Combined Propeller Cap Reducing Hub Vortex Cavitation
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Solution Overview
Problem
Existing propeller cap designs, such as the PBCF, are difficult and expensive to manufacture due to precise machining requirements for small fins, and they do not efficiently reduce hub vortex cavitation, leading to noise, vibration, erosion, and corrosion issues while increasing fuel consumption.
Innovation Solution
A combined propeller cap structure is introduced, where a diffusion type cap is coupled with a contraction type cap, and plate-shaped guide fins are added to the contractive or diffusive sections, simplifying the design and reducing manufacturing costs while effectively reducing hub vortex cavitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a PBCF with multiple small fins is used to reduce hub vortex, then hub vortex cavitation is reduced, but manufacturing difficulty and cost increase due to precise machining requirements
Solution Approach 1:
The invention extracts and eliminates the complex fin structure from the propeller boss cap design. Instead of attaching multiple small fins that require precise machining, the patent uses a simple cap structure with a specific height-to-diameter ratio (0.28-0.76 times the propeller diameter) that reduces hub vortex cavitation through its geometric form alone, thereby simplifying manufacturing while maintaining effectiveness.
Solution Approach 2:
The invention replaces the expensive, precisely-machined PBCF with a simpler, more economical cap structure. The new design uses standard machining processes without requiring precise fin attachment, making it cheaper and easier to manufacture while still achieving the goal of reducing hub vortex cavitation.
2Object-affected harmful factors
If a PBCF with multiple small fins is used to reduce hub vortex, then hub vortex cavitation is reduced, but manufacturing cost increases due to precise machining
Solution Approach 1:
The invention removes the expensive fin components from the design, keeping only the essential cap structure. By relying on the cap's geometric dimensions (height of 0.28-0.76 times the propeller diameter) rather than complex fins, the design achieves cavitation reduction at lower manufacturing cost.
Solution Approach 2:
The invention substitutes the costly PBCF with an economical cap structure that can be manufactured using standard machining processes. The simplified design eliminates the need for precise fin attachment, significantly reducing manufacturing cost while maintaining the ability to reduce hub vortex cavitation.
3Object-affected harmful factors
If a diffusion type propeller cap is used, then hub vortex cavitation is reduced, but propulsive efficiency decreases
Solution Approach 1:
The invention optimizes the critical parameter of cap height, setting it to 0.28-0.76 times the propeller diameter. This specific range balances two opposing effects: reducing hub vortex cavitation (by having sufficient height) while minimizing propulsive efficiency loss (by not excessive height). The optimized parameter range achieves both goals simultaneously.
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 combined cap design enhances propulsive efficiency, reduces noise and vibration, prevents erosion and corrosion, and saves fuel by efficiently managing hub vortex cavitation at a lower manufacturing cost compared to traditional PBCF designs.
Implementation Method 1
the propulsive efficiency is improved by pressure recovery due to the shape from the propeller to the contractive sections at the middle portion
Implementation Method 2
pressure of a flow passing the propeller cap from the propeller is recovered by the contractive section, so the propulsive efficiency is improved
Implementation Method 3
rotational flow (vortex) of a flow from the propeller is weakened by the second diffusive section, so hub vortex cavitation is reduced
Implementation Method 4
rotational flow by rotation of the propeller is changed into a straight flow in a rotational axial direction, so the hub vortex cavitation is further reduced
Implementation Method 5
the propeller cap reduces noise and vibration in a vessel by decreasing hub vortex cavitation behind a propeller
Data Source
Figure 1(a)~1(c)
Figure 2
Figure 3a
AI summary
The present invention relates to the structure of a propeller cap. According to the present invention, in order to solve the problem with the existing PBCF (Propeller Boss Cap Fin) whereby manufacturing is difficult expensive due to precise machining, there is provided a combined propeller cap for reducing rotational flow and hub vortex and improving propulsive efficiency, the combined propeller cap being capable of reducing hub vortex cavitation that is generated behind a propeller by using a structure in which a diffusion type propeller cap is coupled to the end of a contraction type propeller cap, and being capable of additionally reducing the hub vortex cavitation by attaching guide fins at a contractive section or between the contractive section and a diffusive section of the propeller cap.