Counter-Rotating Marine Propeller Alignment Around the Drive Leg
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Solution Overview
Problem
Existing marine propulsion systems with concentric counter-rotating propellers face inefficiencies and increased vibrations and noise due to non-uniform flow conditions, particularly in forward and rearward drive configurations.
Innovation Solution
Angularly position the first and second propellers such that during one revolution, one blade of the first propeller aligns with the drive leg while the blade gap of the second propeller aligns with the drive leg in forward drive, or one blade of the first propeller aligns with one blade of the second propeller in rearward drive, utilizing visual or shape irregularities for precise mounting on shafts to optimize alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If concentric counter-rotating propellers are used, then propulsion efficiency and acceleration are improved, but vibrations and noise increase due to non-uniform flow conditions
Solution Approach 1:
The patent applies asymmetry by angularly offsetting the second propeller relative to the first propeller. Specifically, the second propeller is rotated by an angle of 15-30 degrees around the common rotational axis, creating an asymmetric configuration where propeller blades are staggered angularly. This asymmetric arrangement ensures that when one propeller blade passes through the drive leg, the other propeller's blade is at a different angular position, preventing simultaneous interaction with the drive leg and thereby reducing vibrations and noise while maintaining propulsion efficiency
2Object-generated harmful factors
If propellers are angularly positioned to reduce vibrations, then harmful factors are reduced, but mounting precision and alignment requirements increase
Solution Approach 1:
The patent implements preliminary action by incorporating pre-configured angular position features directly into the propeller designs before assembly. The first propeller includes a first angular position feature and the second propeller includes a second angular position feature that are预先 designed to achieve the required 15-30 degree angular offset. These features guide the propellers into the correct angular positions during mounting, ensuring precise alignment without requiring complex adjustment procedures during installation
3Manufacturing precision
If angular positioning features are added to propellers, then mounting precision is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by adding angular position features only at specific locations on the propellers where they are most effective for mounting alignment. Rather than modifying the entire propeller structure, the invention incorporates localized features such as asymmetric blade root configurations, keyed sections on the hub, or positioning protrusions on specific blades. These localized features provide the necessary angular guidance while minimizing additional complexity and maintaining the overall simplicity of the propeller design
Data Source
AI summary
A marine propeller combination for a marine propulsion unit includes a first propeller and a second propeller arranged to rotate simultaneously in opposite directions about a common rotational axis. The marine propeller combination is configured such that the first and second propellers are angularly positioned such that during one revolution one of the blades of the first propeller is aligned with a drive leg of the marine propulsion unit when a blade gap of the second propeller is aligned with the drive leg, or one of the blades of the first propeller is aligned with the drive leg when one of the blades of the second propeller is aligned with the drive leg. The disclosure further relates to a marine vessel and to a method of operating a marine propeller combination.