• Title/Summary/Keyword: 5-hole probe

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Comparisons of Aerodynamic Loss Generated by a Squealer-Tip Turbine Rotor Blade with That by a Plane-Tip One (평면팁과 스퀼러팁 터빈 동익의 압력손실 특성 비교)

  • Chae, Byoung-Joo;Lee, Sang-Woo
    • 유체기계공업학회:학술대회논문집
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    • 2006.08a
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    • pp.161-164
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    • 2006
  • Three-dimensional flow and aerodynamic loss in the tip-leakage flow region of a high-turning first-stage turbine rotor blade with a squealer tip have been measured with a straight miniature five-hole probe for the tip gap-to-chord ratio, h/e, of 2,0%. This squealer tip has a indent-to-chord ratio, $h_{st}/c$, of 5.5%. The results are compared with those for a plane tip ($h_{st}/c\;=\;0.0%$). The squealer tip tends to reduce the mass flow through the tip gap and to suppress the development of the tip-leakage vortex. Therefore, it delivers lower aerodynamic loss in the near-tip region than the plane tip does. At the mid-span, however, the aerodynamic loss has nearly the same value for the two different tips.

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Three-Dimensional Flow and Aerodynamic Loss Downstream of a Turbine Rotor Blade with a Squealer Tip (스퀄러팁 터빈 동익 하류에서의 3차원 유동 및 압력손실)

  • Chae, Byoung-Joo;Lee, Sang-Woo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.9 s.252
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    • pp.913-920
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    • 2006
  • Three-dimensional flow and aerodynamic loss in the tip-leakage flow region of a high-turning first-stage turbine rotor blade with a squealer tip have been measured with a straight miniature five-hole probe for the tip gap-to-chord ratio, h/c, of 2.0%. This squealer tip has a indent-to-chord ratio, $h/{st}/c$, of 5.5%. The results are compared with those for a plane tip $(h_{st}/c=0.0%)$. The squealer tip tends to reduce the mass flow through the tip gap and to suppress the development of the tip-leakage vortex. Therefore, it delivers lower aerodynamic loss in the near-tip region than the plane tip does. At the mid-span, however, the aerodynamic loss has nearly the same value for the two different tips.

An experimental study for reduction of B.P.F. noise level of multi-blade fan (다익 송풍기의 이산 주파수 소음 저감을 위한 실험적 연구)

  • 김영찬;이상환
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.2
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    • pp.167-175
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    • 1999
  • B.P.F.(Blade Passing Frequency) levels were measured with the cut-off clearance changes. The velocity inside the scroll, pressure fluctuation at cut-off region, and the scroll surface pressure distribution along the scroll from the cut-off to outlet were measured. With a certain cut-off clearance the improvement of efficiency and attenuation of B.P.F. noise level could be achieved. The measured results of pressure fluctuation and scroll surface pressure distribution showed that the secondary flow inside the scroll increased B.P.F. noise level at the cut-off region as the cut-off clearance got wide.

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Effect of Do-In (Prunus persica L. BATSCH) Water Extract (PPE) on Concentration of Extracellular Acetylcholine in the Rat Hippocampus

  • Gong Dae-Jong;Kim Geun-Woo;Koo Byung-Soo
    • The Journal of Korean Medicine
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    • v.25 no.4
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    • pp.1-7
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    • 2004
  • Objective : This study was designed to examine the effects of orally administered Prunus persica water extract (PPE), which is used as herbal medicine, for treatment of Yu Xue (stasis of blood) and tacrine on the basal concentration of extracellular acetylcholine in the hippocampus of rats. Methods: To investigate the effects of PPE and tacrine on concentration of extracellular acetylcholine in the hippocampus of rats, the microdialysis technique, under the same experimental conditions, was used. And we used male Wistar rats which were 7 weeks of age and 210-290 g. PPE was extracted with boiling water, and the rats were anesthetized with pentobarbital Na. Their skulls were exposed and a hole was drilled for implantation of a microdialysis probe. In order to increase the recovery of acetylcholine, a probe with a long membrane was used. One day after surgery, the microdialysis probe was perfused with Ringer's solution at a flow rate of 1.5 l/min. The acetylcholine concentration in dialysis samples was measured by high-performance liquid chromatography (HPLC) with electrochemical detection. AChE activity was measured using the radiometric method, as described by Sherman. Results : The comparative effects of PPE and tacrine on hippocampal extracellular acetylcholine concentration was that these cholinesterase inhibitors produced dose-dependent increases in the extracellular acetylcholine concentration. And the effect of PPE and tacrine on rat brain AChE activity was that PPE produced maximal inhibition at 1 h after administration, when AChE activity was 44% of the intact level. AChE activity gradually recovered thereafter, and reached 78% of the intact level at 12 h after administration. Conclusion : In this study, PPE has a potent activity and a long-lasting effect on the central cholinergic system, in terms of the basal concentration of extracellular acetylcholine in the hippocampus and the AChE activity in the brain of rats. And oral administration of PPE increased dose-dependently the basal concentration of extracellular acetylcholine in the hippocampus of rats. PPE may be one of the more useful cholinesterase inhibitors for the treatment of Alzheimer's disease.

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Effects of Incidence Angle on the Three-Dimensional Flow and Aerodynamic Loss Downstream of a High-Turning Turbine Rotor Blade (입사각이 고선회 터빈 동익 하류에서의 3차원 유동 및 압력손실에 미치는 영향)

  • Chae, Byoung-Joo;Lee, Sang-Woo
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2591-2596
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    • 2007
  • The effect of incidence angle on the three-dimensional flow and aerodynamic loss in the downstream region of a high-turning turbine rotor blade has been investigated with a straight miniature five-hole probe. The incidence angle is changed to be +10, +5, 0, -10, -20, -30 and -40 degrees. The results show that the positive incidence reinforces the three-dimensional vortical flows within the turbine passage including the passage vortex, but the negative incidence weaken them significantly. A small increment in the positive incidence angle results in a remarkable aerodynamic loss increase, while increasing the incidence angle in the negative range leads to a very small change in the aerodynamic loss.

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Development of Three-Dimensional Flow Velocity Component Measurement System with Straight-Type Five-Hole Pressure Probe Using Ch Language (Ch를 이용한 직선형 5공 압력 프로브의 3차원 유동속도 계측시스템 개발)

  • Oh, S.H.;Kim, J.K.
    • Journal of Power System Engineering
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    • v.14 no.1
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    • pp.40-46
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    • 2010
  • This paper shows the development process for measuring three-dimensional flow velocity components in a web-browser. The system is developed in an embeddable C/C++ interpreter Ch and Ch-CGI toolkit. The interface for the web-based measurement system consists of a set of web HTML files and Ch files for CGI. All of data in web browser are passed to Ch-CGI script to generate the output of new HTML file. PC-Server and PC-Client can submit measurement parameters and receive the text/graphical results each other. PC-Client can control the test equipment by using a parameters that received from PC-Server. It also can pass the test results between the web-based measurement system. In summary, the designed measurement system is evaluated, the outputs shown well on the web browser.

ULTRAFAST INTERFACIAL ELECTRON TRAPPING AND RECOMBINATION IN PHOTOEXCITED COLLOIDAL CADMIUM SULFIDE

  • Kim, Seong-Kyu
    • Journal of Photoscience
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    • v.4 no.1
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    • pp.11-16
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    • 1997
  • We measured, using femtosecond pump-probe experiment, the time evolution of transient absorption in aqueous CdS colloids. The signal rises within the time resolution (= 0.5 ps) of the experiment and decays with two exponential time constants, 4.8 ps and 132 ps. The ultrafast rise of the transient absorption is considered to be for shallowly trapped conduction band electrons after photoexcitation. The amplitude ratio of the two decaying components varies with the pump intensity and the decay times increase in the presence of hole scavengers. Even though a biexponential function fits the decay well, we object hat two independent first order processes (geminate and nongeminate recombinations) are responsible for the decay. A function with an integrated rate equation for second order nongeminate recombination plus a long background fits the decay well. The long background is considered to be for deeply trapped charges at the CdS particle.

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Measurement of Flow and Scalar Distribution at Gas Turbine Inlet Section (가스터빈 입구에서의 유동 및 스칼라 분포 특성)

  • Hong, Sung-Kook;Ireland, Peter;Denman, Paul
    • The KSFM Journal of Fluid Machinery
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    • v.13 no.4
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    • pp.45-50
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    • 2010
  • The goal of paper is to investigate the flow and scalar distribution through the HP Nozzle Guide Vane (NGV) passage. Flow and scalar distribution measurement are conducted by using 5-hole pressure probe and $CO_2$ tracing technique, respectively. Three different experimental cases are considered depending on cooling flow condition. The result shows that the vortical secondary flow patterns are observed clearly and these flow characteristics maintain through the NGV passage regardless of cooling flow injection. Compared to center region, the high axial velocity flow is observed near wall region due to cooling flow injection. Without cooling flow, the $CO_2$ (scalar) distribution becomes to be uniform quickly due to the strong flow mixing phenomenon. However, in cases of cooling flow, scalar distribution is significantly non-uniform.

The Effect of Tip Clearance Height on the Three-Dimensional Flow and Aerodynamic Loss in the Wake Region of a High-Turning Turbine Rotor Cascade (끝틈새가 선회각이 큰 터빈 동익 익렬 후류영역에서의 3차원유동 및 압력손실에 미치는 영향)

  • Kwon, Hyun-Goo;Park, Jin-Jae;Lee, Sang-Woo
    • The KSFM Journal of Fluid Machinery
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    • v.7 no.5 s.26
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    • pp.36-42
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    • 2004
  • The effect of tip clearance height on the three-dimensional flow and aerodynamic loss in the wake region of a high-turning turbine rotor cascade has been investigated with a miniature cone-type five-hole probe. Distributions of velocity magnitude, secondary velocity vectors, and total-pressure loss coefficient are presented for three tip gap-to-span ratios of h/s = 0.0, 0.5 and 1.0 percent. The result shows that with the increment of h/s, tip leakage vortex tends to be intensified and aerodynamic loss due to the leakage vortex is increased as well. In the case of h/s = 1.0 percent, aerodynamic loss in the tip-leakage flow region is found dominant in comparison with that in the passage vortex region. With increasing h/s, mass-averaged secondary loss coefficient has a greater portion in the mass-averaged total-pressure loss coefficient.

Three-dimensional flow and pressure loss of a film-cooling jets injected in spanwise direction (폭방향으로 분사되는 막냉각 제트의 3차원 유동특성 및 압력손실)

  • Lee, Sang-U;Kim,Yong-Beom
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.4
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    • pp.1363-1375
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    • 1996
  • Oil-film flow visualizations and three-dimensional flow measurements using a five-hole probe have been conducted to investigate three-dimensional flow characteristics and total pressure losses of a row of film-cooling jets injected in spanwise direction. For several span-to-diameter ratios, experiments are performed in the case of three velocity ratios of 0.5, 1.0 and 1.5. The flow measurements show that downstream flow due to the injection is characterized by a single streamwise vortex instead of a pair of counter-rotating vortices, which appear in the case of streamwise injection, and the vortex strength strongly depends on the velocity ratio. Regardless of the velocity*y ratio, presence of the spanwise film-cooling jets always produces total pressure loss, which is pronounced when the velocity ratio is large. It has also been found that the production of the total pressure loss is closely related to the secondary vortical flow. In addition, effects of the span-to-diameter ratio on the flow and total pressure loss are discussed in detail.