Marine Propulsion Mode Switching for Low-Speed Electric Cruising
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Solution Overview
Problem
Existing marine propulsion systems with both engine and electric motor power sources face challenges in optimizing performance across varying speed ranges, particularly in enhancing merchantability by efficiently switching between power sources during idling and low-speed operations.
Innovation Solution
A marine propulsion system comprising a propeller shaft, engine, electric motor, battery, and controller that allows switching between multiple drive modes, where mechanical power is transmitted solely from the engine at high speeds and solely from the electric motor at low speeds when the engine is idling, with the controller managing the transition to prevent electric power shortages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the engine is used to drive the propeller shaft at high speeds, then the propulsion power is sufficient, but the fuel consumption increases and the system cannot operate efficiently at low speeds
Solution Approach 1:
The propulsion system is segmented into two independent power sources: an engine for high-speed operation and an electric motor for low-speed operation. The controller divides the operating range into high-speed and low-speed zones, selecting the appropriate power source based on the required propulsion power, thereby avoiding fuel consumption during low-speed operations while maintaining sufficient propulsion power when needed
Solution Approach 2:
The system dynamically switches between engine-driven and electric motor-driven modes based on real-time operating conditions. The controller monitors the required propulsion power and automatically transitions between power sources, enabling the system to adapt its energy usage to match the actual propulsion needs, thus optimizing fuel consumption across varying speed ranges
2Use of energy by moving object
If the electric motor is used to drive the propeller shaft at low speeds, then the fuel consumption is reduced, but the system may experience electric power shortages
Solution Approach 1:
The system performs preliminary charging of the battery during engine operation at high speeds. The controller manages the battery charge state by utilizing excess engine power to charge the battery when the vessel is operating at higher speeds, ensuring that sufficient electric power is available for subsequent low-speed operations, thereby preventing electric power shortages
Solution Approach 2:
The controller continuously monitors the battery charge state and adjusts the operating mode accordingly. When the battery charge level drops below a predetermined threshold during electric motor operation, the controller transitions to engine-driven mode to recharge the battery, creating a feedback loop that maintains reliable electric power supply while optimizing fuel consumption
3Adaptability or versatility
If the system switches between engine and electric motor drive modes, then the versatility across speed ranges is improved, but the device complexity increases
Solution Approach 1:
The propeller shaft serves as a universal transmission element for both the engine and the electric motor. The same propeller shaft receives mechanical power from either the engine or the electric motor depending on the operating mode, eliminating the need for separate transmission systems and reducing overall device complexity while maintaining versatility across speed ranges
Solution Approach 2:
The controller acts as an intermediary that manages the switching between engine and electric motor drive modes. By centralizing the control logic in a single controller that monitors operating conditions and manages power source selection, the system achieves complex multi-mode operation without proportionally increasing 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
This configuration enhances the merchantability of the marine propulsion system by enabling efficient power utilization across speed ranges, allowing extended low-speed cruising and reducing fuel consumption by utilizing the electric motor during idling engine states.
Implementation Method 1
The battery supplies an electric power to the electric motor
Implementation Method 2
a mechanical power source for rotating a propeller shaft of a watercraft (Japan Laid-open Patent Application Publication No. 2013-147186)
Data Source
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AI summary
A marine propulsion system includes a marine propulsion device, a battery and a controller. The marine propulsion device includes a propeller shaft, an engine and an electric motor. The marine propulsion device transmits mechanical power from at least one of the engine and the electric motor to the propeller shaft. The battery supplies electric power to the electric motor. The controller controls the marine propulsion device such that the marine propulsion device is switchable among a plurality of drive modes including a first drive mode and a second drive mode. The first drive mode brings about a state where the mechanical power is transmitted from only the engine to the propeller shaft. The second drive mode brings about a state where the mechanical power is transmitted from only the electric motor to the propeller shaft when the engine is in an idling state.