Sungwook Park

Characterization of the spray atomization process of a multi-hole gasoline direct injector based on measurements using a phase Doppler particle analyser

The main objective of this experimental study was to investigate the spray atomization process of a multi-hole gasoline direct injector by characterizing the basic process of single-jet atomization as well as complex phenomena such as air entrainment and jet interactions. We measured the droplet size and velocity using a phase Doppler particle analysis system at different measurement distances and different injection pressures in both the parallel direction and the orthogonal direction with respect to spray propagation. In addition, we calculated the Weber numbers to characterize further the spray atomization process. Our experimental results showed that the droplet velocities followed similar trends for different measurement distances but that the peak value decreased as the distance increased. Furthermore, a leading edge of the spray was observed at the initial stage of injection but disappeared as the measurement distance increased. Based on the droplet diameter distribution, we confirmed that increasing the distance and air entrainment had effects on the jet atomization process. Air entrainment was seen at the edges of both sides of the jet when the droplet diameter was less than 23 µm and the droplet was travelling at a low velocity, and the spray atomization process was more activated under air entrainment conditions. A comparison of different injection pressures confirmed that the injection pressure plays an important role in droplet break-up.

Dosimetry calculations for internal electron sources using a Korean reference adult stylised phantom

Absorbed fractions (AFs) and specific absorbed fractions (SAFs) for internally deposited electron were calculated using a Korean reference adult stylised phantom, where a total of 15 internal organ volumes and external body dimension were designed to match average Korean adult male. The walls of oesophagus, stomach, colon and urinary bladder were additionally divided into the mucosal layer and residual wall to accommodate dose calculation for weakly penetrating electron. The mucosal wall thicknesses were determined by the data reported in the International Commission on Radiological Protection Publication 89 and other literature resources and by direct measurements. The Monte Carlo transport code MCNPX (version 2.5.0) was employed to calculate the electron energy deposited. The SAFs and AFs for monoenergetic electrons with the energies ranging from 10 keV to 2 MeV were calculated. The results were compared with those of the revised Oak Ridge National Laboratory phantoms and showed considerable differences up to 150% in SAFs, whereas no substantial differences were observed in the AFs.

Simultaneous reduction in the exhaust emissions by a high exhaust gas recirculation ratio in a dimethyl-ether-fuelled diesel engine at a low-load operating condition

The purpose of this study was to investigate the effect of the exhaust gas recirculation rate on the combustion and exhaust emission reduction characteristics of dimethyl ether fuel in a single-cylinder diesel engine. To investigate the effects on emission reduction, the test set-up was composed of a dimethyl ether supply system, a spray visualization system, an engine combustion system and an emissions analysis system. In this work, the spray visualization and exhaust emissions were measured using a high-speed camera with a metal halide lamp, a smoke meter and an emission gas analyser. The spray tip penetration and tip velocity of dimethyl ether fuel were lower than those of conventional diesel fuel. The reduction slope of the spray cone angle for dimethyl ether was less than that for diesel fuel owing to its low density and superior evaporation characteristics. The increase in the exhaust gas recirculation rate caused an extension of the ignition delay for dimethyl ether. During the extended ignition delay, the improved mixing characteristics influenced the slight decrease in the combustion period. An increase in the exhaust gas recirculation rate caused a significant reduction in the emission of nitrogen oxides. In addition, the soot emission was very low owing to the intrinsic characteristics of dimethyl ether (no direct carbon–carbon bonds). At the given equivalence ratio condition, the indicated specific hydrocarbon and indicated specific carbon monoxide emissions for dimethyl ether were extremely low when dimethyl ether spray was injected into the piston bowl (from 25° before top dead centre to top dead centre). Also, in this case, a change in the exhaust gas recirculation rate for dimethyl ether combustion had minimal effects on the indicated specific hydrocarbon and indicated specific carbon monoxide emissions. These results suggest that the use of high exhaust gas recirculation with dimethyl ether fuel can achieve near-zero exhaust emissions (nitrogen oxides, soot, hydrocarbons and carbon monoxide).

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.

Effect of the Fuel Injection Strategy on Diesel Particulate Filter Regeneration in a Single-Cylinder Diesel Engine

This research was supported by the Center for Environmentally Friendly Vehicle (CEFV) as a Global-Top Project of Ministry of Environment, Korea (KMOE).

Numerical and experimental study of combustion and emission characteristics in gasoline direct-injection compression ignition engines using intake preheating

This paper presents a numerical and experimental study of the combustion and emission characteristics of a gasoline direct-injection compression ignition engine using intake preheating. The gasoline direct-injection compression ignition engine was predicted to reduce emissions compared with the emissions from a conventional diesel engine. To compare the combustion and emission characteristics of the gasoline direct-injection compression ignition and diesel engines, numerical modelling was conducted using the KIVA-3V release 2 code, which is integrated with the Chemkin chemistry solver II. Numerical simulations were performed under a variety of conditions to determine the optimal conditions for gasoline direct-injection compression ignition engine operation. In order to achieve the gas pressure in the cylinder and the emission characteristics, experiments were performed using a single-cylinder engine. The simulation results agreed well with the experimental data. The gasoline autoignition was in the parcels with a lower equivalence ratio of 0.6–0.8 as opposed to the diesel autoignition parcels with a high equivalence ratio of greater than 1. The ignition delay of gasoline was longer than that of diesel; therefore, the gasoline direct-injection compression ignition engine could reduce the soot emissions. The nitrogen oxide emission levels for gasoline direct-injection compression ignition were increased because of the intake preheating.

Effect of the fuelling strategy on the combustion and emission characteristics of a gasoline-diesel dual-fuel engine

Since improving the energy efficiency and reducing the air pollution are two of the largest issues in the automobile industry, many researchers have developed various combustion and emission technologies to solve these challenges. Among these various technologies, the gasoline–diesel dual-fuel method is of interest to improve the thermal efficiency and to reduce the emissions in diesel engines. The gasoline allows formation of a premixed fuel–air mixture without early ignition owing to its high evaporation rate and low reactivity. In order to investigate the effect of gasoline on the dual-fuel combustion and emission characteristics, combustion of gasoline–diesel blend fuels was simulated in a compression ignition engine by using the KIVA-3V code. For the multi-fuel simulations, a modified KIVA-3V code with a discrete multi-component model was used to represent the multi-fuel evaporation processes. This study showed that the gasoline in the dual-fuel blend improved the fuel–air mixing process to form homogeneous mixtures for the two different injection strategies: port fuel injection and direct injection of gasoline. In addition, the combustion characteristics of gasoline–diesel blend fuel were discussed by comparing them with those of the conventional diesel fuel. The gasoline in the dual-fuel blend increases the indicated power because of the release of high fuel energy and decreases the soot emissions. In this study, various gasoline-to-diesel ratios and various injection timings were used in order to enhance the understanding of the dual-fuel engine. The present study showed that low emissions and a high indicated power were achieved as the gasoline content is increased up to a certain value. However, an increase in the gasoline content in the dual fuel caused the autoignition and the combustion performance to deteriorate.

Spray evolution, engine performance, emissions and combustion characterization of Karanja biodiesel fuelled common rail turbocharged direct injection transportation engine

Internal combustion engine research on alternative fuels has gained momentum because of growing awareness about energy security and environmental issues worldwide. Biodiesel offers an ideal solution to these problems and is an excellent partial replacement to mineral diesel. In this study, Karanja biodiesel blended with mineral diesel has been investigated for macroscopic spray characterization vis-à-vis baseline mineral diesel by varying fuel injection pressures (50, 100 and 150 MPa). Spray developed with relatively narrower spray angle for KB20. Injector needle movement for energizing and real injection durations were also compared for diesel and KB20 at fuel injection pressures of 50, 100 and 150 MPa. Needle movement was slightly higher for KB20 because of its relatively higher viscosity. However, with increasing fuel injection pressure, the difference reduced and showed quite similar results. A 2.2 L common rail direct injection sport utility vehicle EURO-IV diesel engine was used for the experiments. Engine performance, emissions and combustion characteristics of KB20 were compared with baseline mineral diesel at (1) the rated engine speed (2500 r/min) with varying engine loads as well as (2) at the rated load at varying engine speeds (1500–3500 r/min). Brake thermal efficiency of KB20 was lower than mineral diesel. Brake-specific carbon monoxide and carbon dioxide emissions decreased with increasing brake mean effective pressure and showed increasing trend with increasing engine speeds. KB20 showed emission of higher number of particles compared to mineral diesel at all engine operating conditions. Higher oxygen content of biodiesel resulted in shorter ignition delay and slightly higher peak cylinder pressure. KB20 showed relatively longer combustion duration compared to mineral diesel at 2500 r/min engine speed.

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.

Effects of DME Additives on Combustion Characteristics and Nano-particle Distributions in a Single Cylinder Compression Ignition Engine

This study describes effects of DME additives on combustion and exhaust emissions characteristics including nano-particle in a single cylinder compression ignition engine. Considered additives include bio-diesel, n-butanol, and MTBE for increasing kinematic viscosity. Among three additives, n-butanol showed the greatest kinematic viscosity. In addition MTBE showed the highest vapor pressure. In the present study mixing ratios of additives were kept constant at 1 and 10% by volume. Experiments were performed at 1200rpm engine speed and nano-particles were measured by SMPS (Scanning mobility particle sizer) devices. Results of combustion characteristics showed that considered additives had little effects on combustion pressure. However, patterns of heat release rate were dependent on properties of additives. Nano-particles of MTBE were the lowest among considered additives.This study describes effects of DME additives on combustion and exhaust emissions characteristics including nano-particle in a single cylinder compression ignition engine. Considered additives include bio-diesel, n-butanol, and MTBE for increasing kinematic viscosity. Among three additives, n-butanol showed the greatest kinematic viscosity. In addition MTBE showed the highest vapor pressure. In the present study mixing ratios of additives were kept constant at 1 and 10% by volume. Experiments were performed at 1200rpm engine speed and nano-particles were measured by SMPS (Scanning mobility particle sizer) devices. Results of combustion characteristics showed that considered additives had little effects on combustion pressure. However, patterns of heat release rate were dependent on properties of additives. Nano-particles of MTBE were the lowest among considered additives.