Reuse of Pressurized Air in Ship Air-Lubrication Systems A Conceptual Improvement for Energy-Efficient Drag Reduction

Air-lubrication systems (ALS) reduce ship resistance by injecting compressed air beneath the hull to form a thin layer of bubbles between the hull surface and the surrounding water. Although these systems can reduce fuel consumption by approximately 5–10%, they require substantial compressor power, typically ranging from 500 to 2000 kW for large cargo vessels. Large cargo vessels are among the most suitable candidates for ALS installations because their large draft requires significant air pressurization to inject air beneath the hull. A fundamental inefficiency in existing ALS technologies is that the injected compressed air travels along the hull and escapes at the stern without being reused. As a result, a large portion of the benefits obtained from air lubrication is lost as the air bubbles disperse into the wake. .This article analyzes the operational characteristics of existing ALS installations and proposes a concept in which air that has already been pressurized beneath the hull is collected and redirected forward for reuse. The proposed concept may significantly reduce compressor power requirements while maintaining, or potentially improving, drag-reduction performance