US2016319836A1PendingUtilityA1
Axial flow fan with blades twisted according to a blade pitch ratio that decreases (quasi) linearly with the radial position
Est. expiryDec 17, 2033(~7.4 yrs left)· nominal 20-yr term from priority
Inventors:Karl Erik Widell
F04D 29/545F04D 29/384F04D 29/36F04D 19/002F04D 29/386
23
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Claims
Abstract
An axial flow fan has a hub, an annular shroud extending concentric with the axis of the hub, and a number of fan blades connected at a root end to the hub and having a free tip end extending radially towards the shroud. The blades are designed so that the fan in operation at nominal operating conditions generates a fluid flow in the immediate vicinity after the blades, which includes a core flow that is substantially a forced vortex flow where the tangential flow speed component (c 2,u ) is proportional with the radial distance (r) from the axis. Equations define the chord angle θ of the blades.
Claims
exact text as granted — not AI-modified1 . An axial flow fan comprising;
a hub rotatable about an axis, an annular shroud extending concentric with said axis in a radial distance from said hub, a plurality of fan blades connected at a root end to said hub and having a free tip end extending radially towards said annular shroud, a fan driver coupled to said hub and arranged for driving a rotation of said hub around the axis, wherein an angle Δθ between a chord of the blade at any radial position in a radial range from the hub to a radial position of r/R=0.3 and a chord at the radial position of r/R=0.3 substantially follows a curve defined as
Δ
θ
=
arctan
(
1.2
R
r
-
0.2
π
)
-
50.4
°
where R is a radial distance from the axis to the free tip end of the blade, and r is a radial distance from the axis to the radial position.
2 . The fan according to claim 1 , wherein the angle Δθ between the chord of the blade in the radial range from the hub to the radial position of r/R=0.4 and the chord at the radial position of r/R=0.4 substantially follows the curve defined as
Δθ
=
arc
tan
(
1.2
·
R
r
-
0.2
π
)
-
41.7
°
3 . The fan according to claim 1 , wherein the angle θ between a plane of a rotation of the blades and the chord of the blade at the radial position of r/R=0.3 is in a range of 40 to 60.
4 . An axial flow fan 04 comprising;
a hub rotatable about an axis,
an annular shroud extending concentric with said axis in a radial distance from said hub,
a plurality of fan blades connected at a root end to said hub and having a free tip end extending radially towards said shroud,
a fan driver coupled to said hub and arranged for driving a rotation of said hub around the axis,
wherein an angle θ between a direction (M) of a rotation of the blades and a chord of the blade at all positions along a radial extent of the blade substantially follows a curve defined as
θ
=
arctan
⌊
1
15
π
2
Flow
nD
3
[
1.46
r
R
+
0.564
·
r
R
-
0.77
]
⌋
where R is a radial distance from the axis to the free tip end of the blade, r is a radial distance from the axis to the radial position, Flow is a nominal flow for the fan given in [m 3 /h], D=2·R is a rotor diameter given in [m] and n is a nominal rotational speed of the fan given in [rpm].
5 . An axial flow fan comprising;
a hub rotatable about an axis, an annular shroud extending concentric with said axis in a radial distance from said hub, a plurality of fan blades connected at a root end to said hub and having a free tip end extending radially towards said shroud, a fan driver coupled to said hub and arranged for driving a rotation of said hub around the axis, wherein the blades are designed so that the fan when in an operation at nominal operating conditions generates a fluid flow in an immediate vicinity after the blades which comprises a core flow that is substantially a forced vortex flow where a tangential flow speed component (c 2,u ) is proportional with the radial distance (r) from the axis.
6 . The fan according to claim 5 , wherein the core flow extends to a radial distance (r) of at least 0.2 times of the radial distance (R) from the axis to the free tip end of the blades.
7 . The fan according to claim 5 , wherein the fluid flow in the immediate vicinity after the blades outside the core flow is substantially a free vortex flow where the tangential flow speed component (c 2,u ) is inversely proportional with the radial distance (r) from the axis to the radial position, whereas an axial flow speed component (c 2,a ) is substantially constant.
8 . (canceled)
9 . The fan according to claim 1 , wherein an inner radius of the annular shroud is in a range of 600 to 1500 millimetres.
10 . The fan according to claim 1 , wherein a radius (R hub ) of the hub is in a range of 50 to 75 millimetres.
11 . The fan according to claim 1 , comprising a diffuser arranged concentric with said axis at a downstream position of the annular shroud.
12 . The fan according to claim 11 , wherein the diffuser has a conical shape with a diffusion angle in a range of 2 to 15° to the axis of rotation of the rotor.
13 . The fan according to claim 1 , comprising an inlet part provided with a bell-mouth arranged concentric with said axis at an upstream position of the annular shroud.
14 . An axial flow fan comprising;
a hub rotatable about an axis, and at least one fan blade connected at a root end to said hub and having a free tip end extending radially away from said axis, the hub comprising a seating part-allowing the blade or blades to be arranged in a plurality of blade pitch angles and blade locking part for locking the blade pitch angle of the at least one blade into a specific blade pitch angle, wherein said locking part is designed to lock said blade into one specific blade pitch angle only.
15 . The fan according to claim 14 , comprising one locking part for each of the blades.
16 . The fan according to claim 14 , wherein the blades each comprises a recess cooperating with a corresponding pin of the locking part.
17 . (canceled)
18 . The fan according to claim 1 , wherein the angle θ between a plane of a rotation of the blades and the chord of the blade at the radial position of r/R=0.3 is in a range of 45 to 55°.
19 . The fan according to claim 5 , wherein the core flow extends in a range of 0.2 to 0.3 times of said radial distance (R).
20 . The fan according to claim 11 , wherein the diffuser has a conical shape with a diffusion angle in a range of 6 to 10° to the axis.Join the waitlist — get patent alerts
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