Commissioning of a test rig for axial rub investigations of adaptive face seals - concept, error analysis and preliminary tests

This paper presents a novel test rig setup intended to investigate axial rubbing of adaptive face seals. This rig is designed to characterise the wear behaviour of the seal, especially during transient operation, perform thermal measurements, as well as provide the ability to analyse the aerodynamic stiffness of the bearing face flow prior to and after a rubbing event. The rig operating point can be controlled across a wide technically relevant operational range by adjusting the rotational speed, seal incursion depth and rate, as well as the air mass flow through the seal prior to the rub event. A broad variety of instrumentation allows for the build-up of an extensive database in order to better understand the transient behaviour of adaptive face seals during rubbing. The paper presents the overall concept of the rig, including its modular design to allow for extended experiments of axial rub without damage to the rotor and fast variation of bearing face design and material combinations. Moreover, a detailed error analysis of the measured and derived quantities, as well as an initial aerodynamic analysis and rub tests on a generic bearing face geometry, are discussed. In future work, the rig will be employed to investigate the rubbing process and quantify its effects on both the seal bearing face and the rotor disc. Subsequent tests will focus on a parameter study to systematically vary operating conditions and material combinations, therefore informing the design of new adaptive face seals which are robust to contact operation.