Please enable JavaScript.
Coggle requires JavaScript to display documents.
Constructional Details (1/2) - Coggle Diagram
Constructional Details (1/2)
Number of Blades
Usually 3 or 4
More blades
Interference BTW blades
near hub
Blades with higher aspect ratio
Smaller Chord length
Larger thickness
Lift-to-drag ratio will decrease
Better efficiency if
isolated blade have same lift-drag ratio
Balanced by reduced blade efficiency
Increased Speed and Power
Of ships
Need to increase
Blade Area
Delay onset of cavitation
Results in increase
in hull-vibration
due to periodic forces
blade numbers as solution
reduces thrust per blade
Reduce intensity o forces
Increase frequency
helps to avoid resonance
Blades and Hubs
Solid
Blades cast integral with hub
Built-up
Bolted to hub
Advantages
Small adjustment in pitch
Blades easily replaced
Disadvantages
Higher Cost
Greater weight
Smaller efficiencies due to larger hub
Hub
Types
Cylindrical
Conical in outline
Diameter
BTW 0,15D and 0,25D