Retractable Tunnel Thruster Unit for Marine Vessels
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Solution Overview
Problem
Existing retractable tunnel thrusters suffer from high flow resistance and increased turning force due to their lengthy tunnel parts, which decrease efficiency and increase weight, leading to inefficient seawater circulation and maneuvering difficulties.
Innovation Solution
A retractable thruster unit with a tunnel part that has a perimeter and inner diameter changing along its axis, featuring a shorter nozzle and curved closing plates that cover less than half of the perimeter, optimizing the nozzle profile and reducing the length of the retractable tunnel part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lengthy tunnel part is used to house the thruster entirely below the keel, then the thruster can be fully retracted into the hull, but the flow resistance of water increases and the force needed to turn the thruster unit increases
Solution Approach 1:
The tunnel part is divided into two functional sections: a stationary tunnel section remaining in the hull and a retractable nozzle section that extends below the keel. This segmentation allows the thruster to be housed in a shorter tunnel structure while maintaining full retraction capability, thereby reducing flow resistance and turning force requirements.
Solution Approach 2:
The invention changes the spatial arrangement by having the nozzle extend vertically below the hull baseline rather than requiring a long horizontal tunnel. This dimensional change allows the thruster to achieve its lowered position with a compact tunnel structure, reducing the flow path length and associated resistance.
2Reliability
If a lengthy tunnel part is used to house the thruster entirely below the keel, then the thruster can be fully retracted into the hull, but the weight of the thruster unit increases
Solution Approach 1:
The tunnel structure is segmented into a stationary portion and a retractable nozzle portion, eliminating the need for a lengthy tunnel that would otherwise be required to house the entire thruster. This reduces the overall weight of the moving thruster unit while preserving full retraction functionality.
3Reliability
If a lengthy tunnel part is used, then the thruster can be fully retracted, but the steering moment increases making maneuvering difficult
Solution Approach 1:
By segmenting the tunnel into stationary and retractable sections, the invention reduces the length of the tunnel part that must be rotated during steering operations. This reduces the steering moment and improves maneuverability while maintaining full retraction capability.
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 design minimizes flow resistance, reduces the steering moment, and decreases the weight and projected area of the thruster unit, enhancing thrust efficiency and maneuverability, particularly beneficial in wind turbine park projects.
Implementation Method 1
a propeller (6) having a diameter and an axis and being surrounded by a retractable tunnel part
Implementation Method 2
When the propeller and nozzle are at their lowest position a planar top cover plate attached to the vertical support portion at a distance above the nozzle closes the opening in the hull
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
The present invention discusses a novel retractable thruster unit for a marine vessel using a tunnel thruster. The retractable thruster unit of the invention has a nozzle (44) having an end (60), the end (60) being provided with two closing plates, a top closing plate (62), and a bottom closing plate (64), the closing plates being arranged 180 degrees apart on opposite sides of the axis of the propeller (6) and extending substantially axially from the end (60) of the nozzle (44).