Simultaneous reduction in the exhaust emissions by a high exhaust gas recirculation ratio in a dimethyl-ether-fuelled diesel engine at a low-load operating condition

Park, Su Han,Cha, Junepyo,Park, Sungwook,Lee, Chang Sik SAGE Publications 2012 Proceedings of the Institution of Mechanical Engin Vol.226 No.8

<P>The purpose of this study was to investigate the effect of the exhaust gas recirculation rate on the combustion and exhaust emission reduction characteristics of dimethyl ether fuel in a single-cylinder diesel engine. To investigate the effects on emission reduction, the test set-up was composed of a dimethyl ether supply system, a spray visualization system, an engine combustion system and an emissions analysis system. In this work, the spray visualization and exhaust emissions were measured using a high-speed camera with a metal halide lamp, a smoke meter and an emission gas analyser. The spray tip penetration and tip velocity of dimethyl ether fuel were lower than those of conventional diesel fuel. The reduction slope of the spray cone angle for dimethyl ether was less than that for diesel fuel owing to its low density and superior evaporation characteristics. The increase in the exhaust gas recirculation rate caused an extension of the ignition delay for dimethyl ether. During the extended ignition delay, the improved mixing characteristics influenced the slight decrease in the combustion period. An increase in the exhaust gas recirculation rate caused a significant reduction in the emission of nitrogen oxides. In addition, the soot emission was very low owing to the intrinsic characteristics of dimethyl ether (no direct carbon-carbon bonds). At the given equivalence ratio condition, the indicated specific hydrocarbon and indicated specific carbon monoxide emissions for dimethyl ether were extremely low when dimethyl ether spray was injected into the piston bowl (from 25 degrees before top dead centre to top dead centre). Also, in this case, a change in the exhaust gas recirculation rate for dimethyl ether combustion had minimal effects on the indicated specific hydrocarbon and indicated specific carbon monoxide emissions. These results suggest that the use of high exhaust gas recirculation with dimethyl ether fuel can achieve near-zero exhaust emissions (nitrogen oxides, soot, hydrocarbons and carbon monoxide).</P>

CsPbX3/SiOx (X = Cl, Br, I) monoliths prepared via a novel sol-gel route starting from Cs4PbX6 nanocrystals

Park, Sungwook,An, Mai Ngoc,Almeida, Guilherme,Palazon, Francisco,Spirito, Davide,Krahne, Roman,Dang, Zhiya,De Trizio, Luca,Manna, Liberato The Royal Society of Chemistry 2019 Nanoscale Vol.11 No.40

<P>We developed a facile synthesis of nanocomposite powders of CsPbX3 nanocrystals (NCs) embedded in silica. The synthesis starts from colloidal Cs4PbX6 NCs that are mixed with tetraethyl orthosilicate in the presence of nitric acid, which triggers the sol-gel reaction yielding the formation of SiOx and the conversion of starting NCs into CsPbX3 ones. The overall reaction delivers CsPbX3 NCs encased in a silica matrix. The resulting CsPbX3/SiOx nano-composite powders exhibited enhanced moisture and thermal stability in air. Also, when mixing different CsPbX3/SiOx samples having diverse anion compositions, no interparticle anion exchange processes were observed, which is a further indication that the silica matrix acts as a robust barrier surrounding the NCs. Finallly, we used these composites as down-converter phosphors on top of a blue light-emitting diode (LED), delivering nearly ideal white light emission with the Commission Internationale de l'Eclairage (CIE) color coordinates (0.32, 0.33).</P>

Prediction of wall impingement in a direct injection spark ignition engine by analyzing spray images for high-pressure injection up to 50 MPa

Park, Junkyu,Kim, Taehoon,Kim, Donghwan,Park, Sungwook Elsevier 2018 Fuel processing technology Vol.179 No.-

<P><B>Abstract</B></P> <P>This study was performed to analyze the wall impingement and fuel film formation in a DISI engine with injection strategies using image-based analysis and CFD. The direct injection engine uses a high-pressure injection strategy to improve the homogeneity of the air-fuel mixture, so the spray behavior was analyzed by spray visualization for various injection pressures, and the wall impingement was predicted for various engine operating conditions based on the acquired images. The mass distribution of the injected fuel was calculated using the injection profiles and the spray image, and the amount of fuel that impinges on the piston and wall (i.e., the geometric boundaries of the cylinder) was calculated using data from the spray behavior for various engine operation conditions such as load and engine speed. The image-based analysis was limited to understanding the influence of the injection strategy on the droplet behavior after wall impingement of the fuel spray. Therefore, CFD using KIVA 3 V code was additionally conducted to analyze the effects of the injection strategies on wall film formation and droplet rebounding reflecting in-cylinder conditions. In the early- and late-injection conditions, the initial piston position is high, and most of the injected fuel impinges on the piston. As the injection pressure increases, the injection timing at which wall impingement occurs is advanced because of the rapid spray development. The results of the 3D analysis for the temperature and the intake flow in the engine cylinder showed that both the wall impingement and the fuel film were reduced as the injection pressure increased because the fuel evaporation increased due to improved atomization.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A prediction method of wall impingement in DISI engines is introduced. </LI> <LI> Effects of injection pressure and injection timing on spray wall impingement are analyzed using image-based method. </LI> <LI> 3D CFD are used to analyze effects of the engine conditions on formation of fuel film. </LI> <LI> Higher injection pressure conditions can reduce formation of fuel film due to superior vaporization characteristics. </LI> </UL> </P>

Detection of Avian Influenza Virus from Cloacal Swabs Using a Disposable Well Gate FET Sensor

Park, Sungwook,Choi, Jaebin,Jeun, Minhong,Kim, Yongdeok,Yuk, Seong-Su,Kim, Sang Kyung,Song, Chang-Seon,Lee, Seok,Lee, Kwan Hyi Wiley (John WileySons) 2017 Advanced Healthcare Materials Vol.6 No.13

Front End Carrier의 상부 구조에 따른 강성 비교 연구

박성욱(Sungwook Park),공태윤(Taeyun Kong),김재용(Jaeyong Kim),소원섭(Wonsub So) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11

Front End Module is assembled to the front area of the vehicle. In the case of front crash, the Front End Module should be able to absorb the impact and the deformation of Front End Module should be minimized. If the vehicle’s hood deformed by crash is opened, it can make the wind shield of vehicle broken and injure passengers. Because deformed and opened hood can cause the additional accidents, the stiffness supporting hood is very important. The stiffness of all developed vehicles must be verified in the development stage through Hood Latch Retention Test. And the test must be controlled strongly. The stiffness supporting hood & latch has the relationship with the Front End Carrier’s upper structure. The Higher inertia of Upper Section is advantageous, but the upper section can not be secured often because of vehicle’s styling or engine room layout or limitation of cost & weight , ETC, and these factor is different according to the vehicles We have developed several vehicle’s Front End Module since 1999 and we will introduce some kinds of knowhow from the development history of 2 vehicle’ Front End Module.

Effects of Nozzle Design Parameters of a Common-rail Diesel Injector on Nozzle flow and Spray Characteristics

( Junkyu Park ),( Donghwan Kim ),( Hyuckmo Kwon ),( Joonkyu Lee ),( Soohong Lee ),( Sungwook Park ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-

This paper describes effects of nozzle design parameters including number of nozzle hole, spray angle, and HFR on nozzle flow and spray characteristics. Injection profiles were measured using Bosch method in order to analyze flowrate depending on the nozzle design parameters and spray visualization was performed under various injector driving conditions to compare the macroscopic spray behavior in terms of the spray tip penetration and the spray cone angle. The experimental results were validated against through the Hiroyasu equation after modifying adjustable constants to fit to high pressure injection region. The flowrate was proportional to the size of HFR, which means the static flow at 100 bar. Under various injection pressure, flowrate was proportional to square root of increment of injection pressure and corresponded well to the predicted formula based on the Bernoulli equation. As number of nozzle holes increased under fixed total flow rate condition, the slower spray development was observed due to reduced nozzle outlet diameter, and the spray cone angle was similar for the cases of various nozzle diameter. For nozzle condition in which the spray angle was changed from the reference (153°), there was no significant difference in terms of macroscopic spray characteristics, but the emission characteristics can be deteriorated due to differences in air entrainment in the cylinder.

방호 성능 향상을 위해 개발된 HPFRCC 구조 부재 실험 및 수치 해석

김성욱(Sungwook Kim),박강규(Gangkyu Park),문재흠(Jaeheum Moon),박기준(Gijoon Park),김원우(Wonwoo Kim) 한국콘크리트학회 2023 콘크리트학회지 Vol.35 No.2

인공지능을 이용한 잣나무재 표면 옹이 분류 및 구획화

최종규 ( Jonggyu Choi ),김현빈 ( Hyunbin Kim ),황운택 ( Untaek Hwang ),양상윤 ( Sang-yun Yang ),박용건 ( Yonggun Park ),김민규 ( Mingyu Kim ),심국보 ( Kug Bo Shim ),황성욱 ( Sungwook Hwang ),여환명 ( Hwanmyeong Yeo ) 한국목재공학회 2020 한국목재공학회 학술발표논문집 Vol.2020 No.1

컴퓨터 이미지 분석 기술을 이용한 목재 표면 화상 분석은 목재 품질의 객관적인 평가와 이를 통한 목재 생산의 고속화를 위해 필요하다. 인공지능을 활용한 딥러닝(Deep Learning) 기술은 높은 정확도와 빠른 속도로 이미지 화상 분석 분야에서 높은 활용도를 보여주고 있다. 본 연구에서는 여러 딥러닝 기술 중 이미지 구획화에서 활용되는 합성곱 신경망(Convolutional Neural Network, CNN)을 이용하여 잣나무재 표면 옹이를 구획화하고, 그 종류를 분류하였다. 잣나무 각재에서 획득한 128개의 제재목 사진을 사용하였고, 이들 제재목 사진에서 추출한 227개의 옹이 이미지를 4가지 종류로 분류하였다. VGG Image Annotator를 이용하여 옹이의 위치와 종류에 대한 데이터베이스를 만들고, 이를 통해 제재목 표면의 옹이를 구획화하여 표시하고, 종류를 분류하는 알고리즘 모델 학습을 진행하였다. 또한, 색상으로 인한 분류 오차가 생길 수 있다고 판단하여 흑백으로 변환한 잣나무재 이미지에서도 옹이 구획화 및 분류를 진행하였다. 잣나무재 표면 옹이 구획화 및 분류 학습을 진행한 결과 옹이의 종류나 크기 등의 변수가 존재함에도 높은 정확도로 목재 표면 옹이를 탐지할 수 있었고, 옹이 종류 분류에서도 준수한 정확도를 보여주었다. 그리고 RGB 이미지보다 흑백으로 변환한 이미지를 분류할 때 조금 더 높은 정확도를 보였는데, 이를 통해 이미지 분류에서 색상으로 인한 변수가 존재함을 추론할 수 있었다. 옹이 종류에 따라 이미지 개수의 현저한 격차가 존재하여 분류 학습에 어려움이 있었는데, 이미지 개수가 적은 희귀 종류 옹이를 추가로 학습시킨다면 더 높은 정확도를 얻을 수 있을 것으로 기대된다.

전기자동차 배터리 성능저하 관리 제도

박성욱(Sungwook Park) 한국자동차공학회 2023 오토저널 Vol.45 No.7

가계부문 신용사이클이 채무불이행 위험에 미치는 영향 분석

박성욱 ( Sungwook Park ),임진 ( Lim Jean ),김영일(논평) 한국금융연구원 2018 韓國經濟의 分析 Vol.24 No.3

호황기에는 차입자와 금융회사 모두 투자의 수익성과 대출의 상환가능성에 대해 낙관적이게 되고 금융회사도 자기자본 개선 등으로 대출을 적극 확대하는 과정에서 금융회사의 대출태도가 관대해진다. 그 결과 사후적으로 보면 채무상환능력이 부족한 차입자에게도 대출이 일어나는 과잉대출이 발생하게 된다. 이에 따라 신용사이클 상의 호황기때 부적격 차입자에 대한 대출이 늘어나면서 대출의 질이 악화되는 경향이 있다. 본 연구는 2010년 이후 2017년까지 신규로 개설된 578.6만 개인대출 계좌의 미시 정보를 이용하여 각 계좌가 개설된 시기의 가계대출 증가율이 해당 계좌의 연체확률에 유의한 영향을 미쳤는지를 실증분석을 통해 살펴보았다. 분석 결과 가계대출 증가율이 높았던 시기에 실시된 대출일수록 부실확률이 더 높음을 발견할 수 있었다. 더 나아가 본 연구는 주택담보대출보다는 신용대출이, 은행대출보다는 비은행대출이, 그리고 임금근로자대출보다는 비임금근로자대출이 신용사이클에 더 민감하게 반응함을 보여 주었다. 또한 가계대출 부실확률은 경기사이클보다는 신용사이클에 더 민감하게 반응할 뿐만 아니라, 신용사이클을 통제한 상태에서는 경기사이클이 대출의 부실확률에 미치는 영향이 거의 없는 것으로 추정되었다. 이와 같은 실증분석 결과를 토대로 본 연구는 대표적인 거시건전성 정책인 동태적 대손충당금이나 경기대응완충자본이 경기사이클보다는 신용사이클에 따라 적립되는 것이 금융안정에 더욱 직접적인 효과를 나타낼 수 있다고 보았다. 또한 동태적 대손충당금이나 경기대응완충자본도 가계대출의 종류에 따라 적립규모를 차별화할 필요가 있다고 보았다. 예를 들면 주택담보대출 증가분보다는 신용대출 증가분에 대손충당금을 더 많이 적립하는 것이 금융안정에 더 효과적임을 주장하였다. During the period of economic boom, financial companies are far more lenient on lending in compliance with their loan expansion policy. This is because not only the equity of financial companies improves, but both borrowers and financial companies come to enjoy optimistic views on investment profitability and loan redemption. Consequently, financial companies give out loans even to borrowers with poor debt service ability. These loans granted to ineligible borrowers during the credit cycle boom are excessive loans, in hindsight, deteriorating the quality of loans as a whole. This study investigates whether the growth rate of household debt has significant effect on the delinquency rate by using the micro information of 5.786 million accounts newly opened during 2010 to 2017. Analysis result shows that the higher the growth rate of household debt in a certain period, the higher the insolvency rate of loans made in the corresponding term. Furthermore, this study demonstrates through empirical analysis that credit loans than mortgage loans, non-bank loans than bank loans, and non-wage workers’ loans than wage workers’ loans are more sensitive to credit cycles. In addition, the probability of insolvency is more affected by the credit cycle than economic cycle; and it is estimated that there is little effect of economic cycle on insolvency when credit cycle is controlled. Based on these results, this study suggests that the dynamic loan loss provisions and Countercyclical Capital Buffer (CCyB), the two most typical macroprudential policies, should be accumulated in line with the credit cycle rather than economic cycle for a more direct impact on financial stability. Moreover, it is necessary to differentiate the amount of the dynamic loan loss provisions and CCyB depending on the type of loan. That is, for instance, more loan loss provisions should be accumulated for increment of credit loan than that of mortgage loan to better enhance the overall financial stability.