CFD ESTIMATION OF PRESSURE DROP COEFFICIENTS FOR SQUEEZE FILM DAMPERS WITH PISTON RING GROOVES

Abstract

Squeeze film dampers (SFDs) are used in aeronautical engines to add damping to flexible rotors guided by ball and roller bearings. Theoretical analysis of SFDs faces challenges due to high-speed operation and grooves geometry which contradicts the thin film hypothesis on which the theory of lubrication is built on. Reynolds' equation yields acceptable predictions only for simple SFDs at low speeds, inadequate for modern ensemble dynamic analyses of aircraft engines. Computational Fluid Dynamics (CFD) offers accurate but computationally intensive solutions. An alternative, the bulk flow (BF) system of equations, is capable of handling convective inertia-dominated regimes (prohibitive with a Reynolds-like approach), with significantly lower computational costs. Feeding and piston ring grooves are taken into account in the BF model by using local pressure drop or recovery coefficients. Therefore, the BF approach relies on the determination of these externally defined coefficients, challenging to predict experimentally. CFD predictions are then a viable alternative to estimate these coefficients. In this work, we show how local information about pressures and velocities obtained from CFD can be used to improve the BF models.