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.

정전탐침과 레이저 단층 촬영에 의한 예혼합 난류화염의 구조

홍명석,박용태 朝鮮大學校 機械技術硏究所 1998 機械技術硏究 Vol.1 No.1

The structure of premixed turbulent flames in a constant-volume vessel was investigated by using the electrostatic-probe method and the laser tomography. The eletrostatic-probe method, which perceives a flamelet by detecting its flame potential signal was used to measure the flame propagation speed, the thickness of flame zone and the number of existing flamelets. And the laser tomography was used to visualize the deeper structure of flames, where the laminar burning velocity and the turbulence intensity where varied independently. A laser sheet, 200 micrometers and 2.2cm wide, was passed through the turbulent flame, then 2-D cross section of the flame front was obtained by the intensity variation of the scattered light corresponding to the change in the gas density. As a result, at least on the 2-D cross section, reactant islands were found in a strong turbulence field.

스파크 점화 엔진의 냉간시동 중 탄화수소 배출의 시간분해 측정

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

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.

스파크 점화에 직접분사식 스파크 점화 성층 연소에 관한 연구

洪明錫,張完植 조선대학교 환경연구소 1993 環境公害硏究 Vol.10 No.-

The direct injection stratified charge engine is considered to be a alternative to conventional spark ignition engines. It has the favourable features of high thermal efficiency, low carbon monoxide and nitric oxide emission levels as well as multifuel capability. It has, however, the unfavourable feature of a high unburned hydrocarbon emission level, especially during light load operations. In this paper, fundamental studies on this system were carried out using a pancake type constant volume bomb. The effects of intensification of local premixing by tangential and radial fuel injection were examined experimentally. Unburned hydrocarbon emission levels with radial fuel injection were shown to be lower than those of tangential fuel injection cases. The stratification and mixing process of fuel jet and combustion process were observed by Schlieren photography.

直接噴射式 成層燃燒方式에서 未燃炭化水素의 低減

洪明錫,張完植 조선대학교 동력자원연구소 1993 動力資源硏究所誌 Vol.15 No.2

The direct-injection stratified-charge engine is considered to be a promising alternative to conventional spark-ignition engines. It has, however, an unfavourable feature of high unburned hydrocarbon emission levels, especially during light-load operations. In crjer to conquer this problem, the effects of intensification of local premixing of fuel with air on combustion process were investigated using a pancake type constant volume bomb. Considerable improvements in the maximum combustion pressure, combustion duration and the amount of unburned hydrocarbons were obtained in this study.

경부하 조건에서 SI 엔진의 배기시스템 내의 HC성분의 산화에 관한 연구

홍명석 조선대학교 에너지.자원신기술연구소 1999 에너지·자원신기술연구소 논문지 Vol.21 No.1

An exhaust gas quenching technique was used to study the relationship of the fuel type to both the evolution and the extent of oxidation of the HC species in the exhaust port/runner system of a SI engine a t light load condition. The fuel set consisted of gasoline, several alkanes(methane, ethane, propane, butane, iso-octane), an alkane(ethane), and an aromatic(to1uene). There are significant fuel-to-fuel differences in cylinder-out HC emissions, which ranged from ~500 ppm Cl(for ethene) to ~3350 ppm Cl(for toluene). There is no significant fuel dependence on the percentage of the cylinder-out HC oxidized in the exhaust port/runner system, which ranges form 35 to 45%. Most of the reduction of total HC during passage through the exhaust system occurs on the port, although the distribution of HC species changes throughout the port/runner system. A large portion of the runner-out HC emissions consists of the fuel species: the fuel fraction is ~80 to 95 % in methane, ethene and toluene, and ~40-70 % for the non-methane alkanes. For the latter, the dominant non-fuel species are alkanes with a carbon number lower than or equal to the fuel carbon number. Because of the much higher specific ozone reactivity, of the alkenes, the total HC reduction in the exhaust port/runner system is accompanied by an increase in reactivity which results in a smaller reduction in ozone reactivity for the alkane fuels than would be expected based on total HC emissions alone.

4행정 SI엔진의 연소효율에 대한 준평형 모델

홍명석,안철봉 조선대학교 동력자원연구소 1996 動力資源硏究所誌 Vol.18 No.2

A simple but accurate model for the combustion efficiency of 4-stroke homogemeous charge spark ignition engines has been developed based upon thermochemical equilibrium arguments. This model assumes that the combustion efficiency is a function of only the fuel-air equivalence ratio for hydrocarbon fules with a hydrogen-to-carbon ratio similar to that of iso-octane. This model was shown to accurately predict experimental data for ranges of compression ratio, load, ignition timing, and speed typical of the normal engine design and operation. The model slightly overpredicts the data for high than typical engine speeds and is not applicable to engines operating near the partial burn, ignition, or lean misfire limits. An example of the potential usefulness of this model is also briefly discussed.

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.

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.

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.