Significance of Propeller curve for EEXI.

Answer

For EEXI, the propeller curve is important because it represents the power–speed relationship of the ship in normal propulsion condition.

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For a fixed-pitch propeller:

where P = engine/shaft power and N = propeller rpm.

In EEXI calculation, the ship’s reference speed VrefVref​ has to correspond to a specified engine power, normally related to 75% of MCR or 75% of the limited MCR where an approved Engine Power Limitation (EPL) / Shaft Power Limitation (ShaPoLi) is used.

The propeller curve is therefore used to:

• establish the corresponding propeller rpm and ship speed at the EEXI power point;
• determine the effect of engine power limitation on attainable ship speed;
• support calculation or verification of VrefVref​ where direct sea-trial data at the required power are unavailable;
• ensure that the selected EEXI power point lies on the ship’s actual propulsion characteristic, rather than simply assuming that speed varies linearly with engine power.