Analysis of shear heating and effect of temperature dependant viscosity on hydrodynamic lift of oil brush seals /
Duran, Ertuğrul Tolga (2006) Analysis of shear heating and effect of temperature dependant viscosity on hydrodynamic lift of oil brush seals /. [Thesis]
Due to their superior performance and stable leakage characteristics, brush seals are one of the dynamic seals used in oil and oil mist applications in aero-engines and turbines. The viscous medium between the high speed rotor surface and brush seal bristles generates a hydrodynamic lifting force that determines seal clearance and leakage rate in oil sealing applications. The analytical solution to bristle lifting force can be obtained by using Reynolds formulation. Following a short bearing approximation, a closed form solution of the lifting force has been previously presented. However. solution to hydrodynamic lift force suggests a strong dependence on oil temperature and viscosity, This work presents an analytical solution to oil temperature rise due to shear healing. Stalling with continuity and Navier Stokes equations, temperature distribution is derived by solving thermal energy equation. The hydrodynamic lift force relation has been expanded to include oil temperature and viscosity variability due to rotor speed and lift clearance. Results are also compared with the experimental data obtained from the dynamic oil seal test rig. In addition to temperature analysis, pressure distribution for the brush seal is also derived by tracking three different ways, all of which gives consistent results with each other and real life applications. Derivation of shear heat effect included lift clearance, which is the most important parameter for leakage performance of brush seals, is also done and compared with experimental lift clearance data.
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