The modelling, prediction, and experimental evaluation of gear pump meshing pressures with particular reference to aero-engine fuel pumps

This paper presents the development of a model for the evaluation of pressure transients occurring within an involute tooth form twin-pinion gear pump and addresses, in particular, the influence of cavitation. The latter can cause erosion, limiting the life of such pumps, and liberate hard particles, leading to secondary damage elsewhere. The model considers the inter-tooth volumes that are formed at the roots of the driver and driven gears and utilizes the continuity equations by considering compressible flow into and out of these volumes. Cavitation arising from insufficient flow into the expanding inter-tooth volumes is taken into account. The continuity equations are expressed in terms of fluid density rather than pressure. Hence correct solutions are ensured even during cavitating conditions, when the minimum void pressure is fixed at the appropriate vapour pressure. The effectiveness of the model is assessed through gear pump meshing pressure measurement and flow visualization. The significant influence of inlet pressure ripple on low-pressure predictions is also investigated.