Side Thruster Cavitation Suppression via Return Channel
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Solution Overview
Problem
Existing side thruster equipment with flat blades experiences cavitation due to low-pressure regions around the blades, leading to complex structures and increased manufacturing costs.
Innovation Solution
The side thruster equipment incorporates a cylindrical tunnel with a propeller having flat blades, first and second slit holes on the tunnel walls, and a return channel that communicates with the tunnel through these slit holes, allowing water flow to return upstream and reduce the angle of attack on the blades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a jet mechanism with pressurization impeller is used to increase water flow speed upstream of the propeller, then cavitation is suppressed, but the structure becomes complex and manufacturing cost increases
Solution Approach 1:
The patent extracts the essential function of the jet mechanism (increasing water flow speed upstream of the propeller) and implements it through a simplified structure. Instead of using a complex pressurization impeller system, the patent uses a jet mechanism that directly increases water flow speed by utilizing the pressure difference created by the propeller rotation itself, thereby suppressing cavitation without adding complex components
Solution Approach 2:
The patent makes the system self-servicing by using the propeller's own rotation to create the pressure difference that drives the jet mechanism. The propeller rotation naturally creates high pressure at the downstream side and low pressure at the upstream side, and this pressure difference is directly utilized to drive water through the jet mechanism, eliminating the need for an external pressurization impeller
2Force
If flat blades are used in the propeller, then thrust is equally generated in port and starboard directions, but leading edge load increases and cavitation occurs due to low-pressure regions
Solution Approach 1:
The patent applies preliminary anti-action by increasing the water flow speed upstream of the propeller blades before the blades encounter the water. The jet mechanism pre-accelerates the water flow, which reduces the angle of attack and the resulting low-pressure regions on the blade surfaces, thereby preventing cavitation before it can occur
Solution Approach 2:
The patent changes the flow velocity parameter of the water upstream of the propeller. By increasing the water flow speed through the jet mechanism, the relative velocity between the water and the propeller blades changes, which reduces the angle of attack and the pressure difference across the blades, thereby suppressing cavitation while maintaining equal thrust in both directions
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 configuration effectively suppresses cavitation by reducing the angle of attack and pressure difference at the blade tips, maintaining propulsive force, and reducing energy loss through a simpler structure.
Implementation Method 1
a return channel that is a tubular channel located such that the tunnel penetrates an inside of the tubular channel, the return channel communicating with an inside of the tunnel through the first slit holes and the second slit holes
Data Source
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AI summary
Side thruster equipment includes: a cylindrical tunnel extending in a width direction of a hull; a propeller including flat blades and located in the tunnel such that a rotation axis of the propeller coincides with a central axis of the tunnel; first slit holes located on a portion of a wall of the tunnel, which is closer to starboard than the propeller, so as to be lined up in a circumferential direction of the tunnel, the first slit holes being openings each located so as to extend in a direction intersecting with an extending direction of the tunnel; second slit holes located on a portion of the wall of the tunnel, which is closer to port than the propeller, so as to be lined up in the circumferential direction of the tunnel, the second slit holes being openings each located so as to extend in a direction intersecting with the extending direction of the tunnel; and a return channel that is a tubular channel located such that the tunnel penetrates an inside of the tubular channel, the return channel communicating with an inside of the tunnel through the first slit holes and the second slit holes.