• International Journal of Automotive Technology
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• v.2 no.3
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• pp.93-101
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• 2001

Distribution of fuel-air mixture has a strong influence on performance and emissions of a compressed natural gas (CNG) engine. In this paper, parametric study is performed by KIVA-3V to investigate fuel-air mixture with respect to injection timing, cycle equivalence ratio and engine speed. With open-valve injection intensive mixing during intake and compression stroke results in relatively homogeneous mixture in the cylinder. Sequential induction of fuel-air mixture and fresh air results in stratification in the cylinder among the test cases at closed-valve injection. There is close similarity in the calculated distributions of the mixture in the cylinder with different cycle equivalence ratios and engine speeds. The results are compared against pressure traces and flame images obtained in a single cylinder engine converted from a 11L six-cylinder heavy duty diesel engine.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.83-88
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• 2003

The concept of lean-premixed combustion in gas turbine combustor operation has become a standard in recent years as an effective means to meet stringent environmental standards on NOx emissions. Various types of air-fuel premixer, which affect greatly NOx emission and stability of lean-premixed low NOx combustor, were investigated experimentally to reduce the NOx emission. One type of the premixers is selected by experiments and applied it to 70kW class lean-premixed gas turbine combustor. The exit temperature and emissions of CO and NOx were measured with equivalence ratios at ambient pressure. From the results, the emissions of CO and NOx were influenced by the type of air-fuel premixer. As the mixing length of air and fuel is longer, the NOx and CO emission were decreased in the primary reaction zone. Compared with of conventional combustor, the lean-premixed low NOx combustor has low NOx emission characteristics.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.319-322
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• 2006

Rapid mixing of air-fuel (<1 ms) is needed to accomplish supersonic combustion. In this experiment, helium was injected laterally in to the Mach 1.92 air flow. 2 kinds of model, flat plate/cavity, were used in this experiment and images were taken by schlieren visualization. Pressure was affected by shock structure in the supersonic duct, and penetration height was increased by increasing J. Penetration height was higher in the cavity model than flat plate model.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.3
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• pp.149-155
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• 2009

In this work a numerical study to find the characteristics of the internal flow and mixing process has been conducted in a static mixer used in the system of catalytic combustor of the fuel cell power plant. After introducing the model description and final governing equations the present numerical approach is applied to the analysis of static mixer, which may have one or more helical elements inside the circular tube by changing such various parameters as incoming mass flow rates and the number of helical elements. The results show that although the static mixer is efficient in mixing fuel and air, more optimization processes are required to achieve the appropriate mixing characteristics in front of the honeycomb type catalytic combustor used in the MCFC power plant

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.339-342
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• 2008

The PSP(Pressure Sensitive Paint) is a technique to measure continuous pressure distribution on medel surface by oxygen quenching. The objective of this study is to apply PSP which is measured pressure for analyzing that air-fuel mixing characteristics in SCRamjet combustor. Experimentation is performed at freestream Mach number of 2.5 and used fuel jet injection. The result shows that growing air-fuel mixed proportions by increasing in cavity size. Also, PSP results compared with conventional pressure tap and CFD. They are coincided with qualitative and the inclination.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.594-597
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• 2009

The mixing characteristics of pylon injection in a Scramjet combustor and effects of film cooling to protect pylon from air-heating. Three-dimensional Navier-Stokes equations with $k-{\omega}$ SST turbulence model were used. Fuel hydrogen and air were considered as coolants. There were remarkable improvements of penetration and mixing rate with the pylon injection. There also over-heating on the front surface of pylon without film cooling. The coolant injected parallel to the front surface of the pylon protect the pylon from over-heating.

• Journal of ILASS-Korea
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• v.18 no.2
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• pp.100-105
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• 2013

While variable valve actuation or variable valve lift (VVL) is used increasingly in spark ignition (SI) engines to improve the volumetric efficiency or to reduce the pumping losses, it is necessary to understand the impact of variable valve lift and timing on the in-cylinder gas motions and mixing processes. In this paper, characteristics of the in-cylinder flow and fuel distribution for various valve lifts (4, 6, 8, 10 mm) were simulated in a GDI engine. It is expected that the investigation will be helpful in understanding and improving GDI combustion when a VVL system is used. The CFD results showed that a increased valve lift could significantly enhance the mixture and in-cylinder tumble motion because of the accelerated air flow. Also, it can be found that the fuel distribution is more affected by earlier injection (during intake process) than that of later injection (end of compression). These may contribute to an improvement in the air-fuel mixing but also to an optimization of intake and exhaust system.

• Journal of ILASS-Korea
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• v.26 no.2
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• pp.81-87
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• 2021

This study was performed to calculate the swirl ratio of a diesel engine intake port by a 1D computer simulation under actual engine operating conditions. The swirl ratio of the intake port was simulated according to the change of the engine speed during the operation of the motoring without fuel injection. The swirl ratio of the intake port was simulated according to changes in the crank angle during the four-cycle operation of intake, compression, expansion and exhaust. The swirl ratio represented by the three regions of the piston, center and squish was simulated. Among the three regions, the piston-region swirl ratio is important for effective air-fuel mixing in the engine cylinder. In particular, it was confirmed during the simulation that the piston swirl ratio before and after the compression top dead center (TDC) point when fuel is injected in the DI diesel engine can have a significant effect on the mixing of air and fuel. It was desirable to set the average piston swirl ratio over a crank angle section before and after compression TDC as the representative swirl ratio of the cylinder head intake port according to the change of the engine speed.

• Journal of Power System Engineering
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• v.10 no.1
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• pp.19-24
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• 2006

This work treats a controlled auto-ignition (CAI) single cylinder gasoline engine, focusing on the extension of operating conditions. The fuel was injected indirectly into electrically heated inlet air flow. In order to keep a homogeneous air-fuel mixing, the fuel injector was water-cooled by a specially designed coolant passage. The engine performance and emission characteristics were investigated under the wide range of operating conditions such as 40 in the air-fuel ratio, 1000 to 1800 rpm in the engine speed, 150 to $180^{\circ}C$ in the inlet-air temperature, and $60^{\circ}$ BTDC in the injection timing. The ultra lean-burn with self-ignition of gasoline fuel by heating inlet air was achieved in a controlled auto-ignition gasoline engine. It could be also achieved that the emission concentrations of carbon monoxide, hydrocarbons and nitrogen oxide significantly reduced by CAI combustion compared with conventional spark ignition engines.

• Resources Recycling
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• v.20 no.5
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• pp.52-57
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• 2011

This study was conducted to examine the possibilities to utilize the mixture of domestic and organic wastes from B-city as a fuel. All types of mixing ratio for uncarried waste, sludge cake, and food waste were found 10 generate heating value with 6,000 kcal/kg, and in case of sludge cake the concentration of toxic substance produced was found to be decreased as air-fuel ratio and temperature were increased. It was noted that toxic gases such as CO, NOx, and SOx were observed below concentration of emission standard, and temperature inside the incinerator was stabilized at 2 of air-fuel ratio and 800$^{\circ}C$. It was observed that a heating value of 6000 kcal/kg generated using RDF(Refuse Derived Fuel) was appropriate to utilize a fuel if a complete combustion was attained.