• Title, Summary, Keyword: diffuser

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Effect of Diffuser Width on Rotating Stall in Centrifugal with Vaneless Diffuser (원심형 송풍기에서 베인리스 디퓨저의 폭변화가 선회실속에 미치는 영향)

  • Kim, Jin-Hyeong;Jo, Gang-Rae
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.10
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    • pp.1293-1302
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    • 2001
  • It is generally known that radial vane blowers with vaneless diffuser may generate mostly only a rotating stall but backward curved vane blowers may do both an impeller and a diffuser rotating stalls. In this study, it was found from the numerical and experimental results that the diffuser rotating stall does not appear in a radial vane because of the suppression for the diffuser stall appearance by occurring of impeller rotating stall in a large flow rate coefficient. The diffuser rotating stalls occurring when the width of diffuser is broaden fur a backward curved vane blower are classified definitely by the diffuser flow rate coefficient defined by adopting the varying diffuser width.

Experimental Study on Surge Inception in a Centrifugal Compressor

  • Tamaki, Hideaki
    • International Journal of Fluid Machinery and Systems
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    • v.2 no.4
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    • pp.409-417
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    • 2009
  • An investigation of surge inception in a centrifugal compressor was done with measurements of steady and unsteady static pressure. Vaneless diffuser and vaned diffuser were tested. Analyses of the static pressure and the pressure fluctuation showed that stall at the impeller leading edge occurred at first, and then it extended to downstream. In case of the vaneless diffuser, deterioration of the pressure rise in the impeller triggered instability. For the vande diffuser, instability that was generated in the impeller propagated into the vaned diffuser, however the pressure recovery by the vaned diffuser made the operation of the compressor stable at low flow rate.

A study on the Development and Evaluation of Sludge Occlusion Reduced Diffuser (폐색 저감형 산기관의 개발 및 적용성 평가)

  • Kim, Young-Hoon;Kim, Kwan-Yeop;Lee, Eui-Jong;Nam, Jong-Woo;Lee, Chang-Ha;Jeon, Min-Jung;Kim, Hyung-Soo
    • Journal of Korean Society of Water and Wastewater
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    • v.25 no.1
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    • pp.41-49
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    • 2011
  • The diffuser which is conventionally adapted to MBR, has problem that decreasing the cleaning effect of membrane module by inflexible air supply due to the occlusion of sludge from diffuser hole. To solve this problem, diffuser structure of submerged module should be improved to discharge sludge which is flow into the diffuser for prevent occlusion in the diffuser. In this study, the structure of the diffuser was reformed to open lower part for preclusion the blocking. And the outlet diameter of the diffuser was drawn through the condition for the depth of water and air rate, to prevent air-leak condition of improved diffuser. Moreover, application is evaluated by comparing test with occlusion effect of the conventional and improved diffuser. From the results, air-water boundary changes are steady with changes of water depth and it shows linear relation about air rate. By using this linear numerical formula, the height of diffuser's outlet can be decided. Also, it displays that it can prevent the occlusion effect during the comparing test. Hereafter, if this diffuser is applied to practical MBR process, the occlusion problem of diffuser will be disappeared.

Experimental Study of High-Altitude Simulation using Small-Scale Supersonic Diffuser (소형 초음속 디퓨저를 이용한 고고도환경 모사에 대한 시험적 연구)

  • Lee Ji-Hyung;Oh Jong-Yun;Byun Jong-Ryul
    • Journal of the Korea Institute of Military Science and Technology
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    • v.7 no.4
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    • pp.138-145
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    • 2004
  • Experimental study was conducted on cylindrical supersonic diffuser in order to investigate the effects of the ratios of diffuser area to nozzle throat area (Ad/At), diffuser area to nozzle exit area (Ad/Ae), nozzle exit area to its throat area (Ae/At), and diffuser length to its diameter (L/D), the free volume of vacuum chamber, and the relative distance between nozzle exit and diffuser inlet on the diffuser performance. The study showed that the minimum diffuser starting pressure (Po/Pa)st increased monotonically with increase in (Ad/At) as predicted by the normal shock and momentum theory models and the volume of vacuum chamber affected vacuum pressure level during diffuser operation at lower value of (Ad/Ae). The results of this investigation will be utilized in the design of real-scale high-altitude simulation test facility.

A New pattern Diffuser for LCD Backlight Application

  • Tai, Tsai-Lin;Li, Yu-Tang;Chu, Chang-Sheng;Tien, Wan-Ting;Fan, Chih-Hsun
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.1450-1452
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    • 2009
  • In this work, a plastic diffuser which has a surface similar to Sinusoidal wave profile for application of LC D backlighting is proposed. This new pattern diffuser is achieved the values of the transmission efficiency an d diffusion efficiency all over 70%, and it also has the value about gain over 1.1. Additionally, this new patter n diffuser has high uniformity when we put it in the LCD backlight module and its thickness is only 2mm. With these foregoing properties, this diffuser film can widely applied to LCD displays systems etc.

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A Study on The Performance of Ventilation and Thermal Environment for a Combined Type Diffuser in a Residential Space (거주공간에 대한 급·배기 일체형 디퓨저의 환기 및 온열환경 유지성능에 대한 연구)

  • Lim, Seok-Young;Chang, Hyun-Jae
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.29 no.2
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    • pp.74-81
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    • 2017
  • In this study, the combined-type diffuser developed by the Authors, in a previous study, was applied to a residential space. The performance of a ventilation and thermal environment, created by the use of a combined-type diffuser was compared to the pan-type diffuser widely used in apartment houses. In cooling conditions, because of the relatively high air flow rate of ceiling cassette-type air conditioners, the characteristics of airflow distribution in a room were governed by the air conditioner's airflow. In heating conditions, because of the low air flow rate of the diffuser, the characteristics of airflow distribution were governed by the buoyancy effect created by cold external walls and a hot floor. In terms of the Air Diffusion Performance Index (ADPI), which is a thermal environmental index, the result of a combined-type diffuser was greater than a pan-type diffuser in both of cooling and heating conditions. Consequently, the combined-type diffuser showed equal or superior ventilation and thermal environment performance compared to a pan-type diffuser.

Application of Constant Rate of Velocity or Pressure Change Method to Improve Annular Jet Pump Performance

  • Yang, Xuelong;Long, Xinping;Kang, Yong;Xiao, Longzhou
    • International Journal of Fluid Machinery and Systems
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    • v.6 no.3
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    • pp.137-143
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    • 2013
  • To improve annular jet pump (AJP) performance, new ways named constant rate of velocity/pressure change method (CRVC/CRPC) were adopted to design its diffuser. The design formulas were derived according to the assumption of linear velocity/pressure variation in the diffuser. Based on the two-dimensional numerical simulations, the effect of the diffuser profile and the included angle on the pump performance and the internal flow details has been analyzed. The predicted results of the RNG k-epsilon turbulence model show a better agreement with the experiment data than that of the standard and the realizable k-epsilon turbulence models. The AJP with the CRPC diffuser produces a linear pressure increase in the CRPC diffuser as expected. The AJP with CRPC/CRVC diffuser has better performance when the diffuser included angle is greater or the diffuser length is shorter. Therefore, the AJP with CRPC/CRVC diffuser is suitable for applications requiring space limitation and weight restriction.

Effect of Diffuser Shape on the Performance of Water-Chilled Heat Storage (축열조 성능에 미치는 디퓨저 형상의 영향)

  • 정재동;박주혁;조성환
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.4
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    • pp.374-382
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    • 2004
  • Diffuser design is crucial for water-chilled heat storage. Its impact on the system performance is more significant for the underground tank due to inherent limit on the aspect ratio and tank shape. The effect of diffuser shape on the performance of the water-chilled heat storage is numerically investigated. Three dimensional simulation has been conducted for fully incorporating the complex diffuser shape and the non-symmetric tank shape. Mixing at the inlet of the diffuser depends on the inlet Reynolds number, Froude number and the diffuser shape. Three types of the diffuser shape and the broad range of Reynolds number (Re=400, 800, 1200) and Froude number (Fr=0.5, 1.0, 2.0) are examined. The performance of the heat storage tank is evaluated by the thermocline thickness which is reverse to the degree of stratification. The radial regulated plate diffuser, which is the suggested diffuser shape in this study, shows the lowest thermocline thickness in the condition considered.

A Study on Performance Characteristics Planar angle diffuser with PIV (PIV를 이용한 평판형 디퓨저의 유동특성에 관한 실험적 연구)

  • Oh, Jeong Hun;Cho, Dae-Hwan;Seok, Baek Un
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • pp.261-262
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    • 2012
  • In planar angle diffuser, the increasement of cross-sectional area so rapidly cause possibly separate from the diffuser wall and forming areas of backflow. The flow characteristics of planar angle diffuser was investigated for three kind of inclined angle. Judging from the results, wide planar diffuser can be used as an effective means of improvement for diffuser performance and inclined angle of diffuser was through to be the best among three cases.

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ANALYSIS OF THE MIXING BEHAVIOR OF THE HEATED WATER FROM THERMAL DIFFUSER

  • Seo Il Won;Jeon Tae Myoung;Son Eun Woo;Kwon Seok Jae
    • Water Engineering Research
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    • v.6 no.1
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    • pp.1-15
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    • 2005
  • The numerical model, FLUENT, was employed to investigate the effect of the heated water discharged from the diffuser of Boryung Power Plant. Temperature patterns of the thermal effluent discharged from two proposed types of the diffusers was evaluated for maximum flood and maximum ebb tide. The hydraulic model experiments were also performed in the reduced scale of 1/150 to verify the numerical simulation results. The buoyant jets discharged from the diffusers were found to be significantly affected by the ambient flows beyond the region where the effluent momentum was dissipated. Both the numerical and experimental results showed that the area of the excess isotherm for Type 1 diffuser was larger than that for Type 2 diffuser. Type 2 diffuser system was observed to be a more effective diffuser design than Type 1 diffuser system based on the temperature reduction and excess isotherm obtained from the numerical simulation in the ambient flows.

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