AdjiE Propeller - Fin Propeller

Fin Propeller is screw propeller which have been modified by enhancing two fin on each of back of propeller blade. Its purpose is to improve thrust power by the propeller performance. According to blade element and propeller momentum theory, adding of the fin could increase the fluid flow Va at the back of propeller blade so the pressure goes down. So theoretically, Fin propeller can produce thrust bigger than original screw propeller. Hence, the ship running faster. The basic function of this propeller is the ship’s owners can speed up their ship without changing the engine.

This propeller created by lecture of Marine Engineering Sepuluh Nopember Institute of Technology – Surabaya, Indonesia.
Together with his students, execute his first experiment in year 2004. The experiment result prove that using the fin propeller make the ship run up to 20% faster than using original screw propeller. However, this adding of the fins cause the fuel oil consumption of the ship increase because of propeller load. Because of that case, this research still being developed mathematically and computerized.

Blade Element Theory
Forces that happened at foil yielded by fluid flow phenomenon that is changing of kinetic energy and momentum. At foil, the velocity of fluid flow on backside is faster than on faceside. According to law of bernoully, that will cause pressure on face go up and pressure on back go down so that lift of force happened.

To Fin propeller, adding of fin will cause increasing fluid flow Va on backside so the pressure goes down.

Propeller Momentum Theory
According to this theory, thrust yielded by working of propeller in water caused by the existing of difference of momentum so propeller efficiency depend on blade loading. This drawing below show that a propeller moving forward in water where the water moveless.

So force reaction generated by the propeller to the fluid or Thrust (T) is proportion with increasing of the pressure (P) multiplied by surface of propeller discus (Ao):
T = P. Ao
P = P1 – P2
Where,
P1 = Pressure on face side
P2 = Pressure on back side

In Fin propeller, the pressure on backside (P1) goes down so the pressure difference between face and back (P’) increase.
P’ = P1-P’2

So
T’ = P’. Ao

And,
T’ > T

P’2 = Pressure on back side have decreased.
T’ = Thrust at Fin propeller

Summary,

Fin Propeller produce Thrust higher than Original Propeller.