• 한국산업융합학회 논문집
• /
• 제20권2호
• /
• pp.157-168
• /
• 2017

The pressure drop characteristics of air particle flow in a powder transport piping system were analyzed in this study. The pressure drop characteristics of air particle flow in the piping system have not well understood due to the complexibility of particle motion mechanism. Particles or powders suspended in the air flow cause the increase of the pressure drop and affect directly transport efficiency. In this study, the pressure drop in a powder transport piping system was analyzed with interactions of air flow and particle motion in straight and curved pipes. The total pressure drop increased with pipe length, mixture ratio, and friction factor of particles because of increased friction loss of air and particles in the piping system. For the coal powders of $74{\mu}msize$ and powder-to-air mass mixture ratio of 0.667, the total pressure drop under the consideration of powders and air flow was calculated as much as 30% higher than that air flow only.

• 대한기계학회논문집A
• /
• 제33권12호
• /
• pp.1375-1382
• /
• 2009

The objective of this paper is to apply the load ratio method to the measurement of the crack length of the real scale pipe specimen. The load ratio method was modified and finite element analyses were performed to derive the relationship between the normalized compliance and the normalized crack length for the pipe specimen. In order to measure the crack length, the direct current potential drop method and the modified load ratio method were applied to the pipe test. The applicability of the modified load ratio method was confirmed by comparing the calculated crack length with the measured crack length from the pipe experiment.

• 한국전산유체공학회지
• /
• 제16권2호
• /
• pp.62-65
• /
• 2011

Characteristics of the pressure drop in an expanded bed have been compared to those in a packed bed for numerical study of the interphase drag in gas-particle flows. A numerical analysis of the pressure drop by the particle drag has been conducted according to the tube-to-particle diameter ratios and Reynolds numbers for comparison. As the tube-to-particle diameter ratios increase at the same Reynolds number, the pressure drop tends to converge. It has been confirmed that characteristics of the pressure drop in the expanded bed are similar to those in the packed bed.

• 한국분무공학회지
• /
• 제3권2호
• /
• pp.1-13
• /
• 1998

A theoretical and experimental study was carried out to predict the drop size distribution of the pressure swirl atomizer. Various analytical methods using the Kelvin-Helmholtz instability theory were tried to examine the wave growth on cylindrical liquid sheets. Cylinderical liquid sheets were extended to the case with the conical sheets. Perturbations due to tangential motion as well as longitudinal one were taken into account. And it was assumed that the breakup occurs when amplitude ratio exceeds exp(12), drop sizes were predicted only by theoretical approach. Drop size distribution was obtained by using maximum entropy formalism. Seven constraints in the form of the definition of mean diameter were used in this formulation in order to avoid the difficulties of estimating source terms. In this study $D_{10}$ only was introduced into the formulation as a constraint. The predicted drop size and drop size distribution agreed well with the measured data.

• 전자공학회논문지S
• /
• 제34S권8호
• /
• pp.20-26
• /
• 1997

In this paper, we propose a tunable drop/pass filter in the form of composed of Mach-Zehnder interferometer, to which a fiber grating and two PZTs are attached. The proposed drop/pass filter drops a part of signal power at a specific wavelength and pass the remnant of the signal to the next node in WDM network. Our simulation results show that the optical feedback is less than 2% and the drop to pass ratio can be made bigger than 10% if the phase difference between the two arms is within .+-.0.2.pi. from (2m+1).pi.. Also, the output powers at drop prot and pass port are measured to be maximum at the phase difference of .pi./2 and .pi., respectively, as expected.

• 한국에너지공학회:학술대회논문집
• /
• 한국에너지공학회 1999년도 춘계 학술발표회 논문집
• /
• pp.23-31
• /
• 1999

가압 조건하에서의 석탄가스화 특성을 규명하기 위해, 온도, 압력, 산소/석탄비, 수증기/석탄비 등을 변화시켜가며 로토탄(Sub A)에 대하여 PDTF(Pressurized drop tube furnace) 실험을 수행하였다. 실험결과, 상압 조건에서보다 가압조건에서의 가스화가 탄소 전환율과 냉가스효율의 측면에서 더 유리한 것으로 측정되었다. 최대의 냉가스효율을 보이는 산소/석탄비(무게기준)는 0.5∼0.7(g/g)로 측정되었고, 온도가 충분히 높은 경우에만 수증기/석탄비의 증가가 냉가스효율의 증가를 가져왔다. 압력이 증가할수록 열분해에 의한 탄소전환의 비중은 감소하고 대신 기고반응(heterogeneous reaction)에 의한 탄소전환의 비중이 증가하였다.

• 대한전자공학회논문지SD
• /
• 제37권10호
• /
• pp.51-56
• /
• 2000

본 논문에서는 용융-인장형 광섬유커플러 내부에 격자를 새겨 넣음으로써 광섬유커플러형 add/drop 필터를 구현해 보았다. 결합비가 99.8%인 광섬유커플러와 길이가 10mm인 광섬유격자로 구성된 add/drop 필터의 투과스펙트럼상의 최대 반사효율과 drop 효율은 각각 99%와 83%를 보여주었다.

• Tribology and Lubricants
• /
• 제38권5호
• /
• pp.213-221
• /
• 2022

This paper presents performance measurements of pressure drop and leakage flow rate of test flat seals with asymmetric inclined grooves. This study aims to reveal the influence of groove shapes, often machined in radial film riding-face seals, in forming a hydrodynamic wedge on leakage performance. A test facility was developed, and test seals were manufactured to study the effects of the inlet pressure level, ratio of inlet to outlet pressure, seal groove length, and seal groove height on the steady-state pressure drop and leakage performance. A series of tests were conducted, and the test data were compared to the predictions from a simple and efficient mathematical model using a one-dimensional Reynolds equation. The test results revealed that an increase in the inlet pressure increased the pressure drop through the test seals. The leakage flow rate increased significantly as the inlet pressure and ratio of the inlet to outlet pressure increased. The groove shape also affects seal performance. An increase in the groove length and height resulted in an evident increase in the leakage flow rate. The simple model predictions underestimated the leakage flow rates but showed good agreement with the trend in the measurements for all test operating conditions and changes in the groove shape.

• 한국전산유체공학회지
• /
• 제21권4호
• /
• pp.90-95
• /
• 2016

Leidenfrost drops with ellipsoidal shaping can control the bouncing height by adjusting the aspect ratio(AR) of the shape at the moment of impact. In this work, we focus on the effect of the AR and the impact Weber number(We) on the non-axisymmetrical spreading dynamics of the drop, which plays an important role in the control of bouncing. To understand the impact dynamics, the numerical simulation is conducted for the ellipsoidal drop impact upon the perfect non-wetting solid surface by using volume of fluid method, which shows the characteristics of the spreading behavior in each principal axis. As the AR increases, the drop has a high degree of the alignment into one principal axis, which leads to the consequent suppression of bouncing height with shape oscillation. As the We increases, the maximum spreading diameters in the principal axes both increase whereas the contact time on the solid surface rarely depends on the impact velocity at the same AR. The comprehensive understanding of the ellipsoidal drop impact upon non-wetting surface will provide the way to control of drop deposition in applications, such as surface cleaning and spray cooling.

• 대한안전경영과학회지
• /
• 제10권4호
• /
• pp.145-152
• /
• 2008

According to the Korea Agency for Technology and Standards under the Commerce Ministry, OLED device's lifetime is defined 50% drop of luminance. OLED device is self-emitting operating device, that means it becomes different color between pixels under using environment. That's reason of the different luminance drop ratio & chromaticity coordinates shift ratio with time. The problem is there is not recovered after luminance drop and color shift. We can recognize the difference of color as image sticking. First we studied when human recognize the difference of color and second we apply the method of OLED device's lifetime test that's able to check different color between pixels.