Oil Temperature Analysis of Brush Seals

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. However, there is a strong dependence on oil temperature and viscosity. This work presents a solution to oil temperature using nonlinear pressure distribution. Starting with continuity and Navier Stokes equations, temperature and nonlinear pressure distribution is derived by solving the thermal energy and reduced continuity equations simultaneously. Results of oil temperature estimates using nonlinear pressure analysis are compared with the results of a previous work using linear pressure assumption. Findings indicate that for low rotor surface speeds oil temperature distribution is almost the same for both linear and nonlinear pressure cases. Difference in oil temperature estimates increases with increasing rotor surface speeds.