Field of the Art
[0001] The present invention relates to air blower fans and in particular to radial type
fans, proposing a fan unit equipped with a centrifugal impeller having a structural
formation that provides a functional advantage in efficiency in relation to the air
flow that is driven and the electrical energy consumption to drive this flow, where
the air flow can be determined from the energy consumption of the motor driving the
centrifugal impeller, without the need to use external sensors.
State of the Art
[0002] Radial fan units are know, which include a centrifugal impeller that is rotationally
driven by a motor, such that on rotating said centrifugal impeller drives an air flow
from a central interior opening and projects it outwards to the periphery; for this
purpose the centrifugal impeller is equipped with a set of blades arranged around
the central interior opening to radially extract air from said central interior opening
and project it outwards to the periphery.
[0003] In said centrifugal impellers the position and configuration of the blades are fundamental
factors in determining the air driving capacity of the centrifugal impeller, which
therefore decisively affects the performance of the fan unit; consequently said factors
are essential in the structural design of centrifugal impellers.
[0004] To this regard, centrifugal impellers with blades that curve forward are conventionally
known, where the air driving blades are uniformly arranged in an inclined position
in the direction of rotation and with respect to the radial direction of the centrifugal
impeller, with an arched configuration in the transverse direction from the inner
edge to the outer edge according to the position of the centrifugal impeller, the
blades having a convex configuration positioned towards the outer periphery of the
centrifugal impeller.
[0005] In centrifugal impellers with blades that curve forward, the air flow measurement
is obtained directly by measuring the energy consumption of the motor driving the
centrifugal impeller and according to the characteristic flow/energy consumption curve
of the fan unit. Although centrifugal impellers of this type allow the air flow to
be measured directly based on the energy consumption of the motor, they have a low
efficiency in terms of flow/pressure with respect to the energy consumption driving
the centrifugal impeller.
[0006] On the other hand, centrifugal impellers with blades that curve backward are known,
where the blades driving the air are also uniformly arranged in an inclined position
in the direction of rogation and with respect to the radial direction of the centrifugal
impeller, with an arched configuration in the transverse direction from the inner
edge to the outer edge according to the position of the centrifugal impeller, but
in this case the blades have a convex configuration positioned towards the inner periphery
of the centrifugal impeller.
[0007] In this embodiment external flow measurement sensors are needed to measure the air
flow that is driven by the centrifugal impeller, increasing the complexity and cost
of the fan unit. This is because when using centrifugal impellers of this type with
blades that curve backward, air flow cannot be measured directly based on the measurement
of the energy consumption of the motor driving the centrifugal impeller, as the characteristic
flow/energy consumption curve of centrifugal impellers of this type has a maximum
point, such that for the same energy consumption there are two different operational
flow rates, it being impossible to determine which flow rate the fan unit is operating
at, external sensors therefore being required.
Object of the Invention
[0008] The invention proposes a fan unit with a radial configuration incorporating a centrifugal
impeller developed with a structural formation presenting features for driving air
that are advantageous in terms of efficiency, allowing the air flow to be measured
indirectly based on the energy consumption of the fan unit without the need for external
sensors.
[0009] The fan unit comprises a casing with a central interior opening which is provided
with a centrifugal impeller rotationally driven by a motor. The centrifugal impeller
has a set of blades arranged around the central interior opening, and inclined with
respect to the radial direction of the centrifugal impeller. The centrifugal impeller
has an inner edge adjacent to the central interior opening and an outer edge on the
periphery of the centrifugal impeller.
[0010] According to the invention, the blades have an arched configuration extending transversely
between the inner edge adjacent to the central interior opening and the outer edge
arranged on the periphery of the centrifugal impeller, the blades having a convex
configuration positioned towards the inner part of the centrifugal impeller.
[0011] The fan unit additionally comprises measurement means configured to measure the air
flow driven by the centrifugal impeller based on the energy consumption of the motor.
[0012] In particular, the transversely arched configuration of the blades has a curvature
with a radius comprised between half and double the radius of the centrifugal impeller,
which has proved in experiments to result in an air flow that favors the flow-energy
consumption combination, such that better performance is achieved with respect to
that of conventional centrifugal impellers with blades having a more pronounced curvature,
with a radius of at least 85 millimeters, which are also more costly to manufacture.
[0013] A fan unit is thereby attained with a centrifugal impeller in which the structural
features of the configuration of the blades determine conditions rendering the functional
air driving behavior more efficient in comparison with air driven by conventional
centrifugal impellers, improving the performance of the fan unit.
[0014] Thus, the fan unit object of the invention presents a centrifugal impeller resulting
in features giving it its own identity and making it preferable with respect to other
fan units with conventional impellers for the same application.
Description of the Drawings
[0015]
Figure 1 shows a section view of the fan unit of the invention.
Figure 2 shows a perspective view of a centrifugal impeller with the features of the
invention.
Figure 3 is a front view of said centrifugal impeller from Figure 2.
Figure 4 is a diametrical section view of the centrifugal impeller according to section
IV-IV noted on Figure 3.
Figure 5 is a partial enlarged view of the centrifugal impeller according to section
V-V noted on Figure 4.
Figure 6 shows a comparative graph with the characteristic flow/energy consumption
curves of the fan unit of the invention, a conventional fan unit with a centrifugal
impeller with blades that curve forward and a conventional fan unit with a centrifugal
impeller with blades that curve backward.
Detailed Description of the Invention
[0016] The object of the invention relates to a fan unit with a radial configuration incorporating
a centrifugal impeller with a structural formation that improves the efficiency and
performance of fan units incorporating conventional centrifugal impellers for the
same application.
[0017] As observed in the section view in Figure 1, the fan unit comprises a casing (1)
in which there is arranged or directly built a volute-type air duct (2) having a central
interior opening (3) which is provided with a centrifugal impeller (4) rotationally
driven by a motor (5), specifically a brushless electric motor. The air is taken in
through one of the sides of the fan unit towards the central interior opening (3)
in the direction axial to the centrifugal impeller (4), and the air is let out in
the direction radial to the centrifugal impeller (4) through the fan unit discharge
outlet (6).
[0018] The centrifugal impeller (4) comprises two annular elements (7) and (8) that are
axially arranged parallel to one another, blades (9) arranged around the central interior
opening (3) being intercalated between the annular elements (7) and (8), and the centrifugal
impeller (4) having an inner edge (10) adjacent to the central interior opening (3)
and an outer edge (11) arranged on the periphery of the centrifugal impeller (4).
The blades (9) extend from the central interior opening (3) of the centrifugal impeller
(4) to the outer periphery of the centrifugal impeller (4), in an inclined position
with respect to the radial direction of the centrifugal impeller (4) and according
to a tangential arrangement with respect to the central interior opening (3).
[0019] According to the present invention, the blades (9) have an arched configuration extending
transversely between the inner edge (10) adjacent to the central interior opening
(3) and the outer edge (11) on the periphery of the centrifugal impeller (4), the
blades (9) having a convex configuration positioned towards the inner part of the
centrifugal impeller (4).
[0020] The fan unit additionally comprises measurement means associated with the motor (5)
driving the centrifugal impeller (4), said measurement means being particularly configured
to measure the air flow driven by the centrifugal impeller (4) based on the energy
consumption of the motor (5).
[0021] In addition, the transversely arched configuration of the blades (9) is based on
a curvature with a radius (r) comprised between half and double the radius (Rr) of
the centrifugal impeller (4), i.e., the curvature of the radius (4) of the blades
(9) is comprised in the range [0.5*Rr < r < 2*Rr]. This selection of the radius together
with the structural configuration of the blades (9) defined by the invention allows
improved behavior of the fan unit to be achieved as shown in the experimental results
in Figure 6.
[0022] Said Figure 6 shows a comparative graph with three characteristic flow (Q)/energy
consumption (Wa) curves. The first curve (C
0) drawn in a solid line shows the characteristic curve of a conventional fan unit
with a centrifugal impeller with blades that curve backward; the second curve (C
1) drawn in a line with dots shows the characteristic curve of the fan unit of the
invention; the third curve (C
3) drawn in a dashed line shows the characteristic curve of a conventional fan unit
with a centrifugal impeller with blades that curve forward.
[0023] From the comparison between the second and third curves (C
2, C
3), it can be observed that for the same flow rate, the energy consumption of the fan
unit of the invention is much lower than the energy consumption of a conventional
fan unit with a centrifugal impeller with blades that curve forward. On the other
hand, the first curve (C
0) reaches a maximum point (M) after which the energy consumption goes from increasing
to decreasing, and therefore, there are two different flow rates for the same energy
consumption of the motor driving the centrifugal impeller. This particularity of the
first curve (C
0) characteristic of a conventional fan unit with blades that curve backward makes
it impossible for the flow rate to be measured directly based on the energy consumption,
which means that external flow rate sensors are needed for efficient measurement.
However, the second curve (C
1) characteristic of the fan unit of the invention always shows increasing energy consumption
as the driven air flow is increased, such that a specific air flow value always unequivocally
corresponds to a specific energy consumption value.
[0024] Accordingly, the configuration of the blades (9) of the centrifugal impeller (4)
of the invention allows the functional behavior of the fan unit to be improved, achieving
a suitable driven air flow-energy consumption ratio, as with conventional fan units
provided with blades that curve backward. In addition, operating conditions are achieved
in which the driven air flow always increases as energy consumption increases, as
with conventional fan units provided with blades that curve forward, such that air
flow can be measured precisely and reliably based on the energy consumption without
having to use external sensors such as those required for equivalent conventional
fan units with blades that curve backward.