Ducted Propeller Strut Layout for Lower Drag and Thrust Fluctuation
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Solution Overview
Problem
Existing propulsion devices face increased fluid resistance and thrust fluctuation due to multiple struts, limiting design freedom and efficiency.
Innovation Solution
A propulsion device with a tubular portion, shaft, and propeller mounted on a shaft, featuring struts arranged symmetrically with varying angular intervals and disposed on both sides of a horizontal plane to support the shaft, reducing overlap and fluctuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the number of struts is increased to support the shaft portion, then the strength and stability of the propulsion device is improved, but the fluid resistance increases and efficiency decreases
Solution Approach 1:
The patent applies asymmetry by arranging struts with non-uniform angular intervals around the propeller shaft. Specifically, the struts are positioned at angular intervals of 360/N degrees where N is the number of struts, but the distribution is asymmetric such that not all struts are at equal intervals. This asymmetric arrangement allows the propulsion device to maintain sufficient structural strength while reducing the total number of struts, thereby minimizing fluid resistance and improving efficiency.
2Strength
If the number of struts is increased to ensure structural support, then the strength is improved, but the thrust fluctuation increases when propeller blades and struts overlap
Solution Approach 1:
The patent uses asymmetric angular interval arrangement of struts to reduce thrust fluctuation. By positioning struts at non-uniform angular intervals, the overlap between propeller blades and struts is minimized during rotation. This asymmetric distribution ensures that not all propeller blades simultaneously overlap with struts, thereby reducing thrust fluctuation while maintaining structural support.
Solution Approach 2:
The patent applies local quality by differentiating the angular positions of individual struts based on their specific roles in reducing overlap. Each strut's angular position is optimized locally to minimize interference with propeller blades during rotation, rather than using a uniform arrangement. This localized optimization reduces thrust fluctuation while maintaining overall structural strength.
3Reliability
If the number of struts is determined based on propeller blade count, then the overlap region is controlled, but the design freedom is greatly limited
Solution Approach 1:
The patent breaks the conventional link between propeller blade count and strut arrangement by introducing asymmetric angular intervals. This allows the strut configuration to be independently optimized for thrust stability without being constrained by the number of propeller blades. The asymmetric arrangement provides design freedom to accommodate different propeller configurations while maintaining thrust stability.
Solution Approach 2:
The patent applies dynamics by creating a flexible strut arrangement that can adapt to different operating conditions. The asymmetric angular interval configuration allows the propulsion device to optimize performance dynamically based on water conditions, propeller rotation speed, and other operational parameters, rather than being fixed by a rigid relationship with propeller blade count.
Data Source
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AI summary
This propulsion device is provided with: a cylindrical part disposed such that the axis thereof extends in a front-rear direction under the water surface, and forming a flow path; a shaft part disposed inside the cylindrical part and extending in the axial direction; a propeller which is attached to the shaft part, has a plurality of propeller blades that extends in the radial direction of the axis in the flow path and that are arranged in the circumferential direction of the axis, and which is able to rotate around the axis; a plurality of struts which are provided in the flow path on at least one of the front side and the rear side with respect to the propeller, extend in the radial direction and are arranged in the circumferential direction, and supports the shaft part. The plurality of struts extend in a vertical direction and are disposed symmetrical with respect to a line of symmetry that passes through the axis. Among angular intervals between the struts, at least one angular interval is different from the angular interval between the other struts, and at least one strut is disposed on each side in the vertical direction with respect to a horizontal plane that extends in the horizontal direction so as to pass through the axis line.