....
A
further solution finally consists in providing only the aerial part of
the rope with a sheath made of plastic material that is aerodynamically
profiled.
A completely new solution instead consists in manufacturing only the second sector 5 of the rope 3,
usually circular, in order to assign it an elongated section, with a
ratio between loner axis and shorter axis ranging between 1.5 and 5.
This is technically possible, though the resulting section has not yet
the desired aerodynamic features. An improvement of the aerodynamic
features can be obtained by winding the rope 3 manufactured
with an elongated section with a braid and filling the recesses with
low-density material in order to obtain an elliptical section.
Alternatively, it is possible to extrude along the rope 3,
manufactured with an elongated section, a sheath made of plastic
material and flexible, in order to obtain an elliptical section. A
further great improvement with respect to this solution however
consists in using, in place of the single rope 3, two or
more ropes with different diameter that are mutually placed in
parallel, so that the sum of the resisting sections of the single
ropes 3 is equal to the resisting section adapted to
support the mechanical stresses provided when designing. By suitably
filling the recesses between the ropes 3 with
different diameter with low-density material, it is possible to assign
a wing-shaped profile to the section, in which the rope 3 with greater diameter will occupy the area with maximum thickness (FIG. 4 b). The multiple rope 8 profiled in this way, as shown for example in FIGS. 4 a, 4 b and 5, can be coated with a woven protecting braid suitable to take part in the global mechanical resistance.
Alternatively, the multiple rope 8 profiled
in this way can be covered with a flexible sheath made of plastic
material in order to reduce its surface roughness to a minimum.
Alternatively, the rope itself can be woven in order to obtain an aerodynamic section.
Alternatively, the rope can be woven according to traditional
methodologies, then annealed into a plastic or elastomeric material and
deformed under pressure in order to obtain an aerodynamic section.
The possible protecting braid made of fabric or the possible sheath
made of plastic material can be interrupted at regular intervals (such
as shown, for example, in FIG. 5),
leaving the single rope or the set of multiple ropes composing the
global rope, free of flexing, in order to increase the flexibility of
the aerial part of the rope and facilitate the re-winding on the winch
drums.
Moreover,
taking into account the different flight speeds to which different
areas of the aerial part of the profiled rope move with respect to air,
the chosen wing profile can have different geometric, and therefore
aerodynamic, features in different areas of the aerial part of the rope.
Profiling
the rope according to shapes that are different from the circular
section, however, implies the occurrence of instability phenomena
similarly to what occurs for aircraft wings. In fact, we know that the
elliptical profiles and the symmetric wing profiles are unstable,
namely a positive variation of the incidence angle generates an
aerodynamic moment that tends to further increase the incidence angle,
till the profile is oriented orthogonal to the current. This behaviour
can obviously induce separations of the slipstream, resistance increase
and aero-elastic instability of the rope as a whole.
For this reason, with particular reference to FIGS. 2, 4 a, 4 b, 5, 6 and 7, another preferred embodiment of the rope 3according to the present invention can comprise a second sector 5 equipped
with real tail planes, similarly to those used by aircrafts, that are
able to balance the aerodynamic moment generated by incidence
variations on the rope and guarantee a stable behaviour. With reference
therefore in particular to FIG. 2, it is possible to note that another preferred embodiment of the rope 3 according to the present invention for a tropospheric aeolian generator 1 is further composed, in length, of at least one third sector 6, such third sector 6 being equipped with a profiled section 9 such that its own transverse section has an aerodynamic resistance coefficient CD3 preferably included between 1.2 and 0.05, still more preferably between 0.6 and 0.05 so that CD3<CD1; moreover, such third sector 6 can be equipped with stabilising tail planes 10 in such a number and placed at such mutual distance as to guarantee the global rope stability.
With reference to FIGS. 5 and 6, the tail planes 10 are preferably constrained to the third sector 6 of the rope 3 through at least one hinge 12 and one pin 13 that, allowing the rotation of the tail planes 10 around an orthogonal axis to the axis of the rope 3, guarantee an ordered rewinding of the third sector 6 of the rope 3 including the tail planes 10 on the collecting drum of the rope 3 during the landing procedure. Preferably, the hinge is constrained to the profiled section 9 through at least one strap 11. As shown in FIG. 7, the tail planes 10 can rotate around the axis of the hinge 12 in order to be re-bent towards the rope 3.
The number and the mutual position of the tail planes 10 will obviously depend on the aerodynamic features of the rope 3 and the maximum speed of the rope 3 with respect to air, choosing the solution that guarantees the stability of the rope 3 under all operating conditions and the minimum additional aerodynamic resistance due to the tail planes 10.
The tail planes 10 can
be finally constrained to the aerial part of the rope, or can be
fastened to the cable automatically with a clip-type mechanism upon
starting up the generator and slowly unwinding the aerial part of the
rope; similarly, they can be disconnected when rewinding the aerial
part of the cable and stopping the generator.
If the tail planes 10 are
finally constrained to the aerial part of the rope, they must be able
to be wound onto the collecting winches integrally with the rope during
the limited takeoff and landing phases.
It has been found that, by constraining the tail planes on the hinge 12 next to the escape edge of the aerodynamically profiled section 9, it is possible to make the tail planes 10 bend next to the winch drums and be orderly arranged on the collecting drum.
It is clear that the tail planes 10 can be more easily wound on the last, more peripheral, rope layer wound on the collecting drum.
In order to guarantee the correct orientation of the tail planes 10 during the flight phases, it has been found that a spring, for example a torsion spring, placed next to the hinge 12 and with enough stiffness as to keep in position the tail planes 10 in spite of the action of the aerodynamic forces, can efficiently solve this technical problem.
As
already stated, the innovations brought about by the present invention
can be profitably used by any tropospheric or high-altitude aeolian
generator.
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