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하동흔(Dongheun Ha),김민철(Mincheol Kim),박종상(Jongsang Park),염정국(Jungkuk Yeum),하종률(Jongyul Ha),정성식(Sungsik Chung) 한국자동차공학회 2008 한국자동차공학회 지부 학술대회 논문집 Vol.2008 No.11
This study was carried out to investigate the availability of using CNG fuel in a commercial two-cylinder gasoline engine and to derive the optimum performance of the engine. The results of this study is used to determine the optimized injection quantity at the time of dual injection and to improve the engine efficiency through comparing and investigating the performance of a PFI(Port Fuel Injection) and a sub-chamber DI(Direct Injection) type engine in order to establish the base of using PFI and sub-chamber DI type together in a multi-cylinder engine. A gasoline engine was adapted for this study, and air excess ratio was controlled using Lambda sensor and handle accelerator, and spark timing and injection timing were controlled using the ECU that was made personally. Combustion characteristics in accordance with air excess ratio and injection timing were investigated by multi-point injection using CNG fuel. On the basis of PFI type, the standard of fuel injection duration is obtained and it is applied to DI type. According to the air excess ratio, in-cylinder pressure, rate of heat release, IME(Indicated Mean Effective pressure), mass fraction burned, COVimep(Coefficient Of Variation), and so on are derived. As a result, the engine operation in PFI type is the safest at stoichiometric ratio and the engine operation in sub-chamber DI type is the safest at lean mixture ratio. This result is applied to the next study in order to obtain the optimized injection quantity and to improve the efficiency.
정적연소기에서 라디칼 유도분사를 이용한 예혼합기의 연소특성에 관한 연구 (제3보)
박종상(Jongsang Park),오동헌(Dongheon Oh),하종률(Jongyul Ha),정성식(Sungsik Chung) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
A prior fundamental study was executed using a constant volume chamber to improve the burning properties<br/> of lean pre:-mixture by the injection of active radicals generated in the sub-chamber. In consequence. RI method shows<br/> remarkable progress in the aspects of burning velocity and combustible lean limit compared with SI method. In this :study, the necessary additional works have been performed to be: based on the: former results. We changed parameters as the initial temperature and the initial pressure of mixture. And the: effects of resident gas at issue in a ureal engine were investigated. As a result, the effects of initial temperature were significant, but on the other hand. those of initial pressre were slight. The correlation of passage hole number between overall passage hole area was grasped. And the more detailed analysis is required on resident gas.
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.
레이저시트광을 이용한 가시화 디젤엔진에서의 Soot 계측 제1보:가시화 디젤엔진의 제직 및 레이저를 이용한 Soot의 2D 화상촬영
이명준(Myungjun Lee),박태기(Taegi Park),하종률(Jongyul Ha),정성식(Sungsik Chung) 한국자동차공학회 2000 한국 자동차공학회논문집 Vol.8 No.2
In order to clarify the characteristics of soot formation and oxidation in-cylinder of diesel engine, it is necessary to diagnose accurately for combustion of in-cylinder. The past techniques for soot measurement have limitations in providing the characteristics of soot in a diesel engine, whereas, laser-based 2D imaging diagnostics have the potential to provide better temporally and spatially resolved measurements of the soot distribution.<br/> We rebuilt an optically accessible diesel engine which is similar to the conditions of a conventional engine and tried to measure soot distribution in a cylinder of the diesel engine using laser induced scattering(LlS) and laser induced incandescence(LII).<br/> Some results were acquired in this study. LIS and LlI signal that show soot distribution of a in-cylinder were taken by ICCD properly. The signal of LIS was intenser than that of LlI. Although they have some differences of signal intensity in early combustion period, both of signals show that they are generally similar in late combustion period, after ATDC 50 degree.
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.
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.
정적연소기에서 라디칼 유도분사를 이용한 희박혼합기의 연소특성에 관한 연구 (1)
박종상(Jongsang Park),이태원(Taewon Lee),하종률(Jongyul Ha),정성식(Sungsik Chung) 한국자동차공학회 2004 한국 자동차공학회논문집 Vol.12 No.2
An experimental study was carried out to obtain the fundamental data about the effects of radicals induced injection on premixture combustion. A constant volume combustor divided to the sub-chamber and the main chamber was used. The volume of the sub-chamber is set up to occupy less than 1.5% of that of whole combustion chamber. Radial twelve narrow passage holes are arranged between the main chamber and the sub-chamber. The products including radicals generated by spark ignition in the sub-chamber will derive the simultaneous multi-point ignition in the main chamber. While the equivalence ratio of pre-mixture in the main chamber and the sub-chamber is uniform. We have examined the effects of the sub-chamber volume, the diameter of passage hole, and the equivalence ratio on the combustion characteristics by means of burning pressure measurement and flame visualization. In the case of radical ignition method(RI), the overall burning time including the ignition delay became very short and the maximum burning pressure was slightly increased in comparison with those of the conventional spark ignition method(SI), that is, single chamber combustion without the sub-chamber. The combustible lean limit by RI method is extended to more ER=0.25 than that by SI method. Therefore the decrease of every emission including NOx and the improvement of fuel consumption is anticipated due to lean burn.