Comparison of Various Computational Methods for Gear Stirring (2nd Report)
-Discussion of prediction accuracy for droplets and proposal of a practical method for improvement-

Takafumi Kawamura (Computational Fluid Dynamics Consulting)･Masaru Shimada (JATCO Engineering)･Tadashi Yamada (Toyota Motor)･Masanori Katou (Honda R&D)･Daiki Saegusa (Honda Motor)･Akira Nakashima (Mazda)･Tomoaki Watamura (University of Tokyo)･Kazuyasu Sugiyama (Osaka University)

In the first report, experimental results for air-oil two-phase flow driven by gears were compared with computations using various methods including particle method, lattice Boltzmann method, finite difference method and finite volume method. In this report, influence of spatial resolution and its relation to surface tension on the prediction accuracy are discussed, and then a practical method is proposed for improving accuracy.

A Study on High Rotational Speed Traction Drive
-High Reduction Ratio Experiment and Unit Configuration-

Yuechen Jia･Takeshi Yamamoto (Tokai University)

With the aim of miniaturization, the trend toward higher rotational speeds of drive motors has advanced, requiring high reduction ratios for the reduction drive. Traction rollers are considered capable of achieving higher reduction ratios than gears, but their performance and limitations remain unclear. Therefore, in the present study, a high-speed test machine with a high reduction ratio was designed and manufactured, and the traction coefficient and transmission efficiency were measured. The results indicated that increasing the reduction ratio from 2.5 to 6 did not lead to any performance degradation.

Emission and system cost reduction by means of bearing friction optimization

Seiya Nishizawa (Schaeffler Japan)･Franz Voelkel (Schaeffler Technologies AG & Co. KG)

Bearing losses add up to a significant share of overall vehicle power losses. On the one side, this influences the downstream emissions, on the other side a BEV’s upstream emissions are heavily affected well as a certain capacity of the battery is only needed to feed these losses. Every piece of energy which is not lost to friction doesn’t have to be stored in an battery.
This lecture discloses the hidden potentials in mechanical power loss reduction, especially for bearings, by means of power density increase, on-the-point optimization and drag loss minimization. The effectiveness of friction improvement relative to on-costs for the measures will be shown in addition.

Electrified Motorcycle Powertrains - Hybrid Concepts Paving the Way to Future Technologies

Wolfgang Johann Schoeffmann･Christian Hubmann･Gernot Fuckar･Christian Martin (AVL List)

Electrification of two-wheelers faces unique challenges, including packaging and mass constraints, limited urban charging infrastructure and stringent cost targets.
Battery electric two wheelers are ideal for city driving whereas hybridization extends operational limits, enabling electric modes for zero-emission driving, while boosting enhances performance and transient response.
An electrified variable power-split hybrid scooter powertrain combines efficiency improvements and electric driving whereas an integral dedicated hybrid transmission is specified for a performance hybrid with minimized mass and packaging.
The paper covers layout criteria for ICE and hybrid system, while addressing operation modes in the relevant drive cycle sections.