Propeller Hub Exhaust Venting for Reverse Thrust

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Solution Overview

Problem

Conventional marine drives face inefficiency and reduced thrust performance when discharging exhaust gases rearwardly of the propeller, particularly during reverse rotation at low speeds, which interferes with joystick-piloted systems requiring sudden and responsive reverse thrust.

Innovation Solution

The propeller device is configured with exhaust vent holes located alongside the propeller blades, specifically at areas of low pressure during forward rotation and at the area of maximum pressure during reverse rotation, to efficiently vent exhaust gases and enhance thrust performance by removing gases from the propeller blades' path during reverse operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If exhaust gases are discharged rearwardly of the propeller, then the marine drive can be operated efficiently during forward rotation, but reverse thrust performance is reduced during reverse rotation at low speeds

Engineering Contradiction:

Improvereverse thrust performanceVSAvoidexhaust gas interference

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The exhaust discharge system is segmented into multiple separate discharge locations: one rearwardly of the propeller for forward operation, and another forwardly of the propeller for reverse operation. This segmentation allows exhaust gases to be discharged away from the propeller blades during reverse rotation, eliminating the harmful interference while maintaining efficient forward thrust.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The exhaust discharge direction is inverted based on rotation direction: during forward rotation, exhaust is discharged rearwardly (conventional direction), but during reverse rotation, exhaust is discharged forwardly (opposite direction). This inversion ensures that exhaust gases never interfere with the propeller blades regardless of rotation direction, thereby improving reverse thrust performance.

Inventive Principle:

Principle #13The other way round (Inversion)

2Productivity

If exhaust vent holes are positioned to vent exhaust forwardly of the propeller during reverse rotation, then reverse thrust performance is enhanced, but the system complexity increases

Engineering Contradiction:

Improvereverse thrust performanceVSAvoidexhaust venting system complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The propeller hub is designed with multiple exhaust discharge passages that serve dual purposes: rearward discharge during forward rotation and forward discharge during reverse rotation. This multi-functional design eliminates the need for separate venting systems for different rotation directions, reducing overall system complexity while maintaining enhanced reverse thrust performance.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The exhaust venting system utilizes the natural rotation direction of the propeller to automatically select the appropriate discharge location. During forward rotation, rearward discharge occurs; during reverse rotation, forward discharge occurs. This self-regulating mechanism eliminates the need for complex control systems, sensors, or actuators, thereby reducing system complexity while achieving the desired performance enhancement.

Inventive Principle:

Principle #25Self-service

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 configuration improves thrust efficiency and responsiveness during joystick-piloted operations by reducing interference from exhaust gases, especially at low speeds, and enhances acceleration and reverse thrust performance.

Implementation Method 1

when the propeller device is reversely rotated, the second blade face encounters a positive pressure and the first blade face encounters a relatively lower pressure or suction

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Data Source

PatentUS11459078B1Marine drives and propeller devices having exhaust venting for enhanced reverse thrust performance

Publication Date: 2022.10.04 BRUNSWICK CORP

AI summary

A propeller device has a propeller hub which is elongated along the rotational axis and a propeller blade which radially extends from the propeller hub. The propeller hub and propeller blade are configured so that when the propeller device is forwardly rotated, a first portion of the propeller hub on a first side of the propeller blade encounters a positive pressure and a second portion of the propeller hub on an opposite, second side of the blade encounters a relatively lower pressure or suction, and further so that when the propeller device is reversely rotated, the second portion of the propeller hub encounters a positive pressure and the first portion of the propeller hub encounters a relatively lower pressure or suction. An exhaust vent hole is located in the first portion of the propeller hub and configured to vent exhaust gases from the marine drive via the propeller hub as the propeller device is reversely rotated, thereby enhancing reverse thrust performance of the propeller device.