Marine Propeller Asymmetric Blade Spacing Noise Reduction
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Solution Overview
Problem
Existing propellers generate unwanted noise due to resonant vibrational excitation caused by pressure waves, which can lead to mechanical imbalances and reduced propulsion efficiency, as they often have blades of uneven size or weight distribution, resulting in irregular pressure surge transmission to the ship's hull.
Innovation Solution
A propeller design with uniformly pitched blades where the angular distance between consecutive blades is consistent, but the angular distance between wing tips varies, disrupting harmonic excitation and achieving balanced weight distribution by adjusting the skew and generatrix courses of individual blades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If blades are arranged at irregular intervals around the circumference of the propeller, then noise is reduced by canceling regular pressure surges, but the propeller loses dynamic balance and develops imbalance
Solution Approach 1:
The patent applies asymmetry by arranging blades at irregular angular intervals around the propeller hub. Specifically, the angular distance between consecutive blades varies (e.g., 100°, 110°, 120°, 110° instead of uniform 90°), creating an asymmetric pattern that disrupts the regularity of pressure surges and reduces noise while maintaining acceptable dynamic balance through careful design
Solution Approach 2:
The patent applies local quality by varying specific geometric parameters of individual blades, including blade length, width, pitch angle, and skew. Each blade can have different dimensions and characteristics tailored to compensate for the irregular arrangement, allowing local adjustments that maintain overall propeller balance while achieving noise reduction through irregular blade spacing
2Reliability
If blades are arranged evenly around the circumference with uniform pitch, then dynamic balance is maintained, but regular pressure surges cause resonant vibrations and noise
Solution Approach 1:
The patent breaks the symmetry of uniform blade arrangement by introducing irregular angular intervals between blades. This asymmetric arrangement disrupts the periodicity of pressure pulses generated during rotation, preventing resonant vibrations and noise while the overall propeller design maintains acceptable dynamic balance through compensating measures in blade geometry
3Object-affected harmful factors
If blades of different sizes and weights are used, then irregular pressure surge transmission may occur, but manufacturing complexity increases and propulsion efficiency decreases
Solution Approach 1:
The patent applies local quality by allowing individual blades to have different geometric characteristics (length, width, pitch, skew) while maintaining similar overall mass. This enables local variations in blade properties to achieve irregular pressure surge transmission patterns without requiring dramatically different blade sizes or weights, thus limiting the increase in manufacturing complexity
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 significantly reduces noise by canceling out resonant vibrations and maintaining dynamic balance, ensuring effective propulsion and extending the service life of the propulsion system.
Implementation Method 1
the pressure waves or pressure pulses generated by the individual blades can lead to resonant vibrations in the watercraft
Implementation Method 2
the pressure waves or pressure pulses generated by the individual blades can lead to resonant vibrations in the watercraft and thus to unwanted noise
Implementation Method 3
generate mechanical forces that can affect the service life of the ship's drive
Data Source
Figure 1~3
Figure 2
Figure 4~5
AI summary
The invention relates to a propeller for a water vehicle, comprising a hub (12, 112, 212, 312) and at least two blades, said blades extending outwards from the hub (12, 112, 212, 312) in the radial direction, and the propeller having a uniform blade distribution. The problem addressed by the invention is to provide a propeller for a water vehicle which allows unwanted generation of noise to be efficiently reduced or avoided. According to the invention, the angular distance between the blade tips of two consecutive blades of the propeller varies in relation to the angular distance between the blade tips of two other consecutive blades.