The tunnel sprayer is made of two vertical concave
shields with opposite concavity, with the function of
capturing the liquid o!-target and two basal collectors
from where it is sent back to the tank. The shields enclose
the canopy on two sides and are connected by a roof that
closes the upper side of the chamber as shown in Fig. 1.
Each shield is divided along its vertical axis by a separation
wall supporting two 600 mm diameter axial fans,
powered by hydraulic motors. They produce an air
stream directed against a vertical boom with eight #atfan
nozzles, spaced at 0)45 m intervals.
During operation, the fans rotate at 167 rad s~1 and
globally produce an air#ow rate of 11 m3 s~1 at an average
velocity of about 8 ms~1 at the nozzles. The power
consumption at the power take o! of the entire equipment,
including the pump of the sprayer, is about 16 kW.
The two shields are supported by a frame linked to
a trailed carrier on which the components of the
sprayer are mounted (membrane pump, tank, constant
pressure regulator and hydraulic motor for operating the
fans).
The reciprocal position of the shields is adjustable
with an hydraulic system to "t the thickness of the
plants and to simplify the manoeuvres and the turns.
The same circuit allows the folding of the shields behind
the tank to reduce the width of the machine during the
transport.
The equipment can be classi"ed as an air circulation
tunnel sprayer with recovery of surplus spray. The peculiarity
of the system is an internal air circulation which
has the function of keeping the spray in the space occupied
by the foliage until it is intercepted either by the
leaves or by the shields and the collectors. In other words,
the concept is that no external air is forced to enter the
chamber and no air is pushed out.
This equipment was compared in the "eld trials with
a classical trailed air-blast sprayer without de#ectors
with a 900 mm diameter axial fan, rotating at
1600 min~1 and producing an air#ow rate at an outlet of
10 m3 s~1 in the trial conditions. These settings were
chosen according to the structure of the vegetation and
were obtained at 420 min~1 of the power take o!. There
are 16 hydraulic hollow-cone nozzles shared, as usual,
between two half-booms. The nozzles have di!erent #ow
rates to achieve a vertical distribution as uniform as
possible.