Computational Prediction of Primary Breakup in Fuel Spray Nozzles for Aero-Engine Combustors

[EN] Primary breakup of liquid fuel in the vicinity of fuel spray nozzles as utilized in aero-engine combustors is numerically investigated. As grid based methods exhibit a variety of disadvantages when it comes to the prediction of multiphase flows, the ”Smoothed Particle Hydrodynamics“ (SPH)-method is employed. The eligibility of the method to analyze breakup of fuel has been demonstrated in recent publications by Braun et al, Dauch et al and Koch et al [1, 2, 3, 4]. In the current paper a methodology for the investigation of the two-phase flow in the vicinity of fuel spray nozzles at typical operating conditions is proposed. Due to lower costs in terms of computing time, 2D predictions are desired. However, atomization of fluids is inherently three dimensional. Hence, differences between 2D and 3D predictions are to be expected. In course of this study, predictions in 2D and based on a 3D sector are presented. Differences in terms of gaseous flow, ligament shape and mixing are assessed.This work was performed on the computational resource ForHLR Phase II funded by the Ministry of Science, Research and Arts Baden-Württemberg and DFG (”Deutsche Forschungsgemeinschaft“). In addition the authors would like to thank Rolls-Royce Deutschland Ltd & Co KG for the outstanding cooperation. The authors also are grateful for many lively and fruitful discussions with Simon Holz.Dauch, T.; Braun, S.; Wieth, L.; Chaussonnet, G.; Keller, M.; Koch, R.; Bauer, H. (2017). Computational Prediction of Primary Breakup in Fuel Spray Nozzles for Aero-Engine Combustors. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 806-813. https://doi.org/10.4995/ILASS2017.2017.4693OCS80681

Modeling of the Deformation Dynamics of Single and Twin Fluid Droplets Exposed to Aerodynamic Loads

Droplet deformation and breakup plays a significant role in liquid fuel atomization processes. The droplet behavior needs to be understood in detail, in order to derive simplified models for predicting the different processes in combustion chambers. Therefore, the behavior of single droplets at low aerodynamic loads was investigated using the Lagrangian, mesh-free Smoothed Particle Hydrodynamics (SPH) method. The simulations to be presented in this paper are focused on the deformation dynamics of pure liquid droplets and fuel droplets with water added to the inside of the droplet. The simulations have been run at two different relative velocities. As SPH is relatively new to Computational Fluid Dynamics (CFD), the pure liquid droplet simulations are used to verify the SPH code by empirical correlations available in literature. Furthermore, an enhanced characteristic deformation time is proposed, leading to a good description of the temporal initial deformation behavior for all investigated test cases. In the further course, the deformation behavior of two fluid droplets are compared to the corresponding single fluid droplet simulations. The results show an influence of the added water on the deformation history. However, it is found that, the droplet behavior can be characterized by the pure fuel Weber number

Numerical Modeling of Oil-Jet Lubrication for Spur Gears using Smoothed Particle Hydrodynamics

Understanding and optimizing the lubrication and cooling in aero engine gearbox applications is crucial for a reliable and efficient sub-system design of future aircraft engines. Due to the complex design of gearboxes with its various rotating parts, space and access for experimental investigations are severely limited. Thus, suitable numerical methods need to be developed in order to thoroughly investigate the evolving oil-air two-phase flow in the vicinity of the gear teeth. In this paper, the impingement of a single oil-jet on a single rotating spur gear was analyzed using the Smoothed Particle Hydrodynamics (SPH) method. The study was conducted with a simplified 2D setup under typical operating conditions met in reduction gear units of novel large civil aircraft engines. Results of the predicted oil-air two-phase flow are presented and compared to conventional Volume-of-Fluid (VOF) simulations. The wetting behavior and the impingement depth of the oil-jet between the gear teeth are investigated for varying oil-jet velocities and rotational speeds. In order to capture three-dimensional flow effects, a 3D setup and preliminary results are presented