Duo-Propeller Blade Loading for Tip Vortex and Swirl Recovery
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Solution Overview
Problem
Conventional contra-rotating propellers face limitations due to tip vortices causing drag, swirl energy loss, and interference between propellers, restricting the aft propeller's diameter and efficiency.
Innovation Solution
The duo-propeller design features a forward propeller with optimized loading and higher swirl near the tip, and an aft propeller with improved loading distribution to cancel tip swirl, using unique rake and skew values to minimize vortices and reduce fluid flow interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the forward propeller operates with conventional loading, then tip vortices are created causing drag, but the patent optimizes loading distribution to increase swirl energy while minimizing vortex formation
Solution Approach 1:
The patent changes the loading distribution parameter along the blade span, specifically reducing loading near the tip region compared to conventional uniform or root-loaded distributions. This parameter modification reduces tip vortex strength while optimizing swirl generation in the mid-span region, resolving the contradiction between energy loss and harmful vortex effects
Solution Approach 2:
The patent applies different loading characteristics to different regions of the blade - higher loading in the mid-span region to generate swirl energy, and reduced loading near the tip to minimize vortex formation. This local differentiation of quality resolves the contradiction by allowing beneficial swirl generation without the harmful tip vortex penalties
2Productivity
If the aft propeller diameter is limited to be equal to or less than the forward propeller, then tip vortex impingement is prevented, but the aft propeller's efficiency and energy capture capability are restricted
Solution Approach 1:
The patent changes the geometric parameter of propeller diameter relationship, allowing the aft propeller to have a larger diameter than the forward propeller. This is made possible by the optimized loading distribution that prevents excessive tip vortices, thus resolving the contradiction between productivity and harmful factors
Solution Approach 2:
The patent inverts the conventional design rule where the aft propeller is limited to equal or smaller diameter. By reversing this approach and allowing the aft propeller to be larger, the patent captures more swirl energy while the optimized loading distribution prevents vortex impingement issues that would normally constrain such a design
3Loss of energy
If the forward propeller generates high swirl near the tip, then more energy is available for capture, but conventional designs cannot utilize this due to vortex-induced drag limitations
Solution Approach 1:
The patent applies localized loading optimization where the mid-span region generates high swirl while the tip region has reduced loading to minimize vortices. This spatial differentiation allows the system to capture the benefits of high swirl energy generation without suffering from vortex-induced drag penalties
Solution Approach 2:
The patent modifies the loading distribution parameter along the blade, creating a non-uniform profile that peaks in the mid-span region rather than at the root or tip. This parameter change enables high swirl generation where it is most beneficial while avoiding the harmful effects of tip vortices
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 enhances energy capture and efficiency by allowing the aft propeller to be equal or larger in diameter, increasing swirling energy recovery and reducing drag, while maintaining high efficiency compared to conventional duo-propellers.
Implementation Method 1
the energy lost to the swirling flow of the forward propeller's outflow is captured by the second aft-ward propeller, which is configured to utilize that outflow to improve overall system performance
Implementation Method 2
The amount of swirl energy generated by the forward propeller depends in part on the loading at the tip of the propeller blades
Data Source
AI summary
A duo propeller disclosed having a forward propeller having increased loading distribution and high swirl near the tip. The duo propeller has an aft propeller with a more optimal loading distribution that can cancel the high tip swirl from the forward propeller. The duo-propeller an enhanced ability for the aft propeller to capture the energy lost to the swirling flow of the forward propeller's outflow.