Propeller blade selection
The propeller strikes a balance between processing difficulty, production cost, static and dynamic balance and propulsion efficiency，There are few high-speed blades and many low-speed blades.
1. At low speed, the more blades of the propeller, the higher the efficiency of kinetic energy conversion. Most submarines use 7 blades to improve propulsion efficiency at low speed and reduce noise.
2. High speed, on the contrary, the fewer the number of blades, the turbulence of the blades will affect each other-reduce the efficiency-theoretically the single blade is the best-but in terms of balance adjustment, axial pressure balance, etc., a blade is required The number of leaves increases.
In order to eliminate the resonance between the blades, most of the propellers are prime number of blades: 3, 5, 7 blades (there used to be submarines with 11 blades), but partly considering the cost and efficiency factors, 4 blades are also selected paddle. Among commercial-grade underwater propellers, most of the three-blade propellers are considered high-speed propellers, and the five-blade propellers are mostly used in large ships, and most of them are low-speed propellers.
