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.

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.

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.

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.

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.

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.

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.

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.

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.

직접분사 성층 연소방식에서 수소의 첨가에 의한 연소성능의 개선

홍명석,하옥남 조선대학교 생산기술연구소 1995 生産技術硏究 Vol.17 No.1

The direct injection stratified charge (DISC) engine is considered to be an alternative to the conventional spark ignition engines. Its actual utilization is, however, prevented by high emission levels of unburned hydrocarbons during light load operation. Over-lean mixtures due to the long combustion duration and wall quenching due to these lean mixtures will be the main causes of unburned hydrocarbons in the DISC system. In order to solve this problem, small amount of hydrogen was added to the charging air or injected fuel. When hydrogen was added to the charge of air, the combustion pressure was increased and the unburned hydrocarbons was reduced with increasing the amount of hydrogen addition. In the case hydrogen was added to the fuel, the combustion pressure was more increased than the case that the same amount of hydrogen was added to the charge.