Contra-rotating Marine Propulsor with Planetary Gears

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Solution Overview

Problem

Conventional ship propulsion systems face inefficiencies due to being optimized for specific performance points, leading to reduced performance at off-design operating conditions, and struggle to efficiently transfer horsepower to water without cavitation in high-speed, shallow-water naval applications.

Innovation Solution

A contra-rotating propulsor system with planetary gears, shafting, clutches, and electric or hydraulic feedback elements allows for energy redistribution and flexible operation, enabling efficient thrust delivery across the operating range and reducing cavitation, while accommodating smaller transom space requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If conventional single-impeller waterjets are used to increase horsepower delivery, then thrust is improved, but cavitation occurs and transom space requirements increase

Engineering Contradiction:

Improvehorsepower deliveryVSAvoidcavitation

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The single impeller is segmented into two contra-rotating impellers working in sequence. The first impeller accelerates water while the second impeller further accelerates it without causing cavitation, dividing the total horsepower delivery function between two stages. This allows equivalent thrust with smaller diameter impellers that consume less transom real estate.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of using one large impeller that directly delivers all horsepower (which causes cavitation), the system uses two smaller impellers in reverse sequence - the first creates a controlled flow pattern and the second completes the acceleration. This inverted approach of staged acceleration eliminates cavitation while maintaining power delivery.

Inventive Principle:

Principle #13The other way round (Inversion)

2Speed

If propellers are optimized for top-end speed, then maximum speed performance is improved, but efficiency at off-design operating points deteriorates

Engineering Contradiction:

Improvetop-end speedVSAvoidoperating efficiency

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The system dynamically adjusts the operational characteristics of the contra-rotating impellers to adapt to different operating conditions. By controlling the speed and pitch of each impeller independently through the planetary gear system, the propulsor maintains optimal efficiency across the entire operating range rather than being fixed for a single design point.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes operational parameters (rotational speeds, pitch angles) of the contra-rotating impellers based on operating conditions. This allows the propulsor to optimize performance for both maximum speed and fuel efficiency at part-throttle conditions, adapting to varying mission requirements.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If conventional planetary gears with restrained output elements are used, then gear mechanism simplicity is improved, but energy efficiency deteriorates due to unrecovered restraining energy

Engineering Contradiction:

Improvegear mechanism simplicityVSAvoidrestraining energy

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The system implements feedback by capturing the restraining energy from the restrained output element and redirecting it to drive the unrestrained output element. This energy recovery mechanism converts what would be wasted energy into useful work, improving overall system efficiency while maintaining the simplicity of the planetary gear structure.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The restraining energy, which would normally be a harmful loss, is converted into a beneficial resource by using it to drive the second output element. This transforms the energy loss into useful propulsion power, improving fuel efficiency without adding complex external energy sources.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS10392089B2Contra-rotating propulsor for marine propulsion

Publication Date: 2019.08.27 MICHIGAN MARINE PROPULSION SYST

AI summary

A system for providing marine propulsion is provided including an input shaft driven by a prime mover, a pinion gear coupled to the input shaft, a plurality of planet gears coupled to the pinion gear, a planet carrier having the plurality of planet gears rotationally mounted thereto, and a ring gear surrounding the planet gears and coupled thereto. The planet carrier and ring gear are coupled to internal and external output shafts that are coaxially aligned, which are coupled to aft and forward propulsor elements. The ring gear and planet carrier rotate in opposite directions to provide contra-rotating forward and aft propulsor elements. The ring gear and planet gear are each coupled to rotation altering devices that, when at least one is activated, the rotation of both the planet carrier and ring gear will be altered, thereby altering the rotation of the propulsor elements.