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[디젤엔진부문] 분사기공형상이 디젤 분무특성에 미치는 영향
공장식(Jangsik Kong),유준(Jun Yu),배충식(Choongsik Bae) 한국자동차공학회 2001 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2001 No.11_1
Spray characteristics of fuel injection system is one of the most important factors in combustion and emission control, especially in HSDJ (High Speed Direct Injection) diesel engine where interval between burning and evaporation of atomized fuel is relatively short. An investigation into spray characteristics obtained from different geometric hole shapes of VCO (Valve Covered Orifice) nozzles was performed. General spray characteristics were evaluated as a function of factor representing the taper ratio of the injector hole of the injector using spray images frozen by a CCD camera incorporating a strobo light Macroscopic spray visualization showed that tapered nozzle hole with higher K factor resulted in faster penetration, especially at lower ambient pressure, and smaller spray angle.
승용디젤엔진에서 연소실 형상 변화에 따른 성능 및 배기 특성
공장식(Jangsik Kong),배충식(Choongsik Bae),김장헌(Jangheon Kim),조성환(Sunghwan Cho) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The main objective of this study is to investigate the effect of aspect ratio of combustion bowl. The aspect ratio is defined as the ratio of a torus diameter to a depth. In order to understand the effect of the aspect ratio on engine performance and emissions, four piston bowls with different aspect ratios were tested. The experiments were carried out on a single cylinder direct injection diesel engine equipped with a high pressure common-rail injection system. Engine power output, emissions and cylinder pressure were obtained and analyzed. Tests were performed at various injection timings with 7-hole injector under medium load and speed conditions. Also, different protrusions and injection angles of injectors were tested. Optimized aspect ratio of combustion bowl, injector protrusion and injection angle was sought to reduce the particulate emission and to improve the power output.
분사기공형상이 HSDI 디젤 엔진의 성능과 배기에 미치는 영향
공장식(Jangsik Kong),국상훈(Sanghoon Kook),이승원(Seungwon Lee),최욱(Wook Choi),배충식(Choongsik Bae) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In the study, the influence of nozzle hole geometry, rail pressure and injection timing on combustion was analyzed in an optical access single-cylinder diesel engine equipped with a high pressure common-rail injection system. The K factor represents the taper ratio of the nozzle hole of the injector. The injection rate showed that tapered nozzle hole with bigger K factor result in a higher injection speed. A tapered nozzle produced some favorable results; a greater heat release and decreased THC (Total Hydrocarbon) and PM (Particulate Matter), despite an increase in NOx (Nitrogen Oxides) level.
커먼레일시스템의 비증발 디젤 분무에서 분사율과 주변기체의 압력에 따른 주변기체 유입
공장식(Jangsik Kong),강진석(Jinsuk Kang),배충식(Choongsik Bae) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Entrainment of ambient gas is a crucial characteristics of transient diesel spray. Recently, it was found that the mass flow rate of ambient gas into transient diesel spray increased with the distance from the nozzle, i.e., axial momentum flow rate of entrained gas increased along spray axis. This tendency is different from the turbulent jet whose momentum flow rate is independent from axial positions.<br/> To understand more detailed spray behaviors, it is necessary to quantify the entrainment characteristics of transient diesel sprays under realistic injection and ambient conditions In this study, measured was the entrained velocity of ambient gas into a diesel spray with LDV (Laser Doppler Velocimetry) technlmique. Non-evaporating transient diesel sprays from a common-rail injection system with triangular injection rate profile were observed. The effects of ambient gas density and nozzle hole geometry were assessed with entrainment coefficient.<br/> There appeared a region where entrainment coefficients were remaining almost constant after onset of entrainment while iIjection rates were changing The effect of common-rail pressure, which altered the slope of injection rate curve, was hardly noticed at this region. Entrainment coefficient increased with ambient gas density, that is, the effect of ambient gas density on entrainment of transient diesel spray is larger than that of turbulent jet whose entrainment coefficient remains constant.<br/> Non-dimensional distance was defined to reflect the effect of nozzle hole diameter and ambient gas density together. Mean value of entrnainment coefficient was found to increase with non-dimensional distance from the nozzle.<br/>
소형 디젤 엔진에서 파일럿 분사 및 배기 가스 재순환이 부분 예혼합 압축 착화 연소에 미치는 영향
박영수(Youngsoo Park),공장식(Jangsik Kong),배충식(Choongsik Bae) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
The effect of pilot injection and EGR on the partially PCCI combustion was investigated in a single-cylinder small diesel engine under low load and low speed condition. The injection timing of partially PCCI combustion has been fixed 20 ~ 30 CA BTDC based on the information of ignition delay and CA 10 point. It was found that EGR was effective to decrease negative work during the compression stroke. Therefore IMEP increased as EGR rate increased to certain threshold point. The NOx emission could be also reduced by applying EGR due to decreased combustion temperature. The effect of pilot injection was also explored. The pilot injection was effective to reduce wall wetting of fuel under certain conditions including split ratio and dwell time, so the level of UHC emission was reduced compared with the case of single injection. Consequently, IMEP and emissions characteristics could be improved by adopting EGR and pilot injection.
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.
예혼합 압축착화 디젤 엔진에서 압축비, 운전속도 및 분사시기에 따른 혼합기 및 연소 특성
박세익(Seik Park),국상훈(Sanghoon Kook),공장식(Jangsik Kong),배충식(Choongsik Bae) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The application of early diesel injection for near-homogeneously premixed charge has been tested in the single-cylinder engine. HCCI engine combustion has been investigated with the variety of engine operating parameters e.g. compression ratio, engine speed and, injection timing. Low compression ratio (14.8) with the advanced injection timing earlier than 50℃A BTDC was applied for achieving well-mixed charge and appropriate combustion phasing. The variation of injection timings were tested for two different engine speed (800 and 1200 rpm) and the results showed that 6.2 ms of ignition delay was required to reduce engine-out NOx emissions to negligible level regardless of engine speed. A sudden increase of power-output was captured at around injection timing=70℃A BTDC. A visualization of the spray explained that the power-output was high due to the increased air utilization by the spray directing the bowl-lip area resulting in improved mixture preparation and combustion efficiency.
고압 가솔린/디젤, 액상 LPG 분사의 저온 연료분무 특성
최재준(Jaejoon Choi),이석환(Seokhwan Lee),최동석(Dongseok Choi),공장식(Jangsik Kong),강진석(Jinsuk Kang),배충식(Choongsik Bae) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_1
Engine emission during cold start below zero temperature condition is one of the issues as the emission emitted during that period covers 80% of the total emission for passenger cars. Spray characteristics(vaporization, atomization and penetration) in the low temperature condition is, therefore, important as they affect engine combustion followed by engine-out emission.<br/> A wide range of injectors were tested and characterized. Spray characteristics were evaluated in two typical temperatures( 15°C and -10°C). Spray characteristics with the DISI and HSDI injectors seemed to be independent on temperatures selected in the reported work while LPG injector exhibited the growth of the liquid droplet size and the increase of liquid penetration to lead a difference of engine combustion condition and engine-out emission.