EGR을 이용한 천연가스차량(NGV)의 배출물 저감에 관한 연구

홍명석 조선대학교 환경공해연구소 1999 環境公害硏究 Vol.15 No.2

CNG(compressed natural gas) is becoming the alternative fuel that appears to offer the most promise of success. NGVs are available as bifuel conversions and uses a high compression ratio to take advantage of the very high octane rating of CNG. The goal of this study was to develop a natural gas conversion technique that has superior performances in comparison to the gasoline version of this vehicle while producing low emission. But the difficulty is the emission control, especially for NOx. The solution to this problem is to use a high rate of EGR to control the peak temperature and a three-way catalyst for additional control of the emitted pollutants. This EGR system can be applied to any NGV that has been designed to control exact air/fuel ratio and adequate EGR rate.

이온 프로브법에 의한 예혼합 난류화염의 전파기구에 관한 연구

홍명석,하옥남,정낙규 조선대학교 동력자원연구소 1995 動力資源硏究所誌 Vol.17 No.1

A method using an ion probe to detect a flame by its plasma potential signal has been developed. The spatial resolution of the probe is demonstrated to be well improved over that of the conventional one. The plasma potential signal obtained by this method from a premixed propagating turbulent flamelet in the reaction zone of the flame. Based on this consideration, the propagating speed, the thickness of the reaction zone and number of flamelets in the zone, the separation distance between two adjacent flamelets, etc. of the flame, were then obtained. Results of this experiment suggest the existence of "reactant islands" in the reaction zone, and show that the averaged number of flamelets in the zone increases in the turbulence intensity and /or a decrease in the Damko¨hler number.

LDV에 의한 실린더 내부 유동의 속도분포 측정

홍명석,하옥남 조선대학교 동력자원연구소 1995 動力資源硏究所誌 Vol.17 No.1

Swirling flow in a motored engine with a bowl-in type piston was measured by Laser Doppler Velocimetry(LDV). Through the detailed measurements at several sections along the cylinder axis, flow characteristics in the piston bowl and squish area were revealed. Rising of swirl level occurs from the upper section near the bowl rim and propagates to the lower part decreasing its rising level. At the rising peak, swirl profile in the bowl shows the solid-body-rotation pattern. On the other hand, swirl in the squish area near TDC decreases rapidly to have a free-vortex-like profile. Although the periodic oscillation and uneven axial distribution of swirl are detected in the early compression stroke, the angular momentum averaged over measuring planes decays monotonously.

SI 엔진에서 Fractal Geometry를 이용한 난류 연소 모델

홍명석,손정배 조선대학교 에너지.자원신기술연구소 1998 에너지·자원신기술연구소 논문지 Vol.20 No.2

Use of fractal geometry to model the effects of turbulence on flame propagation in an engine is explored using a quasidimensional, 4-stroke, homogeneous charge, SI engine code. Various assumptions are made in the model formulation to allow this technique to be investigated as expeditiously as possible. Model predictions are compared to experimental data from an engine with an axisymmetric pancake-shaped combustion chamber. The sensitivity of the model predictions to the fractal dimension, to the effects of flame stretch, and to the ratio of maximum-to-minimum flame wrinkling scales is invested. It is shown that the predicted initial rate of pressure rise is a strong function of fractal dimension but is relatively insensitive to the flame wrinkling scales or the effects of stretch over the ranges of these parameters expected for the engine application. This model and a modification of this model appear to be reasonable and yield values for the fractal dimension which agree with the limited experimental engine data avaliable. It is shown that flame stretch is dominated by flame strain and decrease throughout the combustion process. By allowing the maximun flame wrinkling scale to be equal to the instantaneous flame radius, the correct trend of the turbulent flame speed is predicted. The model results that the use of fractals to model turbulent combustion is an important new tool for engineering design.

스파크 점화 엔진의 냉간시동 중 탄화수소 배출의 시간분해 측정

홍명석 조선대학교 환경연구소 1999 環境硏究 Vol.15 No.1

The effects of ignition timing and idle speed on the required starting enrichment, hydrocarbon emissions and exhaust temperature are explored. The measurements are focused upon the first 20 seconds of operation after starting with the engine and coolant initially at ambient temperature because this period has a major effect on HC emissions, decreasing cold start enrichment and decreasing the time to catalyst light-off are desirable. Increasing the idle speed is interest as a means to improve in-cylinder oxidation. Speciated HC emissions from the exhaust system of a production engine have been obtained with 3 second time resolution during cold start using two control strategies for the conventional cold start, the emissions were initially enriched in light fuel alkanes and depleted in heavy aromatic species. The light alkanes fell rapidly while the lower vapor pressure aromatics increased over a period of 50sec. These results indicate early retention of low vapor pressure fuel components in the atmospheric reactivity of the exhaust HC emissions for photochemical smog formation increases as the engine warms.

Hot Wall Epitaxy(HWE)법에 의한 CdGa₂Se₄ 단결정 박막 성장과 열처리 효과

홍명석,홍광준,Hong, Myung-Seok,Hong, Kwang-Joon 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.10

The stochiometric mix of evaporating materials for the $CdGa_2Se_4$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CdGa_2Se_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $630^{\circ}C$ and $420^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD).The carrier density and mobility of $CdGa_2Se_4$ single crystal thin films measured from Hall effect by van der Pauw method are $8.27{\times}10^{17}\;cm^{-3},\;345\;cm^2/V{\cdot}s$ at 293 K. respectively. The temperature dependence of the energy band gap of the $CdGa_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $Eg(T)\;=\;2.6400\;eV\;-\;(7.721{\times}10^{-4}\;eV/K)T^2/(T+399\;K)$. After the as-grown single crystal $CdGa_2Se_4$ thin films were annealed in Cd-, Se-, and Ga -atmospheres, the origin of point defects of single crystal $CdGa_2Se_4$ thin films has been investigated by PL at 10 K. The native defects of $V_{Cd}$, $V_{Se}$, $Cd_{int}$, and $Se_{int}$ obtained by PL measurements were classified as donors or accepters. We concluded that the heat-treatment in the Cd-atmosphere converted single crystal $CdGa_2Se_4$ thin films to an optical p-type. Also, we confirmed that Ga in $CdGa_2Se_4/GaAs$ did not form the native defects because Ga in single crystal $CdGa_2Se_4$ thin films existed in the form of stable bonds.

액화 LPG 다중분사 시스템을 가진 차량의 개발

홍명석,박용태,장원 조선대학교 환경공해연구소 1999 環境公害硏究 Vol.15 No.-

The two aspects of design are that we have developed a liquid-phase LPG port injection system and it includes a fuel rail pressure control system designed to solve the hot start difficulties associated with liquid-LPG injection. The injection and the spark timing are controlled by programmed electronic management unit. To achieve the goal of ULEV emission, the engine was operating in condition of stoichiometric fueling for all conditions, air/fuel ratio control around a slightly rich set point with closed-loop feedback from a heated oxygen sensor, ceramic-coated exhaust manifolds plus a close-coupled LPG specific catalyst for rapid catalyst light-off, and advantage of port injection system compare to upstream LPG addition. In this paper, we report the result that we can have more torque, fuel economy and drive ability than those of the production gasoline vehicle while having much lower emissions.

過飽和 氣-液 溶液內 가스氣泡 形成 理論

홍명석,하옥남,오율권 조선대학교 동력자원연구소 1985 動力資源硏究所誌 Vol.7 No.1

spontaneous bubble formation ay occurs, gas-liquid supersaturated solution at high pressure is rapidly decompressed. The nonequilibrium situation is created by suddenly reducing the pressure of a liquid which contains a large amount of dissolved gas, a nucleation theory for the formation of gas bubble is presented. For a given temperature, the theory predicts the amount of pressure reduction required for the massive bubble formation. Results form the theory show good agreement with experiments for various organic solution dissolved with nitrogen gas.

가솔린엔진의 냉간시동시 배기가스 포집과 재연소에 관한 연구

홍명석 朝鮮大學校 機械技術硏究所 2000 機械技術硏究 Vol.3 No.1

The emission characteristics of hydrocarbons during the cold start have been investigated. The measurements are focused upon the first 20 seconds of operation after starting with the engine and coolant initially at ambient temperature because this period has a major effect on HC emissions, over the FTP cycle, therefore decreasing cold start enrichment and decreasing the time to catalyst light-off are desirable. The engine examined is a 4-cylinder, 4-valve SI engine. The engine started using the starter motor. HC emissions from the exhaust system of the engine have been storaged over a period of 60 sec. during cold start using a exhaust gas storage system. Then the storaged gas was recombustioned at normal engine condition. These results indicate high reduction of engine emissions is available instead of very low torque loss using a storage bag and recombustion system.

액화 LPG 다중분사 시스템을 가진 차량의 개발

홍명석,박용태,장원 조선대학교 환경연구소 1999 環境硏究 Vol.15 No.1

The two aspects of design are that we have developed a liquid-phase LPG port injection system and it includes a fuel rail pressure control system designed to solve the hot start difficulties associated with liquid-LPG injection. The injection and the spark timing are controlled by programmed electronic management unit. To achieve the goal of ULEV emission, the engine was operating in condition of stoichiometric fueling for all conditions, air/fuel ratio control around a slightly rich set point with closed-loop feedback from a heated oxygen sensor, ceramic-coated exhaust manifolds plus a close-coupled LPG specific catalyst for rapid catalyst light-off and advantage of port injection system compare to upstream LPG addition. In this paper, we report the result that we can have more torque, fuel economy and drive ability than those of the production gasoline vehicle while having much lower emissions.