증발디젤분무의 발달 과정에 관한 연구

염정국,박종상,정성식,하종률,김시범,Yeom, Jeong-Kuk,Park, Jong-Sang,Chung, Sung-Sik,Ha, Jong-Yul,Kim, Si-Pom 한국자동차공학회 2007 한국 자동차공학회논문집 Vol.15 No.3

In this study, the effects of change in ambient gas viscosity on spray structure have been investigated in the high temperature and pressure field. To analyze the structure of evaporative diesel spray is important in speculation of mixture formation process. Emissions of diesel engines can be reduced by the control of the mixture formation process. Therefore, this study examines the evaporating spray structure in the constant volume chamber. The viscosity of ambient gas was selected as the experimental parameter, is changed from 21.7 mPa s to 32.1 mPa s by changing 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 taken with 35mm still camera and CCD camera, respectively. 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 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.03

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.

연료의 임계조건을 고려한 디젤 액상분무거동에 관한 연구

염정국,박종상,김시범,정성식,하종률 대한기계학회 2007 大韓機械學會論文集B Vol.31 No.5

A Proposal of Quantitative Analysis Method of Emission Characteristics of Biodiesel Fuel in Diesel Engine

염정국,윤정환 한국정밀공학회 2015 International Journal of Precision Engineering and Vol.16 No.7

In this study, the exhaust characteristics of the diesel engine for the change of the mixing ratio of biodiesel fuel were quantitatively analyzed by using the numerical analysis method. As the fuel in the experiment, the diesel and biodiesel (waste cooking oil, soybean oil), mixture BD2 (diesel only), BD3, BD5, BD20, BD50 and BD100 were used. The injection pressure (pinj) was set at 400 bar, 600 bar, 800 bar, 1000 bar and 1200 bar as the experimental variables. The concept of the standard deviation, Pearson’s correlation coefficient and Spearman rank-order correlation coefficient based on the statistics were introduced in order to analyze the exhaust characteristics of the quantitative NOx and Soot according to the injection pressure and the mixing ratio of biodiesel blended fuel. The regression method was introduced in order to obtain the increasing and decreasing aspects of NOx and Soot that can not be known from the correlation coefficients alone. From the study it is inferred that, for the waste cooking oil, NOx and Soot can be simultaneously reduced through control of the mixing ratio in the region of pinj=400 bar and pinj=600 bar, and the Soot can be reduced without affecting the emission of NOx for pinj more than 800 bar. For the soybean oil, NOx and Soot can be simultaneously reduced at pinj=400 bar and the Soot can be reduced without affecting the emission of NOx at pinj=600 bar.

Effect of Fuel Injector-type Spark Plug on Combustion Characteristics

염정국,정성식 한국분무공학회 2009 한국액체미립화학회지 Vol.14 No.4

This study proposes a new stratified charge system for low emission and ultra lean burn. In order to examine combustion characteristics of the new system, sparkplug with a hole at positive pole and a common CNG injector for injecting fuel were used in this study as injector-type spark plug. The new stratified charge system injects fuel of extremely small quantities and ignites mixture around sparkplug gap. Also, the system was fitted in a visualized constant volume chamber. Then, for analysis of the combustion characteristics, we examined combustion pressure, lean inflammable limit, and visualized combustion flame according to equivalence ratio by comparison with homogeneous charge (HC) method and the new stratified charge (SC) method. As results of this study, in the case of using this system, the propagation speed of initial flame was increased and total combustion period was reduced in the ultra lean burn in the same equivalence ratio. These phenomena occurred clearly under the conditions of lean equivalence ratio. Furthermore, the lean inflammable limit of mixture was extended by using the injector-type spark plug.

Diagnosis of the behavior characteristics of natural gas jet

염정국 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.1

We analyzed natural gas fuel (Methane, CH4) jet at STP (standard temperature and pressure) using a commercial program, ANSYSCFX release 11.0, and compared the results with experimental ones obtained by using shadowgraph method. The combined MCM(multicomponentmodel) and k-ε turbulence model is used in the simulation. Injection pressure is selected as a main parameter in both experimentaland numerical study. In the analysis, longer jet tip penetration was measured each time after start of injection for high injectionpressure. Also, the process of mixture formation before combustion was examined by comparing the experimental and the numericalresults on the behavior of jet and ambient gas flow. It was found that the experimental and the numerical results are consistent with eachother. Further, the use commercial CFX program for the analysis of the macro jet behavior characteristics such as jet tip penetration, andflow of ambient gas can be recommended. In particular, in the analysis of the jet development process it is important to investigate themixture formation by the interaction between the injected fuel and ambient gas.

Diagnosis of the behavior characteristics of the evaporative diesel spray by using images analysis

염정국 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.9

In this study, the effects of change in injection pressure 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 a constant volume chamber. 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 behavior variation of the evaporative diesel spray. Analysis of 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.

An experimental study on the effects of impingement-walls on the spray and combustion characteristics of SIDI CNG

염정국,정성식,Liu Yu 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.8

Compressed natural gas (CNG) is regarded as one of the most promising alternative fuels, and maybe the cleanest fuel for the sparkignition (SI) engine. In the SI engine, direct injection (DI) technology can significantly increase the engine volumetric efficiency and decrease the need of throttle valve. During low load and speed conditions, DI allows engine operation with the stratified charge, and the use of extremely lean fuel-air mixture enables relatively higher combustion efficiency. In this study, a combustion chamber with a visualization system is designed. The spray development and combustion propagation processes SIDI CNG were digital recorded. It was found that high injection pressure reduced the ignition probability significantly because of quenching of flame kernel. To improve the ignition probability, three kinds of impingement-walls were designed to help the mixture preparation. It was found that the CNG-air mixture can be easily formed after spray-wall impingement and the ignition probability was also improved. The results of this study can contribute important data for the design and optimization of spark-ignition direct injection (SIDI) CNG engine.

에멀젼연료 증발특성에 관한 기초 연구

염정국(Jeong Kuk Yeom),윤정환(Jeong Hwan Yoon) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.9

본 연구는 대체혼합연료의 디젤엔진 적용 적합성 검토를 목적으로 수행되었다. 실험연료로서 디젤과 과산화수소의 혼합연료인 에멀젼연료를 사용하였고, 실험과 수치해석의 주요변수로서 경유와 과산화수소 혼합비를 선택하였다. 에멀젼연료의 증발거동 특성은 슐리렌 방법을 이용한 실험과 실험에서 구한 결과를 바탕으로 상용 프로그램(ANSYS CFX)을 이용한 수치해석을 실시하였다. 본 연구의 주요결과로서 과산화수소의 혼합비가 증가할수록 에멀젼연료의 증발특성인 미세폭발 현상이 활발해짐을 확인하였고, 또한 수치해석으로 디젤연료 계산영역 내부 디젤의 체적분율 계산을 통하여 에멀젼연료의 증발현상을 정량적으로 모사 가능하였다. The goal of this study is to consider the application of alternative blended fuel to diesel engine. In this study, as the test fuels, we use a blended fuel mix of diesel and hydrogen peroxide. As the primary variable, we vary the mixing ratio of diesel and hydrogen peroxide in the experimental and numerical analysis. We perform an evaporative behavior characteristics analysis of the emulsified fuel using the Schlieren method. The numerical analysis was carried out based on results obtained from the experimental analysis using the commercial code(ANSYS CFX). Consequently, we found that the micro-explosion depends on the fraction of hydrogen peroxide, and we propose a numerical method for the quantitative evaporation analysis of emulsified fuel droplets using the calculation of the volume fraction in the oil domain.

내연기관에서 열발생률의 산출방법에 관한 연구

염정국(J.K.Yeom),탁영조(Y.J.Tak),이상석(S.S.Lee),하종률(J.Y.Ha) 한국자동차공학회 1992 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

In spite of economical efficiency, high reliability, a excellent chracteristic of generating power, internal combustion engine has problem of environmental pollution. Because of such reason, CO, HC, particulate and NOx must be reduced and the technique of combustion analysis need. This study aims to compare heat release by ensemble average of the existing method .with a consequence get by least squares method for pressure data. This paper proposes heat release computation method that can analyze combustion phenomenon of close the most truth straight, simple.<br/> In conclusion, we found that the least squares method of third-order fits computational method of heat release very well.<br/>