Counter-Rotating Marine Propeller Phasing for Lower Vibration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing marine propulsion systems with concentric propellers rotating in opposite directions do not optimally address angular positioning to reduce vibrations, noise, and improve efficiency, particularly in varying flow conditions.
Innovation Solution
Angularly position the first and second propellers with respect to the drive leg, ensuring one blade of the first propeller aligns with the drive leg when a blade gap of the second propeller aligns, or vice versa, utilizing shape irregularities in the propeller's internal spline patterns for precise mounting, and rotating the propellers in opposite directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If two concentric propellers are arranged to rotate in opposite directions, then propulsion efficiency and acceleration are improved, but vibrations and noise increase due to unoptimized angular positioning
Solution Approach 1:
The patent applies asymmetry by deliberately positioning the propellers at specific non-symmetric angular orientations relative to each other and the drive leg. The first propeller is positioned at a first angular position and the second propeller at a second angular position, creating an asymmetric configuration that optimizes the interaction between propeller blades and water flow, thereby reducing vibrations and noise while maintaining propulsion efficiency.
Solution Approach 2:
The patent changes the angular position parameters of the propellers relative to the drive leg. By adjusting these angular parameters to specific optimized values, the system achieves reduced vibrations and noise. The angular positions are deliberately set rather than being arbitrary, representing a parameter optimization approach.
2Object-affected harmful factors
If propellers are angularly positioned to reduce vibrations, then noise and efficiency are improved, but device complexity increases due to precise mounting requirements
Solution Approach 1:
The patent incorporates position features directly into the propeller designs during manufacturing. These position features pre-establish the correct angular relationships between propellers and the drive leg, eliminating the need for complex field adjustments or alignments during installation. The correct angular positioning is built into the components themselves in advance.
Solution Approach 2:
The position features on the propellers enable self-alignment and self-positioning during assembly. The first propeller has a first position feature and the second propeller has a second position feature that automatically guide the propellers into their correct angular positions relative to the drive leg without requiring external alignment tools or complex mounting procedures.
3Ease of operation
If standard propeller mounting is used, then ease of installation is maintained, but angular positioning precision is insufficient to optimize performance
Solution Approach 1:
The position features are pre-formed as integral parts of the propeller designs during manufacturing. These features encode the precise angular positioning information needed for optimal performance, allowing the propellers to be correctly positioned simply by engaging these pre-formed features with corresponding mounting structures, without requiring complex alignment procedures.
Solution Approach 2:
The position features create asymmetric geometric relationships between the propellers and the drive leg. This asymmetry is deliberately designed to establish unique, repeatable angular positions that optimize the hydrodynamic interaction between the propellers and water flow, going beyond standard symmetric mounting arrangements.
Data Source
Figure 1~4
Figure 5~9
AI summary
The present disclosure relates to a marine propeller combination for a marine propulsion unit (1), the marine propeller combination comprising a first propeller (10) and a second propeller (20) arranged to rotate simultaneously in opposite directions about a common rotational axis (A), wherein the marine propeller combination is configured such that the first and second propellers (10, 20) are angularly positioned such that during one revolution one of the blades of the first propeller (10) is aligned with a drive leg (2) of the marine propulsion unit (1) when a blade gap of the second propeller (20) is aligned with the drive leg (2), or one of the blades of the first propeller (10) is aligned with the drive leg (2) when one of the blades of the second propeller (20) is aligned with the drive leg (2). The disclosure further relates to a marine vessel (50) and to a method (100) of operating a marine propeller combination.