Analysis of the windage losses of spur gears with computational fluid dynamics

In this thesis, windage power losses of spur gears are investigated with Computational Fluid Dynamic tools. Single phase (air) and two-phase (air – oil) media analysis are conducted. Firstly, gear is modeled for the single tooth space in single-phase medium. 2D and 3D grids of the tooth space are generated by using Pointwise software. Grids with different number of cell numbers are examined for mesh analysis and mesh independency of the results are assured. Metacomp CFD++ software is used for the modeling and computing purposes. Motion of the gear is modeled by using the Moving Reference Frame (MRF) method. In order to validate the numerical model, a gear geometry with readily available experimental and numerical data is used. Initially, this gear is analyzed without shrouding around it. Numerical analysis are conducted with varying angular velocities between 300 rad/s and 700 rad/s. Then, gear is surrounded by axial and radial shroudings to reduce windage power losses. Two different radial shrouding configurations are used in 2D analysis and two different axial and radial shrouding configurations is used in 3D anaylsis. Simulation results agree well with the data taken from the literature. Moreover, using shrouds significantly reduces the windage power losses. Secondly, two phase (air – oil) media is modeled by utilizing Eulerian Dispersed Phase (EDP) Model. The same geometry, which was used in the single-phase analysis, is again adopted with a different shrouding configuration from literature. 2D and 3D computational domains with several cell counts are generated for that shrouding configuration. Simulations with oil particle diameters varying between 2 and 16 μm are carried out. In addition, effects of change in number of particles and different angular velocities are also studied and discussed. The results agree well with the simulation data taken from literature. Finally, effects of the oil density inside of the tooth space are investigated. EDP model equations are solved for five different particles diameters simultaneously while particle distribution of the oil is calculated by using Rosin-Rammler distribution function. In conclusion, using shrouds reduced the windage power losses while oil addition to the domain increased it.