• 한국수소및신에너지학회논문집
• /
• 제27권6호
• /
• pp.737-746
• /
• 2016

This article describes a comparison on laminar burning velocity measured by Bunsen and spherical flame methods of synthetic natural gas (SNG) with various composition of hydrogen. In this study, the laminar burning velocity measurements were employed by Bunsen burner and cylindrical constant combustor at which flame images were captured by Schlieren system. These results were also compared with numerical based on CHEMKIN package with GRI 3.0, USC-II and UC Sandiego mechanism. In case of spherical flames, the suitable flame radius range and theoretical models were verified using the well-known previous results in methane/air flames. As an experimental condition, hydrogen content of SNG was adjusted 0% to 11%. Equivalence ratios of Bunsen flames were adjusted from 0.8 to 1.6. On the other hand, those of spherical flames were adjusted from 0.6 to 1.4, relatively. From results of this study, the both laminar burning velocities measured in Bunsen and spherical flame methods were resulted in similar tendency. As the hydrogen content increased, the laminar burning velocity also increased collectively. Laminar burning velocity of measured SNG-air flames was best coincided with GRI 3.0 mechanism by comparison of reaction mechanisms.

• 한국항공우주학회지
• /
• 제47권2호
• /
• pp.107-113
• /
• 2019

본 논문에서는 대기 속도 센서가 없는 항공기에서의 강인 필터 기반의 바람 추정 기법을 제안한다. 바람 속도(wind velocity)는 항공기의 유도 및 제어를 더욱 정밀하게 수행하기 위해 사용되는 정보이다. 일반적으로 바람 속도는, 대기 속도와 지면 속도의 차이를 계산하여 얻을 수 있다. 이때 대기 속도는 피토 튜브와 같은 항공기와 대기의 상대 속도를 측정하는 대기 속도 측정 센서에서 얻을 수 있고, 지면 속도는 항법 시스템으로부터 얻을 수 있다. 그러나 항공기의 구성을 간단하게하기 위하여 대기 속도 측정 센서를 장착하지 않는 경우, 바람 속도를 직접적으로 얻을 수 없기 때문에 필터를 이용한 바람 추정 기법이 필수이다. 이때 난류에 의해 항공기의 공력 계수가 변하게 되는데, 이는 바람 추정 필터의 시스템 모델의 불확실성을 유발하게 되고, 결국 바람 추정 성능이 저하된다. 따라서 본 연구에서는 공력계수 불확실성에 강인함을 확보하기 위해 $H{\infty}$ 필터를 적용한 바람 추정 기법을 제안하였다. 시뮬레이션을 통해 제안하는 기법이 공력계수의 불확실성이 있는 상황에서 성능을 개선하는 것을 확인하였다.

• 한국항공우주학회지
• /
• 제36권4호
• /
• pp.352-356
• /
• 2008

수소제트와 동축공기를 사용한 본 연구에서, 난류확산화염의 화염안정성 특징을 실험적으로 수행하였다. 목적은 연료속도 증가에 따라 감소하는 부상화염길이의 경향을 보고하고, 부상 메커니즘을 포함한 화염구조를 분석하는 것이다. 수소연료는 100에서 300 m/s 사이에서 조절되었으며, 이때 동축공기는 16 m/s 고정되고, 주위류는 0.1 m/s 이하로 유지되었다. 유동장과 연소장 동시측정을 위하여, 두 대의 Nd:Yag 레이저와 CCD 카메라를 이용하여 PIV와 OH PLIF 기법이 사용되었다. 결론적으로 난류화염전파속도는 난류강도에 비례하였으며, 제트 레이놀즈수의 0.017승에 비례하였다.

• 한국항공우주학회지
• /
• 제30권5호
• /
• pp.71-78
• /
• 2002

동축공기 수소확산 화염에서 세 가지 동축공기 조건과 화염의 유무에 따라 실험조건을 분류하고, 이에 대해 PIV를 이용하여 실험을 수행하였다. PIV를 통해 얻은 속도장을 이용하여 평균속도, 난류강도, Reynolds stress 등을 구하여 유동장을 분석하였다. 우선 단순제트에 대해 상사성을 살펴본 결과 이전의 다른 연구자의 실험결과와 일치하였다. 동축공기가 있는 경우 중심축 속도 감쇠는 $x^{-1}$에 비례하여 감소하는 것을 확인하였다. 축방향 길이를 유효밀도에 의해 정의된 유효 제트 지름으로 무차원화한 값으로 중심축 속도를 도시한 결과 하나의 선분에 떨어지는 것을 확인하였다. 평균속도 분포를 살펴보면 일정한 연료유량에 동축공기 유량을 증가시킨 경우 동축공기가 증가함에 따라 속도 분포의 형태가 바뀌게 되어 자기상사성이 유지되지 않는 것으로 보인다. 난류강도는 평균속도 분포의 경우보다 후류에서 자기상사성이 나타난다.

• 한국해양공학회지
• /
• 제29권2호
• /
• pp.154-162
• /
• 2015

In this study, experimental and numerical methods were applied to observe sloshing impact phenomena. A two-dimensional rectangular tank filled with water and air was considered with a specific excitation condition that induced a hydrodynamic impact without an air pocket at the top corner of the tank. High-speed cameras and a pressure measurement system were synchronized, and a particle image velocimetry (PIV) technique was applied to measure the velocity field and corresponding pressure. The experimental condition was implemented in a numerical computation to solve incompressible two-phase flows using a Cartesian-grid method. The discretized solution was obtained using the finite difference and constraint-interpolation-profile (CIP) methods, which adopt a fractional step scheme for coupling the pressure and velocity. The tangent of the hyperbola for interface capturing (THINC) scheme was used with the weighed line interface calculation (WLIC) method to capture the interface between the air and water. The calculated impact pressures and velocity fields were compared with experimental data, and the relationship between the local velocity and pressure was investigated based on the computational results.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2001년도 추계학술대회 논문집
• /
• pp.213-219
• /
• 2001

In this paper, particle velocity of slurry flow, a kind of solid-particle two phase flow, was measured by using a particle tracking velocimetry. Particles are modeled by sphere-shaped glass whose diameters are 3mm, 5mm, and 7mm At first, a particle which is falling in the water is captured and analyzed to give their free falling velocity. The falling velocity was very high up to about 4m/sec in the air, which needs special algorithm for the accurate measurement. For the upwelling slurry flow in the straight duct, there are some noises caused by cavity. However, the effect was so small that it does not affect the measurement of large particles. From the preliminary study of applying the PTV to measurement of particle movement in slurry flow, we could find out the optimum value of parameters: threshold value., searching area radius and correlation area size.

• 설비공학논문집
• /
• 제15권9호
• /
• pp.727-732
• /
• 2003

In the present study, a PIV measurement and image processing technique were applied in order to investigate the flow characteristics in the gas injected liquid bath. The circulation of liquid was induced by upward bubble flow. Due to the centrifugal force, the flow was well developed near both wall sides than in the center of a bath. The vortex flow irregularly repeated generation and disappearance which helped to accelerate the mixing process. The bubble rise velocity in the bottom region was relatively lower than in the upper region because the energy generated by bubbles' behavior in the region near the nozzle was almost converted into kinetic energy But bubble rise velocity increases with the increase of the axial distance since kinetic energy of rising bubbles is added to buoyancy force. In conclusion, the flow increased bubble rise velocity and the flow of the bottom region became more active.

• 한국대기환경학회:학술대회논문집
• /
• 한국대기환경학회 2004년도 추계학술대회 논문집
• /
• pp.371-372
• /
• 2004

• 한국입자에어로졸학회지
• /
• 제5권2호
• /
• pp.37-43
• /
• 2009

Particulate matter (PM) is one of the major indoor air pollutants especially in the subway station in Korea. In order to remove PM in the subway station, several kinds of PM removal system such as roll-filter, auto-washable air filter, demister, and electrostatic precipitator are used in the air handling unit (AHU) of subway stations. However, those systems are prone to operation and maintenance problems since the filter-regeneration unit consisting of electrical or water jet parts might malfunction due to the high load of particulates unless the filter medium is periodically replaced. In this study, the use of axial-flow cyclone was proposed for particulate filter unit in the AHU for its low operation and maintenance cost. Novel shape of axial-flow cyclone was designed by using computational fluid dynamics (CFD). The shape of vortex vane was optimized in terms of pressure drop and tangential velocity. In addition, CFD analysis was validated experimentally through the pressure drop measurement of mock-up model. We found that pressure drop and tangential velocity of fluid through the axia-flow cyclone was significantly affected by the rotating degree of vortex vane and the numerical prediction of pressure drop agreed well with experimental measurement.

• 센서학회지
• /
• 제15권6호
• /
• pp.442-448
• /
• 2006

Ultrasonic anemometers using pulse envelope detection-based method are standard instruments in most meteorological studies. In this paper, a new phase measurement method is tried to achieve the enhanced resolution without changing dimensions. The measurement sensitivity, dynamic range, and measurement speed of the new instrument are 0.2 mm/s, 13.3 m/s, and 13 measurements/sec, respectively. A graphic user interface is added to show the velocity and direction of the wind with the speed of sound and temperature of the wind in the 3 dimensional space. The new anemometer could be useful for the measurement of the air speed, the flow of fluids, and even air flow inside the downtown buildings.