Propeller Torque Coefficient KQ
Non-dimensional torque KQ = Q / (ρ·n²·D⁵). Open-water charts typically tabulate 10·KQ to keep KQ and KT on the same chart scale.
Torque coefficient KQ
0.0448 -
10·KQ (chart convention)
0.4479 -
Formula, assumptions, and limits
Typical merchant KQ at design J ≈ 0.025–0.045. Shaft torque and KQ drive the engine match - propeller curve must fit inside the engine layout diagram.
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| Shaft torque | N·m (input as kN·m) | torsionmeter | |
| Sea-water density | kg/m³ | 1025 | |
| Shaft rev/s | rev/s | rpm/60 | |
| Propeller diameter | m | drawing | |
| Torque coefficient | - | result |