The paper presents results from film thickness measurements in a bearing chamber test rig. The measurements were performed at different operating conditions and with two offtake designs. A discussion of the measurement technique using in situ calibrated capacitive sensors shows good accuracy and repeatability. The film thickness results are first compared to measurements with the same chamber in a vented configuration. The analysis of the measurements at various operating conditions shows a strong influence of the shaft speed, the chamber pressure, and the offtake design. In contrast to that, flow rate and scavenge ratio have only minor influence. Furthermore, the momentum flux of the core air flow is proposed as a suitable parameter with which the influence of shaft speed and pressure can be correlated to the film thickness distribution.

The aim of the presented work was to identify factors that influence the oil split between the two offtakes of a vented aero-engine bearing chamber. The impact of different vent and scavenge offtake designs was experimentally investigated with a test rig at the ITS. The generic bearing chamber was also equipped with ten film thickness sensors. The film measurements allowed a further evaluation of the mechanisms behind different oil splits. Two of the examined offtake features ensured a very constant oil split: a protruding vent and a covered ramp offtake. The latter also decreased the oil film thickness on the bearing chamber walls significantly. Furthermore, an influence of a non-uniform seal gap was detected which altered the oil split by several percent.

The paper discusses an approach to predict the two-phase flow regime in an aero engine bearing chamber. In general, one of two distinct flow regimes can occur in a bearing chamber. At lower shaft speeds, the oil flow is only partially affected by the air flow, which is driven by the rotating shaft. At higher shaft speeds, however, the rotating air flow forces the oil film at the chamber walls to rotate, too. Thus, the two flow regimes correspond to two very different oil film distributions inside a bearing chamber presumably with significant consequences for the internal wall heat transfer. In order to determine the driving parameters for the flow regimes and the change between them, experiments were carried out with a bearing chamber test rig. With this test rig all relevant operating parameters as well as the geometry of the bearing chamber could be varied independently. The analysis of the experimental data allowed defining a general parameter which takes into account the chamber pressure, shaft speed, oil viscosity and chamber length. The influence of the oil flow rate and the overall dimensions are assessed qualitatively.

In order to prevent hot-gas ingestion into the rotating turbo machine’s inside, rim seals are used in the cavities located between stator- and rotor-disc. The sealing flow ejected through the rim seal interacts with the boundary layer of the main gas flow, thus playing a significant role in the formation of secondary flows which are a major contributor to aerodynamic losses in turbine passages. Investigations performed in the EU project MAGPI concentrate on the interaction between the sealing flow and the main gas flow and in particular on the influence of different rim seal geometries regarding the loss-mechanism in a low-pressure turbine passage. Within the CFD work reported in this paper static simulations of one typical low-pressure turbine passage were conducted containing two different rim seal geometries, respectively. The sealing flow through the rim seal had an azimuthal velocity component and its rate has been varied between 0–1% of the main gas flow. The modular design of the computational domain provided the easy exchange of the rim seal geometry without remeshing the main gas flow. This allowed assessing the appearing effects only to the change of rim seal geometry. The results of this work agree with well-known secondary flow phenomena inside a turbine passage and reveal the impact of the different rim seal geometries on hot-gas ingestion and aerodynamic losses quantified by a total pressure loss coefficient along the turbine blade. While the simple axial gap geometry suffers considerable hot-gas ingestion upstream the blade leading edge, the compound geometry implying an axial overlapping presents a more promising prevention against hot-gas ingestion. Furthermore, the effect of rim seals on the turbine passage flow field has been identified applying adequate flow visualisation techniques. As a result of the favourable conduction of sealing flow through the compound geometry, the boundary layer is less lifted by the ejected sealing flow, thus resulting in a comparatively reduced total pressure loss coefficient over the turbine blade.

The prediction of the two-phase flow in an aero-engine bearing chamber using the meshless Lagrangian Smoothed Particle Hydrodynamics (SPH) method is presented in this paper. The prediction of the prevailing flow types, like shear-driven wallfilms, droplet-wall- and droplet-film-interactions require an accurate numerical method, which is robust and efficient. Therefore, a code based on the SPH method was developed and validated to numerically predict such technical relevant multi-phase flows in gas turbines. The simulations to be presented in this paper are focused on an aero-engine bearing chamber configuration, which was experimentally investigated previously. For time saving reasons, the bearing chamber is modeled as two-dimensional problem. This requires special boundary conditions for the oil- and sealing-air flow inlet and outlet, which must physically reflect those of the experiments. In the experiments different operating regimes at different boundary conditions could be identified. The major objective of the simulations is to investigate if those different flow regimes can be captured by the numerical method. The simulations do reproduce the different flow regimes highly accurate and demonstrate the ability of this new approach.