Ship Propulsion System Using Direct Electrical Drive
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Solution Overview
Problem
Cargo ships with multi-propeller drives face inefficiencies due to mechanical, electrical, and hydrodynamic losses, particularly in complex drive concepts with multiple propellers, which increase manufacturing costs and fuel consumption, and are limited by structural constraints.
Innovation Solution
A cargo ship with a main propulsion system where a single heat engine drives one propeller mechanically and another electrically via a direct electrical connection, eliminating the need for complex transmission shafts and allowing for a larger, more efficient engine, reducing losses and simplifying design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple propellers are used to increase propulsion area, then hydrodynamic efficiency is improved, but device complexity and mechanical losses increase
Solution Approach 1:
The propulsion system is segmented into two independent drive trains, each with its own propeller. The first drive train is mechanically coupled to the heat engine output shaft, while the second drive train is electrically coupled through a traction current generator and electric traction motor. This segmentation allows each propeller to be driven independently, providing flexibility in propulsion while reducing the complexity of transmitting power to multiple propellers from a single engine.
Solution Approach 2:
The second drive train replaces the traditional mechanical transmission system with an electrical system. Instead of using complex mechanical shafts and gears to transmit power from the heat engine to the second propeller, the patent uses a traction current generator to convert mechanical energy to electrical energy, which is then transmitted via electrical lines to an electric traction motor. This substitution reduces mechanical losses and simplifies the transmission system.
2Productivity
If multiple smaller propulsion motors are used, then propulsion area is increased, but specific fuel consumption increases
Solution Approach 1:
The patent merges the propulsion functions into a single heat engine that drives both drive trains. The first drive train is mechanically coupled to the heat engine output shaft, while the second drive train uses a traction current generator coupled to the same output shaft. This merging allows the use of a single larger heat engine instead of multiple smaller engines, which generally results in lower specific fuel consumption due to better operating efficiency and reduced total mechanical losses.
3Productivity
If a reduction gear is used between motors and propeller, then propulsion area is increased, but mechanical losses increase
Solution Approach 1:
The patent replaces the mechanical reduction gear system with an electrical system for the second drive train. The traction current generator converts mechanical energy to electrical energy, which is then transmitted to the electric traction motor. This eliminates the need for mechanical reduction gears, thereby reducing mechanical losses associated with gear friction and meshing inefficiencies.
4Device complexity
If a single heat engine drives both propellers mechanically, then device complexity is reduced, but power transmission requirements increase
Solution Approach 1:
The patent uses a traction current generator to convert mechanical power to electrical power, which can then be transmitted to the second propeller through electrical lines. This approach reduces the mechanical power transmission requirements from the heat engine, as the electrical system can more efficiently transmit power over distances and to different locations on the vessel.
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 enables higher efficiency, reduced fuel consumption, and lower maintenance costs by utilizing a single larger engine, minimizing mechanical and electrical losses, and providing symmetrical propulsion for improved stability.
Implementation Method 1
a traction current generator (41) driven by the heat engine for generating electrical power
Implementation Method 2
an electric traction motor (43) for driving the propeller shaft (21) of the second drive train (2)
Data Source
Figure 1~2
Figure 3~4
AI summary
A cargo ship with a multi-propeller drive as the main propulsion system, comprising at least two drive trains (1, 2), each with a propeller (12, 22) and a propeller shaft (11, 21) that mechanically drives the propeller. According to the invention, the drive trains (1, 2) are jointly driven by the same heat engine (3). A first drive train (1) is mechanically driven and mechanically coupled to an output shaft (31) of the heat engine (3). A second drive train (2) is electrically driven by means of a direct electrical connection (4), which comprises a traction current generator (41) coupled to the output shaft (31) and an electric traction motor (43) that drives the second propeller shaft (21) of the second drive train (2). The traction current generator (41) and the electric traction motor (43) are connected to one another via a direct electrical line (42). The direct connection (4) does not require a frequency converter and is therefore efficient.Thanks to the electrical power transmission to the second drive train (2), a single heat engine is sufficient, eliminating the need for complex and efficiency-reducing transmission shafts. This increases efficiency and facilitates space-saving installation of the components.