• Title/Summary/Keyword: Internal-Mixing

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NUMERICAL STUDY OF MIXING ENHANCEMENT EFFECT DUE TO THE CONFIGURATION RATIO OF CAVITY (Cavity 형상비에 따른 혼합 중대 효과의 수치적 연구)

  • Oh Juyoung;Bae Y.W.;Kim K.S.;Byun Y.H.;Lee J.-W.
    • 한국전산유체공학회:학술대회논문집
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    • 2005.10a
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    • pp.245-248
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    • 2005
  • SCRamjet is the key technology for hypersonic flight over mach number 6. It is characterized by very short residence time in combustor because its internal flow is supersonic. In this short time, the whole process of combustion must be done. Especially numerical study of combustor is important because air-fuel mixing rate influences the performance of combustor. Various methods of air-fuel mixing enhancement are proposed. Among these, cavity injection method is selected to study in this paper. The numerical study is conducted with the variation of the cavity length at the fixed height of unit and jet injection on the downstream of cavity.

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Studies on the Properties of Fiber Reinforced Porous Concrete Using Polymer (섬유보강 폴리머 포러스콘크리트의 특성에 관한 실험적 연구)

  • Park, Seong-Bum;Lee, Byung-Jae;Lee, Jun;Son, Sung-Woo;Cho, Kwang-Yeon
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.05b
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    • pp.581-584
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    • 2006
  • This study is analyzed mechanical properties and durability of permeability porous concrete to mix polymer and steel fiber for the enhance of performance and durability of porous concrete. It proves that void ratio and permeability are tallied with internal and external standard of paving porous concrete. A property of strength is increased according as the mixing rate of polymer and steel fiber increase, but it showed the tendency to be reduced on the contrary when mixed upwards of 20% of polymer mixing rate and 0.9vol.% of steel fiber mixing rate. As a result, it is possible to make an enhanced which increased 16% of compressive strength and 30% of flexural strength steel fiber reinforced polymer porous concrete at the mixing rate of 10vol.% of polymer and 0.6% of steel fiber.

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Identification of Internal Flow Pattern in Effervescent Atomizers (기체주입노즐의 내부유동양식의 구분)

  • Kim, Joo-Youn;Lee, Sang-Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.2
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    • pp.306-315
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    • 2000
  • An experimental study was conducted to examine the internal flow patterns inside the mixing chamber of effervescent atomizers. The mixing chamber has the rectangular cross section ($8mm{\times}2mm$) and made of transparent acrylic plate for flow visualization. The parameters tested were the air/liquid ratio (ALR), injection. pressure, and the nozzle orifice diameter. Three different flow regimes were observed; bubbly, annular, and intermittent flows. In the bubbly flow regime, the discharged mixture was disintegrated into drops through the bubble expansion and the ligament breakup. On the other hand, in the annular flow regime, the liquid annulus was disintegrated into small drops by the aerodynamic interaction between the phases due to the high relative velocities between the gas and the liquid. In the intermittent flow regime, the bubble-expansion/ligament-disintegration mode and the annulus-disintegration mode appeared alternatively. The correlations representing the transition criteria between the two-phase flow patterns within the mixing chamber were proposed based on the drift-flux models.

Investigation of Hydrodynamic Mass Characteristic for Flow Mixing Header Assembly in SMART (SMART 유동혼합헤더집합체의 동수력 질량 특성 고찰)

  • Lee, Gyu Mahn;Ahn, Kwanghyun;Lee, Kang-Heon;Lee, Jae Seon
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.16 no.1
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    • pp.30-36
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    • 2020
  • In SMART, the flow mixing header assembly (FMHA) is used to mix the coolant flowing into the reactor core to maintain a uniform temperature. The FMHA is designed to have enough stiffness so the resonance with reactor internal structures does not occurs during the pipe break and the seismic accidents. Since the gap between the FMHA and the core support barrel assembly is very narrow compared with the diameter of FMHA, the hydrodynamic mass effect acting on the FMHA is not negligible. Therefore the hydrodynamic mass characteristics on the FMHA are investigated to consider the fluid and structure interaction effects. The result of modal analysis for the dry and underwater conditions, the natural frequency of primary vibration mode for the horizontal direction is reduced from 136.67 Hz to 43.76 Hz. Also the result of frequency response spectrum seismic analysis for the dry and underwater conditions, the maximum equivalent stress are increased from 13.89 MPa to 40.23 MPa. Therefore, reactor internal structures located in underwater condition shall consider carefully the hydrodynamic mass effects even though they have sufficient stiffness required for performing its functions under the dry condition.

Atomization Characteristics of 2-Phase Atomizer with the change of Mixing Chamber Structure (혼합실 구조 변경에 의한 2상 노즐의 미립화 특성)

  • Ha, M.H.;Kim, K.C.;NamKung, J.H.;Lee, S.G.;Rho, B.J.;Kang, S.J.
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.699-704
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    • 2001
  • The purpose of this study is to present the atomization characteristics of 2-phase internal mixing nozzle. The obtained results are considered as the essential information of understanding the spray characteristics from the nozzle exit of an aerated nozzle. In this study, SMD and AMD are mainly measured at the distance of Z=10, 20, 50, 80, 120 and 170mm from the nozzle tip. The liquid flow rate was kept at 1.8g/s and the air feeding pressure was changed from 10kpa to 100kpa increasingly. The analysis of the acquired data was performed by 2-D PDPA system and in order to get the realibility, the number of data used in calculating the SMD & AMD were 10,000 samples.

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THE EFFECTS OF IMPELLER CONFIGURATION ON MIXING AND HEAT TRANSFER IN A STIRRED TANK WITH A HELICAL COOLING COIL (나선형 냉각 코일이 설치된 교반기에서 임펠러 배치가 교반과 열전달에 미치는 영향)

  • Kim I.S.;Song H.-S.;Han S.P.
    • 한국전산유체공학회:학술대회논문집
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    • 2005.10a
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    • pp.55-59
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    • 2005
  • CFD analysis has been conducted to find the two stage impeller configuration which is the most suitable for a stirred tank with an internal helical cooling coil and a cooling jacket, which is frequently used in chemical industries for highly exothermic reactions ranged from low to medium viscosity. Two typical types of impellers are considered; pitched paddle impellers and Rushton turbine impellers. Interestingly, pitched paddle impellers show a good mixing performance for multi-species, whereas Rushton turbine impellers achieve a good mixing performance for multi-phases. Besides the type of an impeller, the location of an impeller is another important factor to be considered in order to accomplish an effective mixing. The best set of types and locations of two impellers is recommended based on the coefficient of variation(CoV) value and the heat removal capability obtained from CFD results. The former is a measure to quantify the degree of mixing.

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INTERNAL FLOW PROPERTIES AND THRUST CHARACTERISTICS OF AXI-SYMMETRIC ANNULAR BELL TYPE EJECTOR-JET (축대칭 환형 이젝터 제트의 내부 유동과 추력특성)

  • Park, G.H.;Kwon, S.J.
    • Journal of computational fluids engineering
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    • v.12 no.2
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    • pp.46-52
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    • 2007
  • An experimental and numerical investigation of the ejector-jets focusing on its geometric parameters that effect on thrust performance was carried out. The area ratio of the primary nozzle that was tested in the present study was 2.17 and 3.18, while the ratio of the length to the diameter of the duct downstream the primary nozzle inlet had values of 3.41, 6.82, and 10.23. Internal flow properties of ejector-jet were estimated by comparison experiment data and CFD analysis for basic study of ejector-jet thrust performance. For examination of thrust performance, the thrust ratios increased with increase in L/D. Especially at AR=2.17, the maximum thrust augmentation was 33 percent for the shortest L/D. It is expected that the increase of mixing duct length of ejector-jet will be helpful in a thrust performance by improving mixing efficiency.

INTERNAL FLOW PROPERTIES AND THRUST CHARACTERISTICS OF AXI-SYMMETRIC ANNULAR BELL TYPE EJECTOR-JET (축대칭 환형 이젝터 제트의 내부 유동과 추력특성)

  • Park, G.H.;Kwon, S.J.
    • 한국전산유체공학회:학술대회논문집
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    • 2007.04a
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    • pp.166-170
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    • 2007
  • An experimental and numerical investigation of the ejector-jets focusing on its geometric parameters that effect on thrust performance was carried out. The area ratio of the primary nozzle that was tested in the present studywas 2.17 and 3.18, while the ratio of the length to the diameter of the duct downstream the primary nozzle inlet had values of 3.41, 6.82, and 10.23. Internal flow properties of ejector-jet were estimated by comparison experiment data and CFD analysis for basic study of ejector-jet thrust performance. For examination of thrust performance, the thrust ratios increased with increase in L/D. Especially at AR=2.17, the maximum thrust augmentation was 34 percent for the shortest L/D. It is expected that the increase of mixing duct length of ejector-jet will be helpful in a thrust performance by improving mixing efficiency.

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Correlation between size and velocity of drops in a spray from an internal mixing twin-fluid atomizer (내부혼합형 이류체 분사노즐에서 발생한 분무내 액적들의 크기와 속도의 상관관계)

  • Kim, Sang-Jin;Hiroyasu, H.
    • Journal of ILASS-Korea
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    • v.3 no.1
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    • pp.27-33
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    • 1998
  • Correlations of drop size and velocity in a spray from the disintegration of liquid jet and liquid film from an internal mixing twin-fluid atomizer, were determined by phase Doppler method. The distribution pattern of Sauter mean diameter(SMD) in a spray was changed by a behavior of liquid flow. As smaller droplets became faster and slower easily by the surrounding conditions, the correlation between drop size and mean velocity was found to be varied as next 3 steps; firstly smaller droplets have a higher mean velocity at the area near atomizer, droplets have almost the same mean velocity and finally larger droplets have a higher mean velocity at the area far from an atomizer.

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Spray Characteristics of the Air-Shrouded Injectors (공기쉬라우드형 인젝터의 분무 특성 연구)

  • 김기성;박상규
    • Journal of Advanced Marine Engineering and Technology
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    • v.25 no.4
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    • pp.912-919
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    • 2001
  • Improvement of the atomization characteristics by adopting the air-shrouded injector has been considered as one of the important methods for decreasing HC emissions in SI engines. Thus, in this study to develop air-shrouded injector with a finer spray, atomization characteristics of differ-ent types of commercial air-shrouded injectors were investigated through the spray imaging and the drop size measurements. As a results, it was found that the internal mixing type of air-shroud-ed injector had a good atomization characteristics. But, a number of large droplets were found in the internal mixing type commercial injector, this shortcoming was improved by adopting the thread type air passages in the air nozzle.

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