Asymmetric Pre-nozzle for Ship Propulsion Efficiency
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Solution Overview
Problem
Existing propulsion systems for ships, particularly slow-moving vessels like tankers and tugs, face inefficiencies in propeller inflow and energy loss due to uneven water flow speeds caused by ship hull design, leading to reduced propulsion efficiency and increased energy consumption.
Innovation Solution
A rotationally asymmetrical fore-nozzle design with an integrated fin system is positioned ahead of the propeller, featuring a non-circular water inlet and outlet, and an asymmetric fin arrangement to generate pre-swirl and optimize water flow, addressing the uneven wake areas and reducing vortex generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional propeller system is used without pre-nozzle, then the structure is simple, but the propulsion efficiency is reduced due to uneven water flow speeds caused by ship hull design
Solution Approach 1:
The pre-nozzle is positioned upstream of the propeller to pre-condition the water flow before it reaches the propeller. The asymmetric fin system within the pre-nozzle generates pre-swirl and redistributes water flow velocities, creating optimized inflow conditions in advance. This preliminary action addresses the uneven wake distribution caused by the ship hull, improving propeller efficiency without requiring changes to the propeller itself or the ship hull.
2Loss of energy
If a symmetrical pre-nozzle design is used, then the manufacturing is easier, but the energy losses are increased due to inability to address uneven wake areas
Solution Approach 1:
The pre-nozzle employs an asymmetric design with non-circular water inlet and outlet openings, and an asymmetric fin arrangement within the nozzle. This asymmetry is specifically configured to counteract the uneven wake distribution pattern generated by the ship hull. The asymmetric geometry enables differential flow control in different angular positions, optimizing water flow distribution to the propeller and reducing energy losses that would occur with a symmetrical design.
Solution Approach 2:
The asymmetric fin system within the pre-nozzle provides localized flow control at different angular positions. Each fin is positioned and dimensioned to address specific local wake conditions in different sectors of the flow field. This local quality approach allows targeted correction of uneven wake areas, with different parts of the pre-nozzle performing different flow conditioning functions to minimize overall energy loss.
3Productivity
If the pre-nozzle is positioned close to the propeller, then the flow optimization is more effective, but the vortex generation increases
Solution Approach 1:
The pre-nozzle is positioned at an optimized distance upstream of the propeller, allowing sufficient space for the asymmetric fin system to generate pre-swirl and condition the flow before it reaches the propeller. This preliminary flow conditioning at a distance reduces the intensity of vortices that would form if the pre-nozzle were positioned too close, while still maintaining effective flow optimization at the propeller inlet.
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 design enhances propeller inflow efficiency, reduces energy losses, and allows for increased thrust with the same or reduced power, improving overall propulsion efficiency and energy savings, especially in areas with unfavorable wake conditions.
Implementation Method 1
thanks to the fins or hydrofoils integrated into the fore-nozzle, to reduce losses in the propeller jet caused by pre-swirl generation
Implementation Method 2
The inlet region of the pre-nozzle does not have a fin system and serves exclusively to accelerate the water flow
Data Source
Figure 1~3
Figure 4~6
Figure 7~9
AI summary
In order to further improve the propulsion efficiency of a propeller-less pre-nozzle (10a, 10b, 10c) for a propulsion system of a watercraft, which pre-nozzle has a water inlet opening (12) and a water outlet opening (13), in the interior of which a fin system (14) is arranged, and whose inlet region does not have a fin system (14), it is proposed to design the pre-nozzle (10a, 10b, 10c) in a rotationally asymmetric manner.