Coaxial Shaft Azimuth Thruster Torque Segmentation
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Solution Overview
Problem
Azimuth thruster systems, such as Z-drive and L-drive, face challenges in maintaining orientation and agility due to unwanted torque and mechanical stress, inefficiencies in energy use, and limitations in dynamic maneuvering, especially with low-speed high-torque prime movers, which increase hydrodynamic drag and risk damage to electrical prime movers.
Innovation Solution
The system employs two primary prime movers inside the hull to cooperatively control both the angular speed of the propeller and the azimuth of the pod, using coaxially arranged shafts and bevel gears to efficiently manage torque and reduce mechanical stress, allowing for agile dynamic maneuvering and reducing the power capacity needed in each transmission path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single power drive train from a prime mover to a propeller is used, then the structure is simplified, but unwanted torque is imposed onto the pod making it difficult to maintain or change orientation
Solution Approach 1:
The single drive train is segmented into two separate drive trains, each with its own prime mover. One prime mover (first drive train) is dedicated to driving the propeller, while the other prime mover (second drive train) is dedicated to controlling the azimuth of the pod. This segmentation eliminates the unwanted torque coupling between propeller drive and azimuth control, allowing independent optimization of each function.
2Ease of operation
If an independent azimuth control system is used to counteract unwanted torque, then azimuth control capability is improved, but energy is wasted continuously generating counteracting torque
Solution Approach 1:
The azimuth control function is extracted from the propeller drive system and assigned to a dedicated prime mover. The second prime mover exclusively controls the azimuth by applying torque only to the pod through the second drive train, without needing to counteract propeller drive torque. This extraction eliminates the continuous energy waste associated with generating counteracting torque in integrated systems.
3Stress or pressure
If multiple prime movers are employed to distribute torque burden, then the torque burden is reduced, but agility in dynamic azimuth maneuvering decreases due to limited available power and high gear ratio
Solution Approach 1:
The torque burden is segmented between two prime movers, but the azimuth control prime mover (second prime mover) is specifically optimized for agility with dedicated power and direct drive. This segmentation allows the second prime mover to have sufficient power reserve for rapid azimuth changes without being constrained by the high gear ratios needed for propeller drive, thus maintaining maneuvering agility while distributing the overall torque burden.
4Use of energy by moving object
If a low speed/high torque prime mover is used to drive the propeller shaft, then propeller drive efficiency is improved, but the burden of the azimuth control system increases
Solution Approach 1:
The propeller drive function is segmented into a dedicated first drive train with a prime mover optimized for high torque and low speed operation. This dedicated propeller drive system can use a low speed/high torque prime mover efficiently without imposing torque burden on the azimuth control system, because the azimuth control is handled by a separate second prime mover through the second drive train. The segmentation isolates the high torque requirements from the azimuth control path.
5Adaptability or versatility
If a high speed and low torque prime mover is used with bevel gears for torque amplification, then the prime mover selection is flexible, but the pod becomes voluminous increasing hydrodynamic drag
Solution Approach 1:
The drive system is segmented into two independent paths, allowing each prime mover to be optimized for its specific function. The first prime mover (propeller drive) can be compact because it directly drives the propeller without needing large torque amplification gears. The second prime mover (azimuth control) can be sized appropriately for its lower power requirements. This segmentation eliminates the need for a single oversized pod to accommodate both functions, reducing hydrodynamic drag while maintaining prime mover selection flexibility.
Data Source
AI summary
An azimuth thruster system includes a pod configured to rotate relative the hull of the ship about an azimuthal axis of the pod, a propeller shaft extending from the pod and being configured to rotate relative to the pod about a central axis of the propeller shaft, an outer shaft disposed at least partially in the pod and configured to be driven by a first primary prime mover, an inner shaft disposed at least partially within the outer shaft and configured to be driven by a second primary prime mover, and a pod gear unit disposed within the pod and coupled to the outer shaft, the inner shaft, and the propeller shaft. The outer and inner shafts are configured to rotate at least one of the pod and the propeller shaft based on directions and magnitudes of the torques generated by the first and second primary prime movers.