Numerical investigation on no-load loss reduction in electric vehicle gearbox by surface wettability modification

The model is validated step by step using a rotating disk rig, a transparent case gearbox rig, and a high speed EVG rig. Surface characterization shows that the coating forms a nanoscale rough surface on the gear end faces. The measured oil contact angle increases from 7.8° to 52.7°, and the oleophobicity is retained after abrasion.

The experiments show that the coating reduces the churning loss by approximately 17.3% to 52.3% over the 500 to 10000 r/min range. The MPS simulation shows that the peak oil pressure in the meshing zone is lowered by 41.3%. Finally, the measured power saving ΔP0 is mapped onto the WLTC using the proposed model.

This mapping yields a cumulative energy saving of about 122 Wh per cycle. The driving range extension is concentrated in the medium and high speed range.