Air Lubrication System

Goal

Reduce hull friction to lower fuel consumption and CO_2 emissions of large vessels.

Problem

High fuel costs and greenhouse-gas emissions of container and tanker ships.

Concept Summary

A cavity built into the hull of a displacement vessel is supplied with a controlled airflow. The moving vessel creates a Kelvin-Helmholtz instability at the air-water interface, generating a stable layer of micro-bubbles that act as a lubricating film beneath the hull, thereby reducing hydrodynamic drag.

Principles

• Kelvin-Helmholtz instability
• Micro-bubble drag reduction
• Air-lubrication layer

Scientific Domains

Materials

• steel
• air

Mechanisms of Action

• Air injected into a shallow cavity creates a high-velocity air-water interface
• Instability mixes air and water, forming a durable micro-bubble layer
• Bubble layer reduces skin friction on the hull

Energy Sources

Applications

• large container ships
• oil tankers

Claimed Performance

10-15 % reduction in propulsion energy use, 9 000 t oil saved per year for an 11-13 000 TEU vessel, 36 000 t CO_2 reduction, repayment period ~=2.5 years.

Experimental Evidence

Company estimates of oil and CO_2 savings; no independent test data presented.

Limitations

• Requires hull modification and integration of air-compression system
• Air-compressor power consumption offsets some savings
• Performance depends on vessel speed and sea state

Red Flags

• Performance figures are based on internal estimates, not peer-reviewed data
• No independent replication or sea-trial results reported

Keywords

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