• Journal of Advanced Marine Engineering and Technology
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• 제26권4호
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• pp.472-484
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• 2002

To analyze the characteristics of air flow and $CO_2$ extinguishant transfer when extinguishant is injected into a closed space similar to marine engine room, a numerical simulation on a space was performed. Flow fields and $CO_2$ concentration fields are calculated according with the variation of the location & injection angle of nozzles. The results of simulation showed that the pattern of recirculation flow was affected greatly with the location & injection angle of nozzles and such a recirculation flow accelerated mass transfer of $CO_2$ and greatly affected the diffusion process of $CO_2$ extinguishant. It is considered that this result of this study can be useful to designing the arrangement of nozzles for the $CO_2$ fire fighting equipments in a marine engine room.

• Journal of Power Electronics
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• 제12권6호
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• pp.925-934
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• 2012

Three-phase controlled converters have many applications in the utility interfacing of renewable energy sources and adjustable speed drives as a rectifier or inverter. The utility line currents of these converters have a high harmonic distortion, which is more than the harmonic standards. This paper introduces a new technique for circulating the third harmonic currents from the dc-link to the line currents to reduce their harmonic contents. The proposed system uses a single-phase PWM converter to control the angle and amplitude of the injection current for each of the firing angle of a three-phase converter. A detailed analysis is introduced to achieve a relationship between the firing angle of the three-phase controlled converter and the power angle of the PWM converter. In addition, a detailed design for the other injection path components is introduced. A simulation and experimental work is introduced to prove the mathematical derivations. Analysis, simulation and experimental results prove the superiority of the proposed technique.

• 대한기계학회논문집
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• 제17권10호
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• pp.2590-2600
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• 1993

The present paper describes numerical predictions for the film cooling effectiveness from a row of hole at various injection ratios and injection alngles.Numerical calculations were performed to investigate film cooling effectiveness and the characteristics of flow and temperature distributions in the region near the downstream of injection hole including the region of adverse pressure gradient. The elliptic 3-dimensional governing equations with variable thermal properties were solved by SIMPLE algorithm. The results showed that the presence of adverse pressure gradient in the region near the downstream of injection hole induces large temperature gradient. At injection angle of $35^{\circ}$ the average film cooling effectiveness was increased as increased of injection ratio up to 1.0. At injection angle of $90^{\circ}$ however, the average film cooling effectiveness was decreased from injection ratio larger than 0.4.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.445-448
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• 2005

Recently, injection molding process became more popular than ever to produce large quantities of high precision products or optical products. Injection molding products can cause sensorial problems because of high birefringence or deformation from the residual stresses in the optical media. In the present study, we have focussed on the effect of holding and compression pressures on the optical anisotropy remaining in the MOD by examining the gapwise distribution of birefringence and extinction angle The effect of holding pressure was found to form the inner two birefringence peaks. But the effect of compression pressure on the birefringence distribution was found to make the uniform distribution near the center in the gap-wise direction. Finally, the value of the birefringence near the wall decreased as the mold temperature increased.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.321-325
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• 2008

초음속 유동장내에 분사된 2차제트 주변에서의 열전달 현상을 고찰 하였다. 초음속 유동장내에 분사되는 2차유동의 Jet to freestream momentum ratio(운동량비)의 변화와, 2차유동 분사각도에 따른 2차 분사홀 주변의 열전달 특성을 파악하기 위하여 홀 주변의 표면온도 변화를 고속 적외선 카메라를 통하여 측정하였으며, 이를 이용하여 비정상 열유속 기법을 바탕으로 열유속을 계산하였다. 운동량비가 증가할 수록 열전달 현상이 강화 되었으며, $15^{\circ}$ 기울어진 분사보다는 수직 분사의 경우에 더 강한 열전달 현상이 발생되었다. 이를 통해 분사비와 분사 각도가 표면 열전달 분포에 중요한 요인으로 작용함을 확인할 수 있었다.

• 한국분무공학회지
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• 제5권3호
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• pp.17-26
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• 2000

The main parameter commonly used to evaluate spray distribution is spray angle. Spray angle is important because it influences the axial and radial distribution of the fuel. Spray angles were measured and compared for the two non-air assisted injectors such as 2hole-2stream 4hole-1stream injectors used for port fuel injection gasoline engines with n-heptane as a fuel by three different measuring techniques, i.e., digital image processing, shadowgraphy, and spray patternator, respectively. Fuel was injected with the injection pressures of 0.2-0.35 MPa into the room temperature and atmospheric pressure environment. In digital image processing approach, the selection of the transmittance level is critical to obtain the edge of spray and hence to measure the spray angle. From the measurement results by the shadowgraphy technique, it is dear that the spray angle is varied during the spray injection period. The measurement results from spray patternator show that the different spray angles exist in different region. Spray angle increases with the increase in the injection pressure. it is suggested that the spray angle and stream separated angle should be specified when spray is characterized for 2hole-2stream injector, because spray angle is much different though stream separated angle is same. It was also considerably affected by the measurement techniques introduced in this experimental work. However, the optimal axial distance for measuring the spray angle seems to be at least 60-80 mm from the injector tip for two non-air assisted injectors.

• International Journal of Automotive Technology
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• 제6권2호
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• pp.87-93
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• 2005

Spray patterns were visualized using the shadowgraph method, and the droplet size and velocity were measured using PDPA for high-pressure injections up to 2,600 bars. The spray pattern and spray characteristics, such as penetration, spray width, spray angle, droplet size, injection duration, and droplet velocity, were investigated to determine the suitable injection pressure. Spray penetration, width, angle, and velocity increased continuously up to 2,600 bars with the injection pressure in a high-pressure region. The rate of improvement of the above spray characteristics, however, declined rapidly, when the injection pressure reached 2,000 bars. The injection duration and droplet size generally decreased with the increase in the injection pressure, while the rate of improvement decreased abruptly after 2,000 bars. Consequently, the improvement rate of the spray characteristics became blunt at over 2,000 bars. This means that the suitable injection pressure is around 2,000 bars.

• 한국산학기술학회논문지
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• 제12권5호
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• pp.2054-2060
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• 2011

본 연구의 목적은 경제적이고, 친환경적인 가솔린 직접 분사 인젝터의 분무특성을 연구하는 것에 있다. 분무도달거리, 분무각 그리고 혼합기 형성과 같은 인젝터의 특성을 가시화 실험을 통하여 측정하였다. 특히 분무압력과 분위기압력이 분무 침투거리와 분무각에 미치는 영향을 분석하였다. 가시화 실험을 위하여 정적 연소실과 연료 공급장치를 제작하였다. 초고속 카메라와 LED광원을 이용하여 분무형상을 촬영하였고, 촬영된 영상으로 분무 특성을 분석하였다. 연소실내의 분위기압력이 감소하고, 연료의 분무압력이 증가할수록 도달거리는 증가하였다. 분위기압력과 분무압력에 대해 분무각의 변화는 미소하지만, 분위기압력이 분무각에 더 큰 영향을 미치고 있다.

• 대한치과교정학회지
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• 제47권4호
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• pp.222-228
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• 2017

Objective: To evaluate soft- and hard-tissue changes in the mandibular angle area after the administration of botulinum toxin type A (BoNT-A) injection to patients with masseteric hypertrophy by using three-dimensional cone-beam computed tomography (3D-CBCT). Methods: Twenty volunteers were randomly divided into two groups of 10 patients. Patients in group I received a single BoNT-A injection in both masseter muscles, while those in group II received two BoNT-A injections in each masseter muscle, with the second injection being administered 4 months after the first one. In both groups, 3D-CBCT was performed before the first injection and 6 months after the first injection. Results: Masseter muscle thicknesses and cross-sectional areas were significantly reduced in both groups, but the reductions were significantly more substantial in group II than in group I. The intergonial width of the mandibular angle area did not change significantly in either group. However, the bone volume of the mandibular gonial angle area was more significantly reduced in group II than in group I. Conclusions: The repeated administration of BoNT-A injections may induce bone volume changes in the mandibular angle area.

• 수산해양기술연구
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• 제52권1호
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• pp.65-71
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• 2016

Injection rate, injection quantity and injection timing of fuel are controlled precisely by electric control in CRDI system. Particularly, injection rate being influenced with injection pressure affects to spray characteristics and fuel-air ratio, so it is a very important factor in diesel combustion. In this study, injection rates in accordance with injection pressure at a constant ambient pressure were measured with Zeuch's method. Under the same condition, non-evaporating spray images were taken with a high speed camera and analyzed carefully with Adobe Photoshop CS3. Macroscopic spray characteristics and breakup processes in the spray could be found from the examined and analyzed data. Injection start time and injection period were practically affected with injection pressure. Also, initial injection rate, spray penetration, spray angle and breakup of high density droplets region in the spray were affected with injection pressure. The results and techniques of spray visualization and injection rate measurement in this study would be practically effective to study a high pressure diesel spray for common rail direct injection system.