Session: 01-13 Thermal Management and Aero-engine Oil Systems I

Paper Number: 122481

122481 - Numerical Analysis of the Effect of Geometric Variations on the Mass Flow Distribution for an Under-Race Lubrication System 

Ball bearings play a crucial role in ensuring the safety and reliability of jet engines. Their reliability strongly depends on the underlying lubrication and cooling concept. Under-race lubrication is a widely employed technique that demands uniform and continuous oil distribution in the bearing feed holes axially and circumferentially. This method involves the injection of oil onto a rotating shaft via an oil nozzle and subsequently transporting it within a rotating annular cavity to the feed holes on the outer wall. From there the oil is directed to different bearing components. Proper cavity dimensions are crucial for achieving a uniform oil flow distribution through all feed holes, posing a significant challenge in the design process. To date, there has been limited understanding of how the geometry affects the oil film inside the cavity and its subsequent influence on the oil flow distribution.

A systematic exploration of the key geometric parameters, such as groove length, groove depth, deviation length, hole diameters, and holes axial distance, was conducted in order to identify crucial factors that enable uniform oil distribution while optimizing catch efficiency. Given the complexity of the geometry, multiphase flow characteristics combined with high fluid deformations and high rotational speed, a meshless Lagrangian simulation method provided a considerable advantage compared to classical gridbased CFD methods. Therefore, the simulations were performed using an Incompressible Smoothed Particles Hydrodynamics (I-SPH) method with the software PreonLab.

For the analysis a wedge section of 72° is simulated using periodic boundary conditions, employing a new modeling approach to account for the inherent asymmetry of the single injection location. In order to evaluate its applicability and potential deviations, a comparative study with a full geometry is done. Furthermore, a sensitivity analysis of numerical parameters employed in the surface tension model is included in order to address numerical uncertainty of the results. Additionally, experimental investigations of two geometry combinations are performed to validate the numerical model.

The analysis of the results revealed that groove length, groove depth and deviation length did not significantly impact the oil distribution. However, a minimum cavity volume, determined by the groove length and groove depth, directly affected the system catch efficiency. The primary parameters influencing the oil distribution were the hole diameter and its axial distance between them. These findings offer valuable insights into optimization of under-race lubrication in jet engine bearings, with potential applications in enhancing engine safety and reliability.

Presenting Author: Daniel Mateo Aguirre Bermudez Institute for thermal turbomachines

Presenting Author Biography: Daniel Mateo Aguirre is a Ph.D. candidate in the Institute of thermal turbomachines at the Karlsruher Instute of Technology . He has a B.Sc. degree in mechanical Engineering at the Universidad Nacional de Colombia (2016) with emphasis in Modeling and Simulation, Internal Combustion Engines, and Turbomachinery and a M.Sc. in mechanical Engineering (2020). His research focus on the numerical and experimental investigation of oil jet supply systems for the lubrication and cooling of bearings in aero engines.

Authors:

Daniel Mateo Aguirre Bermudez Institute for thermal turbomachines
Aju Abraham FIFTY2 Technology GmbH
Shreyas Joshi FIFTY2 Technology GmbH
Corina Schwitzke Institut für Thermische Strömungsmaschinen
Hans-Jörg Bauer Institut für Thermische Strömungsmaschinen