PRODUCT SOLUTION

Eco Cap

New-Shape Propeller Cap for Hub Vortex Diffusion

A hub vortex is generated at the trailing edge of a propeller cap due to the circumferential flow created behind the propeller blades.
Since hub vortices cause energy loss, over 500 cap designs were trialed to develop a geometry that could diffuse the vortex and recover the lost energy. Through extensive prototyping, the most effective design was found to be a cap equipped with multiple small blades, which became the foundation for the Eco-Cap.
The vortex diffusion effect has been verified through model tests in a circulating water channel.

The Mechanism of Efficiency Improvement with the Eco-Cap

When examining the pressure distribution at the rear of the cap, conventional caps tend to generate drag due to negative pressure. In contrast, the Eco-Cap generates positive pressure, producing additional thrust and enhancing propulsion efficiency. Model tests showed an efficiency improvement of approximately 1.0% to 1.3%.
While hub vortices are weaker in model-scale testing—resulting in smaller energy loss— it is expected that actual vessels will experience greater energy recovery and efficiency improvements with the Eco-Cap.

Energy-Saving Effect Confirmed on Actual Vessels

On actual vessels, the Eco-Cap features extremely thin FRP (Fiber Reinforced Plastic) blades mounted on a copper alloy cap body to minimize resistance. The use of FRP also keeps the weight difference from a standard cap minimal.
In trials where the Eco-Cap was retrofitted onto existing vessels, fuel consumption was reduced by approximately 2.8% compared to performance before installation.