Numerical modeling of the churning power losses in planetary gearboxes: An innovative partitioning‐based meshing methodology for the application of a computational effort reduction strategy to complex gearbox configurations

Abstract

Thanks to the recent developments in the computer science, simulations are becoming an increasingly widespread approach that can help the designers in the development of new products. In the specific field of gearboxes, simulations are used mainly for structural evaluations. However, while for the structural design beside the simulations, many analytical methods and international standard are available; for the prediction of the power losses and the efficiency of gears, neither accurate analytical methods nor automated simulation tools are available. The authors work on this topic since years and have developed new methodologies based on computational fluid dynamics. With respect to general purpose commercial software, these techniques allow a significant reduction of the computational effort and have the capability to take into account particular physical phenomena that occurs in gears, such as cavitation, and for which no information are available in literature. The purpose of this paper is to introduce a new automated mesh‐partitioning strategy implemented to extend the applicability of the previously developed computational effort reduction method to complex gearboxes getting over the geometrical limitations adopted in the past. To show the capabilities of this new strategy, we simulated a planetary gearbox that represents at the same time one of the most complicated kinematic arrangements of gears and the configuration for which the numerical fluid dynamics simulation can give the major contribution both with planar simplified models as well as with complete 3D models.

Lubrication of Gearboxes: CFD Analysis of a Cycloidal Gear Set

“…In the past some authors have already studied the lubrication of planetary gearboxes with a finite volume (FV) approach [36]- [43]. In this study, the already presented global remeshing method (GRA) [44] was applied to a cycloidal gear-set.…”

“…With the aim of comparing the numerical hydraulic losses of a traditional planetary gearset (already studied in [36]) with a potentially competing cycloidal gear set, geometrical data were chosen in order to have the same gear ratio, comparable dimensions and same nominal torque. 40 mm; 5 mm; 2 mm; 10 ( 1 0 )…”

A new model for predicting the mechanical efficiency of ball screws based on the empirical equations for the friction torque of rolling bearings

“…Therefore, the frictional torque of ball screw can be obtained by combining equations (1), (9), (14), and (15). As introduced in section ''Friction torque due to applied load'', the initial contact angle of a ball screw is usually set as 45°, which means a ball screw with N ball circles can be regarded as a combination of N angularcontact ball bearings.…”

“…A lot of accurate numerical models are available for the calculation of the viscous losses generated in a ball bearing at high rotational speeds. [13][14][15] However, limited by the parameter of DN (\2 3 10 5 mm Á r=min), the critical rotational speed of ball screws is only about one-tenth of the critical rotational speed of ball bearings in the same size. This means the normal rotational speed of ball screws only is a very low rotational speed for ball bearings.…”

Innovative Meshing Strategies for Bearing Lubrication Simulations

“…To partially overcome this problem, in the past several attempts were made. In particular, rotating reference frames [4,5], innovative partitioning strategies [6,7] and, mostly, mesh-handling algorithms [8][9][10][11] have been developed and applied in order to reduce the simulation effort.…”