Within an aero-engine bearing chamber oil is provided to components to lubricate and cool. This oil must be efficiently removed (scavenged) from the chamber to ensure it does not overheat and degrade. To design an effective scavenge it is important to understand the inter-relationship between the flow at the offtake point and the flow structures within the offtake pipe. This paper describes a fundamental project that has experimentally investigated what happens to the flow in the inlet to the offtake and the offtake pipe when a moving liquid film passes over a vertical offtake. In particular the effect film height and momentum have on the flow structure in the offtake pipe is investigated. The rig employed for this work uses an inclined plane to develop a liquid film which then enters the offtake area. The closed circuit test rig is operated at room temperature with tap water as the working fluid. Water is chosen for visualisation reasons and because the viscosity and density of water at room temperature (≈ 25°C) are similar to those of aero-engine oil at a typical operating temperature (≈200°C). At the end of the Perspex inclined plane a fully-developed liquid film enters the scavenge area. The scavenge area is in two parts. The first is a horizontal plane that has a flush vertical offtake pipe mounted centrally to the width. The second section, downstream of the offtake section and connected to it, is a variable angled plane. This allows the rig to be configured so that the liquid film can either overspill the scavenge section or, if the variable angled plane is raised, for flow that passed the offtake to be returned back. The fluid behaviour at the inlet of the offtake and the flow pattern in the offtake pipe are investigated for two different pipe diameters using visualisation. The incoming film height is recorded by the use of a flush conductance probe. The offtake is drained under gravity in its present configuration. The results from the work allow a regime map of flow behaviour to be created, dependent on the incoming flow conditions, that identifies when air is ingested into the offtake and in what form (annular, bubbly etc).
DC inclined-plane tracking and erosion test of insulating materials