Yazar "Aksit, Mahmut F." seçeneğine göre listele

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    Öğe
    Brush seal temperature distribution analysis (Conference Paper)
    (2005) Doğu, Yahya; Aksit, Mahmut F.
    Brush seals are designed to survive transient rotor rubs. Inherent brush seal flexibility reduces frictional heat generation. However, high surface speeds combined with thin rotor sections may result in local hot spots. Considering large surface area and accelerated oxidation rates, frictional heat at bristles tips is another major concern especially in challenging high temperature applications. This study investigates temperature distribution in a brush seal as a function of frictional heat generation at bristle tips. The two-dimensional axisymmetric CFD analysis includes the permeable bristle pack as a porous medium allowing fluid flow throughout the bristle matrix. In addition to effective flow resistance coefficients, isotropic effective thermal conductivity as a function of temperature is defined for the bristle pack. Employing a fin approach for a single bristle, a theoretical analysis has been developed after outlining the brush seal heat transfer mechanism. Theoretical and CFD analysis results are compared. To ensure coverage for various seal designs and operating conditions, several frictional heat input cases corresponding to different seal stiffness have been studied. Frictional heat generation is outlined to introduce a practical heat flux input into the analysis model. Effect of seal stiffness on nominal bristle tip temperature has been evaluated. Analyses show a steep temperature rise close to bristle tips that diminishes further away. Heat flux conducted through the bristles dissipates into the flow by a strong convection at fence height region. Copyright © 2005 by ASME.
  • [ X ]
    Öğe
    Brush seal temperature distribution analysis (conferenceObject)
    (Amer Soc Mechanical Engineers, 2005) Dogu, Yahya; Aksit, Mahmut F.
    Brush seals are designed to survive transient rotor rubs. Inherent brush seal flexibility reduces frictional heat generation. However, high surface speeds combined with thin rotor sections may result in local hot spots. Considering large surface area and accelerated oxidation rates, frictional heat at bristles tips is another major concern especially in challenging high temperature applications. This study investigates temperature distribution in a brush seal as a function of frictional heat generation at bristle tips. The two-dimensional axisymmetric CFD analysis includes the permeable bristle pack as a porous medium allowing fluid flow throughout the bristle matrix. In addition to effective flow resistance coefficients, isotropic effective thermal conductivity as a function of temperature is defined for the bristle pack. Employing a fin approach for a single bristle, a theoretical analysis has been developed after outlining the brush seal heat transfer mechanism. Theoretical and CFD analysis results are compared. To ensure coverage for various seal designs and operating conditions, several frictional heat input cases corresponding to different seal stiffness have been studied. Frictional heat generation is outlined to introduce a practical heat flux input into the analysis model. Effect of seal stiffness on nominal bristle tip temperature has been evaluated. Analyses show a steep temperature rise close to bristle tips that diminishes further away. Heat flux conducted through the bristles dissipates into the flow by a strong convection at fence height region.
  • [ X ]
    Öğe
    Evaluation of flow behavior for clearance brush seals
    (Asme-Amer Soc Mechanical Eng, 2008) Dogu, Yahya; Aksit, Mahmut F.; Demiroglu, Mehmet; Dinc, Osman Saim
    The industrial applications of brush seals have been increasing due to their superior sealing performance. Advances in the understanding of seal behavior have been pushing the design limits to higher-pressure load, temperature, surface speed, and rotor excursion levels. The highest sealing performance can be achieved when the bristle pack maintains contact with the rotor surface. However due to many design and operational constraints, most seals operate with some clearance. This operating clearance cannot be avoided due to rotor runouts, transient operating conditions, or excessive bristle wear. In some applications, a minimum initial clearance is required to ensure a certain amount of flow rate for component cooling or purge flow. Typically, brush seal failure occurs in the form of degraded sealing performance due to increasing seal clearance. The seal performance is mainly characterized by the flow field in close vicinity of the bristle pack, through the seal-rotor clearance, and within the bristle pack. This work investigates the flow field for a brush seal operating with some bristle-rotor clearance. A nonlinear form of the momentum transport equation for a porous medium of the bristle pack has been solved by employing the computational fluid dynamics analysis. The results are compared with prior experimental data. The flow field for the clearance seal is observed to have different characteristics compared to that for the contact seal. Outlined as well are the flow features influencing the bristle dynamics.