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Methodology for evaluation of the gear windage loss and thermal load of a tooth
Bauer, Petr ; Bartoš, Ondřej ; Hrubý, Jan ; Kordík, Jozef ; Krátký, Tomáš ; Sedlář, Milan
This report contains results of experiments identifying thermo-physical properties of a gearbox oil mist. The main part of the report studies a dependency of a gear wheel windage power loss on the radial and axial gap between the wheel and its enclosure. This parametric study relies primarily on the results coming from numerical simulations (CFD analysis). For the default enclosure configuration the evaluated power dissipation is compared with the values obtained using theoretical relationships. The theory is based on one-dimensional turbulent velocity profiles over smooth and rough surfaces. A summary of the theoretical analysis and the derivations are also included in the report.\nThe influence of a tooth shape on the windage power loss is also studied using the numerical simulations. A change of a tooth top surface angle is technologically easily realizable adjustment, and can have a positive effect on the power loss reduction. In the report there are performed simulations for varying angles of this surface and the expected improvements in aerodynamic properties are confirmed.\nThe last part of the report contains the formulation of boundary conditions for numerical evaluation of gear wheel heat balance. This information is documented more in detail in related research reports.\n
Generalization of the methodology for evaluation of the gear windage loss
Bauer, Petr ; Kordík, Jozef ; Krátký, Tomáš ; Sedlář, Milan
The first part of the report proposes a methodology for gear windage loss evaluation using CFD analysis. The methodology includes simplification of gearbox complex geometry and the toothed wheel and pinion are replaced by a rough-walled disks with additional braking volume forces. The values of volume forces were determined using auxiliary computations with a real gear geometry (a gear segment with periodical boundary conditions). The computations included configuration of the gear wheel meshing with the pinion, while distance of wheel enclosure was a variable parameter (the case without enclosure was tested as well). The cases without pinion were computed too, they were compared with earlier results obtained with the gear segment geometry.\nThe second part of the report contains a revision of the earlier proposed analytical approach. The approach can serve for approximate gear windage loss evaluation and its idea dwells in smooth connection of logarithmic velocity profiles. The gear windage loss values obtained from the analytical approach were compared with the results based on CFD analysis. A good agreement between both methods was concluded.\n