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Hironobu Ueki - One of the best experts on this subject based on the ideXlab platform.

  • suppression of rotating stall by wall roughness control in vaneless diffusers of centrifugal blowers
    Journal of Turbomachinery-transactions of The Asme, 2001
    Co-Authors: Masahiro Ishida, Daisaku Sakaguchi, Hironobu Ueki
    Abstract:

    By positioning the completely rough wall locally on the hub side diffuser wall alone in the vaneless diffuser, the flow rate of rotating stall inception was decreased by 42 percent at a small pressure drop of less than 1 percent. This is based on the fact that the local reverse flow occurs first in the hub side in most centrifugal blowers with a backswept blade impeller. The three-dimensional Boundary Layer Calculation shows that the increase in wall shear component normal to the main-flow direction markedly decreases the skewed angle of the three-dimensional Boundary Layer, and results in suppression of the three-dimensional separation. It is also clarified theoretically that the diffuser pressure recovery is hardly deteriorated by the rough wall positioned downstream of R = l.2 because the increase in the radial momentum change, resulting from reduction in the skewed angle of the three-dimensional Boundary Layer, supports the adverse pressure gradient.

  • suppression of rotating stall by wall roughness control in vaneless diffusers of centrifugal blowers
    Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 2000
    Co-Authors: Masahiro Ishida, Daisaku Sakaguchi, Hironobu Ueki
    Abstract:

    By positioning the completely rough wall locally on the hub side diffuser wall alone in the vaneless diffuser, the flow rate of rotating stall inception was decreased by 42% at a small pressure drop less than 1%. This is based on the fact that the local reverse flow occurs firstly in the hub side in most centrifugal blowers with the backswept blade impeller. The 3-D Boundary Layer Calculation shows that the increase in wall shear component normal to the main-flow direction decreases markedly the skewed angle of the 3-D Boundary Layer, and results in suppression of the 3-D separation. It is also clarified theoretically that the diffuser pressure recovery is hardly deteriorated by the rough wall positioned downstream of R = 1.2 because the increase in the radial momentum change, resulting from reduction in the skewed angle of the 3-D Boundary Layer, supports the adverse pressure gradient.Copyright © 2000 by ASME

Masahiro Ishida - One of the best experts on this subject based on the ideXlab platform.

  • suppression of rotating stall by wall roughness control in vaneless diffusers of centrifugal blowers
    Journal of Turbomachinery-transactions of The Asme, 2001
    Co-Authors: Masahiro Ishida, Daisaku Sakaguchi, Hironobu Ueki
    Abstract:

    By positioning the completely rough wall locally on the hub side diffuser wall alone in the vaneless diffuser, the flow rate of rotating stall inception was decreased by 42 percent at a small pressure drop of less than 1 percent. This is based on the fact that the local reverse flow occurs first in the hub side in most centrifugal blowers with a backswept blade impeller. The three-dimensional Boundary Layer Calculation shows that the increase in wall shear component normal to the main-flow direction markedly decreases the skewed angle of the three-dimensional Boundary Layer, and results in suppression of the three-dimensional separation. It is also clarified theoretically that the diffuser pressure recovery is hardly deteriorated by the rough wall positioned downstream of R = l.2 because the increase in the radial momentum change, resulting from reduction in the skewed angle of the three-dimensional Boundary Layer, supports the adverse pressure gradient.

  • suppression of rotating stall by wall roughness control in vaneless diffusers of centrifugal blowers
    Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 2000
    Co-Authors: Masahiro Ishida, Daisaku Sakaguchi, Hironobu Ueki
    Abstract:

    By positioning the completely rough wall locally on the hub side diffuser wall alone in the vaneless diffuser, the flow rate of rotating stall inception was decreased by 42% at a small pressure drop less than 1%. This is based on the fact that the local reverse flow occurs firstly in the hub side in most centrifugal blowers with the backswept blade impeller. The 3-D Boundary Layer Calculation shows that the increase in wall shear component normal to the main-flow direction decreases markedly the skewed angle of the 3-D Boundary Layer, and results in suppression of the 3-D separation. It is also clarified theoretically that the diffuser pressure recovery is hardly deteriorated by the rough wall positioned downstream of R = 1.2 because the increase in the radial momentum change, resulting from reduction in the skewed angle of the 3-D Boundary Layer, supports the adverse pressure gradient.Copyright © 2000 by ASME

Daisaku Sakaguchi - One of the best experts on this subject based on the ideXlab platform.

  • suppression of rotating stall by wall roughness control in vaneless diffusers of centrifugal blowers
    Journal of Turbomachinery-transactions of The Asme, 2001
    Co-Authors: Masahiro Ishida, Daisaku Sakaguchi, Hironobu Ueki
    Abstract:

    By positioning the completely rough wall locally on the hub side diffuser wall alone in the vaneless diffuser, the flow rate of rotating stall inception was decreased by 42 percent at a small pressure drop of less than 1 percent. This is based on the fact that the local reverse flow occurs first in the hub side in most centrifugal blowers with a backswept blade impeller. The three-dimensional Boundary Layer Calculation shows that the increase in wall shear component normal to the main-flow direction markedly decreases the skewed angle of the three-dimensional Boundary Layer, and results in suppression of the three-dimensional separation. It is also clarified theoretically that the diffuser pressure recovery is hardly deteriorated by the rough wall positioned downstream of R = l.2 because the increase in the radial momentum change, resulting from reduction in the skewed angle of the three-dimensional Boundary Layer, supports the adverse pressure gradient.

  • suppression of rotating stall by wall roughness control in vaneless diffusers of centrifugal blowers
    Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 2000
    Co-Authors: Masahiro Ishida, Daisaku Sakaguchi, Hironobu Ueki
    Abstract:

    By positioning the completely rough wall locally on the hub side diffuser wall alone in the vaneless diffuser, the flow rate of rotating stall inception was decreased by 42% at a small pressure drop less than 1%. This is based on the fact that the local reverse flow occurs firstly in the hub side in most centrifugal blowers with the backswept blade impeller. The 3-D Boundary Layer Calculation shows that the increase in wall shear component normal to the main-flow direction decreases markedly the skewed angle of the 3-D Boundary Layer, and results in suppression of the 3-D separation. It is also clarified theoretically that the diffuser pressure recovery is hardly deteriorated by the rough wall positioned downstream of R = 1.2 because the increase in the radial momentum change, resulting from reduction in the skewed angle of the 3-D Boundary Layer, supports the adverse pressure gradient.Copyright © 2000 by ASME

Aktaş Hakkı - One of the best experts on this subject based on the ideXlab platform.

  • Interactive Boundary Layer Calculation Around An Airfoil And Its Wake
    'Nara Institute of Science and Technology', 2015
    Co-Authors: Aktaş Hakkı
    Abstract:

    Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2003Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2003Bu tez kapsamında kanat profili ve iz bölgesi üzerinde basınç dağılımı kompleks düzlemde kompleks panel yöntemiyle hesaplanmış, elde edilen basınç dağılımı yardımıyla sınır tabaka hesabı Cebeci-Smith yöntemiyle hesaplanmıştır. Sınır tabaka denklemlerinin çözümünden elde edilen deplasman kalınlıkları kullanılarak yüzey üfleme hızları hesaplanmış ve bu yüzey üfleme hızları potansiyel akımda sınır şartı teşkil edecek şekilde yeniden potansiyel akım hesabı yapılmıştır. Bu sayede sınır tabakanın etkisi potansiyel akım hesabına ithal edilmiştir. Bu etkileşim kanat profili ve iz bölgesi üzerindeki hız dağılımı yakınsayıncaya kadar devam etmektedir. Cebeci-Smith Yöntemi sonlu farklar esasına dayanmakta olup Thwaites, Pohlhausen, Michel-Couisteix, Couisteix-Head, Walz-Eppler yöntemleriyle karşılaştırılmış ve oldukça tatminkar sonuçlar alınmıştır.In this study Boundary Layer Calculations are performed around an airfoil and its wake. Potential pressure distribution over the airfoil and wake are calculated by using the complex panel method in complex plane and due to the this distribution Boundary Layer Calculation is accomplished via Cebeci-Smith method. Using the displacement thicknesses which are found from the Boundary Layer Calculations, the blowing velocities have been obtained and then this blowing velocities are imported as a Boundary condition to the potential flow Calculations in order to recalculate the potential flow. With the help of this method, the effects of the Boundary Layer have been added to the potential flow Calculations. This procedure is repeated until a converged velocity distribution is achieved around the airfoil and its wake. Depending on the finite difference method, Cebeci-Smith Method tested with the Thwaites, Pohlhausen, Michel-Couisteix, Walz-Eppler, Couisteix-Head, methods and obtained satisfactory results.Yüksek LisansM.Sc

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

  • THE METHOD FOR PREDICTING THE PERFORMANCE OF PROPELLER-RUDDER SYSTEM WITH RUDDER ANGLE AND ITS APPLICATION TO THE RUDDER DESIGN
    1993
    Co-Authors: M Tamashima, S Matsui
    Abstract:

    In this paper the performance of the system of a propeller and a rudder with rudder angle behind a ship is treated hydrodynamically from the propulsion and manoeuvring viewpoint. The propeller and the rudder behind a ship are regarded as a unit to generate the thrust and the lateral force, which is named PRS (Propeller-Rudder- System). In order to calculate the performance characteristics of PRS, for simplicity, the simplified propeller theory is applied to calculate the forces acting on the propeller, assuming an infinitely bladed propeller. The panel method in the lifting body theory is adopted to calculate the forces acting on the rudder, taking into account the friction force obtained by two dimensional Boundary Layer Calculation. The mutual interaction is taken into consideration by superposing the induced velocity by the other on the inflow. The contraction by the simple method is introduced for the free steam of the propeller as the inflow into the rudder. When a PRS is set in uniform flow, the performance characteristics of the PRS is calculated. The calculated results of the thrust and the lateral force acting on PRS show good agreement with the experimental results. The assessment of the performance characteristics of PRS is also discussed. Finally the proposed method to calculate the performance characteristics of PRS is applied to design rudders.