• 항공우주기술
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• 제9권2호
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• pp.193-197
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• 2010

로켓엔진 고공 환경 모사용 디퓨져에는 연소가스의 고열로부터 디퓨져를 보호하기 위해 물을 이용한 냉각시스템이 사용되며 냉각수의 유량 및 압력은 냉각 채널 내부에서 냉각수의 비등이 발생하지 않도록 결정된다. 따라서 냉각수 유량의 변화에 따른 냉각 채널 벽면의 최고온도 예측은 냉각시스템의 운용 압력을 결정하는데 주요한 변수가 된다. 본 연구에서는 열평형 이론에 근거하여 유량 변화에 따른 채널 벽면의 최고온도를 예측하는 방법을 기술하였다.

• 한국태양에너지학회 논문집
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• 제33권2호
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• pp.56-63
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• 2013

Daylighting system is an alternative lighting system using daylight collecting device, light transformer and light diffuser. In this paper, we developed a daylighting system in which the collecting device composed by dual parabolic reflectors, the silica optical fiber adapted to the light transformer and light diffuser made of the polyglass square sheet. We have estimated the system efficiency and general color rendering index(Ra) of the developed system. The system efficiency measured to 23.8% and Ra was revealed as 95. Ra number of the developed system is bigger than the number(65) of the previous fresnel lens based sunlight collector.

• 동력기계공학회지
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• 제16권5호
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• pp.55-62
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• 2012

Centrifugal compressors are widely used and each operating condition is different. However, it cannot be manufactured according to the every operating condition. In the this study, performance of compressor was evaluated with various rotational speeds of impeller and various stagger angles of diffuser in order to apply a typical model widely. A centrifugal compressor was designed and manufactured based on the design point. On this machines, an experiment was conducted and the performance was predicted at off-design point. The performance prediction was validated with the experimental result and the numerical result. Although the isentropic efficiency on the prediction was slightly lower than that on the experimental result due to the heat loss in the experiment, the pressure ratio was predicted well and also the predicted results were matched well with the numerical results. When the rotational speed of the impeller and the stagger angle of the diffuser were changed together, the compressor can be worked in the high efficiency region and avoided operating in the stall region.

• 한국지하수토양환경학회지:지하수토양환경
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• 제11권4호
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• pp.25-32
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• 2006

본 연구는 산기관(diffuser) 형태로 운전되는 중공사막 생물반응기(Hollow Fiber Membrane Diffuser) 시스템을 복합오염물질(benzene, toluene, p-xylene, BTX)처리에 적용해 보고, 생물반응기에 의한 각 물질의 생분해 특성을 평가하기 위하여 수행되었다. 우선 toluene을 단일오염물질로 적용한 예비 실험기간 동안에 75%수준의 안정적인 처리 효율을 확인할 수 있었다. 이후 BTX 복합오염물질을 적용한 본 실험기간 동안에도 별도의 적응기간 및 악영향 없이 70%수준의 처리효율을 얻어낼 수 있었다. 이를 통하여 toluene분해 미생물의 benzene, p-xylene의 분해 능력을 확인하였으며, toluene의 경우 복합오염물질 적용 시 다른 두 물질에 의해 소폭의 분해 저해가 발생하는 것을 알 수 있었다. 또한 분해능 실험에서 측정한 생물반응기의 BTX 분해능은 약 360 $g/m^3/hr$이었으며, 이는 기존의 생물여과공법에 제시된 최대분해능보다 높은 우수한 분해능이었다. 따라서 산기관 형태의 중공사막 생물반응기는 복합오염물질 처리에도 안정적인 운전특성을 나타내었으며, 기존의 VOCs 저감기술을 대체할 수 있는 친환경적인 기술이라고 판단된다.

• 한국산학기술학회논문지
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• 제16권6호
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• pp.3722-3730
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• 2015

하수 처리용으로 사용되는 소형 원심 압축기의 베인 없는 디퓨져와 볼류트 케이싱의 성능 개선을 수행하였다. 기존의 두 모델은 임펠러가 동일하나, 베인 없는 디퓨져의 폭과 길이 및 볼류트 케이싱의 형상은 서로 다르다. 기존 모델에 대한 실험과 유동해석 결과를 바탕으로 베인 없는 디퓨져와 볼류트 케이싱의 설계를 변경하였다. 세 모델에 대한 연구 결과로부터, 볼류트 케이싱의 단면적 및 입구 반경 길이는 볼류트 혀와 베인 없는 디퓨져 및 임펠러와의 상호작용 강도에 영향을 주었고, 시스템 손실량에 변화를 나타내었다. 베인 없는 디퓨져 폭이 감소하면 임펠러의 효율은 증가했지만 디퓨져에서의 손실도 증가하였다. 결과적으로 개선된 모델의 효율이 설계 점에서 기존 대비 약 2.88%p 향상된 것이 유동해석 결과로 확인되었다.

• 대한기계학회논문집B
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• 제29권1호
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• pp.9-15
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• 2005

From the geometric parameter study, an optimal ejector design procedure of pressure recovery system for chemical lasers was acquired. For given primary flow reservoir conditions, an up-scaled ejector was designed and manufactured. In the performance test, secondary mass flow rate of 100g/s air was entrained satisfying the design secondary pressure, $40{\sim}50torr$. Performance validation of a supersonic ejector system along with an investigation of effects of supersonic diffuser was conducted. Placement of the diffuser at the secondary inlet further reduced diffuser upstream pressure to 7torr. Lastly, the duplicate of apparatus (air 500g/s secondary mass flow rate each) was built and connected in parallel to assess proportionality behavior on a system to handle larger mass flow rate. Test and comparison of the parallel unit demonstrated the secondary mass flow rate was proportional to the number of individual units that were brought together maintaining the lasing pressure.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2763-2768
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• 2007

Recently, as the semiconductor production technology develops, there has been growing interest in the cooling system using micro fluid pump. Among the various types of micro fluid pump, the valve-less diffuser/nozzle has been extensively studied in recent years. However, the flat-walled diffuser/nozzle flow has not been clearly looked into due to its non-linear characteristics. In this paper, the flow characteristics of the flat-walled diffuser/nozzle have been analyzed using similitude model and simulations. Similitude models are designed so that the flow pattern is same as that of 1/10 scale flow by using high viscous fluid as working fluid. The results are compared to the simulations. It is shown that the flow characteristics of 2D simulation are different from 3D simulations at high Re region, and the measured pump efficiency is highly dependent on the pressure difference as well as the channel geometry. From these results, the desirable conditions for the efficient pump is discussed.

• 대한조선학회논문집
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• 제41권6호
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• pp.15-23
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• 2004

In order to investigate efficiency and flowfield charateristics of the intake-diffuser for the ship waterjet propulsion, new experimental verification technology was set up in the cavitation tunnel. 1-hole and 5-hole pilot tubes were designed and manufactured to measure the pressure and velocity distributions at intake-diffuser entrance and impeller inlet. The calibration of the 5-hole pilot tubes is conducted at the cavitation tunnel The cavitation inception occurs at the intake lip, and the occurrence position depends on IVR (Inlet Velocity Ratio) condition. The present experimental device will be applied sufficiently for the development of the design and performance improvement technologies.

• 항공우주기술
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• 제11권2호
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• pp.117-121
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• 2012

고공 환경 하에서 작동하는 우주발사체 상단 추진기관의 경우 지상에서 실제 작동 환경에 가까운 조건에서 연소시험을 수행하여 그 성능을 검증하게 된다. KSLV-I 상단 추진기관의 경우 원통형 디퓨저를 이용하여 고공환경 모사시험을 수행하였으며, 디퓨저의 설계 검증 및 시동특성을 확인하기 위해 축소형 디퓨저에 대한 비반응 유동시험 및 연소시험을 수행하였다. 본 논문에서는 축소형과 실물형 디퓨저에 대한 시험 결과를 제시하고 시동특성에 대해 분석하였다.

• 상하수도학회지
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• 제22권3호
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• pp.389-396
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• 2008

The hybrid model can be used to predict the initial near field mixing and the far field transport of the buoyant jets, which are discharged from the submerged wastewater ocean outfall. In the near field, the jet integral model can be used for single port diffusers while the ${\sigma}$ transformed particle tracking model was used in the far field. In this study, the experimental study was performed to verify the developed hybrid model in the previous research. The developed hybrid model properly predict the surface and vertical concentration distribution of the single buoyant jets with various effluent and ambient conditions. The hybrid model can also simulate the surface concentration distribution of the rosette diffuser except for the parallel diffuser with the higher densimetric Froude number due to the assumption that dynamic effects of the effluent plumes are negligible in the far field. The application of the hybrid model to rosette diffusers can predict the concentration near the diffuser more accurately when the line-plume approximation is used.