고정부하량 한계점과 극복하고 초미세먼지 PM2.5, 미세먼지 PM10의 발생량에 따라 IoT센서 감지에 의해 지능형 알고리즘으로 효율적으로 저감 제어 처리량을 극대화하고, 미세먼지 발생량을 최소화한다. 또한 이 시스템의 차별성은 기존의 집진기에서 잡혀지지 않는 초미세먼지를 새로운 형태의 물질인 FAA(Fine-dust Adsorption Agent)를 통해 연료 연소 시 발생되는 초미세먼지 미세입자 자체를 크게 만들어 기존 설비 집진기 필터에 포집되게 하는 혁신적인 방식이다. 이번 연구를 통해 350도~1000도 열원에서 작용할 수 있는 화학물질 FAA 용액(Agent)을 개발 하였으며 지능형 AI 분사장치를 통해 연료에 첨가되어 연소 시 미세먼지를 20배~50배까지 볼륨을 확대시켜 기존 집진필터에 포집될 수 있게 동작된다. 이때, 기존 설계된 집진기의 한계(부하)용량에 상관없이 미세먼지 발생량을 상황인식 반응형 알고리즘(AI제어) 통해 분사량을 능동적으로 조절하여 미세먼지 발생량을 저감하는 진보적 혁신성을 지닌다.

• Journal of radiological science and technology
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• v.46 no.6
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• pp.543-551
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• 2023

In this study, the aim was to assess the shielding performance of different 3D printing materials, specifically those produced using FDM, SLA, and CJP methods, with a focus on their application as shielding devices in clinical settings. Additionally, the weight of lead shielding materials can evoke reluctance in pediatric patients undergoing X-ray imaging. A total of 12 materials were printed using their respective 3D printers. These materials were then subjected to X-ray testing using diagnostic X-ray equipment and an exposure meter. The goal was to evaluate their shielding capabilities in comparison to 1 mm lead. The results of this evaluation revealed that VisiJet PXL-Pastel, produced using the CJP method, exhibited the highest shielding performance. Therefore, VisiJet PXL-Pastel by CJP method was selected for the creation of a shielding device designed for pediatric reproductive organs. Subsequent tests demonstrated that both the newly created shielding device and conventional lead shielding equipment achieved the same maximum shielding rate at 50 kVp. Specifically, the shielding rate for the 3D printed device was measured at 84.53%, while the conventional lead shielding equipment, categorized as Apron1 (85.74%), Apron2 (99.98%), and Apron3 (99.04%), demonstrated similar performance. In conclusion, the CJP-produced VisiJet PXL-Pastel material showcased excellent radiation shielding capabilities, allowing for anatomical observations of the target organs and their surrounding structures in X-ray images. Furthermore, its lower weight in comparison to traditional lead shielding materials makes it a clinically practical and useful choice, particularly for pediatric applications.

• Corrosion Science and Technology
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• v.14 no.2
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• pp.59-63
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• 2015

Airless spray which is widely used for painting to ship blocks and hull sides is the coating method for attaching atomized paint material to the substrate using spray tip nozzle with compressed air. When the paint material which has high solid contents such as epoxy primer paint is atomized by passing through spray tip nozzle with high pressure, the nozzle composed of tungsten carbide(WC) undergoes the erosive wear, leading to widening of nozzle hole. The deformation of nozzle hole induces improper spray pattern and coating failures such as finger pattern and sagging because the conditions of spray pump pressure and paint flow rate for developing full spray pattern are changed. In this study, an appropriate replacement cycle of spray tip was predicted by measuring the erosive wear tendency as increasing the spraying time of epoxy primer paint.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.5
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• pp.91-96
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• 2009

The number of vehicles applied diesel engine are rapidly rising for fuel economy. Accompanying this trend, application of an after-treatment system is strictly required as a result of reinforced emission regulation. The Diesel Particulate Filter (DPF) system is considered as the most efficient method to reduce particulate matter by car makers but also in retrofit market. In this paper we discussed the optimization of active regeneration timing by comparing the fuel consumption from back pressure caused by PM loading and from active regeneration. The effects of back pressure of DPFs during PM loading, active regeneration condition and engine emission(PM) on additional fuel consumption are experimentally investigated and the proper regeneration timings according to DPF systems and fuel loss for 160,000km are determined.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.6
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• pp.96-103
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• 2014

Liquefied Petroleum Gas(LPG) has attracted attention as a alternative fuel. The lean-burn LPG direct injection engine is a promising technology because it has an advantage of lower harmful emissions. This study aims to investigate the effect of combustion strategy and excess air ratio on combustion and emission characteristics in lean-burn LPG direct injection engine. Fuel consumption and combustion stability were measured with change of the ignition timing and injection timing at various air/fuel ratio conditions. The lean combustion characteristics were evaluated as a function of the excess air ratio with the single injection and multiple injection strategy. Furthermore, the feasibility of lean operation with stratified mixture was assessed when comparing the combustion and emission characteristics with premixed lean combustion.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.15-22
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• 2002

As the emission regulations on the automobiles have been increasingly stringent, precise control of air/fuel ration is one of the most important issues on the gasoline engines. Although many researches have been carried out to identify the fuel transport phenomena in the port fuel injection gasolines, mixture preparation in the cylinder has not been fully understood due to the complexity of fuel film behavior, In this paper, the mixture preparation during cold engine start is studied by using a Fast Response Flame ionization Detector.(FRFID) In order to estimate the transportation of injected fuel from the intake port into cylinder, the wall wetting fuel model was used. The two coefficient($\alpha$,$\beta$) of the wall-wetting fuel model was determined from the measured fuel mass that was inducted into the cylinder at the first cycle after injection cut-in. $\alpha$( ratio of directly inducted fuel mass into cylinder from injected fuel mass) and $\beta$ (ratio of indirectly inducted fuel mass into cylinder from wall wetted fuel film on the wall) was increased with increasing cooling water temperature. To reduce a air/fuel ratio fluctuation during cold engine start, the appropriate fuel injection rate was obtained from the wall wetting fuel model. Result of air/fuel ratio control, air/fuel excursion was reduced.