성층희박연소 운전조건에서 분사압과 분사시기에 따른 분무유도식 직접분사 가솔린엔진의 연소특성

오희창(Hee Chang Oh),이민석(Min Seok Lee),박정서(Jung Seo Park),배충식(Choong sik Bae) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.10

단기통 직접분사 가솔린엔진의 성층연소 조건에서 연소실험을 수행하였다. 각 분사압조건마다 실화가 발생하지 않는 성층연소가능 분사시기영역이 존재하였으며 이는 혼합기 형성과정의 분위기압에 따른 영향으로 판단하였다. 연소효율은 분사시기를 지각할수록 증가하며 32~28 CAD BTDC에서 최대값을 갖고 이후 감소하는 경향을 보였고 분사압이 높을수록 높은 연소효율이 나타났다. 이러한 연소효율의 경향은 IMEP와 다른 경향을 보였으며 그 이유는 높은 연소효율 조건에서 연소상이 진각되어 음의 일이 증가하였기 때문으로 판단된다. Smoke의 배출은 분사시기가 지각됨에 따라 증가하였으며 높은 분위기 압에서 국부적으로 농후한 영역이 증가하였기 때문으로 생각된다. NOx 배출도 분사시기를 지각함에 따라 감소하였으며 연소상의 지각으로 최대 연소실압력과 온도가 감소하였기 때문으로 생각된다. In this study, single cylinder engine experiment was carried out to investigate combustion characteristics spray guided direct injection spark ignition engine. In the result of engine experiment , it was shown that flammable window of injection timing was existed. The combustion efficiency increased with retarding injection timing, reaching a peak value, subsequent to decrease again. These results were likely due to the effect of ambient pressure on stratified-premixed mixture preparation. 150 bar injection pressure condition and retarded injection timing from the best combustion efficiency injection timing showed the highest IMEP value due to the advanced combustion phase of the maximum combustion efficiency condition. HC emission showed same trend of combustion efficiency, and smoke emission was increased as injection timing was retarded due to the increased locally rich area in the high ambient pressure. NOx emission showed decreasing trend as injection timing was retarded. This is likely due to the maximum in-cylinder temperature was decreased with retarded combustion phase.

직접분사식 가솔린 엔진의 분사전략 변경 및 EGR 적용을 통한 배기저감에 관한 연구

박철웅(Cheol Woong Park),김홍석(Hong Suk Kim),우세종(Se Jong Woo),김용래(Yong Rae Kim) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.3

자동차배출가스는 이산화탄소(CO2 )에 의한 지구온난화 및 탄화수소(HC)와 질소산화물(NOx )에 의한 오존생성을 야기하는 등, 인체와 환경에 나쁜 영향을 미치기 때문에 이에 대한 관심이 증폭되고 있다. 가솔린 직접분사 (Gasoline Direct Injection; GDI)엔진은 디젤엔진과 같이 연소실내에 연료를 직접 공급하는 방식으로서 가솔린엔진의 취약점으로 지적되어 오던 높은 연료소비율 문제를 획기적으로 개선할 수 있는 기술로 평가되고 있다. 본 연구에서는 분무유도방식(Spray-guided type)의 GDI엔진을 이용하여 공기과잉률 2.0 이상의 초희박 연소를 통해 연료소비율을 개선하였다. 추가적인 연료소비율 개선 및 배출가스 저감을 위해 희박연소시 다단분사전략과 Exhaust Gas Recirculation (EGR)을 적용하였다. 배출가스 수준과 운전성능을 평가하고 이를 배출가스 규제와 비교·검토함으로써 국내 관련기술 개발 방향 및 상용화 가능성에 대해 검토하고자 하였다. Nowadays, automobile manufacturers are focusing on the reduction of exhaust-gas emissions because of the harmful effects on humans and the environment, such as global warming by greenhouse gases. Gasoline direct injection (GDI) combustion is a promising technology that can improve fuel economy significantly compared to conventional port fuel injection (PFI) gasoline engines. In the present study, ultra-lean combustion with an excess air ratio of over 2.0 is realized with a spray-guided-type GDI combustion system, so that the fuel consumption is improved by about 13%. The level of exhaust-gas emissions and the operation performance with the multiple injection strategy and exhaust-gas recirculation (EGR) are examined in comparison with the emission regulations and from the point of view of commercialization.

직접분사식 희박연소 LPG엔진에서 흡배기 밸브시기가 연소 및 배기특성에 미치는 영향

박철웅(Cheolwoong Park),김태영(Taeyoung Kim),조시현(Seehyoen Cho),오승묵(Seungmook Oh) 대한기계학회 2015 大韓機械學會論文集B Vol.39 No.1

최근 강화되는 연료소비율과 배기 규제에 대응하기 위해 자동차용 엔진에 다양한 신기술들이 적용되고 있다. 직접분사식 희박연소 엔진은 안정적인 성층혼합기 연소를 통해 연료소비율 및 배출가스 개선이 가능하지만 과잉공기 조건에서 상대적으로 높은 수준은 질소산화물의 배출은 해결되어야 할 과제이다. 본 연구에서는 직접분사식 희박연소 LPG 엔진에서 가변 밸브 기구를 이용한 흡기 및 배기밸브 시기의 변경이 엔진의 성능 및 배출가스에 미치는 영향을 파악하고자 하였다. 스로틀링을 하지 않은 부분부하 운전 조건에서 흡기밸브 열림 시기의 진각은 공기과잉률의 증가에 의한 질소산화물 배출 증가에 원인으로 작용하였다. 배기밸브 열림 시기를 진각할 경우 팽창일 감소와 펌핑손실 증가에 의해 연료소비율이 악화되었다. In order to meet the enforced emission regulations and reduce fuel consumption, various new technologies are employed in engines. The problem of NOx emissions under a lean mixture condition should be solved, because a lean-burn direct-injection engine can realize stable lean combustion with a stratified mixture, which results in improvements in fuel economy and emissions. This study investigated the effects of intake and exhaust valve timing changes on the performance and emission characteristics of a lean-burn LPG direct-injection engine. Under a partial-load operating condition without throttling, an increase in the intake valve opening led to an increase in NOx emissions due to an increase in the amount of excess air. The fuel consumption deteriorated with an increase in the exhaust valve opening due to a decrease in the expansion work and an increase in the pumping loss.

성층희박연소 운전조건에서 분사시기에 따른 분무유도식 직접분사 가솔린엔진의 분무 및 화염특성

오희창(Heechang Oh),이민석(Minsuk Lee),박정서(Jungseo Park),배충식(Choongsik Bae) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.3

분무유도식 DISI엔진의 성층연소운전조건에서 분무 및 화염특성에 대한 실험적 연구가 수행되었다. 연소가시화를 통하여 성층연소 DISI의 연소는 희박 예혼합 연소와 확산연소의 성격을 모두 가지고 있는 것으로 확인되었다. 분사시기에 따른 혼합기 형성특성이 연소의 특성을 결정하는 중요한 인자임을 관찰하였다. 분무와 혼합기 가시화를 통해 낮은 분위기압에서의 over-mixing , 높은 분위기압에서의 under-mixing이 발생하는 것을 확인하였으며 이러한 혼합기 형성과정의 결과에 따라 화염특성, 연소효율 등의 연소특성이 결정되는 것을 살펴볼 수 있었다. 또한, NOx, IMEP도 분사시기에 따른 경향성을 보였으며, 분사시기에 따른 연소상의 변화에 의한 영향임을 확인하였다. An experimental study was carried out to investigate the effects of the injection timing on the spray and combustion characteristics in a spray-guided direct-injection spark-ignition (DISI) engine under lean stratified operation. An in-cylinder pressure analysis, exhaust emissions measurement, and visualization of the spray and combustion were employed in this study. The combustion in a stratified DISI engine was found to have both lean premixed and diffusion controlled flame combustion characteristics. The injection timing condition corresponding to the stratified mixture characteristics was verified to be a dominant factor for these flame characteristics. For the early injection timing, a non-luminous blue flame and low combustion efficiency were observed as a result of the lean homogeneous mixture formation. On the other hand, a luminous sooting flame was shown at the late injection timing because of an under-mixed mixture formation. In addition, the smoke emission and incomplete combustion products were increased at the late injection timing as a result of the increased locally rich area. On the other hand, the NOx emissions decreased and IMEP increased as the injection timing retarded. The combustion phasing produced by the injection timing was verified as the reason for this observation.

라디칼 점화 부실 혼합형 CNG DI 엔진의 연소특성에 관한 기초연구

정성식,황성일,임춘미 한국동력기계공학회 2018 동력시스템공학회지 Vol.22 No.1

최근 폭스바겐사의 디젤차량 배출가스 조작 사건 이후 배기가스에 포함된 대표적인 오염물질인 질소산화물(NOx)과 미세먼지(PM)에 이목이 집중되고 있다. 가솔린과 디젤 연료를 고압으로 연소실에 직접분사하여 연소시키면 오히려 미세먼지 배출량이 증가하는 문제에 대한 해결책을 제안하고자 청정연료로 인정받고 있는 압축천연가스(CNG)를 직접분사 시스템에 적용하여 CNG의 연소에 최적한 변수를 도출하기 위한 기초연구를 수행하였다. 본 연구의 핵심은 부실 혼합형 개념의 엔진에 압축천연가스 착화기술(RI-CNG) 도입이다. 이전의 연소 사이클로 인한 잔여 가스를 배출하기 위해 부실에 직접 분사 시스템을 도입하였다. 또한, 연료분사시기와 공기과잉률의 변화에 점화시기를 정밀하게 설정함으로써 최적 혼합기 분포를 달성하였다.

성층희박연소 운전조건에서 분사압과 분사시기에 따른 분무유도식 직접분사 가솔린엔진의 연소특성

오희창(Heechang Oh),이민석(Minsuk Lee),배충식(Choongsik Bae) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

In this study, single cylinder engine experiment was carried out to investigate combustion characteristics spray guided direct injection spark ignition engine. In the result of engine experiment, it was shown that flammable window of injection timing was existed. The combustion efficiency increased with retarding EOI, reaching a peak value, subsequent to decrease again. These results were likely due to the effect of ambient pressure on stratified-premixed mixture preparation. 150 bar injection pressure condition and retarded injection timing from the best combustion efficiency injection timing showed the highest IMEP value due to the advanced combustion phase of the maximum combustion efficiency condition. HC emission showed same trend of combustion efficiency, and smoke emission was increased as injection timing was retarded due to the increased locally rich area in the high ambient pressure. NOx emission showed decreasing trend as injection timing was retarded. This is likely due to the maximum in-cylinder temperature was decreased with retarded combustion phase.

직접분사식 LPG 및 가솔린 엔진의 연소 및 배기특성 비교 연구

오승묵(Seungmook Oh),이석환(Seokhwan Lee),조준호(Junho Cho),차경옥(Kyoungok Cha) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11

Combustion and emission characteristics of LPG(Liquefied Petroleum Gas) and gasoline fuels were compared in a single cylinder engine with direct fuel injection. While fuel injection pressure and IMEP(indicated mean effective pressure) were varied with 60, 90, 120 bar and 2 to 10 bar, another parameters for the engine operation as engine speed, air excess, and fuel injection timing were fixed at 1500 rpm, 1.0, and BTDC 300 CA respectively. Experimental results show that MBT timing for LPG is less sensitive to IMEP, and its combustion stablility(COVIMEP) is also better than gasoline fuel. However, LPG is found that thermal efficiency has lower values a little due to increase of pumping loss by higher throttling inherently. Gasoline shows longer burn durations in the early stage of combustion(10% MBF), but when considering total burn duration(90% MBF) gasoline was shorter than LPG for over IMEP 7 bar. Hydrocarbon emissions of gasoline rise to a level of three-fold than those of LPG. In addition, nitric oxides has higher values for gasoline but carbon monoxide for both fuels shows similar level for all test conditions

직접 분사식 가솔린 엔진에서의 입자상 물질을 포함한 배기 수준 시뮬레이션에 관한 연구

김주한(Joohan Kim),김규진(Gyujin Kim),고인석(Insuk Ko),문선영(Sunyoung Moon),민경덕(Kyoungdoug Min) 한국자동차공학회 2014 한국자동차공학회 부문종합 학술대회 Vol.2014 No.5

직접분사엔진의 분사압력 변화에 따른 유동장 및 분무특성에 대한 수치해석적 연구

양희천,정연태,유홍선 대한기계학회 1993 대한기계학회논문집 Vol.17 No.9

Since the rate and completeness of combustion in direct injection engines were controlled by the characteristics of gas flow fields and sprays, an understanding of those was essential to the design of the direct injection engines. In this study the numerical simulations of injection pressure effects on the characteristics of gas flow fields and sprays were preformed using the spray model that could predict the interactions between gas fields and spray droplets. The governing equations were discretized by the finite volume method and the modified k-.epsilon. model which included the compressibility effects due to the compression/expansion of piston was used. The results of the numerical calculation of the spray characteristics in the quiescent environment were compared with the experimental data. There were good agreements between the results of calculation and the experimental data, except in the early stages of the spray. In the motoring condition, the results showed that a substantial air entrainment into the spray volume was emerged and hence the squish motion was relatively unimportant during the fuel injection periods. It was found that as the injection pressure increased, the evaporation rate of droplets was decreased due to the narrow width of spray and the increased number of droplets impinged on the bottom of the piston bowl.

직접분사식 가솔린엔진에서 피스톤 캐비티 형상이 연료 분무의 충돌과 거동에 미치는 영향

김동욱(Dongwook Kim),최경민(Gyungmin Choi),김덕줄(Duckjool Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

This study was carried out to investigate the effects of piston cavity geometry on the spatial and temporal development of injected fuel sprays in a DI gasoline engine. The impingement and behavior of impinged spray is affected the stratification of fuel mixture. Thus, it is informative to understand in detail the behavior and distribution of fuel mixture after impingement in the cavity. Two dimensional spray fluorescence images of liquid and vapor phase were acquired to analyze the behavior and distribution of fuel mixtures inside cylinder by exciplex fluorescence method. To clarify the wall effect of the piston cavity, cavity wall angle were set to 30, 60 and 90 degrees, respectively. The results show that In the case of 30 degrees, the rolling-up moved from the impinging location to the round and fuel-rich mixture distributed at periphery of cylinder. In the case of 60 and 90 degrees, the rolling-up recircurated and accumulated in the cavity and fuel mixtures concentrated at center region. High concentrated fuel vapor phase was observed in the cavity with 90 degrees. From present study, it was found that the desirable piston geometry affected the fuel mixture stratification in a DI gasoline engine.