Corina Schwitzke

Smoothed Particle Hydrodynamics Simulation of Oil-Jet Gear Interaction

In this paper the complex two-phase flow during oil-jet impingement on a rotating spur gear is investigated using the meshless Smoothed Particle Hydrodynamics (SPH) method. A comparison of single-phase SPH to multi-phase SPH simulation and the application of the Volume of Fluid method on the basis of a two-dimensional setup is drawn. The results of the different approaches are compared regarding the predicted flow phenomenology and computational effort. It is shown that the application of single-phase SPH is justified and that this approach is superior in computational time, enabling faster simulations. In a next step, a three-dimensional single-phase SPH setup is exploited to predict the flow phenomena during the impingement of an oil-jet on a spur gear for various jet inclination angles. Thereby, a significant effect of the inclination angle on the oil spreading and splashing process is revealed. Finally, a qualitative comparison to an experimental high-speed image shows good accordance.

Experimental Investigation on the Influence of Geometrical Parameters on the Frictional Heat Input and Leakage Performance of Brush Seals

Because of the superior sealing characteristics compared to labyrinth seals, brush seals found an increased spread in turbomachinery in recent years. Their outstanding sealing performance results mainly from their flexibility. Thus, a very small gap between the rotor and bristle package can be obtained without running the risk of severe detrimental deterioration in case of rubbing. Rubbing between rotor and seal during operation might occur as a result of e.g. an unequal thermal expansion of the rotor and stator or a rotor elongation due to centrifugal forces or manoeuvre forces. Thanks to the flexible structure of the brush seal the contact forces during a rubbing event are reduced, however the frictional heat input can still be considerable. Particularly in aircraft engines with their thin and lightweight rotor structures the permissible material stresses can easily be exceeded by an increased heat input and thus harm the engine’s integrity. The geometry of the seal has a decisive influence on the resulting contact forces and consequently the heat input. The complex interactions between the geometric parameters of the seal and the heat input and leakage characteristics are not yet fully understood. This paper presents the investigation of the influence of the geometric parameters of a brush seal on the heat input into the rotor and the leakage behaviour. Two seals with different packing densities were tested under relevant engine conditions with pressure differences ranging from 1 to 7 bar, relative surface speeds ranging from 30 to 180 m/s and radial overlaps ranging from 0.1 to 0.4 mm. The transient temperature rise during the rub event was recorded with 24 thermocouples in close proximity to the rub contact embedded in the rotor structure. By comparing the temperature curves with the results of a thermal finite element analysis of the rotor the heat input into the rotor was calculated iteratively. It could be shown that the packing density has a decisive influence on the overall operating behaviour of a brush seal. Furthermore, results are obtained for the heat flux distribution between seal and rotor are shown.

Experimental Investigation of the Influence of Chamber Geometry on Bearing Chamber Oil Leakage

This paper presents experimental results identifying the influence of chamber geometry on the oil leakage behaviour of an aero engine bearing chamber. The varied geometrical parameters were the size of the bearing chamber, three different drip lip configurations, and a flinger. The position of the flinger was also varied to simulate mechanical and thermal distortions experienced during engine operations. Previous research has shown that the geometry of a bearing chamber influences the complex two phase flow inside it. This flow in turn influences the tendency of a bearing chamber to leak oil under adverse conditions. Since oil leakage from bearing chambers must be avoided for health and safety reasons, this knowledge is of great importance to the designer of a bearing chamber. The influence of the bearing chamber dimensions on oil leakage behaviour through seals has not yet been identified. The results of this work reveal a link between chamber geometry and leakage behaviour. The dependency of oil leakage rates for different chamber dimensions is also influenced by the investigated bearing chamber components. The complex interplay of these influencing factors was investigated and is described in detail.