Marine Vessel Propulsion Thrust Control for Cavitation Reduction
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Solution Overview
Problem
Marine vessel propulsion systems face challenges with cavitation during reverse gear operations, leading to increased noise and fuel consumption, especially during low-speed maneuvers like docking and sway maneuvers, where precise control of thrust is required to minimize accelerations and jerk levels.
Innovation Solution
A method for controlling marine vessels with multiple propulsion units involves adjusting the thrust of each unit to ensure smooth transitions and balanced thrust delivery, where one unit increases thrust while another decreases, maintaining overall thrust consistency and reducing engine speed to mitigate cavitation and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the engine for the reversing propulsion unit is controlled at a relatively high rotational speed to match the thrust of the forwarding propulsion unit and compensate for cavitation loss, then the thrust matching is improved, but the noise level and fuel consumption increase
Solution Approach 1:
The propulsion units are divided into independent controllable segments, allowing individual thrust adjustment. The control system segments the thrust delivery across multiple propulsion units, enabling one unit to operate at lower speed while another compensates, thereby reducing overall energy consumption while maintaining total thrust.
Solution Approach 2:
The control system dynamically changes operational parameters (rotational speed, thrust level) of individual propulsion units based on real-time conditions. By adjusting parameters optimally for each unit rather than running all units at high speed, the system achieves thrust matching with reduced fuel consumption.
2Force
If the engine for the reversing propulsion unit is controlled at a relatively high rotational speed to match the thrust of the forwarding propulsion unit and compensate for cavitation loss, then the thrust matching is improved, but the noise level increases
Solution Approach 1:
The propulsion system is segmented into independently controllable units, allowing the control system to distribute thrust requirements across multiple units. This segmentation enables operation at lower rotational speeds for individual units, thereby reducing noise while maintaining total thrust through coordinated control.
Solution Approach 2:
The control system dynamically adjusts operational parameters of propulsion units to optimize performance. By changing parameters such as rotational speed and thrust distribution based on real-time conditions, the system achieves thrust matching with minimized noise generation.
3Force
If a propeller is rotated in the opposite direction for reverse gear operation, then the reverse thrust is achieved, but cavitation occurs due to blade profiles interacting with water in an unintended manner
Solution Approach 1:
Instead of rotating propellers in reverse direction which causes cavitation, the system inverts the approach by using forward-rotating propellers on multiple propulsion units and controlling their thrust vectors. The propellers maintain their designed rotation direction while achieving reverse thrust through coordinated control of multiple units with different thrust directions.
Solution Approach 2:
The control system changes operational parameters including rotation direction and thrust magnitude of individual propulsion units. By adjusting parameters optimally, the system achieves reverse thrust while maintaining propeller rotation in the designed direction, thereby avoiding cavitation.
4Force
If the thrust delivered by the second propulsion unit is increased by engaging gear, then the reverse thrust is enhanced, but sudden changes in thrust occur causing high accelerations and jerk levels
Solution Approach 1:
The control system performs preliminary actions by pre-positioning propulsion units and gradually adjusting their thrust before full engagement is needed. This preliminary control of thrust buildup prevents sudden changes and ensures smooth acceleration transitions when gear is engaged or disengaged.
Solution Approach 2:
The control system dynamically adjusts thrust delivery in real-time based on operational conditions. By continuously monitoring and adjusting thrust parameters, the system smooths out sudden changes that would occur with discrete gear engagement, maintaining accelerations within acceptable limits.
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 approach reduces accelerations and jerk levels during low-speed maneuvers by ensuring continuous and smooth thrust delivery, minimizing cavitation and engine noise, and optimizing fuel efficiency.
Implementation Method 1
cavitation typically occurs on the propulsion unit with reverse gear engaged... the cavitation may occur at propellers of the propulsion units... the cavitation may result in a 'grip' of the propellers in the water being reduced
Data Source
AI summary
The invention provides a method for operating a marine vessel (1) comprising a plurality of propulsion units (106, 107, 108, 206, 207, 208), each being arranged to deliver thrust to water in which the vessel (1) is floating, the thrust delivery levels of the propulsion units (106, 7, 108, 206, 207, 208) being individually controllable, the method comprising controlling (S2) a first (106, 207) of the propulsion units so as to deliver a thrust in a direction (T106, T207) which has a component in a first direction (F) of the vessel, simultaneously controlling (S2) a second (107, 208) of the propulsion units so as to deliver less thrust than the first propulsion unit (106, 207), and subsequently increasing (S4) the thrust delivered by the 10 second propulsion unit (107, 208) in a direction (T107, T208) which has a component in the first direction (F), the method further comprising simultaneously with increasing the thrust delivered by the second propulsion unit (107, 208) decreasing (S5) the thrust delivered by the first propulsion unit (106, 207).