• Title/Summary/Keyword: Film Cooling Hole

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Comparative Study on the Film Cooling Effectiveness of 15° Angled Anti-Vortex Hole and 30-7-7 Fan-Shaped Hole Using PSP Technique (PSP를 이용한 15° 반와류 홀과 30-7-7 팬형상 홀의 막냉각 효율 비교 연구)

  • Kim, Ye Jee;Park, Soon Sang;Rhee, Dong Ho;Kwak, Jae Su
    • The KSFM Journal of Fluid Machinery
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    • v.19 no.4
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    • pp.13-18
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    • 2016
  • The various film cooling hole shapes have been proposed for effective external cooling of gas turbine blade. In this study, the film cooling effectiveness by three different hole shapes (cylindrical hole, $15^{\circ}$ angle anti-vortex hole, 30-7-7 fan-shaped hole) were examined experimentally. Pressure Sensitive Paint (PSP) technique was used to measure the film cooling effectiveness. The coolant to mainstream density ratio was 1.0 and three blowing ratios of 0.5, 1.0, and 2.0 were considered. Results clearly showed that the effect of hole shape on the distribution of film cooling effectiveness. For the cylindrical hole case, the film cooling effectiveness decreased remarkably as the blowing ratio increased due to the jet lift off. Because of large hole exit area and low coolant momentum, the 30-7-7 fan-shaped hole case showed the highest film cooling effectiveness at all blowing ratio, followed by the anti-vortex hole case.

Characteristics of Heat/Mass Transfer and Film Cooling Effectiveness Around a Shaped Film Cooling Hole (변형된 단일 막냉각홀 주위에서의 열/물질전달 및 막냉각효율 특성)

  • Rhee, Dong Ho;Kim, Byunggi;Cho, Hyung-Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.5
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    • pp.577-586
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    • 1999
  • Two problems with jet injection through the cylindrical film cooling hole are 1) penetration of jet into mainstream rather than covering the surface at high blowing rates and 2) nonuniformity of the film cooling effectiveness in the lateral direction. Compound angle injection is employed to reduce those two problems. Compound angle injection increases the film cooling effectiveness and spreads more widely. However, there is still lift off at high blowing rates. Shaped film cooling hole is a possible means to reduce those two problems. Film cooling with the shaped hole is investigated in this study experimentally. Film cooling hole used in present study is a shaped hole with conically enlarged exit and Inlet-to-exit area ratio is 2.55. Naphthalene sublimation method has been employed to study the local heat/mass transfer coefficient and film cooling effectiveness for compound injection angles and various blowing rates around the shaped film cooling hole. Enlarged hole exit area reduces the momentum of the jet at the hole exit and prevents the penetration of injected jet into the mainstream effectively. Hence, higher and more uniform film cooling effectiveness values are obtained even at relatively high blowing rates and the film cooling jet spreads more widely with the shaped film cooling hole. And the injected jet protects the surface effectively at low blowing rates and spreads more widely with the compound angle injections than the axial injection.

NUMERICAL STUDY ON FILM-COOLING EFFECTIVENESS FOR VARIOUS FILM-COOLING HOLE SCHEMES (다양한 막냉각 홀 형상에 대한 막냉각 효율의 수치해석)

  • Kim, S.M.;Lee, K.D.;Kim, K.Y.
    • Journal of computational fluids engineering
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    • v.16 no.4
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    • pp.92-99
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    • 2011
  • In order to protect the turbine blade from working fluid of high temperature, many cooling techniques such as internal convection cooling, film cooling, impinging jet cooling and thermal barrier coating have been developed. With all other things, film-cooling has been widely used as the important alternative. In the present work, numerical analysis has been performed to investigate and to compare the film-cooling performance of various film-cooling hole schemes such as cylindrical, crescent, louver, and dumbbell holes. To analyze the turbulent flow and the film-cooling mechanism, three-dimensional Reynolds-averaged Navier-Stokes analysis has been performed with shear stress transport turbulence model. The validation of numerical results has been assessed in comparison with experimental data. The characteristics of fluid flow and the film-cooling performance for each shaped hole have been investigated and evaluated in terms of centerline, laterally averaged and spatially averaged film-cooling effectivenesses. Among the film cooling holes, the dumbbell shaped hole shows better film-cooling effectiveness than the other shaped holes. And the louver and cylindrical shaped hole show the worst film cooling performance, and concentrated flows on near the centerline only.

Effects of Various Injection Hole Shapes and Injection Angles on the Characteristics of Turbine Blade Leading Edge Film Cooling (분사홀 형상과 분사각 변화가 터빈블레이드 선단 막냉각 특성에 미치는 영향)

  • Kim, Yun-Je;Gwon, Dong-Gu
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.7
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    • pp.933-943
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    • 2001
  • Using a semi-circled blunt body model, the geometrical effects of injection hole on the turbine blade leading edge film cooling are investigated. The film cooling characteristics of two shaped holes (laterally- and streamwise-diffused holes) and three cylindrical holes with different lateral injection angles, 30°, 45°, 60°, respectively, are compared with those of cylindrical hole with no lateral injection angle experimentally and numerically. Kidney vortices, which decrease the adiabatic film cooling effectiveness, appear on downstream of the cylindrical hole with no lateral injection angle. At downstream of the two shaped holes have better film cooling characteristics than the cylindrical one. Instead of kidney vortices, single vortex appears on downstream of injection holes with lateral injection angle. The adiabatic film cooling effectiveness is symmetrically distributed along the lateral direction downstream of the cylindrical hole with no lateral injection angle. But, at downstream of the cylindrical holes with lateral injection angle, the distribution of adiabatic film cooling effectiveness in the lateral direction shows asymmetric nature and high adiabatic film cooling effectiveness regions are more widely distributed than those of the cylindrical hole with no lateral injection angle. As the blowing ratio increases, also, the effects of hole shapes and injection angles increase.

Experimental Study on the Film Cooling Effectiveness on a Flat Plate with Anti-Vortex Holes

  • Park, Soon Sang;Park, Jung Shin;Kwak, Jae Su
    • International Journal of Aerospace System Engineering
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    • v.1 no.1
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    • pp.1-9
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    • 2014
  • In this paper, the effects of the anti-vortex hole angle and blowing ratio on the flat plate film cooling effectiveness were experimentally investigated. For the film cooling effectiveness measurement, pressure sensitive paint technique was applied. The experiments were conducted for cylindrical and anti-vortex film cooling holes, and three blowing ratios of 0.25, 0.5, and 1.0 were tested. Two anti-vortex hole angles of 0 and 15 degree with respect to the flow direction were considered. For the cylindrical hole case, the film cooling effectiveness decreased as the blowing ratio increased because of the coolant lift-off. For the angle anti-vortex hole cases, however, higher blowing ratio resulted in higher film cooling effectiveness due to the reduced actual blowing ratio and diminished kidney vortex. For all blowing ratio, the angled anti-vortex hole case showed the highest film cooling effectiveness.

NUMERICAL STUDY ON FILM-COOLING EFFECTIVENESS FOR VARIOUS FILM-COOLING HOLE SCHEMES (다양한 막냉각 홀 형상에 대한 막냉각 효율의 수치해석)

  • Kim, S.M.;Lee, K.D.;Kim, K.Y.
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.104-111
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    • 2011
  • To protect the turbine blade, many cooling techniques has developed. With all other things, film-cooling has been widely used as the important alternative. In the present work, numerical analysis has been performed to investigate and to compare the film-cooling performance of various film-cooling hole schemes such as cylindrical, crescent, louver, and dumbbell holes. To analyze the turbulent flow and the film-cooling mechanism, three-dimensional Reynolds-averaged Navier-Stokes analysis has been performed with shear stress transport turbulence model. The validation of numerical results has been assessed in comparison with experimental data. The characteristics of fluid flow and the film-cooling performance for each shaped hole have been investigated and evaluated in terms of centerline, laterally averaged and spatially averaged film-cooling effectivenesses. The dumbbell shaped hole shows better film-cooling effectiveness than other shaped holes. And the louver and cylindrical shaped hole shows lower one, and concentrated flow on centerline only.

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Design Optimization of a Fan-Shaped Film-Cooling Hole Using a Radial Basis Neural Network Technique (홴형상 막냉각홀의 신경회로망 기법을 이용한 최적설계)

  • Lee, Ki-Don;Kim, Kwang-Yong
    • The KSFM Journal of Fluid Machinery
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    • v.12 no.4
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    • pp.44-53
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    • 2009
  • Numerical design optimization of a fan-shaped hole for film-cooling has been carried out to improve film-cooling effectiveness by combining a three-dimensional Reynolds-averaged Navier-Stokes analysis with the radial basis neural network method, a well known surrogate modeling technique for optimization. The injection angle of hole, lateral expansion angle of hole and ratio of length-to-diameter of the hole are chosen as design variables and spatially averaged film-cooling effectiveness is considered as an objective function which is to be maximized. Twenty training points are obtained by Latin Hypercube sampling for three design variables. Sequential quadratic programming is used to search for the optimal point from the constructed surrogate. The film-cooling effectiveness has been successfully improved by the optimization with increased value of all design variables as compared to the reference geometry.

Effect of Anti-Vortex Hole Angle on the Flat Plate Film Cooling Effectiveness (반와류 홀의 각도가 평판의 막냉각 효율에 미치는 영향 연구)

  • Park, Soon Sang;Park, Jung Shin;Lee, Sang Hoon;Moon, Young Gi;Kwak, Jae Su
    • The KSFM Journal of Fluid Machinery
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    • v.17 no.5
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    • pp.5-10
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    • 2014
  • In this paper, the experimental study was carried to investigate the effect of angle of the anti-vortex holes on the film cooling effectiveness on a flat plate. The pressure sensitive paint technique was applied to measure the film cooling effectiveness. Two anti-vortex hole angles of $0^{\circ}$ and $15^{\circ}$ with respect to the primary hole were considered, and the simple cylindrical hole case was also tested. The blowing ratio based on the cylindrical hole was 0.5 and the same flow rate was kept for all anti-vortex hole cases. Results showed that the film cooling effectiveness for the anti-vortex hole cases were much higher than that of the cylindrical case. Among the anti-vortex hole cases, $15^{\circ}$ angle anti-vortex hole case showed higher film cooling effectiveness than that by the $0^{\circ}$ angle anti-vortex hole case.

Design Optimization of a Cylindrical Film-Cooling Hole Using Neural Network Techniques (신경회로망기법을 사용한 원통형 막냉각 홀의 최적설계)

  • Lee, Ki-Don;Kim, Kwang-Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.12
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    • pp.954-962
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    • 2008
  • This study presents a numerical procedure to optimize the shape of cylindrical cooling hole to enhance film-cooling effectiveness. The RBNN method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport turbulent model. The hole length-to-diameter ratio and injection angle are chosen as design variables and film-cooling effectiveness is considered as objective function which is to be maximized. Twelve training points are obtained by Latin Hypercube Sampling for two design variables. In the sensitivity analysis, it is found that the objective function is more sensitive to the injection angle of hole than the hole length-to diameter ratio. Optimum shape gives considerable increase in film-cooling effectiveness.

Heat/Mass Transfer and Flow Characteristics Within a Film Cooling Hole of Square Cross Sections (I) - Effects of Blowing Ratio and Reynolds Number - (정사각 막냉각홀 내부에서의 열/물질전달 및 유동 특성 (I) - 분사비 및 레이놀즈 수 효과 -)

  • Kang, Seung-Goo;Rhee, Dong-Ho;Cho, Hyung-Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.7
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    • pp.927-936
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    • 2002
  • An experimental study has been conducted to investigate the heat/mass transfer characteristics within a film cooling hole of square cross-section for various blowing ratios and Reynolds numbers. The experiments have been performed using a naphthalene sublimation method and the flow field has been analyzed by numerical calculation using a commercial code. A duct flow enters into a film cooling hole in a cross-direction. For the film cooling hole with square cross-section, it is observed that the reattachment of separated flow and the vortices within the hole enhance considerably the heat/mass transfer around the hole entrance region. The heat/mass transfer on the leading edge side of hole exit region increases as the blowing ratios decrease because the main flow induces a secondary vortex. Heat/mass transfer patterns within the square film cooling hole are changed little with the various Reynolds numbers.