Junepyo Cha

Spray and Engine Performance Characteristics of Biodiesel and Its Blends with Diesel and Ethanol Fuels

The authors aimed to investigate the fuel-atomization, combustion, and exhaust emissions characteristics of dual component fuels. The analysis revealed that the blending of diesel or bioethanol fuel slightly affected the reduction of the spray tip penetration and had little influence on the variation of the spray cone angle. The droplet size of biodiesel fuel was reduced by blending with diesel or bioethanol fuel with low kinematic viscosity and surface tension. Regarding the combustion characteristics, B80D20 fuel had the same combustion characteristics as B100. However, the blending of bioethanol fuel with biodiesel fuel caused an extension of the ignition delay and a decrease of the peak combustion pressure. There was little difference in the exhaust emissions characteristics caused by the blending of diesel fuel. However, EI-NOx emissions were reduced significantly by the blending of bioethanol fuel. However, EI-HC and EI-CO emissions were increased by blending the bioethanol fuel.

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.

Study on Spray and Exhaust Emission Characteristics of DME-Biodiesel Blended Fuel in Compression Ignition Engine

The purpose of this study is to investigate experimentally the spray-atomization and combustion-emission characteristics of biodiesel-DME blended fuel. In this study, two types of test fuels pure biodiesel (BD100) and blended fuel (B-DME20) were used, and the spray and combustion characteristics of different fuel compositions were analyzed. DME constitutes 20% and biodiesel constitutes 80% (by mass fraction) of the blended fuel. The overall spray characteristics, spray tip penetration, and cone angle were evaluated using frozen spray images. In addition, the combustion and emission characteristics were analyzed on the basis of the evaluated data for a single-cylinder CI engine with common-rail injection system. It was revealed that the injection profiles of both the test fuels for a given injection pressure showed similar trends. However, the injection profiles of the blended fuel (B-DME20) indicated shorter ignition delay than those of biodiesel.

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.

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.

Effect of Ethanol Content on Fine Soot Particle Emission from a Diesel-Ethanol Blended Fuel Diesel Engine

The purpose of this study is to investigate the effect of ethanol content on the emission of nanosized particles from a diesel-ethanol blended fuel engine. The engine combustion and exhaust emission characteristics of a singlecylinder diesel engine were analyzed using an emission analyzer and an SMPS(scanning mobility particle sizer). The analysis revealed that soot emission increased with the ignition delay. When the ignition delay was fixed, an increase in the ethanol content caused a decrease in the soot emission. With an increase in the ethanol blending ratio, the number concentration and mass distribution of nanosized particles generally decreased. However, for 30% ethanol blending, large particles were observed because of the agglomeration of soot particles, and consequently, the particle mass increased.