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라디칼유도분사식 희박연소기술의 실엔진 적용에 관한 연구
정성식(Sungsik Chung),신은준(Eunjun Shin),박원호(Wonho Park),박종상(Jong Sang Park),이태원(Taewon Lee),염정국(Jeongkuk Yeom) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_1
This study was carried out to propose an engine which has low emission and high efficiency by using radical induced injection method with rapid combustion of ultra lean mixture. A prechamber diesel engine was reconstructed to a SPI type gasoline engine which can control the injection duration and spark timing. In this study, the volume, orifice diameter and number of subchamber were used as experiment parameter. In this study, the P-Θ diagram as a function of the volume, orifice diameter and number of the subchamber was obtained, and the results of the diagrams were compared with one of SPI engine. As results of experiment study, the reconstruction of a base engine was successfully completed, and the ratio of orifice area and subchamber volume should be optimized in subchamber design of a radical engine. Also, the improvement of the engine efficiency can be expected, because the efficiency of the radical induced injection engine with rapid combustion is higher than the SPI engine.
염정국(Jeongkuk Yeom),정성식(Sungsik Chung),하종률(Jongyul Ha) 한국자동차공학회 2004 한국 자동차공학회논문집 Vol.12 No.6
The effects of change in injection pressure on spray structure have been investigated in high temperature and pressure field. To analyze the structure of evaporative diesel spray is important in speculation of mixture formation process. Also emissions of diesel engines can be controlled by the analyzed results. Therefore, this study examines the evaporating spray structure by using a constant volume vessel. The injection pressure is selected as the experimental parameter, is changed from 72 MPa to 112 MPa with a high pressure injection system (ECD-U2). The PIV (Particle Image Velocimetry) technique was used to capture flow variation of the evaporative diesel spray. A study on the mixture formation process of diesel spray was executed by the results of flow analysis in this study. Consequentially the large-scale vortex flow could be found in downstream spray and the formed vortex governs the mixture formation process in diesel spray.
김민철(Mincheol Kim),정성식(Sungsik Chung),하종률(Jongyul Ha),염정국(Jeongkuk Yeom) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
In this study, an analysis of evaporative diesel spray and an usefulness of a general-purpose program, ANSYS CFX release 11.0, are investigated through the comparison and investigation of the experimental results carried out under an evaporative field, in which there is phase transition, by an exciplex fluorescence method and the results analyzed by the CFX program. Each image of the diesel spray was taken by CCD cameras that contribute to obtain an accurate result. The diesel fuel called n-Tridecane, C₁₂H₂?, is injected from a single-hole nozzle (l/d=1.0㎜/0.2㎜) into a constant volume chamber under a high temperature and pressure. In the same condition as the experimental condition, the analysis was carried out. Both results of the spray tip penetration were almost coincident at each time. The results have validated the usefulness of this analysis. As a result, if the ambient pressure is high, the spray tip penetration will be shortened and move toward the nozzle exit.
염정국(Jeongkuk Yeom),정성식(Sungsik Chung),하종률(Jongyul Ha) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.6
In this study the penetration distance of liquid phase fuel(i. e. liquid phsae length) was investigated in evaporative field. An exciplex fluorescence method was applied to the evaporative fuel spray to measure and investigate both the liquid and the vapor phase of the injected spray. For accurate investigation, images of the liquid and vapor phase regions were recorded using a 35㎜ still camera and CCD camera, respectively. Liquid fuel was injected from a single-hole nozzle (l/d=1.0㎜/0.2㎜) into a constant-volume chamber under high pressure and temperature in order to visualize the spray phenomena. Experimental results indicate that the liquid phase length decreased down to a certain constant value in accordance with increase in the ambient gas density and temperature. The constant value, about 40㎜ in this study the, is reached when the ambient density and temperature of the used fuel exceed critical condition.
염정국(Jeongkuk Yeom),정성식(Sungsik Chung),하종률(Jongyul Ha) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
The effects of density change in ambient gas on mixture formation process have been investigated in high temperature and pressure field. To analyze the mixture formation process of evaporating diesel spray is important for emissions reduction in actual engines. Ambient gas density was selected as experimental parameter. The ambient gas density was changed from ㎩=5.0㎏/㎥ to ㎩=12.3㎏/㎥ with a high pressure injection system(ECD-U2). For visualization of the experiment phenomenon, a CVC(Constant Volume Chamber) was used in this study. The ambient temperature and injection pressure are kept as 700K and 72㎫, respectively. The images of liquid and vapor phase in the evaporating free spray were simultaneously taken by exciplex fluorescence method. As experimental results, with increasing ambient gas density, the tip penetration of the evaporating free spray decreases due to the increase in the drag force from ambient gas.
스파크점화직분식 CNG의 점화성 및 연소화염 특성에 대한 연구
황성일 ( Seongill Hwang ),정성식 ( Sungsik Chung ),염정국 ( Jeongkuk Yeom ),전병열 ( Byongyeul Jeon ),이진현 ( Jinhyun Lee ) 한국분무공학회 2016 한국액체미립화학회지 Vol.21 No.1
For the SI engines, at only full load, the pumping loss has a negligible effect, while at part load conditions, the pumping loss increases. To avoid the pumping loss, the spark-ignited engines are designed to inject gasoline directly into the combustion chamber. In the spark-ignited direct-injection engines, ignition probability is important for successful combustion and the flame propagation characteristics are also different from that of pre-mixed combustion. In this paper, a visualization experiment system is designed to study the ignition probability and combustion flame characteristics of spark-ignited directinjection CNG fuel. The visualization system is composed of a combustion chamber, fuel supply system, air supply system, electronic control system and data acquisition system. It is found that ambient pressure, ambient temperature and ambient air flow velocity are important parameters which affect the ignition probability of CNG-air mixture and flame propagation characteristics and the injected CNG fuel can be ignited directly by a spark-plug under proper ambient conditions. For all cases of successful ignition, the flame propagation images were digitally recorded with an intensified CCD camera and the flame propagation characteristics were analyzed.
상변화를 동반하는 디젤분무의 혼합기형성과정에 대한 고찰
염정국(Jeongkuk Yeom),정성식(Sungsik Chung),하종률(Jongyul Ha) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.10
In this study, the effects of change in ambient gas viscosity on spray structure have been investigated on the high temperature and pressure field. To analyze the structure of evaporative diesel spray is important in speculation of mixture formation process. Also emissions of diesel engines can be controlled by the analyzed results. Therefore, this study examines the evaporating spray structure in the a constant volume chamber. The viscosity of ambient gas was selected as the experimental parameter, is changed from 21.7 μPaㆍs 32.1 μPaㆍs by change in ambient gas temperature. In order to obtain images of the liquid and vapor-phase of injected spray, exciplex fluorescence method was used in this study. The liquid and vapor-phase images were respectively taken with 35mm still camera and CCD camera. Consequentially, it could be confirmed that the distribution of vapor concentration is more uniform in the case of the ambient gas with high viscosity than in that of the ambient gas with low viscosity.
강정호(Jeongho Kang),염정국(Jeongkuk Yeom),정성식(Sungsik Chung),하종률(Jongyul Ha) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
A CNG fuel is one of the most promising alternative fuels because of lower exhaust emissions and lower CO2 emission with high thermal efficiency. However, the brake horse power is reduced because a CNG fuel has a low volumetric efficiency due to the gaseous charge and increase in time loss with lower burning speed as compared with gasoline fuel. To solve these problems, the DI Diesel Engine was modified to the DI CNG Engine which directly supplies natural gas into the engine cylinder. The combustion characteristics of the DI CNG engine such as cylinder pressure, cycle variation, combustion duration and emissions were investigated in this study. Consequently, it could be verified that the volumetric efficiency, overall combustion duration and lean limit were improved by using DI technique in the CNG Engine.
천연가스 전소엔진과 가솔린엔진의 성능과 배출가스 특성비교
김진영(Jinyoung Kim),박원옥(Wonok Park),정성식(Sungsik Chung),하종률(Jongyul Ha) 한국자동차공학회 2003 한국 자동차공학회논문집 Vol.11 No.2
Natural gas is one of the promising alternative fuels becausc of the abundant deposits and the cleanness of emission gas. It can be used in conventional gasoline engine without major modification.<br/> Natural gas has some advantages than gasoline i.e. the high octane number. good mixing condition because of gas and wide inflamable limit.<br/> In the present study, a 1.8 ℓconventional gasoline engine is modified for, using the CNG as a fuel instead of gasoline. performance and emission characteristics are compared between gasoline and CNG with 4 cylinder SI Engine which is controlled by programable ECU.<br/> Parameters of experimentation are equivalence ratio, spark timing and fuels. We analyzed the combustion<br/> characteristics of the engine using the cylinder pressure i.e. ignition delay, combustion duration and cycle variation.<br/> As a result, CNG engine shows lower exhaust emissions but brake torque is slightly reduced compared to gasoline<br/> engine. Ovrall combustion duration is longer than that of gasoline because of lower buming speed<br/>