Integral Bulb Rudder Propulsion Efficiency
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Solution Overview
Problem
Current ship propulsion systems, such as those with screw propellers, face inefficiencies that result in high fuel consumption and compromised maneuverability, despite efforts to combine propellers with streamlined bodies like bulbs for improvement.
Innovation Solution
A rotary propeller with a twisted rudder and an integral streamlined bulb, where the bulb is separated from the propeller by a hub cap, enhancing efficiency by reducing rotational losses and cavitation, and the rudder's twist aligns with water flow to recover kinetic energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a bulb is placed behind the propeller to improve efficiency, then propeller efficiency increases, but the maneuverability may be compromised due to the additional structure
Solution Approach 1:
The patent combines the bulb and rudder into a single integrated structure where the bulb is formed as part of the rudder assembly. This merging allows the bulb to improve propeller efficiency while the rudder portion maintains maneuverability, as the same structure serves both functions simultaneously.
Solution Approach 2:
The rudder is divided into multiple segments including the bulb portion, main rudder blade, and stub rudder. This segmentation allows each part to perform its specific function optimally - the bulb for efficiency and the rudder blades for maneuverability - while working together as a unified system.
2Ease of operation
If the rudder is made larger to improve maneuverability, then side force increases, but steering gear torque increases
Solution Approach 1:
The bulb is designed with a streamlined, curved shape that optimizes water flow around it. This curvature reduces rotational losses and cavitation, allowing the bulb to generate sufficient side force for maneuverability without requiring excessive rudder area that would increase steering gear torque.
Solution Approach 2:
The patent optimizes specific parameters of the bulb including its diameter (1-40% greater than propeller hub diameter), length, and position behind the propeller. These parameter optimizations allow the bulb to achieve maximum efficiency and maneuverability with minimal steering gear torque requirements.
3Productivity
If the bulb is made larger to reduce rotational losses, then efficiency improves, but the gap between bulb and propeller increases
Solution Approach 1:
The patent optimizes the bulb diameter parameter to be 1-40% greater than the propeller hub diameter, which maximizes the bulb's ability to reduce rotational losses while maintaining an appropriate gap distance. This parameter optimization balances efficiency improvement with hydrodynamic considerations.
Solution Approach 2:
The bulb is designed to extend slightly beyond the propeller hub diameter (1-40% greater), which provides excessive action in terms of coverage, but this is optimized to reduce rotational losses while maintaining the gap at a functional distance for hydrodynamic performance.
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 increases propeller efficiency by up to 5%, directly reducing fuel consumption and improving maneuverability without increasing steering gear torque.
Implementation Method 1
sea water pressed backwards by the propeller will flow around the bulb
Implementation Method 2
the rudder's twist aligns with water flow to recover kinetic energy
Data Source
Figure 1
Figure 2
Figure 3~7
AI summary
The invention relates to a steering and propulsion arrangement for a ship. The inventive steering and propulsion arrangement comprises a screw propeller 3 and a rudder 6. A streamlined propulsion bulb 10 is made integral with or fixedly connected to the rudder. The invention also relates to a ship 2 provided with the inventive arrangement.