• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.6
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• pp.102-109
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• 1994

As a fundamental study to apply high pressure injection system to direct injection diesel engine, fuel injection system and constant volume combustion chamber were made and the behaviors of evaporating spray with the variation of injection pressure and the ambient gas temperature were observed by using high speed camera, and the combusion characteristics with the variation of injection pressure and A/F ratio were analyzed. As injection pressure increases, spray tip penetration and spray angle increase and, as a results spray volume increases. This helps an uniform mixing of fuel and air. Spray liquid core length decreases as ambient gas temperature increases, while it decreases as injection pressure increases but the effect of ambient gas temperature is dorminant. As injection pressure increases, ignition delay is shortened and combustion rate being raised, maximum heat release rate increases. It become clear that High injection pressure has high level of potential to improve the performance of DI-diesel engine.

• Journal of ILASS-Korea
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• v.20 no.2
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• pp.114-120
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• 2015

Effects of injection conditions on a pintle injector which is proper to recent liquid rocket engines requiring low cost, low weight, high efficiency and reusability were studied. The pintle injector with a typical moving pintle was used for atmospheric experiment using water and air. Injection pressures of water were considered 0.5 and 1.0 bar, 0.1 to 1.0 bar for injection pressures of air and 0.2 to 1.0 mm for pintle opening distance. Sauter mean diameters (SMD) of spray was measured at 50 mm distance from a pintle tip and SMD was treated as a representative parameter in this study. As a result, because of shape characteristics of the pintle injector, there was a transient region between the pintle opening distances of 0.6 and 0.7 mm and this region affected to mass flow rates and SMDs. Also, Reynolds numbers for gas, Weber numbers and momentum ratios were adopted as major non-dimensional paramters and the momentum ratio has strong correlation with SMD.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.32-39
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• 2004

HCCI (Homogeneous Charge Compression Ignition) combustion has a great advantage in reducing NOx (Nitrogen Oxides) and PM (Particulate Matter) by lowering the combustion temperature due to spontaneous ignitions at multiple sites in a very lean combustible mixture. However, it is difficult to make a diesel-fuelled HCCI possible because of a poor vaporability of the fuel. To resolve this problem, the two-stage injection strategy was introduced to promote the ignition of the extremely early injected fuel. The compression ratio and air-fuel ratio were found to affect not only the ignition, but also control the combustion phase without a need for the intake-heating or EGR (Exhaust Gas Recirculation). The ignition timing could be controlled even at a higher compression ratio with increased IMEP (Indicated Mean Effective Pressure). The NOx (Nitrogen Oxides) emission level could be reduced by more than 90 % compared with that in a conventional DI (Direct Injection) diesel combustion mode, but the increase of PM and HC (Hydrocarbon) emissions due to over-penetration of spray still needs to be resolved.

• Food Science of Animal Resources
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• v.42 no.1
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• pp.98-110
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• 2022

Meat jerky is a type of meat snack with a long shelf life, light weight, and unique sensory properties. However, meat jerky requires a long manufacturing time, resulting in high energy consumption. In this study, beef jerky was prepared by injecting different concentrations of brine at different hot-air drying times (0-800 min). When the brine injection levels were increased to 30%, the drying characteristics of beef jerky, such as drying time and effective moisture diffusivity, were significantly improved owing to the relatively high water content and the formation of porous structures. The physicochemical properties (e.g. meat color, porosity, shear force, and volatile basic nitrogen) of the beef jerky injected with 30% brine were improved owing to the shortened drying time. Scanning electron microscopy images showed that the beef jerky structure became porous and irregular during the brine injection process. Our novel processing technique for manufacturing beef jerky leads to improved quality characteristics and shortened drying times.

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.35-39
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• 2003

A numerical study is carried out to investigate combustion phenomena in a model SCRamjet engine, which has been experimentally studied at the Australian National University using a T3 free-piston shock tunnel. The Mach number is 3.8, the static pressure 110kPa and the static temperature 1100K in the main air flow. The fuel is hydrogen, which is injected in the cavity. Equivalence ratio is set to either 0.25 or 0.5 to access its effect on the fuel-air mixing combustion phenomena. The results show that the cavity generates several recirculation zones, which increase the fuel-air mixing. Self ignition occurs near the point of fuel injection. The flame is anchored by the cavity and generates the precombustion shock on the step. For a high equivalence ratio, the recirculation zones are bigger and the flame is present throughout the combustor.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.140-149
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• 2006

Characteristics of a laminar diffusion flame placed near wall in microgravity have been numerically analyzed in a two-dimension. The fuel for the flame is $C_2H_4$. The flame is initiated by imposing a high temperature ignition source. The flow field, temperature field, and flame shape in microgravity diffusion flame are detailed. Especially, effects of surrounding air velocity and fuel injection velocity on the microgravity diffusion flame have been discussed accounting for standoff distance. And, the effect of curvature rate has been also studied. The results showed that velocities in a diffusion flame were overshoot because of volumetric expansion and distribution of temperature showed regularity by free-buoyancy This means that the diffusion flame in microgravity is very stable, while the flame in normal gravity is not regular and unstable due to buoyancy. Standoff distance decreases with increase in surrounding air velocity and with decrease in fuel injection velocity. With increasing curvature rate, the position of reaction rate moves away the wall.

• Journal of Welding and Joining
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• v.21 no.6
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• pp.46-54
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• 2003

The thermal response of electronic assemblies during forced convection-infrared reflow soldering is studied. Soldering for attaching electronic components to printed circuit boards is performed in a process oven that is equipped with porous panel heaters, through which air is injected in order to dampen temperature fluctuations in the oven which can be established by thermal buoyancy forces. Forced convection-infrared reflow soldering process with air injection is simulated using a 2-dimensional numerical model. The multimode heat transfer within the reflow oven as well as within the electronic assembly is simulated. Parametric study is also performed to study the effects of various conditions such as conveyor speed, blowing velocity, and electronic assembly emissivity on the thermal response of electronic assemblies. The results of this study can be used in the process oven design and selecting the oven operating conditions to ensure proper solder melting and solidification.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.63-67
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• 2004

A field pilot study on remediation of diesel-contaminated soil by hot air injection/extraction process constructing soil piling system was conducted to evaluate the effects of hot air on the removal of diesel and each constituent. After the heating process of 2 months, the equilibrium temperature of soil reached to 10$0^{\circ}C$ and soil TPH concentration was reduced to about 72% against the initial concentration. Additional extraction process of 2 months induced the continuous extraction of residual diesel and the increment of microbial activity, which made soil TPH concentration reduced to 95%. In addition biological removal of non volatile constituents in diesel was verified indirectly and the removal pattern of each DRO(diesel range organic) as soil temperature was explained.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.3
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• pp.353-358
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• 1995

The emission characteristics of a semi-Bunsen type burner for gas boilers were studied experimentally. The experimental results reveal that nitric oxide emission increases with fuel flow rate. It is linearly proportional to total fue flow rate at a small amount of fuel up to 0.4 liters per minute. It does not change significantly within the range of fuel flow rate from 0.4 to 1.2 liters per minute per nozzle and increases at large fuel flow rate. The carbon monoxide emission reveals to be dependent upon the fuel flow rate per each nozzle and the number of fuel injection nozzles. Diameter of an injection nozzle could have an effect on the emission characteristics of this type of burners. However, there is no marked change in the nitric oxide emission if the total fuel flow rate is same with different nozzle sizes.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.57-63
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• 2000

This paper deals with a study on combustion and emission characteristics of a direct injection diesel engine dual fueled with natural gas. Dual fuelling systems tend to emit high unburned fuel especially at low load, resulting in a decreased thermal efficiency. This is because natural gas-air mixtures are too lean for flame to propagate under low load conditions. Suction air quantity and injection timing controls are very useful to improve emissions and thermal efficiency at low load.