• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.4
• /
• pp.437-442
• /
• 2015

The swirl ratio in a SI engine is investigated in a steady flow bench according to the measurement methods: an impulse swirl meter and particle image velocimetry (PIV). When measuring the swirl ratio using the PIV, the torque is evaluated based on the cylinder center and swirl center, respectively. The position of the measurement plane is considered. As a result, in the upstream, the swirl ratio measured by the impulse swirl meter is estimated to be larger than that from the PIV measurements due to the unstable vortex motions. Regarding the PIV measurements, the swirl ratio based on the cylinder center has been found to be lower than that based on the swirl center. On the other hand, the difference in swirl ratio has decreased smaller as the measurement plane moved downstream due to the stabilization of the vortex motion.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.4 no.6
• /
• pp.144-152
• /
• 1996

In the sequential MPI system with one injection for each cycle, engine performance is influenced by the mixture conditions. It can be said that engine performance is improved by being better identical mixture formation conditions for all cylinders. As the fuel injection timing to the intake port effects on the mixture formation conditions and the engine performance, injection timing must be better adjusted to engine requirements. Engine behavior was clearly different depending on the injection time during intake storke. Therefore it was studied that injection timing of fuel effects on the engine performance I. e. combustion stability, COV(imep), A/F excursion, CO,HC emission concentration and fuel consumption. It was found that late intake-synchronous injection was deteriorated the combustion characteristics and performance characteristics, while early intake-synchronous infection resulted in favorable engine behavior.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.11 no.2
• /
• pp.16-21
• /
• 2003

Natural gas is one of the promising alternative fuels because of the abundant deposits and the cleanness of emission gas. It can be used in conventional gasoline engine without major modification. Natural gas has some advantages than gasoline i.e. the high octane number, good mixing condition because of gas and wide inflamable limit. In the present study, a $1.8{\ell}$ conventional gasoline engine is modified for using the CNG as a fuel instead of gasoline. Performance and emission characteristics are compared between gasoline and CNG with 4 cylinder SI Engine which is controlled by programable ECU. Parameters of experimentation are equivalence ratio, spark timing and fuels. We analyzed the combustion characteristics of the engine using the cylinder pressure i.e. ignition delay, combustion duration and cycle variation. As a result, CNG engine shows lower exhaust emissions but brake torque is slightly reduced compared to gasoline engine. Overall combustion duration is longer than that of gasoline because of lower burning speed.

• Journal of the Korean Institute of Gas
• /
• v.25 no.5
• /
• pp.11-18
• /
• 2021

Since hydrogen has the lower minimum ignition energy than that of gasoline, hydrogen could be also appropriate for the IC engine systems. However, due to the low ignition energy, there might be a 'back-fire' and 'pre-ignition' problems with hydrogen SI(Spark-ignition) combustion. In this research, cooling effects of intake gas mixture on the improvement of the maximum power output were evaluated in a 2.4 L SI engine. There were two ways to cool intake gas mixtures. The first one was cooling intake fresh air by adjusting inter-cooler system after turbocharger. The other one was cooling hydrogen fuel before supplying by using heat ex-changer. Cooling hydrogen was performed under natural aspired condition. The result showed that cooling fresh air from 40 ℃ to 20~30 ℃ improved the maximum brake power up to 6.5~8.6 % and cooling hydrogen fuel as -6 ℃ enhanced the maximum brake power likewise.

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.884-889
• /
• 2001

Combustion chamber crevices in SI engines are identified as the largest contributor to the engine-out hydrocarbon emissions. The largest of crevice region is the piston ring pack crevice. To predict and understand the oxidation process of piston crevice hydrocarbons, a 3-dimensional numerical simulation method was developed. A engine shaped computational mesh with moving grid for piston and valve motions was constructed. And a 4-step oxidation model involving 7 species was used and the 16 coefficients in the rate expressions were optimized based on the results from a detailed chemical kinetic mechanism for the oxidation condition of engine combustion chamber. Propane was used as a fuel in order to eliminate oil layer absorption and liquid fuel effect.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.7 no.9
• /
• pp.48-55
• /
• 1999

In this paper, a zero-dimensional two zone model is developed to investigate the effects of variable valve timing on combustion process in SI engine. The simulation results show that the predicted data has good agreement with experimental ones. The useful information of combustion process such like residual gas fraction cylinder pressure, cylinder temperature and NO concentration can be obtained and the effects of engine variables on combustion processes and performances can be evaluated.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.9 no.1
• /
• pp.28-36
• /
• 2001

In this study, a zero-dimensional two zone model is developed to investigate the effects of valve overlap period and valve lift on combustion and gas exchange process in SI engine. The simulation results show that the predicted data has good agreements with experimental ones. The useful information of combustion and gas exchange process such as residual gas fraction, cylinder pressure, mass flow rate and volumetric efficiency can be obtained and the effects of engine variables on combustion processes and performances can be evaluated.

• International Journal of Automotive Technology
• /
• v.6 no.6
• /
• pp.585-590
• /
• 2005

The effects of spark timing and exhaust valve timing change on exhaust gas temperature during cold start period of an SI engine are studied through engine bench tests. The exhaust gas temperature increases when the spark timing or valve timing are retarded individually, due to late combustion or slow flame speed. Therefore, exhaust gas temperature shows a large increase when the two timings are retarded simultaneously. However, it is considered that combustion stability during cold start deteriorated under these retarded conditions. To increase exhaust gas temperature for fast warmup of catalysts while maintaining combustion stability, an optimal condition for spark and valve timing retard should be applied for the cold start period.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.16 no.1
• /
• pp.127-133
• /
• 2008

Since the 1960's, exhaust gas recirculation(EGR) has been used effectively in spark ignition(SI) engines to control the exhaust emissions of the oxides of nitrogen(NOx). The most important requirements for the application of EGR systems to conventional SI engines are controllable flow rate and good dynamic response. In order to evaluate the characteristics of the electronic EGR valve, a test bench which is consisted of blower, heater, air flow meter and driving unit for electronic EGR valve was set up to simulate engine operating conditions. During the tests, the valve actuation parameters were controlled and the valve lifts and flow rates were measured to infer the characteristics of EGR valve. The results confirmed the capabilities of mathematical analysis and it seems that the correction for the valve lift and potentiometer output is necessary to achieve precise control of EGR rates.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.9 no.3
• /
• pp.1-8
• /
• 2001

The flow field inside a cylinder of four-valve Sl engine was investigated quantitatively using a three-dimensional Laser Doppler Velocimetry system, to determine how stroke changes affect the flow field. The purpose of this work was to develop quantitative methods which correlate in-cylinder flows to engine performance. For this study, the sane intake manifold, engine head, cylinder, and the piston were used to examine the flow characteristics in different strokes. Quantification of the flow field was done by calculating three major parameters which are believed to adequately characterize in cylinder motion. These quantities were TKE, tumble and swirl ratios. The LDV results reveal that flow patterns are similar, the flow velocities scale with piston speed but another parameters such as TKE, and tumble and swirl numbers are not the same for different stroke systems.