• Title/Summary/Keyword: Cavity Squealer Tip

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Heat/Mass Transfer Characteristics on the Squealer Tip Surface of a Turbine Rotor Blade (터빈 동익 스퀼러팁 표면에서의 열(물질)전달 특성)

  • Moon, Hyun-Suk;Lee, Sang-Woo
    • The KSFM Journal of Fluid Machinery
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    • v.12 no.1
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    • pp.35-42
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    • 2009
  • The flow and heat/mass transfer characteristics on the squealer tip surface of a high-turning turbine rotor blade have been investigated at a Reynolds number of $2.09{\times}10^5$, by employing the oil-film flow visualization and naphthalene sublimation technique. The squealer rim height-to-chord ratio and tip gap height-to-chord ratio are fixed as typical values of $h_{st}/c$ = 5.5% and h/c = 2.0%, respectively, for turbulence intensities of Tu = 0.3% and 15%. The results show that the near-wall flow phenomena within the cavity of the squealer tip are totally different from those over the plane tip. There are complicated backward flows from the suction side to the pressure side near the cavity floor, in contrast to the plane tip gap flows moving toward the suction side after flow separation/reattachment. The squealer tip provides a significant reduction in tip surface thermal load with less severe gradient compared to the plane tip. In this study, the tip surface is divided into six different regions, and transport phenomena at each region are discussed in detail. The mean thermal load averaged over the squealer cavity floor is augmented by 7.5 percents under the high inlet turbulence level.

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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Effect of Tip Gap Height on Heat/Mass Transfer over a Cavity Squealer Tip (팁간극높이가 전면스퀼러팁 표면의 열전달 특성에 미치는 영향)

  • Kang, Dong Bum;Moon, Hyun Suk;Lee, Sang Woo
    • The KSFM Journal of Fluid Machinery
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    • v.16 no.6
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    • pp.19-25
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    • 2013
  • The effect of tip gap height on heat/mass transfer characteristics on the floor of cavity squealer tip has been investigated in a turbine cascade for power generation by employing the naphthalene sublimation technique. The squealer rim height is chosen to be an optimal one of $h_{st}/c$ = 5.51% for the tip gap height-to-chord ratios of h/c = 1.0, 2.0, 3.0 and 4.0%. The results show that heat transfer on the cavity floor is strongly dependent upon the behavior of the cavity flow falling down onto the floor. For lower h/c, the floor heat transfer is influenced by the tip leakage flow falling down along the inner face of the suction-side squealer, whereas the floor heat transfer for higher h/c is augmented mainly due to the impingement of leakage flow on the floor near the leading edge. Compared to the plane tip surface heat transfer, the cavity floor heat transfer is less influenced by h/c. For h/c = 1.0%, the average thermal load is as low as a half of the plane tip surface one, and the difference in the thermal load between the two cases tends to decrease with increasing h/c.

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

  • Kim, Seon-Ung;Lee, Sang-Woo
    • The KSFM Journal of Fluid Machinery
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    • v.14 no.1
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    • pp.48-54
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    • 2011
  • The effect of channel cutback on three-dimensional flow fields and aerodynamic losses downstream of a cavity squealer tip has been investigated in a turbine rotor cascade for the squealer rim height-to-chord ratio and tip gap height-to-chord ratio of $h_{st}/c$ = 5.51% and h/c = 2.0% respectively. The cutback length-to-camber ratio is changed to be $CB/c_c$ = 0.0, 0.1, 0.2 and 0.3. The results show that longer cutback delivers not only stronger secondary flow but also higher aerodynamic loss in the tip leakage vortex region, meanwhile it leads to lower aerodynamic loss in the passage vortex region. The discharge of cavity fluid through the cutback opening provides a beneficial effect in the reduction of aerodynamic loss, whereas there also exists a side effect of aerodynamic loss increase due to local wider tip gap near the trailing edge. With increasing $CB/c_c$ from 0.0 to 0.3, the aerodynamic loss coefficient mass-averaged all over the measurement plane tends to increase slightly.

Tip Gap Flow and Aerodynamic Loss Generation over a Cavity Squealer Tip with the Variation of Pressure-Side Opening Length in a Turbine Cascade (스퀼러팁의 압력면 개방길이 변화에 따른 터빈 익렬 팁간극 유동 특성 및 압력손실)

  • Cheon, Joo Hong;Lee, Sang Woo
    • The KSFM Journal of Fluid Machinery
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    • v.15 no.6
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    • pp.5-10
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    • 2012
  • The effect of pressure-side opening length on three-dimensional flow fields and aerodynamic losses downstream of a cavity squealer tip has been investigated in a turbine rotor cascade for the squealer rim height-to-chord ratio and tip gap height-tochord ratio of $h_{st}/c$ = 5.05% and h/c = 2.0% respectively. The opening length-to-camber ratio is changed to be $OL/c_c$ = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.7 The results show that longer OL leads not only to weaker secondary flow but also to lower aerodynamic loss in the tip leakage vortex region, while it significantly widens the area with high aerodynamic loss in the passage vortex region. The aerodynamic loss coefficient mass-averaged all over the measurement plane is kept almost constant for $0.0{\leq}OL/c_c{\leq}0.3$, whereas it increases rapidly for $OL/c_c$ > 0.3 in proportion to $OL/c_c$. There is little deterioration in flow turning with increasing $OL/c_c$.

Three-Dimensional Flow and Aerodynamic Loss in the Tip-Leakage Flow Region of a Turbine Blade with Pressure-Side Winglet and Suction-Side Squealer (압력면윙렛/흡입면스퀼러형 터빈 동익 팁누설영역에서의 3차원유동 및 압력손실)

  • Cheon, Joo Hong;Kang, Dong Bum;Lee, Sang Woo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.5
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    • pp.399-406
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    • 2014
  • Three-dimensional flow and aerodynamic loss in the tip-leakage flow region of a turbine blade equipped with both a pressure-side winglet and a suction-side squealer have been measured for the tip gap-to-span ratio of h/s = 1.36%. The suction-side squealer has a fixed height-to-span ratio of $h_s/s$ = 3.75% and the pressure-side winglet has width-to-pitch ratios of w/p = 2.64%, 5.28%, 7.92% and 10.55%. The results are compared with those for a plane tip and for a cavity squealer tip of $h_{ps}/s$ = 3.75%. The present tip delivers lower loss in the passage vortex region but higher loss in the tip-leakage vortex region, compared to the plane tip. With increasing w/p, its mass-averaged loss tends to be reduced. Regardless of w/p, the present tip provides lower loss than the plane tip but higher loss than the cavity squealer tip.

Numerical Analysis of Heat Transfer and Flow Characteristics on Squealer Tip of Gas Turbine Blade (가스터빈 블레이드 팁의 열전달과 유동 특성에 대한 수치적 해석)

  • Jiao, Liu;Kang, Youngseok;Kim, Donghwa;Cho, Jinsoo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.44 no.12
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    • pp.1062-1070
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    • 2016
  • The heat transfer and flow characteristics of gas turbine blade tip were investigated in this paper by using the conjugate heat transfer analysis. The rotor inlet boundary condition profile which was taken from the first stage nozzle outlet was used to analyse. The profile contained the velocity and temperature information. This study presents the influence of tip clearance about aerodynamic loss, heat transfer coefficient and film cooling effectiveness with the squealer tip designed blade model which tip clearance variation range from 1% to 2.5% of span. Results showed that the aerodynamic loss and the heat transfer coefficient were increased when the tip clearance was increased. Especially when the tip clearance was 2% of the span, the average heat transfer coefficient on the tip region was increased obviously. The film cooling effectiveness of tip region was increasing with decreasing of the tip clearance. There was high film cooling effectiveness at cavity and near tip hole region.