• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.35-40
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• 2007

The gaseous fuel injection (GFI) type in LPG fuel supply system has more advantage than the liquified fuel injection type from the viewpoint of durability and cost reduction. But in GFI system, to control pressure and temperature of gaseous fuel is needed to get precision fuel metering for the compressible characteristic of gaseous fuel. In this study, the effects of pressure and temperature on the fuel metering was simulated by commercial flow network analysis package, Flowmaster. And the fuel composition effects on the fuel metering were also studied to figure out the fuel metering characteristics.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.1019-1024
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• 2011

The gaseous fuel injection(GFI) type of LPG fuel-supply system is more advantageous than liquefied fuel injection(LFI) from the viewpoint of durability and cost reduction. However, compared with LFI types of LPG fuel-supply systems, in the GFI systems it is difficult to achieve precision fuel metering because of the compressible characteristic of the gaseous fuel. In this study, a Helmholtz resonator is proposed as an appropriate system for precision fuel metering in GFI systems, and the effects of the Helmholtz resonator on the fuel metering are simulated by the commercial flow-network-analysis package Flowmaster.

• Journal of the korean Society of Automotive Engineers
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• v.12 no.5
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• pp.76-84
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• 1990

To study diesel fuel spray behavior, an experimental study was undertaken to investigate injection characteristics in vary ing back pressure and atomization mechanism in a non-evaporating diesel spray. Generally, injection characteristics is the curve of fuel flow plotted against time. The area under this curve is equal to the total quantity of fuel discharged for one injection. The method that measures rate of injection is long tube-type fuel rate indicator. Diesel spray injected into a quiescent gaseous environment under high pressure is observed by taking high speed camera by the focused shadow photographs. The results show that, at the start of injection, as the injected fuel rushes into the quiescent atmosphere the spray angle becomes large. Finally the spray stabilizes at a constant cone angle. Spray penetration length increases with the injection pressure.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.6
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• pp.31-39
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• 2000

In this paper, characteristics of a port injection type LPG fuel system were investigated to adopt the system to a spark ignition engine through rig test. Engine combustion characteristics for limited conditions and the precise control method of LPG fuel supply were also studied. As a basic experiment, the effects and the relationships of parameters such as orifice area, fuel delivery pressure, fuel temperature and flow coefficient were established. From this, one dimensional compressible flow equation can be applied to control gaseous fuel flow rate by setting pressure difference between vaporizer and manifold to a certain range, for example about 1.2 bar in a naturally aspirated engine. The combustion analysis results of LPG engine were also compared with those of gasoline engine according to spark timing and load change. At part load and stoichiometric condition, the MBT spark timing of LPG fueled engine is retarded by 2$^{\circ}$ - 4$^{\circ}$CA compared to that of gasoline engine. On the contrary, the spark timing of LPG fueled engine can be advanced by 5$^{\circ}$- 10$^{\circ}$ CA at WOT, which results from higher Octane Number and burned fraction of LPG fuel compared to gasoline.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.193-200
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• 2007

Natural gas is one of the most promising alternatives to gasoline and diesel fuels because of its lower harmful emissions, including $CO_2$, and high thermal efficiency. In particular, natural gas is seen as an alternative fuel for heavy-duty Diesel Engines because of the lower resulting emissions of PM, $CO_2$ and $NO_x$. Almost all CNG vehicles use the PFI-type Engine. However, PFI-type CNG Engines have a lower brake horse power, because of reduced volumetric efficiency and lower burning speed. This is a result of gaseous charge and the time losses increase as compared with the DI-type. This study was conducted to investigate the effect of injection conditions (early injection mode, late injection mode) on the combustion phenomena and performances in the or CNG Engine. A DI Diesel Engine with the same specifications used in a previous study was modified to a DI CNG Engine, and injection pressure was constantly kept at 60bar by a two-stage pressure-reducing type regulator. In this study, excess air ratios were varied from 1.0 to the lean limit, at the load conditions 50% throttle open rate and 1700rpm. The combustion characteristics of the or CNG Engine - such as in-cylinder pressure, indicated thermal efficiency, cycle-by-cycle variation, combustion duration and emissions - were investigated. Through this method, it was possible to verify that the combustion duration, the lean limit and the emissions were improved by control of injection timing and the stratified mixture conditions. And combustion duration is affected by not only excess air ratio, injection timing and position of piston but gas flow condition.

• 한국연소학회:학술대회논문집
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• 2006.10a
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• pp.7-8
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• 2006

As a new type of flame, tubular flame has attracted much attention from a fundamental viewpoint and many experimental and theoretical studies have been made on its characteristics. Recently, it is also recognized that the tubular flame has great potentials as practical combustor because its stability range is very wide in fuel concentration and also in injection velocity. Thus, tubular flame burners have been developed for various kinds of fuels. They are gaseous fuels of methane, propane, hydrogen, and by-product fuels gases in steel making processes including BFG (Blast Furnace Gas), LDG (LD Converter Gas), and COG (Cokes-Oven Gas), liquid fuels of kerosene, A-type and C-type heavy oils, and a solid fuel of biomass powder. In this paper, recent developments of the tubular flame burners have been briefly introduced.

• Journal of Energy Engineering
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• v.15 no.4 s.48
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• pp.277-283
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• 2006

In this study, butane 100% was used as fuel to verify the real fuel effect such as vapor pressure variation due to temperature change. A MPI fuel injection system for V-6 engine, which has reverse 'L' type cross section to minimize the possibility of liquid phase injection, was composed and one bank was operated under sequential injection scheme. Flow rate were measured according to injection duration, interval, and pressure. Also occurring of liquid phase injection was monitored with varying vaporizer and fuel rail temperature. The result shows that basic characteristics of injection is a relatively difference between air and LPG injection. Under cold start condition, however, the occurrence of liquid injection becomes more severe as the pressure increases, and sufficiently high temperature both in vaporizer and fuel rail is very important to insure gaseous injection. In addition, the temperature of vaporizer plays more important role in keeping LPG vapor state and the reverse 'L' type cross section of the rail is available to prevent liquid injection.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.205.2-205.2
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• 2010

Optimum operation conditions of low-NOx MILD combustion for gaseous and solid fuels have been investigated by experimental and computer simulation. Loop reactor type MILD combustor without air pre-heater has been used in the present work. The results show that the balance of injection velocities of fuel and surrounding air is major factor for maintaining MILD combustion mode. Temperature difference between lower and upper part can be reduced less than 20 degree of Celsius. It was found that NOx emission in MILD combustion also can be remarkably reduced to more than 85% in comparison with conventional premixed combustion, and reduced to more than 50% in case of nitrogen and carbon dioxide carrying dried waste water sludge and pulverized coal in comparison with the same of air carrying. It was also found that carbon monoxide emission increase was not appeared at the time of changeover to MILD combustion mode from premixed or air carrying combustion at optimum operation condition.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.85-94
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• 2002

Computational flow dynamics(CFD) has been frequently applied to the waste incinerators to understand the flow performance for various design and operating parameters. Though it needs many simplifications and complicated flow models, the reasonability of its results is not fully evaluated. For example, the inlet condition is calculated from an arbitrarily assumed properties of combustion gas release from the waste bed, since the combustion in the bed is difficult to be predicted. In this study, the computational modeling and calculation procedures of CFD for the grate type waste incinerator were evaluated using comparative simulations. Though the assumption method on the generation of the combustion gas directly affected the temperature and gas species concentrations, the overall flow pattern was dominated by the secondary air jets. The gaseous reaction could be included by assuming the release of the products of incomplete combusion from the bed. However, the reaction effficiency cannot not be directly evaluated from the species concentration, since it is not possible to simulate the actual co-existence of fuel rich or oxygen rich puffs over the bed. In predicting the turbulence, the higher order model, such as Reynolds stress model, gave difference shape of local recirculation zones, but similar results was acquired from the standard $k-{\varepsilon}$ model. Introducing radiation model was required for accurate temperature prediction, but it also caused heat imbalance due to the fixed temperature of the inlet, i.e. the waste bed. Thus, the computational modeling procedures on incinerators and the analysis of the predicted results should be progressed carefully. Though not validated experimentally, current simulation method is capable of comparative evaluation on the flow-related parameters such as the furnace shape and secondary air injection using identical inlet conditions. Quantitative analysis using measures of the residence time and mixing is essential to compare the flow performance efficiently.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.3
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• pp.227-240
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• 2010

Coal gasification is heading for a great future as one of the cleanest energy sources, which can produce not only electricity and heat, but also gaseous and liquid fuels from the synthesis. The work focuses on 300MW shell type one-stage entrained flow coal gasifier which is used in the Integrated coal Gasification Combined Cycle(IGCC) plant as a reactor. As constructing an IGCC plant is considerably complicated and expensive compared with a pulverized-coal power plant, it is important to determine optimum design factors and operating conditions using a computational fluid dynamics (CFD) model. In this study, the results of numerical calculations show that $O_2$/Coal ratio, 0.83, Steam/Coal ratio, 0.05, coal particle diameter, $100{\mu}m$, injection angle, $4^{\circ}$ (clockwise) are the most optimum in this research.