• 한국분무공학회지
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• 제2권2호
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• pp.8-15
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• 1997

Combustion chamber systems using spray impinged on walls have been studied for improving combustion characteristics in high speed direct injection diesel engines. The fuel spray injected in a small combustion chamber may be easily impinged and deposited on the wall. The fuel deposit has been considered as the cause for unburned emission due to difficulty of fuel-air mixing. In this paper w-shaped combustion chamber which has four raised pips on the side wall is introduced and discussed by comparing with conventional chamber with no pips. The computer code employing new spray-wall interaction model in general non-orthogonal grids is used in here. The model is applied into the new chamber shape with raised pips. In this chamber system four-hole nozzle is used, and the sprays injected from the each hole impact on lands raised from the chamber wall surface. After impacting, the sprays break up into much smaller drops and distribute over all the chamber space, instead of distributing just near the wall surface in conventional omega-shape. The results showed the potential of the w-shaped chamber employing pips for dispersing droplets so as tn avoid the fuel deposit regions.

• 한국분무공학회지
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• 제22권1호
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• pp.8-12
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• 2017

Recently, manufacture and sales of passenger car with GDI (Gasoline Direct injection) were dramatically increased in Korea. In this study, investigation on the exhaust emission characteristics of GDI vehicles according to mileage were conducted by using chassis dynamometer and emission analyzer. Test cars selected 5 types with G4FD engine (1600 cc) and emissions of total 14 vehicles analyzed. Measurement and evaluation on emissions (CO, NOx, NMOG, $CO_2$) characteristics of GDI vehicles with mileages from 40,000 to 80,000 km in certification driving cycle (CVS-75) were carried out in this study. It is revealed that emission results of all test cars shows below emission standard, NMOG emission value of about 80,000 km doubled that of 40,000 km and emission increased by accumulated mileage. Also, increasing pattern of NOx emissions shows when the vehicle mileages was increased and $CO_2$ emission increasing trend obviously do not show according to mileages.

• 대한기계학회논문집B
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• 제25권2호
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• pp.187-194
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• 2001

Spray impingement and fuel film formation models were developed and incorporated into the computational fluid dynamics code. STAR-CD. The spray/wall interaction process was modeled by considering the change of behaviour with surface temperature conditions and the fuel film formation. We divided the behaviour of fuel droplets after impingement into rebound, spread and splash using the Weber number and the parameter K. The Spray impingement model accounts for mass conservation, energy conservation and heat transfer to the impinging droplets. The fuel film formation model was developed by integrating the continuity, Navier-Stokes and energy equations along the direction of fuel film thickness. Validation of the models was conducted using previous diesel spray experimental data and the present experimental results for the gasoline spray impingement. In all the cases, the prediction compared reasonably well with the experimental results. The spray impingement and fuel film formation models have been applied to the spray/wall impingement in high speed direct injection diesel engines.

• International Journal of Automotive Technology
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• 제7권3호
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• pp.237-244
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• 2006

Limited and nonlimited emissions of scooters were analysed during several annual research programs of the Swiss Agency of Environment Forests and Landscape(SAEFL, BUWAL). Small scooters, which are very much used in the congested centers of several cities are a remarkable source of air pollution. Therefore every effort to reduce the emissions is an important contribution to improve the air quality in urban centers. In the present work detailed investigations of particle emissions of different 2-stroke scooters with direct injection and with carburetor were performed. The nanoparticulate emissions with different lube oils and fuels were measured by means of SMPS, (CPC) and NanoMet. Also the particle mass emission(PM) was measured with the same method as for Diesel engines. It can be stated, that the oil and fuel quality have a considerable influence on the particle emissions, which are mainly oil condensates. The engine technology influences the (nano)particle emissions by: mixture preparation, mixture tuning, oil consumption, postoxidation, quality, condition and temperature of the catalyst. Since the particulate emission of the 2-S consists mainly of lube oil condensates the minimization of oil consumption stays always an important goal.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.981-984
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• 2011

에틸렌 연료의 이중모드 스크램제트 연소기에서 연소와 충격파 열 발생의 과도 과정을 고해상도 기법을 이용하여 수치적으로 연구하였다. 연료 분사 이후 질량 공급에 의한 아음속 유동 감속을 위하여 연소기 확장부에 조절용 공기를 공급한다. 공기와 연료가 충분히 혼합된 수 ms 이후 점화가 이루어지며, 압력 상승은 격리부에 흡입구 노즐까지 전진하는 충격파 열을 형성한다. 이후 후방 공기공급을 중단하면 배출 과정이 진행되면서 후방 공기 공급 이전 상태로 서서히 복원된다. 본 연구의 결과는 이중모드 스크램제트 연소기에서 작동 영역과 특징의 이해를 돕는 상세 과정을 보여주었다.

• 대한기계학회논문집B
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• 제36권7호
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• pp.737-744
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• 2012

차량에 의한 대기오염을 실제 주행 조건에서 시간과 공간에 구애받지 않고 실시간으로 측정하기 위하여 이동형 배출가스 측정장치(MEL)가 제작되었다. 미니밴 차량에 CO, NOx, $CO_2$와 같은 배출가스 측정 장비와 입자의 수농도 및 입경별 개수농도 분포 측정을 위한 FMPS, CPC가 탑재되었다. 차량 전단에 장착되는 흡입 샘플링 포트를 사용하여 여러 종류의 차량 추적 실험을 수행하였다. 본 연구에서는 MEL의 상세 사양 및 이를 이용하여 디젤 및 가솔린 연료를 사용하는 승용차량들을 추적 실험한 결과를 나타내었다. 디젤 차량에서 배출되는 입자의 수농도는 가솔린 차량에서 배출되는 입자의 수농도보다 높았으며 다량의 극미세입자를 포함하고 있었다. 하지만, 직접분사식 가솔린 차량은 DPF가 장착된 디젤 차량에 비하여 50 nm 이상의 입경 영역에서 입자의 농도가 높은 경향을 보였다.

• 대한기계학회논문집B
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• 제25권10호
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• pp.1303-1310
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• 2001

In order to be applicable to the combustion modelling of stratified charged combustion like that of - lean burn and GDI engine, the correlations of laminar burring velocities fur several hydrocarbon fuels and methanol are needed over a wide range of equivalence ratio, pressure and temperature. In this study, these correlations are modeled in the 1311owing form based on the experimental and Muller\`s modeling results for several fuels, where $\alpha$, ξ, and ξ are functions of pressure and temperature, $S_{L}$ =$\alpha$ exp[-ξ($\Phi$-$\Phi$$_{m}$)$^{2}$ -exp {-ζ($\Phi$-$\Phi$$_{m}$)}-ζ($\Phi$-$\Phi$$_{m}$)]. By using the results calculated by PREMIX code with Sloane\`s detailed chemical reaction mechanism for propane, it is verified that the coefficients of the abode modeling can be determined by considering laminar burning velocity data only in a range of equivalence ratio less than $\Phi$$_{m}$. Therefore, Muller\`s modeling results can be adopted leer modeling of the pressure and temperature dependency. Compared with the results of the existing Keck'and Gulder's models, those of the present one showed the good agreement of the recent experimental data, especially in the range of lean and rich sides.s.des.s.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.38-45
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• 2004

This paper studies the effects of intake port configuration on the swirl that is key parameter in the flow field of direct injection diesel engines. In-cylinder flow characteristics is known to have significant effects on fuel air mixing, combustion and emissions. To investigate the swirl flow generated by various intake ports, steady state flow tests were conducted to evaluate the swirl. Helical port geometry, SCV shape and bypass were selected as the design parameters to increase the swirl flow and parametric study was performed to choose the optimal port shape that would generate a high swirl ratio efficiently. The results revealed that a key factor in generating a high swirl ratio was to suitably control the direction of the intake air flow passing through the valve seat. For these purposes, we changed the distance of helical and tangential port as well as installed bypass near the valve seat and the effects of intake port geometry on in-cylinder flow field were visualized by a laser sheet visualization method. From the experimental results, we found that the swirl ratio and mass flow rate had a trade off relation. In addition, the result indicates that the bypass is a effective method to increase the swirl ratio without sacrificing mass flow rate.

• 대한기계학회논문집B
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• 제36권2호
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• pp.217-224
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• 2012

비도로용 차량의 경우 대부분 디젤엔진을 사용하여 엔진의 특성상 PM과 NOx의 배출이 많은 단점이 있다. 승용 및 상용 디젤 차량의 경우 CRDI 및 후처리 장치를 적용하였고 후처리 장치로 DOC/DPF를 장착함으로써 PM은 약 90% 이상 저감 가능하다. 상반관계인 NOx는 EGR 사용을 통해 1차적으로 NOx 배출량을 감소시키고 LNT, LNC, Urea-SCR 등의 DeNOx 시스템으로 NOx의 배출량을 보다 현저히 저감시켜 배기규제를 만족시키고 있다. 본 연구에서는 tier 4 interim 배기규제를 만족하기 위해 56kW급 오프로드 차량으로 연구를 진행하였다. NOx의 감소를 위해 WGT와 전자 제어방식의 HPL EGR 시스템을 적용하였고 CO와 THC, PM 배출가스를 줄이기 위해 DOC와 DPF를 사용하였다. EGR 시스템을 적용하기 위해 각 조건에 대한 기본 실험을 실시하여 EGR map을 작성하였다. 작성된 map을 NRTC 모드에서 시험하여 map의 적용성을 검증하고 tier 4 interim 배기규제 만족여부를 파악하였다.