Sangil Kwon

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.

Variability in operation-based NOx emission factors with different test routes, and its effects on the real-driving emissions of light diesel vehicles

The objective of this study is to quantify the differences in NO(x) emissions between standard and non-standard driving and vehicle operating conditions, and to estimate by how much NO(x) emissions exceed the legislative emission limits under typical Korean road traffic conditions. Twelve Euro 3-5 light-duty diesel vehicles (LDDVs) manufactured in Korea were driven on a chassis dynamometer over the standard New European Driving Cycle (NEDC) and a representative Korean on-road driving cycle (KDC). NO(x) emissions, average speeds and accelerations were calculated for each 1-km trip segment, so called averaging windows. The results suggest that the NO(x) emissions of the tested vehicles are more susceptible to variations in the driving cycles than to those in the operating conditions. Even under comparable operating conditions, the NO(x) control capabilities of vehicles differ from each other, i.e., NO(x) control is weaker for the KDC than for the NEDC. The NO(x) emissions over the KDC for given vehicle operating conditions exceed those over the NEDC by more than a factor of 8. Consequently, on-road NO(x) emission factors are estimated here to exceed the Euro 5 emission limit by up to a factor of 8, 4 and 3 for typical Korean urban, rural, and motorway road traffic conditions, respectively. Our findings support the development of technical regulations for supplementary real-world emission tests for emission certification and the corresponding research actions taken by automotive industries.

Characteristics of on-road NOx emissions from Euro 6 light-duty diesel vehicles using a portable emissions measurement system

This paper presents the on-road nitrogen oxides (NOx) emissions measurements from Euro 6 light-duty diesel vehicles using a portable emissions measurement system on the predesigned test routes in the metropolitan area of Seoul, Korea. Six diesel vehicles were tested and the NOx emissions results were analyzed according to the driving routes, driving conditions, data analysis methods, and ambient temperatures. Total NOx emissions for route 1, which has higher driving severity than route 2, differed by -4-60% from those for route 2. The NOx emissions when the air conditioner (AC) was used were higher by 68% and 85%, on average, for routes 1 and 2, respectively, compared to when the AC was not used. The analytical results for NOx emissions by the moving averaging window method were higher by 2-31% compared to the power binning method. NOx emissions at lower ambient temperatures (0-5°C) were higher by 82-192% compared to those at higher ambient temperatures (15-20°C). This result shows that performance improvements of exhaust gas recirculation and the NOx after-treatment system will be needed at lower ambient temperatures.

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.

Characterization of particulate matter from diesel passenger cars tested on chassis dynamometers

Emission characterization of particle number as well as particle mass from three diesel passenger cars equipped with diesel particulate filter (DPF), diesel oxidation catalyst (DOC) and exhaust gas recirculation (EGR) under the vehicle driving cycles and regulatory cycle. Total particle number emissions (PNEs) decreased gradually during speed-up of vehicle from 17.3 to 97.3km/hr. As the average vehicle speed increases, the size-segregated peak of particle number concentration shifts to smaller size ranges of particles. The correlation analysis with various particulate components such as particle number concentration (PNC), ultrafine particle number concentration (UFPNC) and particulate matter (PM) mass was conducted to compare gaseous compounds (CO, CO2, HC and NOx). The UFPNC and PM were not only emitted highly in Seoul during severe traffic jam conditions, but also have good correlation with hydrocarbons and NOx influencing high potential on secondary aerosol generation. The effect of the dilution temperature on total PNC under the New European Driving Cycle (NEDC), was slightly higher than the dilution ratio. In addition, the nuclei mode (DP: ≤13nm) was confirmed to be more sensitive to the dilution temperature rather than other particle size ranges. Comparison with particle composition between vehicle speed cycles and regulatory cycle showed that sulfate was slightly increased at regulatory cycle, while other components were relatively similar. During cold start test, semivolatile nucleation particles were increased due to effect of cold environment. Research on particle formation dependent on dilution conditions of diesel passenger cars under the NEDC is important to verify impact on vehicular traffic and secondary aerosol formation in Seoul.

Combustion and emission characteristics of a gasoline–dimethyl ether dual-fuel engine

An experimental investigation was performed to investigate the effect of a split-injection strategy on the combustion and exhaust emission characteristics as well as on the particle number distribution for a single-cylinder compression ignition engine with gasoline–dimethyl ether dual fuelling. The gasoline–dimethyl ether dual-fuel injection system utilized port injection for gasoline and direct injection for dimethyl ether. In the present system, premixed fuel (i.e. gasoline) was injected into the premixing chamber at an injection pressure of 3 MPa using gasoline direct injection to mix the air–gasoline mixture sufficiently. However, dimethyl ether fuel was injected at an injection pressure of 50 MPa directly into a combustion chamber in order to control the combustion phase, resulting in a change in the direct-injection timing from −20° to +2° crank angle. The experimental results show that the gasoline–dimethyl ether dual-fuel engine exhibited benefits in the indicated mean effective pressure for early-injection cases (i.e. near −10° crank angle after top dead centre). However, the indicated mean effective pressure of the gasoline–dimethyl ether dual-fuel engine deteriorated for delayed-injection cases owing to incomplete combustion. In addition, a significant reduction in the nitrogen oxide emissions was observed using gasoline–dimethyl ether dual fuel compared with those obtained using conventional dimethyl ether combustion. In particular, soot emissions are almost at zero level for all the cases. On the other hand, hydrocarbon and carbon dioxide emissions increase with an increasing portion of premixed injection fuel (i.e. gasoline) in conventional injection timing, which is near top dead centre.

Data Evaluation Methods for Real Driving Emissions using Portable Emissions Measurement System(PEMS)

* Korea Automotive Technology Institute** Transportation Pollution Research Center, National Institute of Environmental Research*** Dept. of Energy System Engineering, Korea Nat’l Univ. of Transportation**** Dept. of Mechanical Convergence Engineering, Hanyang Univ. (Received June 11, 2015 ; Revised September 18, 2015 ; Accepted November 18, 2015)Key Words: Portable Emissions Measurement System(PEMS, 이동식 배기가스 측정장치), Real Driving Emissions(RDE, 실제도로 주행 배기가스), Moving Averaging Window(MAW, 이동평균구간), Weighted emissions(가중평균 배출량)초록: PEMS(Portable Emissions Measurement System)를 이용한 배기가스 시험절차는 소형 디젤자동차의 실제도로 배출가스를 효과적으로 제어하기 위한 수단으로 최근에 많은 주목을 받고 있으며, 현재의 배기가스 인증규제 시험절차의 제도적 보완장치로 2017년에 한국과 유럽에서 시행될 예정이다. 본 연구에서는 국내에 운행 중인 유로 5 소형 디젤자동차 4대에 대한 실제도로 NOx 배출량을 도심, 교외 및 자동차 전용도로에서 측정하였으며, 측정 결과를 이동평균구간 및 가중평균 배출량 방법으로 분석하였다. 시험 차량 및 주행경로에 대한 두 방법의 실제도로 NOx 배출량 분석결과는 유사한 경향을 갖는 것으로 나타났으며, 이동평균구간 분석방법의 경우 배출 허용기준을 1.8~8.5배, 가중평균 배출량은 허용기준을 2.0~10.6배 초과하는 것으로 분석되었다. 본 결과를 바탕으로 실도로 주행 조건에서 NOx 배출량 분석에 대한 기술적 토대를 확보하였고, 향후 배출가스 관리를 위한 정책적 기반 데이터로 활용가능하다.Abstract: Recently, an emission test procedure using a portable emissions measurement system(PEMS) has received much attention as an effective means of controlling real driving emissions from light-duty diesel vehicles. The PEMS-based test procedure will be implemented from 2017 in Europe and Korea as a complementary test procedure for certification and regulation. In the present study, on-road NOx emissions were measured for four kinds of Euro 5 Korean light-duty diesel vehicles under real driving conditions, including urban, rural, and motorway test routes. The real driving emission characteristics were evaluated using both a moving averaging window(MAW) and the weighted emission method(WEM). The evaluated NOx emission results (under real driving conditions) from the MAW and WEM showed similar tendencies for the test vehicles and routes, while exceeding the certification emission limit by 1.8~8.5 and 2.0~10.6 times, respectively.

A Study on the Characteristics of Simulated Real Driving Emissions by Using Random Driving Cycle

Abstract : This study was conducted in order to estimate the exhaust emissions analysis method of the real driving emission(RDE). The Association for Emissions Control by Catalyst(AECC) has developed a test procedure by using a random cycle method based on the chassis dynamometer. In order to confirm this approach in Korea, Euro 5(DPF), Euro 6(DPF + LNT), and Euro 6(DPF + SCR) were performed on three different vehicles to determine the exhaust gas characteristics of the random cycle, real-road driving test(PEMS), and emission certification driving mode(NEDC). Six different random cycle driving modes were generated by the vehicle specifications(e.g. curb weight, engine power, gear ratio, and maximum acceleration). The NOx emissions were increased in the NEDC, random cycle, and PEMS order in this study regardless of the test vehicles. The random cycle method has the advantage because it utilizes a chassis dynamometer in the laboratories for a repeatable data collection, and it allows any eminent emission improvement checked prior to a real-road driving test with PEMS.