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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.
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.