By Alice | 12 February 2022 | 0 Comments

How to confirm the propeller blades number?

Firstly we should know,to choose the suitable propeller not to choose the more blades for your propeller.
Generally speaking: When design a propeller, first determine the rated speed and diameter according to external conditions, such as thrust and power. After the diameter is determined, to minimize the extension area within a certain range, then it will be the higher efficiency. After the extension area is determined, the more the number of blades within a certain range, the higher the efficiency of the propeller.
In fact, 4-blade propellers are widely used in general ships,
And noise-sensitive submarines use 7-blade propellers in order to reduce vibration noise.
 
A propeller with more blades can provide more thrust when the engine speed is the same, but it will increase the load of the engine. In the later period, the engine power will become larger and more blades can be driven. By a nozzle can make the propeller work more efficiently. It will make the efficiency increase 14%, but this kind of propeller cost is too high and maintenance and repair are too expensive.that is why more customers will not choose this kind of propeller with nozzle.
 
Sinooutput service many customers, especailly some Europ and south America customers like the propeller with nozzle:

No matter what kind of propeller, we need firstly to design it according to your boat.
When designing a propeller, Sinooutput designers will take consideration a variety of parameters, which respectively express different directions required by the design, such as the wake fraction and thrust deduction fraction, and the interaction between the ship and the propeller, and the number of cavitation is the blade void. A quantitative indicator of bubble performance. Mainly analyze the influence of parameters such as diameter, pitch, chord length, pitch, and side slope on propeller thrust, efficiency, cavitation, vibration, noise and other performance.
 
The diameter of the propeller is very important factor
 
When the propeller rotates on the spot, the trajectory of the blade tip is called slightly rounded, and its diameter is the diameter of the propeller, denoted by D. In the preliminary design of the propeller, first select one of the diameter and the speed, and then determine the best value of the other parameter through the atlas method. In the circulation t-heory design method, the diameter is specified based on design experience or ship type.
Generally speaking, the larger the diameter of the propeller, the lower the speed, the higher the efficiency, but when the diameter is too large, the average wake at the blade disc surface will decrease, resulting in a drop in hull efficiency and possibly lower overall propulsion efficiency. In addition, to choose the propeller diameter must consider the ship's draft and the ship's stern frame clearance. For ships that often sail under ballast, a smaller diameter can take care of the efficiency of ballasting and prevent the blade tip from coming out of the water; from the perspective of vibration, the propeller The gap between the hull and the hull should not be too small, otherwise it may cause the vibration of the hull stern structure.
 
We Sinooutput Group O., LTD. In 2019 year sold 6 propellers with 5 blades to one of South America customers for their tug boat, and in 2021 he new tug boat building choose all 4 blades number of propeller although with the same diameter. Do you know why? If you want to make sure your exact propeller, please kindly contact Sinooutput now, to find your suitable propeller.
 

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