Shaft & Gearbox Losses
Convert brake power (engine output) to delivered power at the propeller by subtracting shaft-line and gearbox losses. Needed whenever an SFOC-based fuel model produces brake power but the hydrodynamic stack wants delivered power.
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Formula, assumptions, and limits
| Symbol | Meaning | Unit |
|---|---|---|
| Brake power (engine output) | kW | |
| Delivered power (at propeller shaft) | kW | |
| Shaft-line efficiency - direct-coupled two-stroke ≈ 0.99; long shaft lines ≈ 0.98 | ||
| Gearbox efficiency - 1.0 if direct-drive, 0.97–0.99 otherwise |
Source: ITTC - *Propulsion Committee Standard Procedure 7.5-02-03-01.2*; MAN Energy Solutions - *Basic Principles of Ship Propulsion*
In short
Convert brake power to delivered power by applying shaft-line and gearbox efficiency losses.