Stepped Surface Propeller Blade Pressure Distribution
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Solution Overview
Problem
Current surface piercing propellers fail to maximize thrust due to low pressure zones on the blade face and lack of features to minimize pressure on the vacuum side, leading to inefficient performance and larger propeller diameters.
Innovation Solution
Incorporating geometric steps on both the blade face and vacuum side, specifically located between one fifth and four fifths of the chord length, to create high pressure peaks and controlled water adhesion, enhancing thrust and efficiency by redistributing pressure and reducing the effective blade area at higher RPMs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional flat or cambered blade face geometry with trailing edge annex is used, then the propeller structure is simple and easy to manufacture, but the central portion of the blade face chord creates a low pressure zone that fails to maximize thrust
Solution Approach 1:
The patent applies local quality by introducing a stepped geometry feature specifically at the mid-chord location (between 20-80% of chord length from leading edge) rather than modifying the entire blade surface. This localized modification creates a pressure peak precisely where needed (central portion of blade face) without complicating the overall blade structure, resolving the contradiction between maximizing thrust and maintaining manufacturing simplicity
Solution Approach 2:
The blade face is segmented into distinct pressure zones by the stepped feature, creating separate high-pressure regions (leading edge and mid-chord) and maintaining the trailing edge pressure peak. This segmentation allows each zone to contribute optimally to thrust generation, transforming the previously uniform low-pressure central zone into a productive high-pressure region
2Productivity
If larger propeller diameter is used to compensate for low pressure zone, then total thrust can be increased, but the propeller becomes less efficient and harder to install in shallow waters
Solution Approach 1:
The patent changes the pressure distribution parameters on the blade face by introducing the stepped geometry, which creates additional pressure peaks and redistributes pressure more effectively across the blade surface. This parameter change (pressure distribution) allows the propeller to generate maximum thrust from a given blade area, eliminating the need to increase propeller diameter to compensate for insufficient pressure in the central zone
3Productivity
If no features are added to the vacuum side of the blade, then the blade structure remains simple, but pressure on the blade back is not minimized leading to reduced thrust efficiency
Solution Approach 1:
The patent applies inversion by adding a stepped feature on the vacuum side (back of the blade) that has the opposite effect to the pressure face step - it creates a region that enhances pressure minimization on the back side. This inverted approach (modifying the vacuum side rather than just the pressure side) allows simultaneous optimization of both blade faces, maximizing the pressure differential and thus thrust efficiency while maintaining structural simplicity
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
The solution increases thrust by up to 30% and efficiency by 2-5% while allowing for smaller propeller diameters, easier installation, and more flexible operation in shallow waters, with improved bimodal operation and reverse thrust efficiency.
Implementation Method 1
The addition of a geometric step feature on the blade face between the leading and trailing edges increases the pressure near this feature and increases the overall pressure (blade pressure face loading) thereby increasing thrusting force
Implementation Method 2
The surface piercing propeller blade of the current invention, controls the pressure and water flow over the blade face and/or blade back thereby increasing the thrusting force
Implementation Method 3
The back side of the propeller, the vacuum side, is in a void or cavity which is naturally ventilated from the surface air, and so provides substantially no pressure either positive or negative
Data Source
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AI summary
A marine surface propeller, and blade therefore, which is surface piercing and partially submerged, and includes a blade geometry that improves distribution of pressure and control to wetted and ventilated regions. Preferably, the feature has a positive step (ramp, cup, interceptor, indent or other geometric addition or intervention) between one fifth and four fifths chord length so as to create a high pressure peak or zone in what is now a low pressure zone on either the blade face or back or both and to create speed controllable wetted and ventilated regions.