Gate Rudder Propeller Clearance Layout for Cavitation Control
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Solution Overview
Problem
Existing gate rudder technologies fail to achieve sufficient rudder force for straight travel, leading to high energy consumption and cavitation erosion, while requiring large steering machinery for smaller rudder areas.
Innovation Solution
A gate rudder design with a first rudder portion extending horizontally and a second rudder portion extending vertically, optimized rudder shaft placement, and clearance between the propeller and rudder, along with torsion angles, to enhance Coanda and USB effects for reduced energy consumption and prevent cavitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the clearance between the propeller and the left and right rudders is set to be small in order to increase the efficiency of the propeller, then the propeller efficiency is improved, but cavitation erosion easily occurs on the inner faces of the left and right rudders
Solution Approach 1:
The patent applies local quality by giving different clearance distances to different parts of the rudder system. Specifically, the clearance between the propeller and the inner faces of the rudders is set to a larger value (0.05D to 0.15D) to prevent cavitation erosion, while the clearance at the tips of the rudders is set to a smaller value (0.01D to 0.05D) to maintain propeller efficiency. This localized differentiation of clearance parameters allows the system to simultaneously achieve both goals.
2Area of moving object
If the area of the rudder is made smaller than that in the related art, then the rudder area is reduced, but a large torque is generated and substantially the same capacity of the steering machine as in the related art is required
Solution Approach 1:
The patent transitions from a conventional single-plane rudder to a three-dimensional gate rudder structure with rudders positioned on both sides of the propeller. This spatial reconfiguration in multiple dimensions allows the rudder area to be reduced while the forces are distributed across both left and right rudders, thereby reducing the torque on each individual rudder and enabling the use of a smaller steering machine.
3Reliability
If the gate rudder is designed to move behind the propeller when the ship is stopped, then the stopping performance is improved, but sufficient rudder force due to the Coanda effect and the USB effect cannot be obtained when the ship travels straight
Solution Approach 1:
The patent implements a dynamic gate rudder system where the rudders can change their position relative to the propeller based on operational requirements. During straight travel, the rudders are positioned to maximize exposure to the propeller jet for optimal Coanda effect and USB effect, generating sufficient rudder force. When stopping is required, the rudders move behind the propeller to improve stopping performance. This dynamic adaptability allows the system to optimize performance for different operational states.
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
The design generates large thrust forces for forward motion, minimizes torque, and prevents cavitation, optimizing steering machine capacity and reducing energy consumption.
Implementation Method 1
a large rudder force due to the Coanda effect generated at the front portion of the second rudder portion of the rudder
Implementation Method 2
a large rudder force due to the USB effect generated at the rear portion
Data Source
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AI summary
To provide a gate rudder capable of reducing energy consumption during a voyage of a ship. A gate rudder including a pair of rudders including a left rudder and a right rudder disposed left and right, respectively, of a propeller at a stern, wherein each of the rudders includes a first rudder portion extending in a horizontal direction and a second rudder portion linearly extending in a vertical direction in rear view, wherein a rudder chord length of the second rudder portion in a front-rear direction is 40 to 100% of a diameter of the propeller, wherein the propeller is provided within a range of 15 to 650 of the rudder chord length from a front edge of the second rudder portion in side view, and wherein a rudder shaft that drives each of the rudders is provided at a position within a range of 30 to 500 of the rudder chord length from the front edge of the second rudder portion in side view.