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Edward M. Greitzer - One of the best experts on this subject based on the ideXlab platform.

  • Role of Blade Passage Flow Structurs in Axial Compressor Rotating Stall Inception
    Journal of Turbomachinery, 1999
    Co-Authors: D. A. Hoying, Huu Duc Vo, C. S. Tan, Edward M. Greitzer
    Abstract:

    The influence of three-dimensional flow structures within a compressor Blade Passage has been examined computationally to determine their role in rotating stall inception. The computations displayed a short length-scale (or spike) type of stall inception similar to that seen in experiments; to the authors' knowledge this is the first time such a feature has been simulated. A central feature observed during the rotating stall inception was the tip clearance vortex moving forward of the Blade row leading edge. Vortex kinematic arguments are used to provide a physical explanation of this motion as well as to motivate the conditions for its occurrence. The resulting criterion for this type of stall inception (the movement of the tip clearance vortex forward of the leading edge) depends upon local flow phenomena related to the tip clearance with the implication that for this and possibly other stall mechanisms the flow structure within the Blade Passages must be addressed to explain the stability of an axial compression system that exhibits such short length-scale disturbances.

  • role of Blade Passage flow structures in axial compressor rotating stall inception
    ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition, 1998
    Co-Authors: D. A. Hoying, C. S. Tan, Edward M. Greitzer
    Abstract:

    The influence of three-dimensional flow structures within a compressor Blade Passage has been examined computationally to determine their role in rotating stall inception. The computations displayed a short length-scale (or spike) type of stall inception similar to that seen in experiments; to the authors’ knowledge this is the first time such a feature has been simulated. A central feature observed during the rotating stall inception was the tip clearance vortex moving forward of the Blade row leading edge. Vortex kinematic arguments are used to provide a physical explanation of this motion as well as to motivate the conditions for its occurrence. The resulting criterion for this type of stall inception (which appears generic for axial compressors with tip-critical flow fields) depends upon local flow phenomena related to the tip clearance and it is thus concluded that the flow structure within the Blade Passages must be addressed to explain the stability of an axial compression system which exhibits such short length-scale disturbances.© 1998 ASME

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

  • Role of Blade Passage Flow Structurs in Axial Compressor Rotating Stall Inception
    Journal of Turbomachinery, 1999
    Co-Authors: D. A. Hoying, Huu Duc Vo, C. S. Tan, Edward M. Greitzer
    Abstract:

    The influence of three-dimensional flow structures within a compressor Blade Passage has been examined computationally to determine their role in rotating stall inception. The computations displayed a short length-scale (or spike) type of stall inception similar to that seen in experiments; to the authors' knowledge this is the first time such a feature has been simulated. A central feature observed during the rotating stall inception was the tip clearance vortex moving forward of the Blade row leading edge. Vortex kinematic arguments are used to provide a physical explanation of this motion as well as to motivate the conditions for its occurrence. The resulting criterion for this type of stall inception (the movement of the tip clearance vortex forward of the leading edge) depends upon local flow phenomena related to the tip clearance with the implication that for this and possibly other stall mechanisms the flow structure within the Blade Passages must be addressed to explain the stability of an axial compression system that exhibits such short length-scale disturbances.

  • role of Blade Passage flow structures in axial compressor rotating stall inception
    ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition, 1998
    Co-Authors: D. A. Hoying, C. S. Tan, Edward M. Greitzer
    Abstract:

    The influence of three-dimensional flow structures within a compressor Blade Passage has been examined computationally to determine their role in rotating stall inception. The computations displayed a short length-scale (or spike) type of stall inception similar to that seen in experiments; to the authors’ knowledge this is the first time such a feature has been simulated. A central feature observed during the rotating stall inception was the tip clearance vortex moving forward of the Blade row leading edge. Vortex kinematic arguments are used to provide a physical explanation of this motion as well as to motivate the conditions for its occurrence. The resulting criterion for this type of stall inception (which appears generic for axial compressors with tip-critical flow fields) depends upon local flow phenomena related to the tip clearance and it is thus concluded that the flow structure within the Blade Passages must be addressed to explain the stability of an axial compression system which exhibits such short length-scale disturbances.© 1998 ASME

  • Blade Passage flow structure effects on axial compressor rotating stall inception
    1996
    Co-Authors: D. A. Hoying
    Abstract:

    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1996.

Choonman Jang - One of the best experts on this subject based on the ideXlab platform.

  • Original Paper Numerical Investigation on Aerodynamic Performance of a Centrifugal Fan with Splitter Blades
    2016
    Co-Authors: Jin-hyuk Kim, Kwang-yong Kim, Kyung-hun Cha, Choonman Jang
    Abstract:

    This paper presents a numerical investigation on the aerodynamic performance according to the application of splitter Blades in an impeller of a centrifugal fan used for a refuse collection system. Numerical analysis of a centrifugal fan was carried out by solving three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. A validation of numerical results was conducted by comparison with experimental data for the pressure and efficiency. From analyses of the internal flow field of the reference fan, the losses by the reverse-flows were observed in the region of the Blade Passage. In order to reduce these losses and enhance fan performance, two splitter Blades were applied evenly between the main Blades, and centrifugal impellers having the different numbers of the main Blades were tested with their application. Throughout the numerical analyses of the centrifugal fan with splitter Blades, it was found that the reverse-flow regions in the Blade Passage can be reduced by controlling the main Blade numbers with splitter Blades. The application of splitter Blades in a centrifugal fan leads to significant improvement in the overall fan performance

  • performance characteristics of double inlet centrifugal blower according to inlet and outlet angles of an impeller
    Transactions of the Korean hydrogen and new energy society, 2014
    Co-Authors: Choonman Jang
    Abstract:

    Effects of design variables on the performance of a double-inlet centrifugal blower have been analyzed based on the three-dimensional flow analysis. Two design variables, Blade inlet and outlet angles, are introduced to enhance a blower performance. General analysis code, ANSYS-CFX13, is employed to analyze internal flow and a blower performance. SST turbulence model is employed to estimate the eddy viscosity. Throughout the shape optimization of an impeller at the design flow condition, the blower efficiency and pressure are successfully increased by 4.7 and 1.02 percent compared to reference one. It is noted that separated flow observed near cut-off region can be reduced by optimal design of Blade angles, which results in stable flow pattern in the Blade Passage and increase of a blower performance. The stable flow at the impeller also makes good effects at the outlet of a volute casing.

  • performance characteristics of the double inlet centrifugal blower according to the shape of an impeller
    Journal of Fluid Machinery, 2014
    Co-Authors: Choonman Jang
    Abstract:

    This paper presents the performance enhancement of a double-inlet centrifugal blower by the shape optimization of an impeller. Two design variables, a number of Blade and a length of chord, are introduced, and analyzed by a response surface method. Three-dimensional compressible Navier-Stokes equations are used to analyze the blower performance and the internal flow of the blower. Throughout the numerical simulation of the blower, blower efficiency can be increased by reducing separation flow generating from the Blade leading edge of a Blade pressure surface. It is noted that recirculation flow observed inside the Blade Passage induces low velocity region, thus increases pressure loss. Efficiency and pressure of the optimum blower are successfully increased up to 3% and 3.9% compared to those of reference blower at the design flow condition, respectively. Detailed flow field inside the blower is also analyzed and compared.

  • Numerical Investigation on Aerodynamic Performance of a Centrifugal Fan with Splitter Blades
    International Journal of Fluid Machinery and Systems, 2012
    Co-Authors: Jin-hyuk Kim, Kwang-yong Kim, Kyung-hun Cha, Choonman Jang
    Abstract:

    This paper presents a numerical investigation on the aerodynamic performance according to the application of splitter Blades in an impeller of a centrifugal fan used for a refuse collection system. Numerical analysis of a centrifugal fan was carried out by solving three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. A validation of numerical results was conducted by comparison with experimental data for the pressure and efficiency. From analyses of the internal flow field of the reference fan, the losses by the reverse-flows were observed in the region of the Blade Passage. In order to reduce these losses and enhance fan performance, two splitter Blades were applied evenly between the main Blades, and centrifugal impellers having the different numbers of the main Blades were tested with their application. Throughout the numerical analyses of the centrifugal fan with splitter Blades, it was found that the reverse-flow regions in the Blade Passage can be reduced by controlling the main Blade numbers with splitter Blades. The application of splitter Blades in a centrifugal fan leads to significant improvement in the overall fan performance.

  • effects of the tip clearance on vortical flow and its relation to noise in an axial flow fan
    Jsme International Journal Series B-fluids and Thermal Engineering, 2003
    Co-Authors: Choonman Jang, Tohru Fukano, Masato Furukawa
    Abstract:

    Three-dimensional vortical flow structures and velocity fluctuation near the rotor tip in an axial flow fan having two different tip clearances have been investigated by experimental analysis using a rotating hot wire probe and a numerical simulation. It is found that a tip leakage vortex is observed in the Blade Passage, which has a major role near the rotor tip. The tip leakage vortex formed close to the leading edge of the Blade tip on suction side grows in the streamwise direction, and forms a local recirculation region resulting from a vortex breakdown inside the Blade Passage. The recirculation region is enlarged by increasing the tip clearance. The larger recirculation region induces the acceleration of the through flow, thus resulting in the increase of the broadband noise. High velocity fluctuation is observed at the interference region between the tip leakage vortex and the through flow in the flow field where the tip leakage vortex is tightly rolled up without its breakdown. Near the casing wall, a discrete frequency is formed between tip leakage vortex core and rotor trailing edge.

Ales Hribernik - One of the best experts on this subject based on the ideXlab platform.

  • visualisation of rotating stall in an axial flow fan
    Experimental Thermal and Fluid Science, 2014
    Co-Authors: Matej Fike, Gorazd Bombek, Matjaž Hribersek, Ales Hribernik
    Abstract:

    Abstract Visualisation of a flow field was performed within the rotor Blade Passage of an axial flow fan operating under rotating stall conditions. A PIV system was used to capture the velocity field at an 80% span of the rotor Blade. PIV triggering was synchronized with the observed Blades’ passing, and over 1000 PIV images were obtained. These were then phase-locked averaged, and a sequence of 36 images was composed. The successive images represented the evolution of a flow field within the Blade Passage with 10° angular steps and made it possible for the structure and behaviour of the flow within the rotor Blade Passage to be analysed under rotating stall conditions. The initiation and development of flow distortion were clearly shown to be influenced by the advance of the rotating stall cell and the restoration of normal flow with the rotating stall cell moving away.

Ali Ameri - One of the best experts on this subject based on the ideXlab platform.

  • comparison of steady and unsteady rans heat transfer simulations of hub and endwall of a turbine Blade Passage
    Journal of Turbomachinery-transactions of The Asme, 2011
    Co-Authors: Lamyaa A Elgabry, Ali Ameri
    Abstract:

    The necessity of performing an unsteady simulation for the purpose of predicting the heat transfer on the endwall surfaces of a turbine Passage is addressed. This is measured by the difference between the two solutions obtained from a steady simulation and the time average of an unsteady simulation. The heat transfer coefficient (Nusselt number) based on the adiabatic wall temperature is used as the basis of the comparison. As there is no film cooling in the proposed case, a computed heat transfer coefficient should be a better measure of such difference than, say, a wall heat flux. Results show that the effect of unsteadiness due to wake Passage on the pressures and recovery temperatures on both hub and casing is negligible. Heat transfer on the endwalls, however, is affected by the unsteady wake; the time-averaged results yield higher heat transfer; in some regions, up to 15% higher. The results for the endwall heat transfer were compared with results in open literature and were found to be comparable.

  • heat transfer and flow on the first stage Blade tip of a power generation gas turbine part 2 simulation results
    Journal of Turbomachinery-transactions of The Asme, 2000
    Co-Authors: Ali Ameri, Ronald Scott Bunker
    Abstract:

    A combined experimental and computational study has been performed to investigate the detailed distribution of convective heat transfer coefficients on the first-stage Blade tip surface for a geometry typical of large power generation turbines (>100 MW). This paper is concerned with the numerical prediction of the tip surface heat transfer. Good comparison with the experimental measured distribution was achieved through accurate modeling of the most important features of the Blade Passage and heating arrangement as well as the details of experimental rig likely to affect the tip heat transfer. A sharp edge and a radiused edge tip was considered. The results using the radiused edge tip agreed better with the experimental data. This improved agreement was attributed to the absence of edge separation on the tip of the radiused edge Blade.

  • heat transfer and flow on the first stage Blade tip of a power generation gas turbine part 2 simulation results
    ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition, 1999
    Co-Authors: Ali Ameri, Ronald Scott Bunker
    Abstract:

    A combined experimental and computational study has been performed to investigate the detailed distribution of convective heat transfer coefficients on the first stage Blade tip surface for a geometry typical of large power generation turbines (>100MW). This paper is concerned with the numerical prediction of the tip surface heat transfer. Good comparison with the experimental measured distribution was achieved through accurate modeling of the most important features of the Blade Passage and heating arrangement as well as the details of experimental rig likely to affect the tip heat transfer. A sharp edge and a radiused edge tip was considered. The results using the radiused edge tip agreed better with the experimental data. This improved agreement was attributed to the absence of edge separation on the tip of the radiused edge Blade.Copyright © 1999 by ASME

  • prediction of turbine Blade Passage heat transfer using a zero and a two equation turbulence model
    ASME 1994 International Gas Turbine and Aeroengine Congress and Exposition, 1994
    Co-Authors: Ali Ameri, Andrea Arnone
    Abstract:

    Predictions of the heat transfer rates on the hot surfaces of a turbine cascade Blade Passage as influenced by the turbulence models was examined. A zero equation turbulence model supplemented by a bypass transition model and a two equation low Reynolds number model were chosen for this study. The experimental data of Graziani et. al. were used for comparison. The comparisons suggest that at least for the experimental data considered in this work the use of a two-equation model does not provide an overall more accurate solution than the zero equation model. This conclusion is strengthened if one takes into account the relative economy of computations with the algebraic model.Copyright © 1994 by ASME