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저온 디젤 연소에서 스월비에 따른 CO 배출 및 연비 변화
국상훈(Sanghoon Kook),Paul C. Miles(Paul C. Miles),Michael Bergin(Michael Bergin),배충식(Choongsik Bae) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1
Engine-out CO emission was measured over a wide range of swirl ratios and injection timings on low-temperature diesel combustion regime in a small~bore single-cylinder diesel engine. Our previous work has shown that late-cycle mixing plays an important role even in so-called dilution-controlled low-temperature combustion systems. In this study. we employ multi-dimensional numerical simulation to characterize the flow structures and their impact on CO emissions. 65% exhaust gas recirculation is simulated with additional N₂ and CO₂, The CO emission shows optimal values at swirl ratio of 2.59 and limited ranges of injection timings. The numerical simulations show that the formed CO is trapped inside bowl at high swirl of 7.12. while CO is lifted out due to an enhanced reverse squish flow with a swirl ratio of 2.59. For a lower swirl ratio of 1.44, the existence of a single, large bulk flow structure limits the mixing process. The measured fuel conversion efficiency shows maximum value at low swirl ratio. The source of the maxima is clarified by the analysis of the work conversion efficiency, combustion efficiency, and heat transfer loss. Results show heat loss plays important role in determining the fuel conversion efficiency.
분사기 형상이 예혼합 압축착화 엔진 연소에 미치는 영향
국상훈(Sanghoon Kook),공장식(Jangsik Kong),이승원(Sengwon Lee),최욱(Wook Choi),배충식(Choongsik Bae) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The effect of injector geometries including the injection angle and number of nozzle holes has been investigated in a diesel-fueled homogeneous charge compression ignition (HCCI) engine. The HCCI engine has advantages of simultaneous reduction of PM and NOx emissions by achieving the spatially homogenous distribution of diesel and air mixture, which results in no fuel-rich zones and low combustion temperature. The wall-impingement of the diesel spray to the cylinder liner is a serious problem to achieve the homogeneous charge. It is because the injection timing should be extremely earlier than the conventional direct-injection (DI) diesel engine to achieve the homogeneous charge, so that the in-cylinder pressure and temperature is very low that results in longer spray penetration. A hole-type injector (5 holes) with small injection angle (100°) instead of conventional angle (150°) was applied to resolve this problem. The multi-hole injector (14 holes) was also tested to maximize the atomization of diesel. The macroscopic spray structure was visualized in a spray chamber, and the spray penetration was analyzed. Moreover, effect of injector geometries on the power output and exhaust gases was tested in a single-cylinder diesel engine. Results showed that the small injection angle minimizes the wall-impingement of diesel fuel that results in high power output and low PM emission. The multi-hole injector could not decrease the spray penetration at low in-cylinder pressure and temperature, but still showed the advantages in atomization and premixing.
커먼레일 시스템을 장착한 단긴통 예혼합압축착화 엔진의 Two-Stage 디젤 연료 분사법에 따른 연소 및 배기가스 특성
국상훈(Sanghoon Kook),박철웅(Cheolwoong Park),배충식(Choongsik Bae) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
A small size in-cylinder direct injection diesel engine is modified to operate in HCCI mode. The recent problem to realize a stable HCCI combustion is the need of high inlet air temperature to vaporize a diesel and to achieve a well premixed charge. This high inlet temperature makes lower thermal efficiency. This is the main reason why the Two-Stage injection strategy is applied to control combustion process without intake air heating. The first stage of injection is used as a main fuel injection while the injection timing is varied from BTDC 100˚ to BTDC 300˚ and the smaIl quantity of a diesel fuel is used for the second stage of injection as a pilot fuel while the injection timing is varied from BTDC 10˚ to IDC Also the effect of air-fuel(A/F) ratio is studied to promote the auto ignition.<br/> The experimental result shows the Two-Stage injection could be used as a diesel-fueled HCCI injection strategy when the first main injection timing is near the end of the intake stroke to achieve the highest lMEP and the second pilot injection timing is near TDC to achieve a premixed combustion only. If the second injection timing is advanced, heat release rate indicated the diffusion flame like Dl-Diesel engine. Compared to Dl-Diesel engine in the same lMEP value, HCCI engine result shows more than 80% NOx reduction but higher fuel consumption and more THC value.<br/>
커먼레일 분사 시스템을 장착한 직접 분사식 단기통 디젤 가시화엔진의 연소특성
국상훈(Sanghoon Kook),유준(jun Yu),박철옹(Cheolwoong Park),배충식(Choongsik Bae) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_1
An optical single cylinder diesel engine equipped with a common-rail injection system has been built to investigate diesel combustion and emission characteristics. Three optical widows (piston crown quartz for bottom view of the cylinder, upper piston quartz fur allowing laser sheet and liner quartz fur side view) have been placed in the optical engine to visualize spray characteristics and combustion process inside the cylinder. Before doing further research using various optical diagnostics with the optical engine, fundamental combustion experiments have been carried out with a wide range of engine operating conditions. The engine proved satisfactory; proper motoring in cylinder pressure, allowable low cycle by cycle variation during combustion, similar trend with previousIy published results for various engine operating conditions. The research with the optical engine will. therefore, be extended further with variety of optical and laser diagnostics.
흡기 가열에 따른 예혼합 압축착화 엔진의 연소 및 배기 특성
국상훈(Sanghoon Kook),박철웅(Cheolwoong Park),배충식(Choongsik Bae) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
A diesel-fueled homogeneous charge compression ignition (HCCI) combustion technique with the intake air preheating has been investigated in a single cylinder optical engine. Difficulty in vaporization of a diesel fuel is the main source of low power density of HCCI engine. The auxiliary heating of the intake air could be a solution of this problem. The fuel injection strategy was widely applied. First, the single injection was executed in an extremely early timing as the intake air temperature was varied. A two-stage injection strategy was also applied as the main injection to achieve premixing with air and the second injection to promote the ignition. The optimal timing of the main injection was suggested from the result of combustion images. The optimal second injection timing was also suggested with variation of an intake air temperature.<br/>