Fan blade

Abstract

The invention relates to a fan blade (1) comprising a hub (2) having an axis of rotation (XR) and blades (3) extending generally radially outward from the hub (2), each blade (3) being defined by a span (EN), a leading edge (BA), and a trailing edge (BF), wherein the blade (3) is further defined by a stack of aerodynamic profiles (PA) constructed according to a thickness law (LE1) around a neutral line (FN) connecting the leading edge (BA) to the trailing edge (BF) of the blade (3), wherein the neutral line (FN) is characterised by a parameter called the chord length (LC), representing the distance between the two ends of the neutral line (FN), wherein the thickness law (LE1) represents the progression of the profile thickness along the neutral line (FN), and wherein the thickness law exhibits a variation in the spanwise direction (EN), so as to form, on the blade (3), at least two thickness undulations (3) spaced apart from one another in the spanwise direction (EN).

Description

[0001] Fan propeller

[0002] [1] The present invention relates to a fan propeller, in particular an axial type fan. The fan is in particular configured to be integrated into a front cooling module of a thermal or electric vehicle.

[0003] [2] The present invention aims in particular to reduce the noise in such a fan, without impacting the aeraulic performance of the fan.

[0004] [3] The invention thus relates to a fan propeller comprising a hub having an axis of rotation and blades extending generally radially outwards from the hub, each blade being defined by a span, a leading edge and a trailing edge, the blade being further defined by a stack of aerodynamic profiles constructed with a thickness law around a neutral fiber connecting the leading edge to the trailing edge of the blade, the neutral fiber being characterized by a parameter called chord length representing the distance between the two ends of the neutral fiber, the thickness law representing the evolution of the thickness of the profile along the neutral fiber, the thickness law having a variation in the span direction so as to form on the blade at least two thickness undulations which are spaced from each other in the span direction.

[0005] [4] In the invention, in a way, a thickening or thinning coefficient is controlled on each section (of the aerodynamic profile) which makes up the blade, so as to form undulations when moving from one aerodynamic profile to another.

[0006] [5] Thus the thickness undulations are here due to an alternation, in the spanwise direction, of thinned sections which define low points of the undulations, and thickened sections which define high points of the undulations.

[0007] [6] The applicant has found that the undulation(s) on the blade provide an acoustic and aerodynamic gain. In particular, the invention allows a reduction in the acoustic level without impact on the aeraulic performance and without modification of the manufacturing process. In particular, the undulations provide flow consistency by reducing the aeraulic radial effects. The explanation for the performance gain can be explained in particular by the fact that the boundary layer can be better maintained on the profile, which causes less separation likely to cause a loss of aeraulic performance and which reduces the acoustic fluctuations generating noise.

[0008] [7] It is recalled that the neutral fiber passes through the center of the blade profile, between the leading edge and the trailing edge. The aerodynamic profile corresponds in particular to a circular section of the blade at a given radius, a section obtained by intersection at a given radius with a geometric cylinder of the same axis as the axis of rotation of the propeller.

[0009] [8] The airfoils of the stack may be the same or variable.

[0010] [9] The term "blade span" refers in particular to the length of the blade measured in a plane perpendicular to the axis of rotation of the propeller, on a straight line passing through the axis of rotation and expressed as a percentage. The value 0% corresponds in particular to a point of contact of the blade with the hub (point called blade root) and the value 100% corresponds to a point of contact of the blade with a rim (point called blade tip). The expression "in the direction of the span" refers in particular to the direction which goes from the blade root to the blade tip.

[0011]

[0010] The law of thickness on the neutral fiber is here taken with the following conventions, in the case where the intrados and the extrados are symmetrical to each other: on the abscissa, is the position of the point considered along the neutral fiber expressed as a percentage of the length of the neutral fiber, with 0% when it is the point on the leading edge and 100% when it is the point on the trailing edge, and on the ordinate, we read the thickness of the blade, on one side of the neutral fiber, expressed as a percentage of the chord length, namely the ordinate is determined by a ratio of the chord length to a given radius. The thickness is measured by taking the neutral fiber as Zero reference. For example, the profile of the extrados is defined by the evolution of the thickness along the neutral fiber, this thickness being the distance measured between the neutral fiber and the extrados.

[0012]

[0011] It is possible to have a thickness law to define the intrados of the blade. The thickness is, in this case, the distance between the neutral fiber and the intrados.

[0013]

[0012] It is possible to have a thickness law for the extrados and another thickness law for the intrados.

[0014]

[0013] According to one aspect of the invention, the undulation can be defined, in the spanwise direction, by a low point surrounded by two high points. The low point of the undulation is in particular on a thinned section of the blade and the high point is on a thickened section of the blade.

[0015]

[0014] The amplitude of the undulation is the difference in thickness between the low point and the high point of the undulation, at a given location on the span.

[0016]

[0015] According to one aspect of the invention, this plurality of undulations on the main face (extrados or intrados) has identical thickness amplitudes at least for some of the undulations.

[0017]

[0016] According to another aspect of the invention, the plurality of undulations on the main face (extrados or intrados) have all different thickness amplitudes.

[0017] According to one aspect of the invention, at least some of the undulations on the main face (extrados or intrados) have thickness amplitudes which increase as they approach the blade head. In particular, the undulations have thickness amplitudes which increase as they approach the blade head.

[0018]

[0018] According to one aspect of the invention, the undulation(s) have, depending on the size, a sinusoidal or pseudo-sinusoidal shape.

[0019]

[0019] The undulations are notably contained between two envelope curves, notably polynomial type curves.

[0020]

[0020] According to one aspect of the invention, the undulation comprises a groove which extends substantially transversely to the span of the blade, in particular along a neutral fiber of the blade.

[0021]

[0021] According to one aspect of the invention, the undulations are parallel to each other.

[0022]

[0022] According to one aspect of the invention, the undulations are parallel to the neutral fibers of the blade.

[0023]

[0023] According to one aspect of the invention, the undulations are inclined to form a positive spiral or a negative spiral on the blade.

[0024]

[0024] In the case of a positive spiral, the radius increases as one progresses along the propeller blade. This means that the point on the propeller blade gradually moves away from the central axis.

[0025]

[0025] In contrast, in the case of a negative spiral, the radius decreases as one moves along the propeller blade. This means that the point on the propeller blade gradually moves closer to the central axis.

[0026]

[0026] According to one aspect of the invention, the undulations are present only on a portion of the span of the blade. In other words, the undulations are not present over the entire span, from the blade root to the blade tip. Thus, over a portion of the span, the blade is devoid of undulations, the thickness of the blade then being given by the usual thickness laws, without application of a thickening or thinning coefficient to these sections.

[0027]

[0027] According to one aspect of the invention, the undulations are present over at most 80% of the length of the span of the blade, in particular over at most 60% or 50% of the length of the span of the blade.

[0028]

[0028] According to one aspect of the invention, the undulations only begin beyond the first 20%, or 40%, or 50% of the span length, starting from the blade root.

[0029] Thus, in an area adjacent to the blade root, there are no undulations.

[0029]

[0030] For example, each blade includes a local area with a series of grooves or undulations, and the rest of the blade outside this area has no undulations and may have a relatively smooth curvature.

[0030]

[0031] According to one aspect of the invention, each undulation extends, like a groove, from the leading edge to the trailing edge.

[0031]

[0032] According to one aspect of the invention, only the extrados or the intrados has one or more undulations. The other main face is free of undulations.

[0032]

[0033] Alternatively, both the extrados and the intrados have one or more undulations.

[0033]

[0034] In this case, the undulations on the extrados and intrados can be symmetrical to each other with respect to the neutral fiber, or alternatively, be asymmetrical.

[0034]

[0035] According to one aspect of the invention, the number of undulations is between 3 and 15, for example between 3 and 8.

[0035]

[0036] According to one aspect of the invention, all the blades of the propeller are provided with undulations according to the invention.

[0036]

[0037] According to one aspect of the invention, the blades join, at their blade head, a rim which is axisymmetrical with the hub.

[0037]

[0038] The invention also relates to an electric fan, in particular for a motor vehicle, comprising a propeller as mentioned above.

[0038]

[0039] Other characteristics, details and advantages of the invention will emerge more clearly on reading the description which follows on the one hand, and several examples of embodiment given for informational and non-limiting purposes with reference to the appended schematic drawings on the other hand, in which:

[0039]

[0040] [Fig. 1] Figure 1 is a representation of a propeller according to an exemplary embodiment of the invention;

[0040]

[0041] [Fig. 2] Figure 2 is a sectional view of a blade of the propeller of Figure 1;

[0041]

[0042] [Fig. 3] Figure 3 shows a curve illustrating the variation of the thickness law applied to the blades of the propeller of Figure 1;

[0042]

[0043] [Fig. 4] Figure 4 is a representation of a blade with its characteristic elements;

[0043]

[0044] [Fig. 5] Figure 5 is a sectional representation of a blade with these characteristic elements;

[0045] [Fig. 6] Figure 6 shows a curve illustrating a simple thickness law;

[0044]

[0046] [Fig. 7] Figure 7 shows undulations inclined to form a positive spiral;

[0045]

[0047] [Fig. 8] Figure 8 shows ripples inclined to form a negative spiral.

[0046]

[0048] The features, variants and different embodiments of the invention may be combined with each other in various combinations, provided that they are not incompatible or mutually exclusive. In particular, variants of the invention may be conceived comprising only a selection of features described below in isolation from the other features described, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0047]

[0049] Figure 1 shows a propeller 1 which equips an axial-type fan 100. The fan 100, driven by an electric motor, is configured to be integrated into a front cooling module of a thermal or electric vehicle. Other applications are of course conceivable.

[0048]

[0050] The propeller 1 comprises a hub 2 having an axis of rotation XR and blades 3 extending generally radially (along a radius Ra) outwards from the hub 2 to a rim 4. The number of blades is for example between 5 and 20, being here 7. The blades 3 are regularly distributed (with a regular angular pitch) around the hub 2, or distributed in a non-regular manner around the axis XR, thus creating an asymmetrical distribution.

[0049]

[0051] As illustrated in Figure 4, each blade 3 is defined by a span EN, a leading edge BA and a trailing edge BF. Blade 3 is further defined by a stack of airfoils PA constructed with a thickness law LE1 around a neutral fiber FN connecting the leading edge BA to the trailing edge BF of blade 3 (see Figure 5). The neutral fiber FN is characterized by a parameter called chord length LC representing the distance between the two ends BA and BF of the neutral fiber FN.

[0050]

[0052] Figure 6 shows, on the bottom curve, an example of the LE1 thickness law which represents the evolution of the thickness of the PA profile along the neutral fiber FN.

[0051]

[0053] It is recalled that the neutral fiber FN passes through the center of the profile PA of the blade 3, between the leading edge BA and the trailing edge BF. The aerodynamic profile PA corresponds in particular to a circular section of the blade 3 at a given radius Rd (see figure 4), section obtained by intersection at a given radius with a geometric cylinder of the same axis as the axis of rotation of the propeller XR.

[0054] The curve in Figure 6 shows the thickness law LE1 applied to the neutral fiber FN of a circular section at a given radius to define the extrados curve at this same radius. For example, an ordinate value equal to zero means that the thickness of blade 3 is zero, and an ordinate value of 2% means that, at this point of the neutral fiber FN of the section, the thickness measured by resting on the neutral fiber FN of blade 3, is 2% of the chord length LC.

[0052]

[0055] It is also possible to have a thickness law to define the intrados INT of blade 3. The thickness is, in this case, the distance between the neutral fiber FN and the intrados INT.

[0053]

[0056] It is possible to have a thickness law for the extrados EXT and another thickness law for the intrados INT. In this case, the neutral fiber is offset from the center of the PA profile.

[0054]

[0057] The PA airfoils of the stack can be identical or variable.

[0055]

[0058] The term "blade span EN" refers in particular to the length of blade 3 measured in a plane perpendicular to the axis of rotation XR of propeller 1, on a straight line passing through the axis of rotation XR and expressed as a percentage. The value 0% corresponds to a point of contact of blade 3 with hub 2 (point called blade root PP) and the value 100% corresponds to a point of contact of blade 3 with rim 4 (point called blade head TP).

[0056]

[0059] In the example described, the thickness law LE1 presents a variation (the VAR curve of which is shown in Figure 3) in the spanwise direction so as to form on the blade 3 undulations 5 of thickness which are spaced from each other in the spanwise direction EN.

[0057]

[0060] In the invention, in a way, a thickening or thinning coefficient is controlled on each section (of the aerodynamic profile PA) which makes up the blade 3, so as to form undulations 5 when moving from one aerodynamic profile PA to another.

[0058]

[0061] Thus the 5-thick undulations are here due to an alternation, in the spanwise direction, of thinned sections PA2 which define low points of the 5-thick undulations, and of thickened sections PA1 which define high points of the 5-thick undulations.

[0059]

[0062] The thickening or thinning coefficients can be read on the VAR curve in Figure 3.

[0060]

[0063] In other words, the variation of the VAR curve of the PA profiles of the blade 3, along the span EN, gives thickening or thinning coefficients for each PA aerodynamic profile, compared to usual thickness laws which would not generate undulations within the meaning of the invention.

[0064] Each undulation 5 is defined, in the spanwise direction EN, by a low point surrounded by two high points. The low point of the undulation is on a thinned section PA2 of the blade 3 and the high point is on a thickened section PA1 of the blade 3.

[0061]

[0065] The amplitude of the ripple 5 is the difference in thickness between the low point and the high point of the ripple, at a given location on the span EN.

[0062]

[0066] The 5 undulations have, depending on the span EN, a sinusoidal or pseudosinusoidal shape.

[0063]

[0067] The 5 ripples are contained between two envelope curves ENV1 and ENV2, namely polynomial type curves.

[0064]

[0068] The undulations 5 form furrows which extend substantially transversely to the span EN of the blade 3.

[0065]

[0069] The undulations 5 are parallel to each other, and parallel to the neutral fibers FN of the blade 3.

[0066]

[0070] In other embodiments of the invention, the undulations 5 have an angle of evolution to form a positive spiral (see figure 7) or a negative spiral on the blade (see figure 8).

[0067]

[0071] In the case of a positive spiral, the radius increases as one progresses along propeller blade 3. This means that the point on propeller blade 3 gradually moves away from the central axis XR.

[0068]

[0072] In contrast, in the case of a negative spiral, the radius decreases as one moves along propeller blade 3. This means that the point on propeller blade 3 gradually moves closer to the central axis XR.

[0069]

[0073] The angle of evolution (which is taken on the leading edge BA and measured relative to the line tangent to the geometric circle at this leading edge point) is for example 1° to 10°.

[0070]

[0074] The undulations 5 are present only on a portion 20 of the span EN of the blade. In other words, the undulations 5 are not present over the entire span EN, from the blade root PP to the blade tip TP. Thus, over a portion of the span, the blade is devoid of undulations, the thickness of the blade then being given by the usual thickness laws, without application of a thickening or thinning coefficient on these sections.

[0071]

[0075] The undulations 5 are present over at most 80% of the length of the span EN of the blade 3, in particular over at most 60% or 50% of the length of the span of the blade.

[0076] The 5 undulations only begin beyond the first 20%, or 40%, or 50% of the span length EN, starting from the blade root PP.

[0072]

[0077] Thus, in an area adjacent to the PP blade root, there are no undulations.

[0073]

[0078] In the example described, the undulations 5 are present between 40% and 100% of the span starting from the blade root PP, and therefore the undulations 5 are present over 60% of the length of the blade span.

[0074]

[0079] Thus each blade 3 comprises a local zone with a series of grooves or undulations 5, and the rest of the blade outside this zone does not have undulations and can have a relatively smooth curvature.

[0080] Each ripple 5 extends, like a furrow, from the leading edge to the trailing edge.

[0075]

[0081] Blade 3 may have a certain pitch angle CAL, as illustrated in Figure 5.

Claims

CLAIMS

1. Fan propeller (1) comprising a hub (2) having an axis of rotation (XR) and blades (3) extending generally radially outward from the hub (2), each blade (3) being defined by a span (EN), a leading edge (BA) and a trailing edge (BF), the blade (3) being further defined by a stack of aerodynamic profiles (PA) constructed with a thickness law (LE1) around a neutral fiber (FN) connecting the leading edge (BA) to the trailing edge (BF) of the blade (3), the neutral fiber (FN) being characterized by a parameter called chord length (LC) representing the distance between the two ends of the neutral fiber (FN), the thickness law (LE1) representing the evolution of the thickness of the profile along the neutral fiber (FN),the thickness law (LE1) having a variation in the span direction (EN) so as to form on the blade (3) at least two thickness undulations (3) which are spaced from each other in the span direction (EN).,

2. Propeller (1) according to the preceding claim, in which the undulation (5) is defined, in the spanwise direction (EN), by a low point surrounded by two high points, the low point of the undulation (5) being on a thinned section (PA2) of the blade (3) and the high point being on a thickened section (PA1) of the blade (3).

3. Propeller (1) according to one of the preceding claims, in which the undulations (5) are present over at most 80% of the length of the span of the blade (3), in particular over at most 60% or 50% of the length of the span of the blade (3).

4. Propeller (1) according to the preceding claim, in which the undulations only begin beyond the first 20%, or 40%, or 50% of the span length (EN), starting from the blade root (PP).

5. Propeller (1) according to one of the preceding claims, in which each blade (3) comprises a local area with a series of grooves or undulations (5), and the remainder of the blade outside this area has a relatively smooth curvature.

6. Propeller (1) according to one of the preceding claims, in which the undulations (5) have thickness amplitudes which increase as they approach the blade head (TP).

7. Propeller (1) according to one of the preceding claims, in which each undulation (5) extends from the leading edge (BA) to the trailing edge (BF).

8. Propeller (1) according to one of the preceding claims, in which the number of undulations (5) per blade (3) is between 3 and 15, for example between 3 and 8.

9. Propeller (1) according to one of the preceding claims, in which the undulations (5) are parallel to each other.

10. Fan (100), in particular for a motor vehicle, comprising a propeller according to one of the preceding claims.

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