• Transactions of the Korean Society of Automotive Engineers
• /
• v.6 no.5
• /
• pp.37-44
• /
• 1998

Lean burn combustion is an important concept for improving the fuel consumption and exhaust emissions. However, the lean burning is associated with increased cycle-to-cycle combustion variations due to the ignition instabilities and redu- ced flame propagation rates. Engine stability under lean mixture conditions could be improved by increasing flame speed through enhanced flow characteristics and by securing ignitability with improvement of ignition systems. The effects of flow motion and ignition characteristics on the combustion performances were investigated in a 4-valve SI engine. Flow motions of tumble-swirl were varied with a swirl control valve attached at the inlet ports, while ignition energy and its distribution were controlled in a high -frequency ignition system by changing spark duration and spark frequency. The improvement of lean burn performance by the optimum flow motion and ignition characteristics is discussed.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.9
• /
• pp.869-874
• /
• 2011

In a CNG/diesel dual-fuel engine, CNG is used as the main fuel and a small amount of diesel is injected into the cylinder to provide ignition priming. In this study, a remodeling of the existing diesel engine into a CNG/diesel dual-fuel engine is proposed. In this engine, diesel is injected at a high pressure by common rail direct injection (CRDI) and CNG is injected at the intake port for premixing. The CNG/diesel dual-fuel engine had an equally satisfactory coordinate torque and power as the conventional diesel engine. Moreover, the CNG alternation rate is over 89% throughout the operating range of the CNG/diesel dual-fuel engine. PM emission by the dual-fuel engine is 94% lower than that by the diesel engine; however, NOx emission by the dual-fuel engine is higher than that by the diesel engine.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.19 no.7
• /
• pp.693-698
• /
• 2009

Various acoustic tests were carried out to investigate the acoustic performance of diesel engine exhaust silencers. In order to consider flow effects, the test facility was set up composed of fan, duct and silencer. Using the test facility, insertion loss tests were carried out to improve the acoustic performance in the low-frequency ranges. Through a series of tests, it was found out that the array resonators having multi-perforated holes inside the exhaust silencer, might be very effective in the low frequency range. Consequently, the hybrid-type silencer which is the combination of reflective silencer with array resonators and conventional absorptive silencer, was proposed and its high performance in the low-frequency range was also verified.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.30-35
• /
• 2007

Various acoustic tests were carried out to investigate the acoustic performance of diesel engine exhaust silencers. In order to consider flow effects, test equipment composed of fan, duct and silencer was set up. Using the test equipment, insertion loss tests were carried out to improve the performance in the low-frequency ranges. Through a series of tests, the fact that array resonators may be effective in the low-frequency noise has been verified. Consequently, the hybrid-type silencer which is the combination of reflective silencer with array resonators and conventional absorptive silencer were proposed and its high acoustic performance in the low-frequency range has also been verified.

• Journal of Advanced Marine Engineering and Technology
• /
• v.22 no.6
• /
• pp.816-826
• /
• 1998

The effects of rice bran oil on the characteristics of performance and exhaust emissions have been experimentally examined by a single cylinder four cycle direct injection water-cooled and agricultural diesel engine operating at several loads and speeds. The experiments are conducted with light oil blends of rice bran with light oil and rice bran oil as a fuel. The fuel injection timing if fixed to $22^{\circ}$ BTDC regardless of fuel type engine loads and speeds. Any oxygen is not included in light oil while the oxygen contents of 10.7% are included in rice bran oil. The lower calorific value of rice bran oil is less than light oil and the viscosity is very high compared with light oil. In pre-sent study it is found that these major differences of chemical and physical properties control the combustion parameters that affect the performance and exhaust emissions of diesel engines using a rice bran oil as fuels.

• Journal of Hydrogen and New Energy
• /
• v.26 no.2
• /
• pp.164-169
• /
• 2015

Recent research has focused on alternative fuel to improve engine performance and to comply with emission regulation. Finding an alternative fuel and reducing environment pollution are the main goals for future internal combustion engines. The purpose of this study is to obtain low-emission and high-efficiency by hydrogen enriched CNG fuel in SI engine and is to clarify the effects of hydrogen enrichment in CNG fuelled engine on exhaust emission and performance. An experimental study was carried out to obtain fundamental data for performance and emission characteristics of hydrogen enrichment in SI engine. The experiment was conducted at 2500 rpm, bmep 2 bar, 4 bar conditions while CNG fuel was mixed with 10, 20 and 30% hydrogen blends. From the experimental results, combustion duration was shortened due to rapid flame propagation velocity of hydrogen and these were attributed to the burning velocity increasing exponentially with increasing hydrogen blending ratio. Hydrogen has much wider flammable limit than methane, gasoline and the minimum ignition energy is about an order of magnitude lower than for other combustion. By adding hydrogen, $CO_2$ and HC were reduced. However, $NO_X$ was increased dut to high rate of heat release for hydrogen substitutions.

• Journal of Energy Engineering
• /
• v.14 no.3 s.43
• /
• pp.173-179
• /
• 2005

Fuel injection system has more benefits in power, fuel consumption and emission than carburetor system even in high speed small engine. Up to date fuel injection system is used in motor car but is not used in motorcycles in Korea. EFI (Electronic fuel injection) system which has ECU can control precise fuel supply to variable RPM in engine. The purpose of this study is the investigation of effects of fuel injection system to improve the engine performance and efficiency in variable revolution of high speed small engine which is 4 Valves SOHC single cylinder engine used in motorcycle.

• Journal of ILASS-Korea
• /
• v.16 no.1
• /
• pp.7-14
• /
• 2011

High pressure LPG fuel spray with a conventional swirl injector was visualized and the impact of the injection pressure was also investigated using a DISI (direct injection spark ignition) LPG single cylinder engine. Engine performance and emission characteristics were evaluated over three different injection pressure and engine loads at an engine speed of 1500 rpm. The fuel spray pattern appeared to notably have longer penetration length and narrower spray angle than those of gasoline due to its lower angular momentum and rapid vaporization. Fuel injection pressure did not affect combustion behaviors but for high injection pressure and low load condition ($P_{inj}$=120 bar and 2 bar IMEP), which was expected weak flow field configuration and low pressure inside the cylinder. In terms of nano particle formation the positions of peak values in particle size distributions were not also changed regardless of the injection pressure, and its number densities were dramatically reduced compared to those of gasoline.

• Journal of the Korean Society of Combustion
• /
• v.20 no.3
• /
• pp.13-20
• /
• 2015

The performance of a direct-injection diesel engine often depends on the strength of swirl or squish, the shape of combustion chamber, the number of nozzle holes, etc. This is natural because the combustion in the cylinder was affected by the mixture formation process. Since the available duration to make the mixture formation of air-fuel is very short, it is difficult to make complete mixture. Therefore, an early stage of combustion is violent, which leads to the weakness of noise and vibration. In this paper, the combustion process of a common-rail diesel engine was studied by employing two kinds of pistons. One has several cavities on the piston crown to intensify the squish during the compression stroke in order to improve the atomization of fuel, we call this multi cavity piston in this paper. The other is a toroidal single cavity piston, generally used in high speed diesel engines. To take photographs of flame and flaming duration, a four-stroke diesel engine was remodeled into a two-stroke visible single cylinder engine and a high speed video camera was used.

• Journal of Advanced Marine Engineering and Technology
• /
• v.17 no.4
• /
• pp.49-62
• /
• 1993

It has been a principle research topic on the diesel engine development to increase the efficiency and the performance of engine to satisfy the user's needs for high reliability and durability. However, recently with the worldwide concerns at the global climate change and environmental protection, the main target in the diesel engine research has been changed to solve the exhaust emission problem in order to satisfy the strict emission regulations. To reduce the pollutant for the diesel engine, the researchs on the combustion chamber is the most important and has to be performed first of all. The diesel fuel injection system plays major role to air-fuel mixing process and influences engine output, themal efficiency, reliability, noise, and emissions. The experimental studies were conducted by varying the various parametric conditions and the results were campared with the computation and calculated results by using the fuel injection simulation program developed during previous research. From the experiments, the matching technique of a fuel injection pump and nozzle was conducted to understand under the various parametric conditions. Also, the relations between needle lift and wave propagation characteristics in high pressure pipe were examined. The basic design data from the experimentations and computation works would be applied to actual design works of diesel fuel injection system.