Commissioning of a test rig for axial rub investigations of adaptive face seals

This paper presents a novel test rig set up intended to investigate axial rubbing of adaptive face seals. The rig is designed to characterise the wear behaviour of the seal, especially in transient behaviour, 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. Some of the key instrumentation employed during tests include a piezoelectric load cell to record forces on the seal in all three dimensions as well as thermocouples below the seal surface and high-speed pyrometers aimed at the rotor to measure temperatures. A mass-flow sensor as well as pressure sensors and thermocouples are utilised to acquire data on the aerodynamic state of the seal before, during and after the rub. Resulting wear on the seal can be analysed precisely through a two-dimensional laser scan of the bearing surface before and after the rub as well as the change in its weight. ... mehrThis 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 the future, the rig will be employed to provide profound understanding of the rubbing process as well as the effects of rubbing 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.