Microbubble Generator for Ship Hull Friction Reduction
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Solution Overview
Problem
Existing ship hull friction reduction technologies either generate large air bubbles due to forced air supply, leading to inadequate friction reduction, or require a specific hull shape for microbubble generation, and struggle with low-speed bubble generation and energy efficiency.
Innovation Solution
The use of microbubble generators with a wing to create negative pressure, allowing for the generation of microbubbles with a particle diameter of 1mm or less, utilizing a compressor with minimal power to depress the air-liquid interface and employing an assist compressor with pressure regulators to optimize microbubble production, reducing frictional resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If air is forcedly spouted using a closed type system, then air bubbles are generated, but the bubble diameter becomes large which reduces friction reduction effectiveness
Solution Approach 1:
Instead of forcing air into water using positive pressure (conventional method), the invention uses negative pressure generated by the ship's movement to draw air into water. The air charging line is positioned such that the air-liquid interface is depressed below the microbubble generator opening, allowing air to be sucked in rather than pushed in, thereby generating fine microbubbles instead of large bubbles
Solution Approach 2:
The ship's own movement through water generates the negative pressure needed for air intake. The microbubble generators utilize the kinetic energy of the ship's progression to create the pressure differential that draws air into the water, eliminating the need for external compressors or power sources
2Manufacturing precision
If negative pressure is used to generate microbubbles, then friction reduction effectiveness is improved, but the hull must have a particular shape and low-speed bubble generation is difficult
Solution Approach 1:
The microbubble generator is designed as a universal component that can be attached to various hull shapes without modification. The generator includes an air charging line with a specific structure that automatically creates the necessary negative pressure condition regardless of the hull's geometry, allowing the same device to function effectively on different ship types
Solution Approach 2:
The air charging line is pre-configured with a specific structure that creates negative pressure conditions before the microbubble generation process begins. The line includes features that ensure the air-liquid interface is properly positioned and that air can be drawn in effectively at various speeds
3Quantity of substance
If excessive amount of air is forced out, then bubble generation is enhanced, but air biting of screw or rolling and pitching occurs
Solution Approach 1:
The system automatically regulates air supply based on the negative pressure generated during ship movement. As the ship moves forward, the water flow naturally creates a pressure differential that draws in air at an optimal rate. This self-regulating mechanism prevents excessive air intake that would cause air biting or ship instability, while still generating sufficient microbubbles for friction reduction
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
This approach effectively reduces frictional resistance by utilizing the Kelvin-Helmholtz Instability phenomenon, minimizing energy costs and fuel consumption while maintaining microbubble stability on the hull surface.
Implementation Method 1
a wing (13) for negative pressure generation
Implementation Method 2
utilizing the Kelvin-Helmholtz Instability phenomenon
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
[OBJECT] To provide a frictional resistance reduction ship that decreases the frictional resistances and improves fuel efficiency. [SOLUTION] The below waterline region (L.W.L.) is divided into an upper region (R1) near to a waterline, and a lower region (R2) near to a ship's bottom. In the upper region (R1) and the lower region (R2), the microbubble generators (10) are arranged, and the supply form of the air to the microbubble generators (10) differs for each region (R1) and (R2). That is, supply of the air to the microbubble generators 10 arranged to an upper region (R1) is performed through the air supply pipe 3, one end of the air supply pipe 3 is opened to the atmosphere and supply of the air to the microbubble generators 10 arranged to a lower regions (R2) is performed through the branch pipe 6 from the pipe 5 from the assist compressor 4. That is, supply of air to the microbubble generators 10 arranged in lower region (R2) is performed through pipes of closed system instead of opened to the atmosphere.