Modified Propeller Blade Section for Air-Lubricated Ships
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Solution Overview
Problem
Air inflow into the propeller of air lubrication ships causes propulsion efficiency degradation, despite the drag-reduction benefits of air lubrication systems, necessitating additional energy input and marine biological fouling issues.
Innovation Solution
Installation of wedge-shaped air ducts on the hull, an air distributor, and a specially designed propeller with improved blade cross-section to manage air flow, minimizing energy consumption and preventing air inflow into the propeller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If air is supplied to the hull bottom for drag reduction, then drag force is reduced, but air flows into the propeller causing propulsion efficiency degradation
Solution Approach 1:
The hull surface is segmented into multiple regions with separate air ducts: bottom surface ducts for drag reduction and side surface ducts positioned above the waterline that prevent air from reaching the propeller. This segmentation allows independent control of air supply to different hull areas, achieving both drag reduction and propeller protection.
Solution Approach 2:
An air distributor is introduced as an intermediary component between the air duct and the hull bottom. It disperses air into fine bubbles that reduce drag while controlling their distribution to prevent excessive air accumulation near the propeller intake area.
2Force
If air is injected into the waterline area for air lubrication, then drag reduction is achieved, but marine organisms attach to the air supply system
Solution Approach 1:
Air ducts are strategically positioned at different locations with different functions: bottom surface ducts for drag reduction and side surface ducts above the waterline for preventing fouling. The local positioning optimizes both drag reduction effectiveness and resistance to marine organism attachment by keeping critical air supply points above the fouling-prone waterline area.
3Force
If air ducts are positioned below the waterline for effective air lubrication, then drag reduction is maximized, but air flow is disrupted when the ship is docked
Solution Approach 1:
The air lubrication system is designed to function in multiple operational conditions: bottom surface ducts provide effective drag reduction during navigation, while side surface ducts positioned above the waterline ensure continuous air supply and prevent fouling during docking and low-speed operations. This multi-functional arrangement maintains system reliability across different operating states.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances propulsion efficiency and reduces marine fouling while maintaining drag reduction effects, achieving energy savings and improved hull efficiency.
Implementation Method 1
a low-pressure region is formed near the air outlet (450) at the aft side of the wedge-shaped air duct (300) during navigation, causing air to flow in from the deck (100) through the inlet pipe (400) to the bottom surface (401)
Implementation Method 2
technologies applying air lubrication systems to hulls for drag reduction are being widely introduced internationally in the shipping and shipbuilding industries
Data Source
Figure 1
Figure 2
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AI summary
The present invention relates to an air-lubricated ship equipped with a propeller that overcomes a reduction in driving force due to inflow air, while supplying air using a suction force generated by an increasing flow rate due to the movement of the ship, and minimizing, by air supplied to the bottom of the ship, residual air introduced to the periphery of the propeller, in order to minimize energy for supplying air to the bottom and the sides of the ship.