Petroff's Law Friction
Viscous friction torque on a concentric journal bearing: T = 4π²·η·N·R³·L / c (R, c in consistent units).
Friction torque
4.441N·m
Friction power loss
697.6W
Formula, assumptions, and limits
Petroff assumes concentric shaft (e → 0). For eccentric shaft (loaded), use Sommerfeld + Raimondi-Boyd solution. Valid for low-loaded / high-speed bearings near startup. Marine turbocharger radial bearings operate at ~ Petroff limit.
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| Dynamic viscosity | Pa·s | oil at T | |
| Rotation rate | rpm | tachometer | |
| Journal radius, length, clearance | mm | bearing spec |