Design of the optimized and downsized axial fan for the air carrier orchard sprayers

The new vineyard and orchard installations are made with a high intensity of plants per hectare and therefore with a reduced distance between the rows. The tractors and the air carrier sprayers for plant protection, must therefore have smaller width. In consequence, a method of design of axial fans for the air carrier sprayer, to get a small diameter without losing the performance required by the agrochemical applications, must also be studied. The new method was found by imposing a law of Compound Vortex for the tangential component of absolute air speed. In consequence the equations for: the axial component of the absolute air velocity, the flow rate, the total specific energy and the invariance of the lift coefficient versus the radius, were found. Then, the method consists in the solution of the system of these four equations to determine the fan design parameters. This new method allows to obtain a reduction of the external diameter of the fan by a factor of 0.8 and a reduction of the lift coefficient because imposed constant vs. the radius. Therefore the new method may allow to further increase the total specific energy. Finally, there was no significant difference between the average speed, relative to airfoils, of the new method (Compound Vortex) and of the traditional method one (Free Vortex) and then there are no downgrades in the fluid dynamic efficiency.