Simsoo Park

Effect of the mixture preparation on the nanoparticle characteristics of gasoline direct-injection vehicles

Time-resolved nanoparticle number concentrations and size distribution characteristics were investigated in gasoline direct-injection vehicles, according to fuel preparation methods. Particle number emissions were measured using the golden particle measurement system recommended by the Particle Measurement Programme, and the particle size spectrum was determined using a DMS500 spectrometer installed at the tailpipe of the vehicles. The wall-guided gasoline direct-injection vehicle exhibited the most temperature-dependent nanoparticulate matter exhaust characteristics, owing to direct accumulation of fuel on the piston head and cylinder liner and a high concentration of accumulation mode particles. The air-guided gasoline direct-injection vehicle emitted particle emissions mostly during cold transient driving conditions and high acceleration, which had a weak trimodal characteristic with evenly distributed nucleation and accumulation mode particles. The spray-guided gasoline direct-injection vehicle continuously discharged 105 particles/cm3 during constant-speed driving segments, because of the ultra-lean-burn operation and bulk quenching; particulate matter from the spray-guided gasoline direct-injection vehicle demonstrated a strong bimodal characteristic, spreading over 10–100 nm. The particle number emissions for the gasoline direct-injection vehicles for the New European Driving Cycle test mode were 1.48 × 1012 particles/km, 6.03 × 1011 particles/km and 3.17 × 1012 particles/km for the wall-guided type, the air-guided type and the spray-guided type respectively, and none of these were able to satisfy the proposed particle number regulations for the Euro 6 standard. For gasoline direct-injection vehicles, it should be considered that engine hardware modifications, as well as energy management system calibrations and even the application of the particle filter, may be needed to meet the upcoming particulate matter number regulation.

Experimental study of particle emission characteristics of a heavy-duty diesel engine and effects of after-treatment systems: Selective catalytic reduction, diesel particulate filter, and diesel particulate and NOx reduction

This investigation focused on the particle emission characteristics of a heavy-duty diesel engine and the effects of after-treatment systems such as diesel particulate filter and selective catalytic reduction. The test engine was operated on the worldwide harmonized transient cycle mode, which is a new transient cycle for Euro 6, and the conventional European transient cycle mode. Four combinations of after-treatment systems, engine-out, selective catalytic reduction, diesel particulate filter, and diesel particulate and nitrogen oxide reduction, were evaluated for the transient cycles, respectively. The whole test procedure, as part of the Korea particulate measurement programme and the inter laboratory correlation exercise for domestic heavy-duty diesel engines, complied with the recommended method of particulate measurement programme. The particles that were extracted through the golden particle measurement system the constant volume sampler tunnel consisted of solid particles like carbonaceous fraction, metal ash, etc. The particles emitted from the tail-pipe, as analyzed by the differential mobility spectrometer, included volatile or soluble particles like sulphate fraction, nitrate fraction, and organic fraction. The test results showed that the particle number and size distribution depended on the catalytic activity or filtration efficiency of the after-treatment system. Compared to the accumulation mode, the nucleation mode was easily caught or oxidized by the after-treatment system. Additionally, the nucleation mode was sharply increased by excessive ammonia injection because nitrogen dioxide-assisted diesel particulate filter regeneration resulted in reduced conversion efficiency of the selective catalytic reduction.

An experimental study of the effects of combustion systems and fuel properties on the performance of a diesel engine

Abstract This paper investigates the effects of combustion system and fuel properties on spray, mixture formation, combustion process, and emissions, using a constant volume chamber and single- cylinder engine. In a combustion system, high-pressure injection, exhaust gas recirculation (EGR), and impingement spray are applied while visualizing and analysing exhaust gas. Also, light diesel fuel, which has approximately the same cetane value as the diesel but has low values of PAHs, boiling point, density, viscosity, and surface tension, were used. Spray and combustion images were taken using a high-speed video camera and analysed by their penetration and evaporation characteristics in comparison with current diesel fuel. The results showed that the mixture formation of the high- pressure injection, impingement spray, and light diesel fuel is faster than that of diesel fuel, depending on physical properties. In the engine test, a considerable reduction of smoke emission was observed using the high-pressure injection with supercharging, due to the enhanced fuel atomization and air entrainment. In addition, a high reduction of NOx emission can be achieved with a high EGR rate, and with supercharging can achieve a reduction of NOx emission without deteriorating BSFC.

Study of regulated emissions and nanoparticle characteristics of light-duty direct-injection vehicles fuelled with gasoline and liquefied petroleum gas in the New European Driving Cycle and the Federal Test Procedure 75 driving cycle

This study evaluated the pollutants and nanoparticles, the fuel economy and the levels of carbon dioxide emissions of vehicles equipped with a 1.6 l direct-injection spark ignition engine fuelled by gasoline or by liquefied petroleum gas. The nanoparticles were analysed using a particle measurement system that is used in Europe for regulatory purposes. A fast-response particle size and number spectrometer (model DMS500) were used to characterize the size-resolved particle distributions. The vehicle was tested on a chassis dynamometer for the New European Driving Cycle and Federal Test Procedure 75 in its factory default state (gasoline version) and modified state (for liquefied petroleum gas fuel), and the results were compared. The liquefied-petroleum-gas direct-injection vehicle emitted significantly lower levels of total hydrocarbons than did the gasoline direct-injection vehicle. However, the levels of nitrogen oxide emissions from the liquefied-petroleum-gas direct-injection vehicle were equivalent to those from the gasoline direct-injection vehicle. Because of the higher combustion and exhaust temperatures and relatively higher loads imposed during the driving cycles, the liquefied-petroleum-gas direct-injection vehicle showed a slightly higher level of nitrogen oxide emissions. The particle emissions from the vehicles were mainly affected by the vehicle driving conditions of the test driving cycles. In particular, the particle emissions from the vehicle were pronounced in the cold-start and accelerating phases of the emission certification standards. The nanoparticles from the liquefied-petroleum-gas direct-injection vehicle were significantly fewer in number, exhibiting a reduction of over 99%.

Effect of EGR Rate and Injection Timing on the Characteristics of Exhaust Emissions in Light-duty Diesel Engine

Abstract : Cooled EGR system is widely used to reduce NOx emissions in diesel engine. But when EGR rate was increased, combustion stability was worsened and PM level was increased. So determining optimized control point of EGR rate is important. In order to determine this point, it is important to figure out the effect of EGR system on the exhaust emissions. In this research, NOx and PM emissions were analyzed with various coolant temperature supplied to the EGR cooler at several positions such as downstream of turbocharger, upstream and downstream of DPF. Effects of some variables such as EGR rate, hot / cooled EGR and change of injection timing were estimated. And CO 2 emissions were measured at exhaust and intake manifold to calculate EGR rate at each engine operating condition. Also combustion analysis was performed in each engine operating conditions. In the result of this study, there was trade-off between NOx emissions and PM emissions. When EGR rate was increased, combustion pressure was decreased and COV of IMEP was increased.

Numerical simulation to control rotary-kiln incineration of municipal solid waste

A heat-transfer model has been developed for rotary-kiln incineration of municipal solid waste. Using this model, the transient response of the incinerator system was calculated when the system operated with and without control logic for automatic operation. The kiln-outlet gas temperature and the boiler steam pressure may be controlled by adjusting the flow rate of combustion air and the waste-charging rate when the heating value of waste varies irregularly. Our analysis indicates that the maximum variations of the kiln-outlet gas temperature and boiler steam pressure are reduced to 5 and 33%, respectively, when the system is operated with the control logic.

Predictions of pressure drop for modified power law fluids in conduits of three different cross-sectional shapes

Abstract Numerical solutions are presented for fully developed laminar flow for a modified power law fluid (MPL) in conduits of arbitrary cross sections. The solutions are applicable to pseudoplastic fluids over a wide shear rate range from Newtonian behavior at low shear rates, through a transition region, to power law behavior at higher shear rates. The analysis identified a dimensionless shear rate parameter which, for a given set of operating conditions, specifies where in the shear rate range a particular system is operating, i.e. in the Newtonian, transition, or power law regions. The numerical results of the friction factor times Reynolds number for the Newtonian and power law region are compared with previously published results showing agreement within 0.05% in the Newtonian region, and 0.9% and 5.1% in the power law region.

Investigation of the nitrogen oxide reduction characteristics and in-cylinder controls of the regeneration mode of a lean nitrogen oxide trap catalyst in a light-duty diesel engine:

This investigation focused on an in-cylinder control method to create a rich atmosphere inside a lean nitrogen oxide trap catalyst. The experimental procedures can be summarized as follows. To adjust to the excess air ratio λ values of 0.92 and 0.96, the air mass was fixed using a limited post-injection quantity from an engine management system, the main injection timing was slightly adjusted to create a rich atmosphere inside a lean nitrogen oxide trap catalyst in advance and the precise λ values were adjusted by regulating the post-injection timing together with the post-injection quantity calculated using the logic of the engine control unit. The results were as follows. First, the main-injection quantity was greatly reduced when a post-injection quantity was supplied. Second, it was verified that the post-injection quantity participated in generating the torque. Third, the overall efficiency was 26–63% and included a storage efficiency of 11–51%, a reduction efficiency of 56–89% and a conversion efficiency of 11–50%. Fourth, to control the lean nitrogen oxide trap catalyst temperature and its performance precisely using a small λ value, which was caused by the post-injection quantity, as the speed (r/min) increased, the air mass supply must be increased more during the rich mode than during the lean mode.

Dependence of nanoparticle and combustion characteristics of gasoline direct injection engines on coolant temperature

이에 현재 시중에 판매되고 있는 GDI 차량 Key Words: GDI(가솔린직접분사), DMS(고속 PM 분석기), HFR-400(고속 THC 분석기), CLD-400(고속 NOx 분석기), THC(미연탄화수소), NOx(질소 산화물), PM(입자상 물질) 초록: 본 논문에서는 GDI 엔진의 냉각수 온도에 따른 연소 및 배출가스 특성을 연구하였다. 엔진에서 나오는 입자상 물질의 수와 크기 분포는 DMS-500 장비로 측정하였다. 배기포트 에 장착된 CLD-400 과 HFR-400 을 통해 NOx 및 THC 의 배출 특성을 연소주기 별로 측정하였다. 결과적으로 낮은 냉각수온에서 5~10 nm 의 입자상 물질이 크게 증가하는 특성을 보였다. THC 또한 낮은 냉각수온에서 증가하는 특성을 보였는데 이는 연소실 내 연료의 액막현상 때문이다. 그리고 NOx 는 높은 냉각수온에서 감소하는 특성을 보였는데 이는 내부 EGR 이 증가하기 때문이다. 결론적으로 THC 와 NOx 그리고 입자상 물질의 배출을 줄이기 위해서는 냉각수온을 빠르게 올리는 EMS 변수 설정 필요하다. Abstract: This paper investigated the combustion and exhaust gas characteristics of gasoline direct injection engines for various cooling water temperature. The engine-out nanoparticle emission number and size distribution were measured by a DMS-500 equipped upstream of the catalyst. A CLD-400 and an HFR-400 were equipped at the exhaust port to analyze the cyclic NOx and total hydrocarbon emission characteristics. The results showed that the nanoparticle emission number greatly increased at low coolant temperatures and that the exhaust mainly contained particulate matter of 5–10 nm. THC also increased under low temperature conditions because of fuel film on the combustion chamber. NOx emissions decreased under high temperature conditions because of the increase in internal exhaust gas recirculation. In conclusion, an engine management system control strategy for driving coolant temperature up rapidly is needed to reduce not only THC and NOx but also nanoparticle emissions.

Evaluation of the Time-Resolved Nanoparticle Emissions and the Vehicle Performance Characteristics for a Turbocharged Gasoline Direct-Injection Vehicle with a Metal-Foam Gasoline Particulate Filter

The nanoparticle emissions from gasoline direct-injection engines are of concern because of the high particle number concentrations compared with those from a gasoline port fuel injection engine. A gasoline particulate filter is a potential solution for reducing the particulate matter emissions. In this study, a 2.0 l turbocharged gasoline direct-injection vehicle with a metal-foam-type gasoline particulate filter was tested using the New European Driving Cycle and steady vehicle operating conditions. The particle number concentration, the particle-size distribution and the filtration efficiency were determined using a condensation particle counter and a fast response differential mobility spectrometer (DMS500). The particle number emissions (particle numbers per vehicle travelling distance (particles/km)) over the New European Driving Cycle were 1.95 × 1012 particles/km for a base vehicle equipped with a three-way catalytic converter and 5.68 × 1011 particles/km for the additional installation of a gasoline particulate filter on the base gasoline direct-injection vehicle. The filtration efficiency of the particle number and the particulate matter mass reached approximately 71% and 67% respectively. The nucleation-mode particles in the size range less than 23 nm for the gasoline direct-injection vehicle equipped with a three-way catalytic converter were further reduced on installation of a gasoline particulate filter at the downstream position of the three-way catalytic converter. A sharp pressure drop between the gasoline particulate filter of 21.0 mbar was obtained at a vehicle speed of 120 km/h in the New European Driving Cycle. The exhaust gas temperature before the gasoline particulate filter reached around 380–610 °C at steady vehicle speeds of 60–120 km/h. The installation of the gasoline particulate filter has the potential to satisfy the Euro 6c particle number emissions regulations for light-duty gasoline direct-injection vehicles.