Modeling aerial screw propeller in heliciel Modeling ship screw propeller heliciel Modeling aeraulic screw propeller heliciel
screw propeller Thruster propulsion
Left behind because it seemed overwhelmed by the reactors or jets ,with the search for energy saving, the propeller of the boat and aircraft becomes again a technical solution leading. The reactor was a symbol of power and modernity but its low efficiency (20 to 30 % max)is a fact and the propeller comes to the front of the stage with 80 to 95 % efficiency for the contra rotating propeller

contra rotating propeller

Before discussing the characteristics of marine or air screw propellers, introduce some concepts that will help us better understand the functioning of propulsive screw propellers (aircraft, ships, ventilation)

helice bateau

A ship screw propeller, an aircraft screw propeller or fan ventilation, have different forms , because the implantation constraints, and the ambient fluid are different, but the principles generate the propulsive force, explained here, are identical..

helice avion

Whatever the fluid air or water, the propeller uses the phenomenon of reaction to apply thrust to the vehicle. The force applied to the fluid is equal and opposite to the force applied to the axis of the propeller.
As Newton explained to us, the force is equal to the product of the mass per acceleration F= M x A
The thrust force will be proportional to the mass of the accelerated fluid. To generate the same force we can:: varaition de quantité de mouvement provoqué par l'hélice
Accelerate slightly a large amount of fluid. Propeller large size generating little lift on the blade surface) this case corresponds to a propeller lightly loaded. Greatly accelerate a small amount of fluid. (Propeller small size generating a lot of lift on the surface of the blade) this case corresponds to a heavily loaded propeller.

masse importante petite accéleration grande accéleration petite masse

In your opinion, who will waste the most energy in leakage around the surface, transmitting force to the fluid? one who rowing at high speed with a teaspoon, or one who chose the pizza shovel? You choose what, instinctively without thinking?

 

grande masse de fluide avec grande accélération

There is a cheat, he rowed at high speed with a pizza shovel!

All that to say that the greater the propeller, the less there will be leaks, and the better you will. This applies to ship screw propeller, aircraft screw propellers or fan ventilation. A further more theoretical point of view, but very important, allows us to evaluate the profitability of our effort relative to the speed of movement: the propulsive efficiency

see also: rotation speed, fluid speed and screw propeller diameter: