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Hyung Hee Cho - One of the best experts on this subject based on the ideXlab platform.

  • Effects of Vane/Blade Relative Positions and Showerhead Film Cooling on a Stationary Blade: Heat Transfer
    Volume 4: Heat Transfer Parts A and B, 2010
    Co-Authors: Dong Hyun Lee, Dongho Rhee, Kyung Min Kim, Hyung Hee Cho
    Abstract:

    The present study investigates the effects of relative position on heat transfer distributions of a showerhead film-cooled Stationary rotor Blade. Detailed heat/mass transfer coefficients were measured using the naphthalene sublimation method. A low-speed wind tunnel was used, with a single annular turbine stage consisting of sixteen guide vanes and Blades. The axial chord length of the test Blade was 136 mm. The inlet and exit angles of the test Blade were 56.4° and −62.6°, respectively, which produced a turning angle of 119.0°. Three rows of film cooling holes were drilled in the leading edge region of the Blade. Each row had 10 circular cooling holes along the spanwise direction, and the diameter of each cooling hole was 1.2 mm. Detailed heat transfer coefficients were measured at two different guide vane and rotor Blade relative positions, while changing the blowing rate (M) from 1.0 to 2.0. The inlet Reynolds number was fixed at 1.3×105 based on the Blade axial chord length. As the blowing rate increased, overall heat transfer rates increased, and the lower peaks formed on the pressure side by the separation bubble were reduced, and disappeared at M = 2.0. The effects of vane/Blade relative position were significant because the incoming flow condition was changed. However, the spanwise average Sherwood number became similar as the blowing rate increased.Copyright © 2010 by ASME

  • effect of vane Blade relative position on heat transfer characteristics in a Stationary turbine Blade part 1 tip and shroud
    International Journal of Thermal Sciences, 2008
    Co-Authors: Dongho Rhee, Hyung Hee Cho
    Abstract:

    Abstract This study was carried out to investigate the effect of relative Blade position on heat transfer in a Stationary Blade and shroud. A low speed wind tunnel with a single stage Stationary annular turbine cascade was used. The test section is composed of sixteen guide plates and sixteen Blades. The chord length of the Blade is 150 mm and the mean tip clearance of the Blade is 2.5% of the Blade chord. Detailed mass transfer measurements were conducted for the Stationary Blade fixed at six different relative Blade positions within a single pitch using a naphthalene sublimation method. The Reynolds number based on Blade inlet velocity and chord length ranged between 1.0 × 10 5 and 2.3 × 10 5 and mean turbulence intensity was about 3%. As the Blade position changed, the incoming flow field condition also changed significantly due to a blockage effect. As a result, the heat transfer on the tip and the shroud was significantly affected by the Blade position because the incoming flow condition is changed. Especially, the mass transfer coefficients in the upstream region of the tip vary up to ± 25% of their average values. On the shroud, the size and the level of peak regions due to flow acceleration, transition and tip leakage vortex were strongly affected by the relative Blade position.

  • Effect of vane/Blade relative position on heat transfer characteristics in a Stationary turbine Blade: Part 1. Tip and shroud
    International Journal of Thermal Sciences, 2008
    Co-Authors: Dongho Rhee, Hyung Hee Cho
    Abstract:

    Abstract This study was carried out to investigate the effect of relative Blade position on heat transfer in a Stationary Blade and shroud. A low speed wind tunnel with a single stage Stationary annular turbine cascade was used. The test section is composed of sixteen guide plates and sixteen Blades. The chord length of the Blade is 150 mm and the mean tip clearance of the Blade is 2.5% of the Blade chord. Detailed mass transfer measurements were conducted for the Stationary Blade fixed at six different relative Blade positions within a single pitch using a naphthalene sublimation method. The Reynolds number based on Blade inlet velocity and chord length ranged between 1.0 × 10 5 and 2.3 × 10 5 and mean turbulence intensity was about 3%. As the Blade position changed, the incoming flow field condition also changed significantly due to a blockage effect. As a result, the heat transfer on the tip and the shroud was significantly affected by the Blade position because the incoming flow condition is changed. Especially, the mass transfer coefficients in the upstream region of the tip vary up to ± 25% of their average values. On the shroud, the size and the level of peak regions due to flow acceleration, transition and tip leakage vortex were strongly affected by the relative Blade position.

Dongho Rhee - One of the best experts on this subject based on the ideXlab platform.

  • Effects of Vane/Blade Relative Positions and Showerhead Film Cooling on a Stationary Blade: Heat Transfer
    Volume 4: Heat Transfer Parts A and B, 2010
    Co-Authors: Dong Hyun Lee, Dongho Rhee, Kyung Min Kim, Hyung Hee Cho
    Abstract:

    The present study investigates the effects of relative position on heat transfer distributions of a showerhead film-cooled Stationary rotor Blade. Detailed heat/mass transfer coefficients were measured using the naphthalene sublimation method. A low-speed wind tunnel was used, with a single annular turbine stage consisting of sixteen guide vanes and Blades. The axial chord length of the test Blade was 136 mm. The inlet and exit angles of the test Blade were 56.4° and −62.6°, respectively, which produced a turning angle of 119.0°. Three rows of film cooling holes were drilled in the leading edge region of the Blade. Each row had 10 circular cooling holes along the spanwise direction, and the diameter of each cooling hole was 1.2 mm. Detailed heat transfer coefficients were measured at two different guide vane and rotor Blade relative positions, while changing the blowing rate (M) from 1.0 to 2.0. The inlet Reynolds number was fixed at 1.3×105 based on the Blade axial chord length. As the blowing rate increased, overall heat transfer rates increased, and the lower peaks formed on the pressure side by the separation bubble were reduced, and disappeared at M = 2.0. The effects of vane/Blade relative position were significant because the incoming flow condition was changed. However, the spanwise average Sherwood number became similar as the blowing rate increased.Copyright © 2010 by ASME

  • effect of vane Blade relative position on heat transfer characteristics in a Stationary turbine Blade part 1 tip and shroud
    International Journal of Thermal Sciences, 2008
    Co-Authors: Dongho Rhee, Hyung Hee Cho
    Abstract:

    Abstract This study was carried out to investigate the effect of relative Blade position on heat transfer in a Stationary Blade and shroud. A low speed wind tunnel with a single stage Stationary annular turbine cascade was used. The test section is composed of sixteen guide plates and sixteen Blades. The chord length of the Blade is 150 mm and the mean tip clearance of the Blade is 2.5% of the Blade chord. Detailed mass transfer measurements were conducted for the Stationary Blade fixed at six different relative Blade positions within a single pitch using a naphthalene sublimation method. The Reynolds number based on Blade inlet velocity and chord length ranged between 1.0 × 10 5 and 2.3 × 10 5 and mean turbulence intensity was about 3%. As the Blade position changed, the incoming flow field condition also changed significantly due to a blockage effect. As a result, the heat transfer on the tip and the shroud was significantly affected by the Blade position because the incoming flow condition is changed. Especially, the mass transfer coefficients in the upstream region of the tip vary up to ± 25% of their average values. On the shroud, the size and the level of peak regions due to flow acceleration, transition and tip leakage vortex were strongly affected by the relative Blade position.

  • Effect of vane/Blade relative position on heat transfer characteristics in a Stationary turbine Blade: Part 1. Tip and shroud
    International Journal of Thermal Sciences, 2008
    Co-Authors: Dongho Rhee, Hyung Hee Cho
    Abstract:

    Abstract This study was carried out to investigate the effect of relative Blade position on heat transfer in a Stationary Blade and shroud. A low speed wind tunnel with a single stage Stationary annular turbine cascade was used. The test section is composed of sixteen guide plates and sixteen Blades. The chord length of the Blade is 150 mm and the mean tip clearance of the Blade is 2.5% of the Blade chord. Detailed mass transfer measurements were conducted for the Stationary Blade fixed at six different relative Blade positions within a single pitch using a naphthalene sublimation method. The Reynolds number based on Blade inlet velocity and chord length ranged between 1.0 × 10 5 and 2.3 × 10 5 and mean turbulence intensity was about 3%. As the Blade position changed, the incoming flow field condition also changed significantly due to a blockage effect. As a result, the heat transfer on the tip and the shroud was significantly affected by the Blade position because the incoming flow condition is changed. Especially, the mass transfer coefficients in the upstream region of the tip vary up to ± 25% of their average values. On the shroud, the size and the level of peak regions due to flow acceleration, transition and tip leakage vortex were strongly affected by the relative Blade position.

  • local heat mass transfer characteristics on a rotating Blade with flat tip in low speed annular cascade part i near tip surface
    Journal of Turbomachinery-transactions of The Asme, 2006
    Co-Authors: Dongho Rhee
    Abstract:

    The present study focuses on local heat/mass transfer characteristics on the near-tip region of a rotating Blade. To investigate the local heat/mass transfer on the near-tip surface of the rotating turbine Blade, detailed measurements of time-averaged mass transfer coefficients on the Blade surfaces were conducted using a naphthalene sublimation technique. A low speed wind tunnel with a single stage annular turbine cascade was used. The turbine stage is composed of sixteen guide plates and Blades with spacing of 34 mm, and the chord length of the Blade is 150 mm. The mean tip clearance is about 2.5% of the Blade chord. The tested Reynolds number based on inlet flow velocity and Blade chord is 1.5 ×10 5 and the rotational speed of Blade is 255.8 rpm for the design condition. The result at the design condition was compared with the results for the Stationary Blade to clarify the rotational effect, and the effects of incoming flow incidence angle were examined for incidence angles ranging from -15 to +7 deg. The off-design test condition is obtained by changing the rotational speed maintaining a fixed incoming flow velocity. Complex heat transfer characteristics are observed on the Blade surface due to the complicated flow patterns, such as flow acceleration, laminarization, transition, separation bubble and tip leakage flow. The Blade rotation causes an increase of the incoming flow turbulence intensity and a reduction of the tip gap flow. At off-design conditions, the heat transfer on the turbine rotor changes significantly due to the flow acceleration/ deceleration and the incoming flow angle variation.

  • local heat mass transfer characteristics on a rotating Blade with flat tip in a low speed annular cascade part ii tip and shroud
    Journal of Turbomachinery-transactions of The Asme, 2006
    Co-Authors: Dongho Rhee
    Abstract:

    The local heat/mass transfer characteristics on the tip and shroud were investigated using a low speed rotating turbine annular cascade. Time-averaged mass transfer coefficients on the tip and shroud were measured using a naphthalene sublimation technique. A low speed wind tunnel with a single stage turbine annular cascade was used. The turbine stage is composed of sixteen guide plates and Blades. The chord length of Blade is 150 mm and the mean tip clearance is about 2.5% of the Blade chord. The tested Reynolds number based on inlet flow velocity and Blade chord is 1.5×10 5 and the rotational speed of the Blade is 255.8 rpm at design condition. The results were compared with the results for a Stationary Blade and the effects of incidence angle of incoming flow were examined for incidence angles ranging from -15 to +7 deg. The off-design test conditions are obtained by changing the rotational speed with a fixed incoming flow velocity. Flow reattachment on the tip near the pressure side edge dominates the heat transfer on the tip surface. Consequently, the heat/mass transfer coefficients on the Blade tip are about 1.7 times as high as those on the Blade surface and the shroud. However, the heat transfer on the tip is about 10% lower than that for the Stationary case due to reduced leakage flow with the relative motion. The peak regions due to the flow reattachment are reduced and shifted toward the trailing edge and additional peaks are formed near the leading edge region with decreasing incidence angles. But, quite uniform and high values are observed on the tip with positive incidence angles. The time-averaged heat/mass transfer on the shroud surface has a level similar to that of the Stationary cases.

Theodore H Okiishi - One of the best experts on this subject based on the ideXlab platform.

  • An Investigation of Wake-Shock Interactions in a Transonic Compressor With Digital Particle Image Velocimetry and Time-Accurate Computational Fluid Dynamics
    Journal of Turbomachinery, 2005
    Co-Authors: Steven E. Gorrell, David Car, Steven L. Puterbaugh, Jordi Estevadeordal, Theodore H Okiishi
    Abstract:

    The effects of varying axial gap on the unsteady flow field between the stator and rotor of a transonic compressor stage are important because they can result in significant changes in stage mass flow rate, pressure rise, and efficiency. Some of these effects are analyzed with measurements using digital particle image velocimetry (DPIV) and with time-accurate simulations using the 3D unsteady Navier-Stokes computational fluid dynamics solver TURBO. Generally there is excellent agreement between the measurements and simulations, instilling confidence in both. Strong vortices of the wake can break up the rotor bow shock and contribute to loss. At close spacing vortices are shed from the trailing edge of the upstream Stationary Blade row in response to the unsteady, discontinuous pressure field generated by the downstream rotor bow shock. Shed vortices increase in size and strength and generate more loss as spacing decreases, a consequence of the effective increase in rotor bow shock strength at the Stationary Blade row trailing edge. A relationship for the change in shed vorticity as a function of rotor bow shock strength is presented that predicts the difference between close and far spacing TURBO simulations.

  • An Investigation of Wake-Shock Interactions in a Transonic Compressor With DPIV and Time-Accurate CFD
    Volume 6: Turbo Expo 2005 Parts A and B, 2005
    Co-Authors: Steven E. Gorrell, David Car, Steven L. Puterbaugh, Jordi Estevadeordal, Theodore H Okiishi
    Abstract:

    The effects of varying axial gap on the unsteady flow field between the stator and rotor of a transonic compressor stage are important because they can result in significant changes in stage mass flow rate, pressure rise and efficiency. Some of these effects are analyzed with measurements using Digital Particle Image Velocimetry (DPIV) and with time-accurate simulations using the 3D unsteady Navier-Stokes CFD solver TURBO. Generally there is excellent agreement between the measurements and simulations, instilling confidence in both. Strong vortices of the wake can break up the rotor bow shock and contribute to loss. At close spacing vortices are shed from the trailing edge of the upstream Stationary Blade row in response to the unsteady, discontinuous pressure field generated by the downstream rotor bow shock. Shed vortices increase in size and strength and generate more loss as spacing decreases, a consequence of the effective increase in rotor bow shock strength at the Stationary Blade row trailing edge. A relationship for the change in shed vorticity as a function of rotor bow shock strength is presented that predicts the difference between close and far spacing TURBO simulations.Copyright © 2005 by ASME

  • Modification of Axial-Flow Compressor Stall Margin by Variation of Stationary Blade Setting Angles
    1
    Co-Authors: John P Rukavina, Theodore H Okiishi
    Abstract:

    Abstract : The useful operating range of the multistage, axial-flow compressor component of a gas turbine engine limits the extent of operation of that engine. Generally, the compressor stalls or surges at a low flow rate and chokes a a high flow rate. Thus, any improvement in the range between these compressor aerodynamic limits is normally of benefit to the engine also. An idea for delaying the onset of rotating stall in a multistage, axial-flow compressor which involved circumferentially varying the Blade setting angles of Stationary Blades upstream of the compressor rotors was investigated. Tests involving two low-speed, multistage, axial-flow compressors and an intermediate-speed, three- stage, axial-flow compressor were completed. Comparisons between baseline compressor (circumferentially uniform setting angles) and modified compressor (circumferentially varying setting angles) performance data were made. A variety of Blade setting angle circumferential variation patterns were tested.

Steven E. Gorrell - One of the best experts on this subject based on the ideXlab platform.

  • An Investigation of Wake-Shock Interactions in a Transonic Compressor With Digital Particle Image Velocimetry and Time-Accurate Computational Fluid Dynamics
    Journal of Turbomachinery, 2005
    Co-Authors: Steven E. Gorrell, David Car, Steven L. Puterbaugh, Jordi Estevadeordal, Theodore H Okiishi
    Abstract:

    The effects of varying axial gap on the unsteady flow field between the stator and rotor of a transonic compressor stage are important because they can result in significant changes in stage mass flow rate, pressure rise, and efficiency. Some of these effects are analyzed with measurements using digital particle image velocimetry (DPIV) and with time-accurate simulations using the 3D unsteady Navier-Stokes computational fluid dynamics solver TURBO. Generally there is excellent agreement between the measurements and simulations, instilling confidence in both. Strong vortices of the wake can break up the rotor bow shock and contribute to loss. At close spacing vortices are shed from the trailing edge of the upstream Stationary Blade row in response to the unsteady, discontinuous pressure field generated by the downstream rotor bow shock. Shed vortices increase in size and strength and generate more loss as spacing decreases, a consequence of the effective increase in rotor bow shock strength at the Stationary Blade row trailing edge. A relationship for the change in shed vorticity as a function of rotor bow shock strength is presented that predicts the difference between close and far spacing TURBO simulations.

  • An Investigation of Wake-Shock Interactions in a Transonic Compressor With DPIV and Time-Accurate CFD
    Volume 6: Turbo Expo 2005 Parts A and B, 2005
    Co-Authors: Steven E. Gorrell, David Car, Steven L. Puterbaugh, Jordi Estevadeordal, Theodore H Okiishi
    Abstract:

    The effects of varying axial gap on the unsteady flow field between the stator and rotor of a transonic compressor stage are important because they can result in significant changes in stage mass flow rate, pressure rise and efficiency. Some of these effects are analyzed with measurements using Digital Particle Image Velocimetry (DPIV) and with time-accurate simulations using the 3D unsteady Navier-Stokes CFD solver TURBO. Generally there is excellent agreement between the measurements and simulations, instilling confidence in both. Strong vortices of the wake can break up the rotor bow shock and contribute to loss. At close spacing vortices are shed from the trailing edge of the upstream Stationary Blade row in response to the unsteady, discontinuous pressure field generated by the downstream rotor bow shock. Shed vortices increase in size and strength and generate more loss as spacing decreases, a consequence of the effective increase in rotor bow shock strength at the Stationary Blade row trailing edge. A relationship for the change in shed vorticity as a function of rotor bow shock strength is presented that predicts the difference between close and far spacing TURBO simulations.Copyright © 2005 by ASME

David Car - One of the best experts on this subject based on the ideXlab platform.

  • An Investigation of Wake-Shock Interactions in a Transonic Compressor With Digital Particle Image Velocimetry and Time-Accurate Computational Fluid Dynamics
    Journal of Turbomachinery, 2005
    Co-Authors: Steven E. Gorrell, David Car, Steven L. Puterbaugh, Jordi Estevadeordal, Theodore H Okiishi
    Abstract:

    The effects of varying axial gap on the unsteady flow field between the stator and rotor of a transonic compressor stage are important because they can result in significant changes in stage mass flow rate, pressure rise, and efficiency. Some of these effects are analyzed with measurements using digital particle image velocimetry (DPIV) and with time-accurate simulations using the 3D unsteady Navier-Stokes computational fluid dynamics solver TURBO. Generally there is excellent agreement between the measurements and simulations, instilling confidence in both. Strong vortices of the wake can break up the rotor bow shock and contribute to loss. At close spacing vortices are shed from the trailing edge of the upstream Stationary Blade row in response to the unsteady, discontinuous pressure field generated by the downstream rotor bow shock. Shed vortices increase in size and strength and generate more loss as spacing decreases, a consequence of the effective increase in rotor bow shock strength at the Stationary Blade row trailing edge. A relationship for the change in shed vorticity as a function of rotor bow shock strength is presented that predicts the difference between close and far spacing TURBO simulations.

  • An Investigation of Wake-Shock Interactions in a Transonic Compressor With DPIV and Time-Accurate CFD
    Volume 6: Turbo Expo 2005 Parts A and B, 2005
    Co-Authors: Steven E. Gorrell, David Car, Steven L. Puterbaugh, Jordi Estevadeordal, Theodore H Okiishi
    Abstract:

    The effects of varying axial gap on the unsteady flow field between the stator and rotor of a transonic compressor stage are important because they can result in significant changes in stage mass flow rate, pressure rise and efficiency. Some of these effects are analyzed with measurements using Digital Particle Image Velocimetry (DPIV) and with time-accurate simulations using the 3D unsteady Navier-Stokes CFD solver TURBO. Generally there is excellent agreement between the measurements and simulations, instilling confidence in both. Strong vortices of the wake can break up the rotor bow shock and contribute to loss. At close spacing vortices are shed from the trailing edge of the upstream Stationary Blade row in response to the unsteady, discontinuous pressure field generated by the downstream rotor bow shock. Shed vortices increase in size and strength and generate more loss as spacing decreases, a consequence of the effective increase in rotor bow shock strength at the Stationary Blade row trailing edge. A relationship for the change in shed vorticity as a function of rotor bow shock strength is presented that predicts the difference between close and far spacing TURBO simulations.Copyright © 2005 by ASME