A study of brush seal oil pressure profile including temperature-viscosity effects

Official URL: http://pdf.aiaa.org/preview/CDReadyMJPC08_1874/PV2008_4622.pdf

After proven performance in air applications, brush seals are being considered for oil and oil mist sealing in aero-engines, turbines and generators. The viscous medium between the high speed rotor surface and bearing surfaces formed by brush seal bristle tips generates a hydrodynamic lifting force that determines seal clearance and leakage rate in oil sealing applications. Hydrodynamic lift force and seal clearance have strong dependence on oil temperature and viscosity. In a previous study, short bearing theory has been applied to a single bristle to obtain a solution for hydrodynamic lift force developing at a bristle tip. Rather than individual bristles, this work evaluates pressure for the bristle rows. Applying the Reynolds bearing theory to the control volume between bristle tips and the rotor surface fluid pressure distribution is obtained under each bristle row. Effective temperature and effective viscosity approach has been adopted. Pressure distribution for each bristle row in the rotor axial direction is evaluated. Then, pressure profiles for each bristle row are combined to yield the axial pressure profile under the entire brush pack.