화상상관법을 이용한 증발 디젤분무의 구조해석

염정국(Jeongkuk Yeom),정성식(Sungsik Chung),하종률(Jongyul Ha) 한국자동차공학회 2004 한국 자동차공학회논문집 Vol.12 No.6

수치해석을 이용한 가솔린연료 분무 거동특성 연구

염정국(Jeongkuk Yeom) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.12

The focus of this study is placed on the behavior characteristics of gasoline spray under condition field of room temperature and pressure. To analyze the behavior and flow characteristics of injected fuel spray is important in speculation of mixture formation process. Also the exhausted emissions from actual engines can be controlled by the analyzed results. The φ(degree of freedom) and K(energy ratio of particle motion) are selected as the simulation parameter. The factors affect characteristics of spray structure, and the factors are included in the sub-program of the KIVA-II code. In this study, the simulation study by modified KIVA-II code was conducted and the calculated results obtained by the modified KIVA-II code show good agreements with experimental results. As a result, applying the improved TAB model with φ=8 and K=2 to simulation analysis of the KIVA-II code is sufficiently useful for analyzing the macro characteristics in spray structure, such as the spray tip penetration of injected fuel spray.

주위조건 변화에 대한 증발 디젤분무 거동특성 연구

염정국(Jeongkuk Yeom) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.6

To analyze the mixture formation process of evaporating diesel spray is important for emissions reduction in actual engines. Then the effects of change in density of ambient gas on spray structure in high temperature and pressure field have been investigated in this study. The ambient gas density was changed from ρa=5.0㎏/㎥ to ρa=12.3㎏/㎥ with CVC(Constant Volume Chamber). Also, simulation study by modified KIVA-Ⅱ code was conducted and compared with experimental results. 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. The spatial structure of a diesel spray can be verified as 2-regions consisted of liquid with momentum decrease and vapor with large-scale vortex. The calculated results obtained by modified KIVA-Ⅱ code show good agreements with experimental results.

비정상 증발디젤분무의 측정과 그 응용해석

염정국(Jeongkuk Yeom),박종상(Jongsang Park),김시범(Sipom Kim),정성식(Sungsik Chung),하종률(Jongyul Ha) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.7

The characteristics of combustion process in an internal combustion engine are affected by the mixing process between injected fuel and ambient gas. Therefore, it is necessary to understand the mixture formation process of diesel spray. In this study, the spray structure was visualized by the exciplex fluorescence method, which can provide the simultaneous 2-D images of vapor and liquid phase in inner spray. For accurate investigation, the liquid-phase images were recorded with a 35mm still camera and CCD camera. Consequentially, it could be confirmed that the high-concentration vapor phase is formed in the region of spray tip and the edge of the liquid phase where droplets exist in the evaporating diesel spray, and the formed vapor is spread by diffusion. Also, the distribution of vapor is determined by the motion of droplets that exist in the edge of the liquid phase and the spray-tip region.

다성분연료 분무에 있어서 증발과정의 해석모델 제안

염정국(Jeongkuk Yeom),田中智之(Tomoyuki Tanaka) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.5

The evaporation process of multi-component fuel is different from one of a single component, because the properties of each component affects among the components. In actual engine, the spatial distribution of fuel vapor concentration dominates auto-ignition and initial combustion, and depends on the volatility and diffusivity of each component fuel contained in the multi-component fuel. Then, this study proposes a simplified numerical scheme for analysis of evaporation process of multi-component fuel sprays. Evaporation process is calculated by KIVA-II code based on the simple two-phases region that is approximated by modified saturated liquid-vapor line, which was obtained by connecting the 50% distillation temperature for each component under several pressure fields. Consequently, it can be quantitatively simulated that vapor of low boiling fuel component mostly exists around nozzle and spray tip region, the high boiling duel component, on the other hand, mostly appears near the spray tip.

증발자유디젤분무의 거동특성에 관한 연구

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.

설계변수에 따른 디젤 인젝터 캐비테이팅 유동에 관한 연구

염정국(Jeongkuk Yeom),정우성(Woosung Jeong),이무연(Mooyeon Lee),김시범(Sipom Kim),정성식(Sungsik Chung),하형수(Hyeongsoo Ha) 한국자동차공학회 2013 한국자동차공학회 지부 학술대회 논문집 Vol.2013 No.4

In this study, the CFD simulation analysis(ANSYS 13.0 CFX) about inner flow of the multi-hole injector was conducted directly. Based on these processes, DOE was applied to obtain the effect of injector nozzle design parameters on cavitation. The design parameters that is judged affecting cavitating flow are defined to nozzle hole diameter, nozzle hole length, nozzle hole angle and K-factor of the nozzle hole for design sensitivity and S/N ratio analysis. Also the 16 experimental points were used to analyze the effect of each parameter. In order to reveal inner flow of nozzle, the numerical analysis program and analysis of S/N ratio are applied in this paper. Consequently, it was founded that effect of K-factor is larger than any other parameters (hole diameter and hole angle) on generating cavitation.

디젤분무거동에 관한 실험적 연구

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.

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.

증발디젤분무의 혼합기 형성과정에 대한 열역학적 접근

염정국(Jeongkuk Yeom) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.3

The focus of this work is placed on the analysis of the mixture formation process under the evaporative diesel-free spray conditions. In order to examine homogeneity of mixture within the vapor phase region of the injected spray, image analysis was carried out based on the entropy of statistical thermodynamics. As an experimental parameter, the injection pressure and ambient gas density were selected, and effects of the injection pressure and density variation of ambient gas on the mixture formation process in the evaporative diesel spray were investigated. In the case of application of the thermodynamic entropy analysis to evaporative diesel spray, the value of the dimensionless entropy always increases with increase in time from injection start. Consequently, the dimensionless entropy in the case of the higher injection pressure is higher than that of lower injection pressure during initial injection period.