• 제목/요약/키워드: Clearance flow

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Numerical Study of Film Cooling Characteristics in Turbine Blade Cavity (터빈 블레이드 캐버티 내 막냉각 특성에 관한 수치해석적 연구)

  • Kim, Kyung-Seok;Cho, Hyung-Hee;Kang, Shin-Hyoung
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.648-651
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    • 2008
  • Numerical calculations are performed to simulate the film cooling effect of turbine blade tip with squealer rim. Because of high temperature of inside rim, squealer rim is damaged easily. Therefore many various cooling systems were used. The calculations are based on 100,000 Reynolds number in linear cascade model. A blade has 2% tip clearance and 8.4% rim height. The axial chord length and turning angle is 237mm, 126$^{\circ}$. Numerical calculations are performed without and with film cooling. In a film cooling in the cavity, hot spots of cavity were cooled effectively. However hot spots of suction side rim still remains. The CFD results show that the circulation flow in cavity of squealer tip affects the temperature rise of squealer rim. To maintain the blade integrity and avoid the excessive hot spot of blade, rearrangement of cooling hole is needed.

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Performance of Roots-type Vacuum Pump with Cassini Oval Lobe Shape (Cassini 형 루츠 진공 펌프의 성능에 관한 연구)

  • Kim, H.J.;Cho, J.H.;Kim, Youn-J.
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.813-818
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    • 2000
  • The objective of this study is to elucidate the characteristic performance of Roots-type vacuum pump with Cassini oval lobe shape. The modelled lobe shape of Roots-type vacuum pump is two-lobe spur gear. The numerical analyses are performed fer leak flows, using 4th-order Runge-Kutta method and are compared with experimental results. Results show that for the case of involute lobe shape the total amount of the leak flow conductance is greater than that of cycloid and Cassini oval lobe shapes.

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Feasibility Study on Design of Thrust Bearing for Micro Gas Turbine Generator (초소형 가스 터빈 제너레이터용 스러스트 베어링의 설계 및 타당성에 관한 연구)

  • 이용복;곽현덕;김창호;장건희
    • Tribology and Lubricants
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    • v.17 no.6
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    • pp.467-475
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    • 2001
  • Feasibility study of gas-lubricated bearing in micro gas turbine was performed. Based on Reynolds equation, finite difference method with coupled boundary was developed to analyze bearing characteristics, such as load capacity, mass flow rates and stiffness. By the bearing force and mass flow rates analysis with the variation of supply pressure, bearing clearance and capillary radius, acceptable range of design parameters were suggested in terms of load capacity and stiffness of bearings. Additionally, coupled boundary effect on pressure distribution was investigated and it is stated that coupling could reduce an excitation force due to narrow pressure distribution.

Feasibility Study on Design of Thrust Bearing for Micro Gas Turbine/Generator (초소형 가스 터빈/제너레이터용 스러스트 베어링의 설계 및 타당성에 관한 연구)

  • 곽현덕;이용복;김창호;장건희
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2001.11a
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    • pp.273-281
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    • 2001
  • Feasibility study of gas-lubricated bearing in micro gas turbine was performed. Based on Reynolds equation, finite difference method with coupled boundary was developed to analyze bearing characteristics, such as load-carrying capacity, mass flow rates and stiffness. By the bearing force and mass flow rates analysis with the variation of supply pressure, bearing clearance and capillary radius, acceptable range of design parameters were suggested in terms of load capacity and stiffness of bearings. Additionally, coupled boundary effect on pressure distribution was investigated and it is stated that coupling could reduce all excitation force due to narrow pressure distribution.

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A Study on te Dynamic Behavior of a Scroll Compressor Considering Tangential Leakage (접선방향의 누설을 고려한 스크롤 압축기의 동적 거동에 관한 연구)

  • 김태종;한동철
    • Tribology and Lubricants
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    • v.12 no.2
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    • pp.20-31
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    • 1996
  • Pressures in compression pockets consists of two identical spiral scrolls are influenced by gas flow resistance in discharge process and leakages in radial and tangential directions between two scroll wraps. In this paper, considering geometrical characteristics of these members, flow resistance and refrigerant gas leakage losses, pressure variations in compression pockets are calculated. For a scroll compressor model with fixed crank mechanism, acting load on crankshaft is analyzed. And, for a vertical type crankshaft-journal bearing system used in scroll compressor, nonlinear transient response is calculated including nonlinear fluid film reaction forces of journal bearings.

Crankshaft Bearing Design Adapting Discontinuous Oil Supply System (불연속 오일공급 형태의 크랭크샤프트 베어링 설계)

  • Yun, Jeong-Eui
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.6
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    • pp.90-95
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    • 2004
  • In this study, for the crankshaft bearing design adapting discontinuous oil supply system, analyses were conducted to determine the lubrication characteristics such as oil flow rate and increase of oil temperature at main bearing and connecting rod bearing. Additionally, supplied oil pressure and temperature effects on the bearings were simulated to figure out lubrication characteristics on the bearings. Finally the effects of increasing the bearing width and clearance were introduced on the lubrication characteristics.

Performance Analysis of Orbiter Vacuum Pump (오비터 진공펌프 성능해석)

  • Kim, Hyun-Jin;Shim, Jae-Hwi
    • The KSFM Journal of Fluid Machinery
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    • v.9 no.5 s.38
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    • pp.28-35
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    • 2006
  • Orbiter mechanism has been applied to vacuum pump design for small oxygen generator where low vacuum of about 200 mmHg is required. Performance of the designed vacuum pump has been numerically investigated: calculated volumetric and adiabatic efficiencies were 69.7% and 83.9%, respectively for leakage clearance of $10{\mu}m$. Total efficiency of the orbiter vacuum pump was 77.5%. At the shaft speed of 1700 rpm suction displacement volume of 6.3cc provided discharge flow at the rate of 2.3 liter/min with power consumption of 10.1Watt. Torque variation of the orbiter pump was only about 20% of that of diaphragm pump.

OPERATION OF TILTING 5-PADS proceeding BEARING AT DIFFERENT GEOMETRIC PARAMETERS OF PADS

  • Strzelecki, S.
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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    • pp.99-100
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    • 2002
  • Radial, tilting-pad proceeding bearings are applied in high speed rotating machines operating at stable small and mean loads and the peripheral speeds of proceeding reaching 150 m/s. The operation of bearing can be determined by static characteristics including the oil film pressure, temperature and viscosity distributions, minimum oil film thickness, load capacity, power loss, oil flow. The operation of 5-lobe tilted-pad proceeding bearing has been introduced at the assumption of adiabatic oil film. The oil film pressure, temperature and viscosity distributions habe received by iterative solution of the Reynolds', energy and viscosity equations. The resulting oil film force, minimum oil film thickness, power loss. oil flow, maximum oil film pressure, maximum temperature were computed for different sets of bearing geometric parameters as: bearing length to diameter ratio, pad angular length and width as well as pad relative clearance.

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Heat/Mass Transfer Characteristics on Stationary Turbine Blade and Shroud in a Low Speed Annular Cascade (I) - Near-tip Blade Surface - (환형 캐스케이드 내 고정된 터빈 블레이드 및 슈라우드에서의 열/물질전달 특성 (I) - 블레이드 끝단 인접 표면 -)

  • Rhee Dong-Ho;Cho Hyung Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.4 s.235
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    • pp.485-494
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    • 2005
  • For the extensive investigation of local heat/mass transfer on the near-tip surface of turbine blade, experiments were conducted in a low speed stationary annular cascade. The turbine test section has a single stage composed of sixteen guide vanes and blades. The chord length and the height of the tested blade are 150 mm and about 125 mm, respectively. The blade has flat tip geometry and the mean tip clearance is about $2.5{\%}$ of the blade chord. Detailed mass transfer coefficient on the blade near-tip surface was obtained using a naphthalene sublimation technique. The inlet flow Reynolds number based on chord length and incoming flow velocity is changed from $1.0{\times}10^{5}\;to\;2.3{\times}10^{5}.$ Extremely complex heat transfer characteristics are observed on the blade surface due, to complicated flow patterns, such as flow acceleration, laminarization, transition, separation bubble and tip leakage flow. Especially, the suction side surface of the blade has higher heat/mass transfer coefficients and more complex distribution than the pressure side surface, which is related to the leakage flow. For all the tested Reynolds numbers, the heat/mass transfer characteristics on the turbine blade are the similar. The overall averaged $Sh_{c}$ values are proportional to $Re_{c}^{0.5}$ on the stagnation region and the laminar flow region such as the pressure side surface. However, since the flow is fully turbulent in the near-tip region, the heat/mass transfer coefficients are proportional to $Re_{c}^{0.8}.$

Analysis of Design Parameters For Shunt Valve and Anti-Siphon Device Used to Treat Patients with Hydrocephalus

  • Lee, Chong-Sun;Jang, Jong-Yun;Suh, Chang-Min
    • Journal of Mechanical Science and Technology
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    • v.15 no.7
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    • pp.1061-1071
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    • 2001
  • The present study investigated design parameters of shunt valves and anti-siphon device used to treat patients with hydrocephalus. The shunt valve controls drainage of cerebrospinal fluid (CSF) through passive deflection of a thin and small diaphragm. The anti-siphon device(ASD) is optionally connected to the valve to prevent overdrainage when the patients are in the standing position. The major design parameters influencing pressure-flow characteristics of the shunt valve were analyzed using ANSYS structural program. Experiments were performed on the commercially available valves and showed good agreements with the computer simulation. The results of the study indicated that predeflection of the shunt valve diaphragm is an important design parameter to determine the opening pressure of the valve. The predeflection was found to depend on the diaphragm tip height and could be adjusted by the diaphragm thickness and its elastic modulus. The major design parameters of the ASD were found to be the clearance (gap height) between the thin diaphragm and the flow orifice. Besides the gap height, the opening pressure of the ASD could be adjusted by the diaphragm thickness, its elastic modulus, area ratio of the diaphragm to the flow orifice. Based on the numerical simulation which considered the increased subcutaneous pressure introduced by the tissue capsule pressure on the implanted shunt valve system, optimum design parameters were proposed for the ASD.

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