• Journal of Korean Society for Atmospheric Environment
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• v.19 no.1
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• pp.25-31
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• 2003

Ceramic filter has been demonstrated as an attractive system to improve the thermal efficiency and to reduce the effluent pollutants. Removal of particulates from the hot gas stream is very important in air pollution control. In particular, the elimination of the particulate matters discharged from a gas turbine at high temperature can prevent the corrosion inside the IGCC. In this study, a Lab. scale test and numerical simulation were carried out to comprehend the relationship between pulse jet pressure and recovery of pressure drop and to characterize the reverse cleaning flow through a ceramic fil-ter element under high temperature and high pressure. When the pulse-jet pressures were 2, 3 and 4 kg/$ extrm{cm}^2$, the cleaning effect increase of about 10~30% by recovery of pressure drop caused by pulse pressure. Cleaning effect at 45$0^{\circ}C$ was greater than that at 55$0^{\circ}C$ or 650$^{\circ}$ for the same pulse pressure. According to the result of the present simulation, high pressure has been formed in terminal and central regions in our models and temperature distribution caused by pulse air is to be uniform comparatively on inner surface of filter.

• Korean Journal of Bronchoesophagology
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• v.14 no.1
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• pp.50-53
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• 2008

Subcutaneous cervicofacial, mediastinal emphysemas are complications associated with head and neck surgery, trauma, infectious processes, tooth extraction. Drill cooling stream and dental syringe air ject are the sources of high pressure air that may enter exposed soft tissue. Since the introduction of the high-speed air turbine drill in the 1960s, The incidence of iatrogenic subcutaneous emphysema has increased. Most cases begin to resolve after 2 to 3 days and residual swelling is usually minimal at the end of 7 to 10 days. Surgical approach is not advised because it is likely to be ineffective. The differential diagnosis of neck swelling after dental procedure includes hematoma, cellulitis, angioedema, allergic reaction, subcutaneous emphysema. We report a rare case of patient with subcutaneous cervicofacial emphysema and mediastinal emphysema secondary to third molar extraction.

• Journal of ILASS-Korea
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• v.3 no.2
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• pp.42-50
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• 1998

The effect of swirl flows un the fuel spray characteristics were investigated for various swillers in a model combustor. The interaction between the flow field and fuel spray in the main combustion tone made by frontal devices including fuel injection nozzles and swirlers. which were characterized by flow velocities, fuel droplet sizes and their distributions which were measured by APV(Adaptive Phase/Doppler Velocimetry) under atmospheric condition at 320cc/min kerosine fuel flow and 0.04kg/sec air supply. A dual swirler with circumferential two-stage swirl vanes of $40^{\circ}\;and\;45^{\circ}$ vanes in different directions and two single-stage swillers of $40^{\circ}$ vanes with 12 and 16 vanes were tested. It was found that the dual swirler has the largest recirculating zone with highest reverse flow velocity. The strongest swirl flow was found at the boundary of recirculation zone. Small fuel droplets were observed in the main axial stream and inside the recirculation zone when swirling flow field were generated by the frontal devices. These findings could give the tips on the optimal design of frontal devices to realize low emissions in gas turbine combustion.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.7
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• pp.864-870
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• 1999

An experimental study Is conducted in a four-vane linear cascade in order to examine the influence of the wake behind rectangular bars on the flow and heat transfer characteristics. Flow and heat transfer measurements are made for the inlet Reynolds number of 66000(based on chord length and free-stream velocity). Turbulent intensity and stress are measured using a hot-wire anemometer, and to measure the convective heat transfer coefficients on the blade surface liquid crystal/gold film Intrex technique is used. Each of experimental cases is characterized by the unsteadiness measured at the entrance of the cascade. The wake behind the rectangular bars enhances the turbulent motion of the flow in the cascade passage. It also promotes the boundary layer development and transition. The results show that heat transfer coefficients on the blade surface increase with increasing unsteadiness.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.251-253
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• 2017

Numerical study of air-blast type injector for low emission aircraft engines was conducted. Volume-of-fluids approach was used to track interface of fuel and air. Primary atomization of fuel stream was visualized, and thickness and mean velocity at the injector exit was calculated. Liquid fuel injected from fuel slots joined together as a thin film on preflimer surface, and interacted with swirling air. As instability on the fuel surface increased, separation of fuel as ligaments and droplets occured. The film thickness and velocity were used to as fuel injection boundary condition for reactive flow simulation. Primary reaction zone was formed in vicinity of the fuel nozzle, creating a stable flame inside the combustor.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.2
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• pp.212-219
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• 2017

As an environmental pollution and global warming due to an excessive carbon emission are intensified, the importance of renewable energy is in rise today. TCP (Tidal Current Power), one of the renewable energy sources, generates electricity by converting kinetic energy of current into rotational energy of turbine. Also the TCP has a great advantages of predictability and reliability. Because the generating power is proportional to cubic of stream velocity, amplifying current speed by applying duct is highly effective to increase the generating power. SPM (Single Point Mooring) can be applied for the weather vane with various current direction and also augments generating power of the system. In addition, simple installation and retrieval could be a merit of SPM system. By combining duct and SPM, TCP system for relatively low-speed-current and shallow water region can be feasible and economical. In this study, single point moored duct-type TCP system was designed and the motion of submerged structure was investigated in both numerical and experimental method. DNV wadam V4.8-1 and OrcaFlex 10.0a were used for the frequency and time domain motion analysis of system respectively. Duct model scaled by 0.05 of Froude conformity ratio and CWC (Circulate Water Channel) are used for experiment.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1599-1603
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• 2008

발전소 냉각수 배수로에는 유속 2 m/s 이상의 빠른 흐름의 수로가 존재하여 수력발전을 꾀할 수 있어, 하동화력의 경우 조류발전 수차인 헬리컬 수차를 이용한 수력 개발이 진행 중이다. 하동화력 배수로는 약 630 m의 암거와 약 250 m의 개수로로 이루어져 있는데, 현재 상업용 발전설비 개발을 위해 시험용 수차발전 설비를 개수로로 이어지는 암거 출구부에 설치하여 성능 시험을 추진하고 있다. 이에 본 연구에서는 발전 설비의 설치로 인한 수위 증가가 냉각수 순환 계통에 미치는 영향을 파악하기 위하여 배수로 구간의 수위변화 또는 압력변화를 수치해석을 통해 분석하였다. 배수로 암거 출구부에 가로 3.6 m ${\times}$ 세로 1.5 m 헬리컬 수차 1 set를 설치하는 경우 저조시에는 seal well 후단(하류측)의 수위가 seal well의 위어 정부표고를 넘지 않아 수차구조물에 의한 압력변화가 상류로 미치는 영향이 없었다. 그러나 고조시에는 seal well 전 후단이 만관 관수로 흐름이 되어 하류의 압력변화가 상류로 전파되었다. 단, 수차구조물을 설치한 경우 순환수 펌프를 처음 기동할 때 압력파의 전파로 인해 초기 약 10 분간 불안정한 압력변화가 발생하나 수차구조물 설치 전인 현상태에서 발생하는 압력변화 범위를 벗어나지는 않고 이내 안정되며, 수차구조물 설치로 인한 수위 증가분만큼의 펌프 양정고 증가로 소요 동력이 증가할 수 있으나 0.2 m 내외의 미약한 증가이므로 정상 운전에는 문제가 없을 것으로 판단되었다. 따라서 수차구조물 설치 시, 저조시에는 순환수계통에 영향을 주지 않으며, 고조시에도 일부 시간 동안 미약한 수두변화만 있을 뿐 순환수 계통의 안전에는 지장을 주지 않을 것으로 확인되었다.

• Journal of the Korean Institute of Gas
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• v.24 no.4
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• pp.25-31
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• 2020

Experimental investigations were conducted to examine the combustion characteristics of a swirl-stabilized double cone premixed burner nozzle used for industrial gas turbines for power generation. Several variants with different fuel injection patterns are tested to compare the combustion characteristics such as NOx and CO emissions, stability, and wall temperature distributions. Main results show that NOx emissions and stability are decreased either when the fuel hole diameter is decreased with the same number of fuel holes, or when the number of fuel holes is reduced with the same total area of fuel holes, both of which are due to a higher penetration of fuel into the air stream. Not only is NOx reduced but also stability is enhanced when the fuel hole diameter varies in an alternating manner with the same total area of fuel holes, showing that NOx reduction is due to a higher penetration of mean fuel injection path while stability enhancement is due to a lowered penetration of minimum fuel injection path.

• Restorative Dentistry and Endodontics
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• v.15 no.1
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• pp.107-119
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• 1990

The purpose of this study was to evaluate the marginal adaptability of the amalgam restorations in applying the cavity varnish (Copalite$^{(R)}$) and dentin bonding agent (Scotchbond 2$^{(R)}$) under the scanning electron microscope. For this study, eighteen sound extracted human molars were selected. Class I cavities in 12 teeth and class V cavities in 6 teeth were prepared using an air turbine with No. 701 tungsten carbide bur and finished using a low speed handpiece with No. 557 fissure bur. The prepared specimens were then divided into three groups including 4 class I cavities and 2 class V cavities in each group and restored as follows ; Group I. All the prepared cavities were restored with amalgam only (Control). Group II. Two layers of Copalite$^{(R)}$ cavity varnish were applied to the cavities with a gentle stream of air after each application and cavities were restored with amalgam. Group III. The enamel cavity margins were etched with 37% phosphoric acid gel for 60 sec., rinsed for 30 sec. and dried. One layer of visible lightcured Scotchbond Dental Adhesive$^{(R)}$ was applied and immediately cured for 20 seconds with visible light-cure unit and cavities were restored with amalgam. All the specimens were cut at the neck of the teeth and the occlusal halves of specimens were sectioned buccolingually in the longitudinal axis centering the amalgam restorations, using the disk. The cut specimens were ground with sandpapers (400, 600, 800, 1000 grit), and cleaned for 5 minutes in the ultrasonic cleaner (Brason Co. U.S.A.). In the cut surfaces, the amalgam - tooth interfaces were examined under the scanning electron microscope (JSM, 35C type, JEOL). The obtained results were as follows ; 1. The amalgam-tooth interfaces were reduced more significantly in the Copalite$^{(R)}$ and Scotchbond 2$^{(R)}$ application group than in the control group. 2. In the class I cavities, the Scotchbond 2$^{(R)}$ application group showed the findings similar to the Copalite$^{(R)}$ application group in the cavity floor, and the marginal adaptability was better in the side wall than in the cavity floor. 3. In the class I cavities, the Scotchbond 2$^{(R)}$ application group showed better marginal adaptability in the occlusal margin than in the gingival margin. 4. The marginal adaptability was in the order of the Scothbond 2$^{(R)}$ application group, the Copalite$^{(R)}$ application group and the control group.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.60-67
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• 2021

This study presented techno-economic analysis of a 500 MWe oxy-coal power plant with CO2 capture. The power plant included a circulating fluidized-bed (CFB), ultra-supercritical steam turbine, flue gas conditioning (FGC), air separation unit (ASU), and CO2 processing unit (CPU). The dry flue gas recirculation (FGR) was used to control the combustion temperature of CFB. One FGR heat exchanger, one heat exchanger for N2 stream exiting ASU, and a heat recovery from CPU compressor were considered to enhance heat efficiency. The decrease in the temperature difference (ΔT) of the FGR heat exchanger that means the increase in heat recovery from flue gas enhanced the electricity and exergy efficiencies. The annual cost including the FGR heat exchanger and FGC cooling water was minimized at ΔT = 10 ℃, where the electricity efficiency, total capital cost, total production cost, and return on investment were 39%, 1371 M$, 90 M$, and 7%/y, respectively.