Lubrication of Gearboxes: CFD Analysis of a Cycloidal Gear Set

Concli, Franco; Maccioni, Lorenzo; Gorla, Carlo

doi:10.2495/mpf190101

Cited by 36 publications

(10 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This consideration is also supported by the computational effort required for the cycloidal kinematic, and the 2D analysis was performed on a single CPU 9.6GFLOP workstation and took about 3 days to perform a complete rotation of the internal cycloid [36]. The corresponding 3D simulation (which number of cells is approximately 10 times higher) took about the same time.…”

Section: Resultsmentioning

confidence: 99%

“…This absence of reliable models for the load-independent power losses of gears is even more significant for cycloidal architectures [36]. In additions to the losses due to sliding in bearings (on the eccentric input shaft), between the rollers and cycloidal disk and in the holes-pins contacts, hydraulic losses play a fundamental role and represent a significant shear of the total losses.…”

Section: Power Loss Of Gearsmentioning

confidence: 99%

See 1 more Smart Citation

Development of a computational fluid dynamics simulation tool for lubrication studies on cycloidal gear sets

Concli¹,

Maccioni²,

Gorla³

2020

Int. J. CMEM

View full text Add to dashboard Cite

In the last decades, the growing mechatronic sector has promoted the development of more and more compact and efficient gearboxes. The margins of improvement are still big even if, sometimes, finding the optimal solutions is a trial and error procedure. For this reason, the development of dedicated tools for the optimization of the geometry and configuration of gearboxes can significantly increase the development effectiveness and help in reducing design costs. Moreover, having a more efficient solution could also reduce thermal problems during operation and increase the system reliability. The so-called 'thermal limit', i.e. the maximum transmittable power without an overheating of the systems, is particularly critical for high power density and compact solutions. Those relies mainly on planetary, harmonic and cycloidal architectures. While many empirical or analytical prediction models can be found in literature for the prediction of the power losses associated with the gear meshing and the bearing, few reliable models are nowadays available for the losses associated with the interaction with the lubricant, i.e. hydraulic losses. Experimental and computational fluid dynamics studies on parallel axis as well as planetary gear sets have been presented in the past. The goal of this research is the extension of the applicability range of those numerical approached to cycloidal kinematics for which no studies at all are available with respect to the hydraulic losses. The main challenge in numerically simulate the lubricant splashing in a cycloidal reduced is related to the topological modification of the computational domain during operation. For this purpose, a specific mesh handling technique, based on a 2.5D mesh, capable to handle the variations of the geometry of the domain was developed in the OpenFOAM® environment. The capability to analytically control the mesh generation at each time step ensures a very high numerical stability and a very high computational efficiency of the solution. Eventually, the approach was systematically applied to a real geometry and the results compared with those obtained for other gear architectures with comparable performances in terms of dimensions and reduction ratios.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Power Loss Of Gearsmentioning

confidence: 99%

Development of a computational fluid dynamics simulation tool for lubrication studies on cycloidal gear sets

Concli¹,

Maccioni²,

Gorla³

2020

Int. J. CMEM

View full text Add to dashboard Cite

show abstract

“…where is the lubricant density, is the velocity vector, is the pressure, is the gravitational acceleration and represents the external forces. The mean temperature was imposed as a variation of the fluid properties according, for the density, to the following formula [50].…”

Section: Computational Fluid Dynamicsmentioning

confidence: 99%

Journal Bearing: An Integrated CFD-Analytical Approach for the Estimation of the Trajectory and Equilibrium Position

Concli

2020

Applied Sciences

Self Cite

View full text Add to dashboard Cite

For decades, journal bearings have been designed based on the half-Sommerfeld equations. The semi-analytical solution of the conservation equations for mass and momentum leads to the pressure distribution along the journal. However, this approach admits negative values for the pressure, phenomenon without experimental evidence. To overcome this, negative values of the pressure are artificially substituted with the vaporization pressure. This hypothesis leads to reasonable results, even if for a deeper understanding of the physics behind the lubrication and the supporting effects, cavitation should be considered and included in the mathematical model. In a previous paper, the author has already shown the capability of computational fluid dynamics to accurately reproduce the experimental evidences including the Kunz cavitation model in the calculations. The computational fluid dynamics (CFD) results were compared in terms of pressure distribution with experimental data coming from different configurations. The CFD model was coupled with an analytical approach in order to calculate the equilibrium position and the trajectory of the journal. Specifically, the approach was used to study a bearing that was designed to operate within tight tolerances and speeds up to almost 30,000 rpm for operation in a gearbox.

show abstract

“…The mean temperature was set acting on the properties of the fluid. The density at a certain temperature was calculated with the following equation [29] ° 15 • 0.0007,…”

Section: Computational Fluid Dynamicsmentioning

confidence: 99%

Equilibrium of a Journal Bearing: A Simplified CFD-Analytical Coupled Approach

Concli

2020

WIT Transactions on Engineering Sciences

Self Cite

View full text Add to dashboard Cite

Journal bearings are historically designed using the half-Sommerfeld theory. The semi-analytical solution of the continuity and momentum conservation equations is used as the starting point. Possible negative values of the pressure were substituted with the ambient pressure. This hypothesis provides acceptable results, even if for a better understanding of the phenomena cavitation effects should be considered and modelled numerically. The authors have already proved the capability to achieve very accurate results with the Kunz cavitation model. The numerical results were validated in terms of pressure distribution with experimental data coming from different setups. In this paper, a simplified CFD-analytical coupled approach for the calculation of the equilibrium position and its trajectory of the journal is shown.

show abstract

Lubrication of Gearboxes: CFD Analysis of a Cycloidal Gear Set

Cited by 36 publications

References 34 publications

Development of a computational fluid dynamics simulation tool for lubrication studies on cycloidal gear sets

Development of a computational fluid dynamics simulation tool for lubrication studies on cycloidal gear sets

Journal Bearing: An Integrated CFD-Analytical Approach for the Estimation of the Trajectory and Equilibrium Position

Equilibrium of a Journal Bearing: A Simplified CFD-Analytical Coupled Approach

Contact Info

Product

Resources

About