Compact Hybrid Pod Drive with Coaxial Counter-Rotating Propellers
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Solution Overview
Problem
Existing marine drive units lack compact, streamlined dimensions and high reliability, particularly in hybrid propulsion systems with electric machines, and do not offer a wide range of applicability.
Innovation Solution
A hybrid pod drive assembly with a horizontal drive shaft connected to a vertical shaft via clutches, incorporating two coaxial electric machines and counter-rotating propellers, optimized for compactness and reliability, with independent control systems for each electric machine and a streamlined pod housing for efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hybrid propulsion system with multiple electric machines is implemented, then reliability and operational flexibility are improved, but device complexity increases
Solution Approach 1:
The drive assembly is segmented into multiple independent electric machines (first and second electric machines with first and second rotor shafts) that can operate independently or in combination. This segmentation allows the system to maintain reliability through redundancy while managing complexity by modularizing the electric propulsion components.
Solution Approach 2:
The electric machines serve multiple functions: they can operate as motors to drive propellers, as generators during regenerative braking, and provide backup power capability. The clutch mechanisms enable the same drive shaft to connect to different power sources (combustion engine or electric machines) based on operational requirements, enhancing versatility without proportionally increasing complexity.
2Shape
If a compact pod drive assembly with streamlined dimensions is designed, then hydrodynamic efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The first propeller shaft is nested within the second propeller shaft in a coaxial arrangement, with the first rotor shaft connected to the first propeller shaft and the second rotor shaft connected to the second propeller shaft. This nested configuration achieves compact, streamlined dimensions that improve hydrodynamic efficiency while maintaining manufacturability through standardized concentric mounting procedures.
Solution Approach 2:
The transition from a conventional horizontal propeller shaft arrangement to a vertical shaft with coaxial propeller shafts represents a dimensional reorganization. This vertical orientation with nested coaxial shafts creates a more compact footprint and streamlined external dimensions, reducing hydrodynamic drag while the modular clutch-and-gear interface maintains ease of assembly and manufacturing.
3Productivity
If counter-rotating propellers are used to improve propulsion efficiency, then power transmission complexity increases
Solution Approach 1:
The lower transmission unit employs asymmetric gear arrangements where the first bevel gear and second bevel gear are positioned at different locations along the vertical shaft, with the first bevel gear engaging a crown gear to drive the first propeller shaft, and the second bevel gear directly driving the second propeller shaft. This asymmetric configuration enables counter-rotating propellers that improve propulsion efficiency by canceling torque reactions, while the modular gear design keeps power transmission complexity manageable through standardized components.
Data Source
Figure 1
AI summary
A hybrid pod drive assembly (1) comprising a horizontal drive shaft (4) which can be driven by a combustion engine (2) and which is connectable to a vertical shaft (6). The hybrid pod drive assembly (1) comprising a lower transmission unit (7) to transmit the power from the vertical shaft (6) to at least a first propeller shaft (12). The hybrid pod drive assembly (1) further comprising a first electric machine (10) with a first rotor shaft (11) which is coaxial with the first propeller shaft (12) and connected to the first propeller shaft (12). The hybrid pod drive assembly (1) further comprising a second electric machine (20) with a second rotor shaft (21) which is coaxial with a second propeller shaft (22) and connected to the second propeller shaft (22). The second propeller shaft (22) is surrounding the first propeller shaft (12). A rear propeller (13) is mounted to a trailing end of the first propeller shaft (12) and a front propeller (23) is mounted to a trailing end of the second propeller shaft (22). The invention further relates to a corresponding hybrid pod drive (102).