• Title, Summary, Keyword: Inlet Part

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A 6 m cube in an atmospheric boundary layer flow -Part 2. Computational solutions

  • Richards, P.J.;Quinn, A.D.;Parker, S.
    • Wind and Structures
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    • v.5 no.2_3_4
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    • pp.177-192
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    • 2002
  • Computation solutions for the flow around a cube, which were generated as part of the Computational Wind Engineering 2000 Conference Competition, are compared with full-scale measurements. The three solutions shown all use the RANS approach to predict mean flow fields. The major differences appear to be related to the use of the standard $k-{\varepsilon}$, the MMK $k-{\varepsilon}$ and the RNG $k-{\varepsilon}$ turbulence models. The inlet conditions chosen by the three modellers illustrate one of the dilemmas faced in computational wind engineering. While all modeller matched the inlet velocity profile to the full-scale profile, only one of the modellers chose to match the full-scale turbulence data. This approach led to a boundary layer that was not in equilibrium. The approach taken by the other modeller was to specify lower inlet turbulent kinetic energy level, which are more consistent with the turbulence models chosen and lead to a homogeneous boundary layer. For the $0^{\circ}$ case, wind normal to one face of the cube, it is shown that the RNG solution is closest to the full-scale data. This result appears to be associated with the RNG solution showing the correct flow separation and reattachment on the roof. The other solutions show either excessive separation (MMK) or no separation at all (K-E). For the $45^{\circ}$ case the three solutions are fairly similar. None of them correctly predicting the high suctions along the windward edges of the roof. In general the velocity components are more accurately predicted than the pressures. However in all cases the turbulence levels are poorly matched, with all of the solutions failing to match the high turbulence levels measured around the edges of separated flows. Although all of the computational solutions have deficiencies, the variability of results is shown to be similar to that which has been obtained with a similar comparative wind tunnel study. This suggests that the computational solutions are only slightly less reliable than the wind tunnel.

Characteristics of Flow Field around Baffle Located Sudden Expansion and Contraction Open Channel using PIV Measurements (PIV실험을 통한 급확대 축소 개방채널에 설치된 배플 주위의 유동장특성)

  • Lee, Cheol-Jae
    • Journal of the Korean Society of Marine Engineering
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    • v.35 no.4
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    • pp.468-474
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    • 2011
  • The flow field around baffle located sudden expansion and contraction channel was measured by PIV method and the effect according to height change of baffle built in the flow field was evaluated. The inlet flow velocity and the baffle height influence mutually to the size and flow pattern of the recycle flow of the back of the baffle and the size of the area of the water power jump passing the upper part of the baffle. In case of Reynolds number $Re=4{\times}10^3$, the critical value of baffle height is estimated around h/H=1.6 and there was a decreasing tendency as the inlet flow velocity was increased.

Application of Guided Ultrasonic Wave Technology for Evaluation of Welding Part in Cooling Water Pipe (냉각수 배관 용접부 평가를 위한 유도초음파 기술의 적용)

  • Gil, D.S.;Ahn, Y.S.;Park, S.K.
    • Journal of the Korea Society For Power System Engineering
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    • v.14 no.5
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    • pp.36-40
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    • 2010
  • The ultrasonic guided wave propagates along with the given structure's wall direction. Because of this specific character, the ultrasonic guided waves arc used in many other fields. Especially, it can be readily utilized for nondestructive inspection of various structures that are made up of gas pipes, heat exchanger tubes, and thin plates. Further, the guided wave technology can be readily utilized when inspecting pipes or thin plates which pose high risk of the accident but for which the nondestructive inspection itself is impossible because it is difficult to get to them since they are coated or buried underground. In the other hand, conventional ultrasonic testing such as thickness gauging uses bulk waves and only tests the region of structure immediately below the transducer. As a result of the application about inlet and outlet cooling water line using guided wave test, we conformed that the overall corrosions were in the lower side of the 304.8 mm inlet valve and these corrosions were engaged in not locally but through the lower side of the valve line. In the near future, we can expect that the detectable defect size is smaller than before along with the development of the sensing technology.

Simulation of Molecular Flows Inside a Guide Block in the OLED Deposition Process (OLED 박막 증착공정에서 유도로 내부의 분자유동 해석)

  • Sung, Jae-Yong;Lee, Eung-Ki
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.17 no.2
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    • pp.45-50
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    • 2008
  • Molecular flows inside a guide block in the OLED(organic luminescent emitting device) deposition process have been simulated using DSMC(direct simulation Monte Carlo) method. Because the organic materials are evaporated under vacuum, molecules flow at a high Knudsen number of the free molecular regime, where the continuum mechanics is not valid. A guide block is designed as a part of the linear cell source to transport the evaporated materials to a deposition chamber, When solving the flows, the inlet boundary condition is proved to affect significantly the whole flow pattern. Thus, it is proposed that the pressure should be specified at the inlet. From the analysis of the density distributions at the nozzle exit of the guide block, it is shown that the longer nozzle can emit molecules more straightly. Finally, a nondimensionalized mass flow profile is obtained by numerical experiments, where various nozzle widths and inlet pressures are tested.

A Numerical Study on the Flow Characteristics in the Catalytic Muffler with Different Inlet and Outlet Configurations (입구 및 출구 형상 변화에 따른 촉매 삽입형 머플러 내부의 유동 해석)

  • An, Tae Hyun;Lee, Seung Yeop;Park, Yun Beom;Kim, Man Young
    • Transactions of the Korean Society of Automotive Engineers
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    • v.21 no.5
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    • pp.59-66
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    • 2013
  • Lack of the space in many diesel vehicles make it difficult to design and install the catalytic muffler to reduce emissions. For this reason, inlet part of the catalytic muffler is made of L-type which has lower flow uniformity than conventional I-type, and catalytic muffler has complex internal structure by various insertions, which affect the flow uniformity and pressure drop of the systems. In this work, the flow characteristics such as flow uniformity and pressure drop have been numerically investigated by changing such various geometries as inlet shape, porosity, and outlet shape inside the muffler with the three-dimensional turbulent incompressible flow solver. Total 4 different cases are considered in order to find optimal configurations of the catalytic muffler in view of high flow uniformity and low pressure drop. The results show that Case 2 which has no induction cone and outlet perforated pipe has higher uniformity index and lower pressure drop than others considered in this work.

Analysis of Design and Part Load Performance for gas Turbine Cogeneration Systems (가스터빈 열병합발전 시스템의 설계점 설정 및 부분부하 성능해석)

  • 김동섭;노승탁
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.8
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    • pp.2167-2176
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    • 1994
  • This paper presents some useful design criteria for the turbine cogeneration system through both the design and off-design analysis. Comparative analysis of the part load performance is carried out for several gas turbines which have different design parameters represented by the turbine inlet temperature and pressure ratio. It is shown that the variation in part load efficiency considerably depends on the design parameter. The off-design operation of the heat recovery steam generator is simulated by introducing adequate assumptions for the heat transfer process. It is turned out that the design parameters of heat recovery steam generator should be determined by considering the favorable operation at the off-design conditions.

Performance Characteristics for Off-design Operation of Micro Gas Turbines (마이크로 가스터빈의 탈설계 운전 성능특성)

  • Kim, T.S.;Hwang, S.H.
    • The KSFM Journal of Fluid Machinery
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    • v.7 no.3
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    • pp.39-47
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    • 2004
  • Micro gas turbines are designed with low turbine inlet temperature and pressure ratio. To overcome the efficiency defect of the simple cycle, adoption of the recuperator is an inevitable choice. In addition to the design performance, we should also pay attention to the off-design performance of gas turbines since they usually operate at part-load conditions lot a considerable amount of their lifetime. This study analyzes off-design performance characteristics of micro gas turbines and addresses the importance of the recuperation process doting the part load operation. Comparative analyses have been performed to evaluate the part load performance differences among various design and operating options : simple vs recuperative cycles, single vs two shaft configurations, various operating strategies for the single shaft configuration, and current vs advanced engines. Major finding is that maintaining high turbine exhaust temperature is crucial for efficient operation of micro gas turbines.

A study for noise properties of Sirroco fan blades (시로코팬 블레이드의 소음특성연구)

  • 최한림;곽지호;송기선;이덕주
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.257-263
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    • 2001
  • The purpose of this study is to find the amount of contributions of each Sirroco fan parameter to noise and performance using experimental and numerical approaches. We made several fans and structures related to fan housing and fan for parameter study like inlet blade angle, outlet blade angle, inlet diameter, outlet diameter, blade shape. etc.. Numerical analysis was performed using commercial code (FANNOISE) for the part not to be possible to do experiment. Using these parameter study, We have found the way to reduce noise and improve performance of fan and had some useful data for designing low noise and high performance fan.

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The Design and Analysis of vacuum Pump Driven by Linear Motor (리니어 모터구동 진공펌프 설계 및 해석)

  • 김동수;안영희;이원희;김광영
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.680-683
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    • 2002
  • In this paper, it has been investigated that the design and simulation of vacuum pump driven by linear motor. Vacuum pump consists of unified plunger and piston part, coils, inlet valve and outlet valve. Operating principal of vacuum pump show that air is to flow to go inside through the inlet valve when the magnetic force (16N) is exerted, whereas, air is to flow to go outside through outlet valve when spring farce (14.8N) is exerted. The results of simulation. it was turned out that reached vacuum pressure was about -0.55 bar at 150 seconds, magnetic force was loaded with 16 Newton, displacement of actuator was about 8mm.

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Design and Analysis of Linear Motor for Medical Appliance Pump (의료용 펌프의 리니어 모터 설계 및 해석)

  • Kim, Dong-Soo;Lee, Won-Hee;Park, Jae-Bum
    • Proceedings of the KIEE Conference
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    • pp.2683-2686
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    • 2002
  • In this paper, it has been investigated that the design and simulation of linear motor for medical appliances. Vacuum pump consists of unified plunger and piston part, coils, inlet valve and outlet valve. Operating principal of vacuum pump show that air is to flow to go inside through the inlet valve, when the magnetic force (16N) is exerted, whereas, air is to flow to go outside through outlet valve, when spring force (14.8N) is exerted. The results of simulation, it was turned out that magnetic force was loaded with 16 Newton, displacement of actuator was about 8mm.

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