Duo-Propeller Blade Loading for Swirl Capture and Vortex Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

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, and an aft propeller with improved loading distribution, minimizing tip vortices and reducing fluid flow interference, allowing for equal or larger aft propeller diameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the forward propeller operates with conventional blade loading, then tip vortices are created causing drag, but the swirl energy that could be captured by the aft propeller is lost

Engineering Contradiction:

Improveswirl energy lossVSAvoidtip vortices causing drag

Core Design Contradiction:

Loss of energyVSObject-generated harmful factors

Solution Approach 1:

The patent applies parameter changes by modifying the blade loading distribution along the span, specifically concentrating more loading toward the root and reducing it toward the tip. This changes the vortex generation characteristics and swirl distribution, enabling the forward propeller to generate controlled high swirl near the tip that can be captured by the aft propeller while minimizing harmful tip vortices

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent inverts the conventional approach by allowing higher swirl generation at the blade tip region rather than minimizing it. The aft propeller is specifically designed to capture this swirl energy, transforming what would normally be a loss into a useful energy source that improves overall system efficiency

Inventive Principle:

Principle #13The other way round (Inversion)

2Productivity

If the aft propeller diameter is limited to be equal to or less than the forward propeller, then tip vortex impingement is avoided, but the aft propeller's efficiency and energy capture capability are restricted

Engineering Contradiction:

Improveaft propeller efficiencyVSAvoidtip vortex impingement

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the geometric parameters of both propellers, allowing the aft propeller to have a diameter equal to or larger than the forward propeller. This is made possible by the modified blade loading distribution that controls vortex trajectories, preventing impingement on the aft propeller blades even with increased diameter

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent utilizes the axial dimension by positioning the aft propeller at a specific distance downstream from the forward propeller. This axial spacing, combined with the modified blade loading, allows the aft propeller to operate in the swirling flow field without suffering from harmful tip vortex impingement, enabling larger diameter operation

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Loss of energy

If the forward propeller generates high swirl near the tip, then more energy is available for capture, but the swirl energy disperses and cannot be effectively utilized by the aft propeller

Engineering Contradiction:

Improveswirl energy available for captureVSAvoidswirl energy utilization

Core Design Contradiction:

Loss of energyVSEase of operation

Solution Approach 1:

The patent applies local quality by creating concentrated swirl generation at specific radial locations near the blade tip rather than uniform swirl distribution. The modified blade loading distribution produces localized high-swirl regions that remain coherent over the axial distance to the aft propeller, making the energy available for capture while maintaining usability

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent ensures continuity of the swirling flow from the forward propeller outlet to the aft propeller inlet by maintaining appropriate axial spacing and optimizing the blade loading distribution. This continuous swirl structure allows the aft propeller to consistently capture the rotational energy without significant dispersion or loss of coherence

Inventive Principle:

Principle #20Continuity of useful action

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

Enhances energy capture and efficiency by minimizing drag and interference, enabling the aft propeller to be equal or larger in diameter while maintaining efficiency advantages over conventional duo-propellers.

Implementation Method 1

The rake values and skew values of the propeller blades together form a loop-shaped blade having an inlet root and an outlet root attached to a hub. This structure minimizes vortices at the blade tips.

Methodology Applied

Scientific EffectVortex: Vortex Ring

Implementation Method 2

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

Methodology Applied

Scientific EffectSwirling flow: Vortex Ring

Data Source

PatentUS12397889B2Duo-propellers and single propellers

Publication Date: 2025.08.26 SHARROW ENGINEERING LLC

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.