External Vessel Propulsion Unit with Hull-Housed Drive Machinery
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Solution Overview
Problem
Conventional propulsion systems for vessels are space-intensive, costly, and difficult to retrofit, with complex mechanical systems that are vulnerable to breakdowns and maintenance challenges, especially in harsh conditions like ice operations.
Innovation Solution
A compact propulsion system with drive machinery housed within the vessel's hull, using a short propeller shaft with fewer bearings and no angle gear, allowing for easy servicing and retrofitting, and featuring fixedly mounted propulsion units that divert water flow to ensure uniform propeller operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional propulsion system with prime mover and propeller shaft is used, then reliable propulsion is achieved, but cargo capacity is reduced due to space requirements
Solution Approach 1:
The drive machinery (prime mover and/or generator) is extracted from the hull interior and relocated to an external propulsion unit mounted on the hull. This extraction removes the space-consuming components from the cargo area, thereby increasing cargo capacity while maintaining the propulsion function through the externally mounted unit connected via a short propeller shaft.
2Reliability
If a long propeller shaft extending through the hull is used, then propulsion function is achieved, but maintenance cost increases due to multiple bearings
Solution Approach 1:
The propeller shaft is extracted from its conventional long configuration extending through the hull and replaced with a short shaft connecting the external propulsion unit to the propeller. This dramatically reduces the number of bearings required (from multiple to just one), thereby reducing maintenance costs and complexity while maintaining the essential propulsion function.
3Ease of operation
If azimuth thrusters with rotatable pods are used, then manoeuvrability is improved, but system vulnerability increases due to mechanical complexity
Solution Approach 1:
The complex azimuth thruster mechanism with rotatable pods and angle gears is replaced by extracting the drive machinery to an external fixed mounting. The propulsion unit remains fixed in position, eliminating the need for complex rotation mechanisms and angle gears, thereby reducing mechanical complexity and system vulnerability while maintaining propulsion capability.
Solution Approach 2:
Instead of making the propeller assembly rotatable (azimuth thruster approach), the invention inverts the approach by making the drive machinery external and fixed, while keeping the propeller shaft and propeller in a fixed position relative to the hull. This inversion eliminates the need for complex rotation mechanisms.
4Volume of moving object
If azimuth thrusters are used, then cargo space is preserved, but accessibility for repair becomes difficult as components are not accessible at sea
Solution Approach 1:
The drive machinery is extracted to an external propulsion unit mounted on the hull, making all components (prime mover, generator, propeller shaft) externally accessible. This allows maintenance and repair to be performed at sea without requiring docking, while the unit can be removed and serviced onshore if needed, combining the space benefits with improved accessibility.
5Volume of moving object
If a compact propulsion system with external drive machinery is used, then cargo capacity is increased, but system complexity must be managed
Solution Approach 1:
The prime mover and generator are merged into a single integrated propulsion unit mounted externally on the hull. This consolidation reduces the number of separate components and connections required, thereby managing system complexity while achieving the space benefits of having drive machinery outside the cargo area.
Solution Approach 2:
The external propulsion unit is designed as a multi-functional assembly that combines the prime mover, generator, and propeller shaft connection in a single integrated package. This universal unit performs multiple functions (power generation, power transmission, propulsion) while occupying minimal space, thereby managing overall system complexity.
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
The system is simple, reliable, fuel-efficient, and cost-effective, with increased cargo capacity and reduced maintenance needs, enabling operation in harsh conditions without the need for frequent docking.
Implementation Method 1
The propeller (48) is used for applying thrust to the propulsion unit (30), thereby for propelling the hull (10)
Implementation Method 2
the leading edge (36) is configured such that the distance from any part of the leading edge (36) to the centre line is larger than the distance between the propeller shaft (46) and the centre line
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
The present invention provides a propulsion system for a vessel such as a service vessel or supply vessel. The vessel has a hull (10) with a midship portion (12) and a stern portion (14). The propulsion system comprises two propulsion units (30, 30^) fixedly mounted to the hull (10) on opposite sides of a centre line of the hull (10) at the stern portion (14), each of the propulsion Units (30, 30·.) comprising a housing carrying a propeller (48) externally of the housing. The housing further defines an interior vol¬ ume in which a drive machinery (52, 54, 56) is provided for driving the propeller 48 via a propeller shaft (48), the interior volume being open to the interior of the hull (1.0). A vessel comprising the propulsion system and a method of retrofitting a hull (10) with the propulsion system are also provided.