The Experts below are selected from a list of 1953 Experts worldwide ranked by ideXlab platform

Sigmar Wittig - One of the best experts on this subject based on the ideXlab platform.

  • influence of a honeycomb facing on the flow through a stepped labyrinth Seal
    Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration, 2000
    Co-Authors: V. Schramm, K Willenborg, Sigmar Wittig
    Abstract:

    This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth Seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a Seal Configuration with a honeycomb facing mounted on the stator wall were investigated. The Seal geometry is representative of typical three-step labyrinth Seals of modern aero engines. The flow field was predicted using a commercial finite-volume code with the standard-k-e-turbulence model. The computational grid includes the basic Seal geometry as well as the three-dimensional honeycomb structures.Copyright © 2000 by ASME

  • Influence of a Honeycomb Facing on the Flow Through a Stepped Labyrinth Seal
    Journal of Engineering for Gas Turbines and Power, 2000
    Co-Authors: V. Schramm, K Willenborg, Soksik Kim, Sigmar Wittig
    Abstract:

    This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth Seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a Seal Configuration with a honeycomb facing mounted on the stator wall were investigated. The Seal geometry is representative of typical three-step labyrinth Seals of modern aero engines. The flow field was predicted using a commercial finite volume code with the standard k-e turbulence model. The computational grid includes the basic Seal geometry as well as the three-dimensional honeycomb structures.

Reza S Abhari - One of the best experts on this subject based on the ideXlab platform.

  • unsteady flow interactions within the inlet cavity of a turbine rotor tip labyrinth Seal
    Journal of Turbomachinery-transactions of The Asme, 2005
    Co-Authors: A Pfau, J Schlienger, Anestis I Kalfas, Dana Rusch, Reza S Abhari
    Abstract:

    This paper focuses on the flow within the inlet cavity of a turbine rotor tip labyrinth Seal of a two stage axial research turbine. Highly resolved, steady and unsteady three-dimensional flow data are presented. The probes used here are a miniature five-hole probe of 0.9 mm head diameter and the novel virtual four sensor fast response aerodynamic probe (FRAP) with a head diameter of 0.84 mm. The cavity flow itself is not only a loss producing area due to mixing and vortex stretching, it also adversely affects the following rotor passage through the fluid that is spilled into the main flow. The associated fluctuating mass flow has a relatively low total pressure and results in a negative incidence to the rotor tip blade profile section. The dominating kinematic flow feature in the region between cavity and main flow is a toroidal vortex, which is swirling at high circumferential velocity. It is fed by strong shear and end wall fluid from the pressure side of the stator passage. The static pressure field interaction between the moving rotor leading edges and the stator trailing edges is one driving force of the cavity flow. It forces the toroidal vortex to be stretched in space and time. A comprehensive flow model including the drivers of this toroidal vortex is proposed. This labyrinth Seal Configuration results in about 1.6% turbine efficiency reduction. This is the first in a series of papers focusing on turbine loss mechanisms in shrouded axial turbines. Additional measurements have been made with variations in Seal clearance gap. Initial indications show that variation in the gap has a major effect on flow structures and turbine loss.

  • unsteady flow interactions within the inlet cavity of a turbine rotor tip labyrinth Seal
    ASME Turbo Expo 2003 collocated with the 2003 International Joint Power Generation Conference, 2003
    Co-Authors: A Pfau, J Schlienger, Anestis I Kalfas, Dana Rusch, Reza S Abhari
    Abstract:

    This paper focuses on the flow within the inlet cavity of a turbine rotor tip labyrinth Seal of a 2 stage axial research turbine. Highly resolved, steady and unsteady 3-dimensional flow data are presented. The probes used here are a miniature 5 hole probe of 0.9mm head diameter and the novel virtual four sensor fast response aerodynamic probe (FRAP) with a head diameter of 0.84mm. The cavity flow itself is not only a loss producing area due to mixing and vortex stretching, it also adversely affects the following rotor passage through the fluid that is spilled into the main flow. The associated fluctuating mass flow has a relatively low total pressure and results in a negative incidence to the rotor tip blade profile section. The dominating kinematic flow feature in the region between cavity and main flow is a toroidal vortex, which is swirling at high circumferential velocity. It is fed by strong shear and end wall fluid from the pressure side of the stator passage. The static pressure field interaction between the moving rotor leading edges and the stator trailing edges is one driving force of the cavity flow. It forces the toroidal vortex to be stretched in space and time. A comprehensive flow model including the drivers of this toroidal vortex is proposed. This labyrinth Seal Configuration results in about 1.6% turbine efficiency reduction. This is the first in a series of papers focussing on turbine loss mechanisms in shrouded axial turbines. Additional measurements have been made with variations in Seal clearance gap. Initial indications show that variation in the gap has a major effect on flow structures and turbine loss.Copyright © 2003 by ASME

  • effects of labyrinth Seal variation on multistage axial turbine flow
    ASME Turbo Expo 2003 collocated with the 2003 International Joint Power Generation Conference, 2003
    Co-Authors: J Schlienger, A Pfau, Anestis I Kalfas, Reza S Abhari
    Abstract:

    The need to increase overall turbine efficiency is always a driving force for redesigning a turbine stage. In particular, the labyrinth leakage flows in the endwall regions contribute to an increase of the overall loss generation. In order to asses this mechanism, a detailed study of the effects of labyrinth Seal geometry variation on the blade performance is presented. Two different shroud Seal geometries have been experimentally investigated in a two stage low speed turbine facility. The Seal geometries differ in the size and shape of the re-entry cavity. The baseline Seal is designed with a large rectangular re-entry cavity volume in order to dissipate the kinetic energy of the accelerated leakage flow after the Seal gap. The re-entry cavity volume of the alternative Seal design is reduced in size and a spline shaped contour is added to the endwall using annular inserts. This modification alters the gas path of the leakage jet and changes the incidence angles on the downstream blade rows. The measurements are performed with state of the art pneumatic and fast response pressure probes at various planes within the turbine stage. It is found that the inserts improved the flow profile uniformity at the endwalls. The measurements within the stator passage reveal the origin of the tip passage vortex formation at the blade suction side, already at the inlet to the stator passage. This result does not conform to the classical secondary flow theory, which suggests that the passage vortex migrates from the pressure to the suction side within the stator passage. The origin and formation of the secondary flow passage vortices at rotor hub and stator tip is described in a flow schematic. The generation of streamwise and tangential vorticity at the interaction area of leakage and main flow field also is studied and discussed. The measured overall polytropic turbine efficiency for the second Seal Configuration, relative to the baseline case, is reduced by 0.3%. The change in the re-entry flow angle of the leakage gas path reduces the negative incidence angle on the rotor hub and increases it at the stator tip leading edge. The secondary flow and mixing loss is reduced at the hub and increased at the tip in the second test case with the smaller cavity volume. Hence, the combination of small clearances and inserts in the re-entry cavities shows no beneficial effect on the overall turbine efficiency.Copyright © 2003 by ASME

V. Schramm - One of the best experts on this subject based on the ideXlab platform.

  • influence of a honeycomb facing on the flow through a stepped labyrinth Seal
    Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration, 2000
    Co-Authors: V. Schramm, K Willenborg, Sigmar Wittig
    Abstract:

    This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth Seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a Seal Configuration with a honeycomb facing mounted on the stator wall were investigated. The Seal geometry is representative of typical three-step labyrinth Seals of modern aero engines. The flow field was predicted using a commercial finite-volume code with the standard-k-e-turbulence model. The computational grid includes the basic Seal geometry as well as the three-dimensional honeycomb structures.Copyright © 2000 by ASME

  • Influence of a Honeycomb Facing on the Flow Through a Stepped Labyrinth Seal
    Journal of Engineering for Gas Turbines and Power, 2000
    Co-Authors: V. Schramm, K Willenborg, Soksik Kim, Sigmar Wittig
    Abstract:

    This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth Seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a Seal Configuration with a honeycomb facing mounted on the stator wall were investigated. The Seal geometry is representative of typical three-step labyrinth Seals of modern aero engines. The flow field was predicted using a commercial finite volume code with the standard k-e turbulence model. The computational grid includes the basic Seal geometry as well as the three-dimensional honeycomb structures.

K Willenborg - One of the best experts on this subject based on the ideXlab platform.

  • influence of a honeycomb facing on the flow through a stepped labyrinth Seal
    Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration, 2000
    Co-Authors: V. Schramm, K Willenborg, Sigmar Wittig
    Abstract:

    This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth Seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a Seal Configuration with a honeycomb facing mounted on the stator wall were investigated. The Seal geometry is representative of typical three-step labyrinth Seals of modern aero engines. The flow field was predicted using a commercial finite-volume code with the standard-k-e-turbulence model. The computational grid includes the basic Seal geometry as well as the three-dimensional honeycomb structures.Copyright © 2000 by ASME

  • Influence of a Honeycomb Facing on the Flow Through a Stepped Labyrinth Seal
    Journal of Engineering for Gas Turbines and Power, 2000
    Co-Authors: V. Schramm, K Willenborg, Soksik Kim, Sigmar Wittig
    Abstract:

    This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth Seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a Seal Configuration with a honeycomb facing mounted on the stator wall were investigated. The Seal geometry is representative of typical three-step labyrinth Seals of modern aero engines. The flow field was predicted using a commercial finite volume code with the standard k-e turbulence model. The computational grid includes the basic Seal geometry as well as the three-dimensional honeycomb structures.

A Pfau - One of the best experts on this subject based on the ideXlab platform.

  • unsteady flow interactions within the inlet cavity of a turbine rotor tip labyrinth Seal
    Journal of Turbomachinery-transactions of The Asme, 2005
    Co-Authors: A Pfau, J Schlienger, Anestis I Kalfas, Dana Rusch, Reza S Abhari
    Abstract:

    This paper focuses on the flow within the inlet cavity of a turbine rotor tip labyrinth Seal of a two stage axial research turbine. Highly resolved, steady and unsteady three-dimensional flow data are presented. The probes used here are a miniature five-hole probe of 0.9 mm head diameter and the novel virtual four sensor fast response aerodynamic probe (FRAP) with a head diameter of 0.84 mm. The cavity flow itself is not only a loss producing area due to mixing and vortex stretching, it also adversely affects the following rotor passage through the fluid that is spilled into the main flow. The associated fluctuating mass flow has a relatively low total pressure and results in a negative incidence to the rotor tip blade profile section. The dominating kinematic flow feature in the region between cavity and main flow is a toroidal vortex, which is swirling at high circumferential velocity. It is fed by strong shear and end wall fluid from the pressure side of the stator passage. The static pressure field interaction between the moving rotor leading edges and the stator trailing edges is one driving force of the cavity flow. It forces the toroidal vortex to be stretched in space and time. A comprehensive flow model including the drivers of this toroidal vortex is proposed. This labyrinth Seal Configuration results in about 1.6% turbine efficiency reduction. This is the first in a series of papers focusing on turbine loss mechanisms in shrouded axial turbines. Additional measurements have been made with variations in Seal clearance gap. Initial indications show that variation in the gap has a major effect on flow structures and turbine loss.

  • unsteady flow interactions within the inlet cavity of a turbine rotor tip labyrinth Seal
    ASME Turbo Expo 2003 collocated with the 2003 International Joint Power Generation Conference, 2003
    Co-Authors: A Pfau, J Schlienger, Anestis I Kalfas, Dana Rusch, Reza S Abhari
    Abstract:

    This paper focuses on the flow within the inlet cavity of a turbine rotor tip labyrinth Seal of a 2 stage axial research turbine. Highly resolved, steady and unsteady 3-dimensional flow data are presented. The probes used here are a miniature 5 hole probe of 0.9mm head diameter and the novel virtual four sensor fast response aerodynamic probe (FRAP) with a head diameter of 0.84mm. The cavity flow itself is not only a loss producing area due to mixing and vortex stretching, it also adversely affects the following rotor passage through the fluid that is spilled into the main flow. The associated fluctuating mass flow has a relatively low total pressure and results in a negative incidence to the rotor tip blade profile section. The dominating kinematic flow feature in the region between cavity and main flow is a toroidal vortex, which is swirling at high circumferential velocity. It is fed by strong shear and end wall fluid from the pressure side of the stator passage. The static pressure field interaction between the moving rotor leading edges and the stator trailing edges is one driving force of the cavity flow. It forces the toroidal vortex to be stretched in space and time. A comprehensive flow model including the drivers of this toroidal vortex is proposed. This labyrinth Seal Configuration results in about 1.6% turbine efficiency reduction. This is the first in a series of papers focussing on turbine loss mechanisms in shrouded axial turbines. Additional measurements have been made with variations in Seal clearance gap. Initial indications show that variation in the gap has a major effect on flow structures and turbine loss.Copyright © 2003 by ASME

  • effects of labyrinth Seal variation on multistage axial turbine flow
    ASME Turbo Expo 2003 collocated with the 2003 International Joint Power Generation Conference, 2003
    Co-Authors: J Schlienger, A Pfau, Anestis I Kalfas, Reza S Abhari
    Abstract:

    The need to increase overall turbine efficiency is always a driving force for redesigning a turbine stage. In particular, the labyrinth leakage flows in the endwall regions contribute to an increase of the overall loss generation. In order to asses this mechanism, a detailed study of the effects of labyrinth Seal geometry variation on the blade performance is presented. Two different shroud Seal geometries have been experimentally investigated in a two stage low speed turbine facility. The Seal geometries differ in the size and shape of the re-entry cavity. The baseline Seal is designed with a large rectangular re-entry cavity volume in order to dissipate the kinetic energy of the accelerated leakage flow after the Seal gap. The re-entry cavity volume of the alternative Seal design is reduced in size and a spline shaped contour is added to the endwall using annular inserts. This modification alters the gas path of the leakage jet and changes the incidence angles on the downstream blade rows. The measurements are performed with state of the art pneumatic and fast response pressure probes at various planes within the turbine stage. It is found that the inserts improved the flow profile uniformity at the endwalls. The measurements within the stator passage reveal the origin of the tip passage vortex formation at the blade suction side, already at the inlet to the stator passage. This result does not conform to the classical secondary flow theory, which suggests that the passage vortex migrates from the pressure to the suction side within the stator passage. The origin and formation of the secondary flow passage vortices at rotor hub and stator tip is described in a flow schematic. The generation of streamwise and tangential vorticity at the interaction area of leakage and main flow field also is studied and discussed. The measured overall polytropic turbine efficiency for the second Seal Configuration, relative to the baseline case, is reduced by 0.3%. The change in the re-entry flow angle of the leakage gas path reduces the negative incidence angle on the rotor hub and increases it at the stator tip leading edge. The secondary flow and mixing loss is reduced at the hub and increased at the tip in the second test case with the smaller cavity volume. Hence, the combination of small clearances and inserts in the re-entry cavities shows no beneficial effect on the overall turbine efficiency.Copyright © 2003 by ASME