EP3271588B1 - Aerodynamically and acoustically improved car fan - Google Patents

Description

The field of the present invention is that of the automobile, and more particularly that of air circulation for cooling engine equipment.

Thermal engine vehicles need to evacuate the calories generated by their operation and are therefore equipped with heat exchangers, in particular cooling radiators, which are generally placed at the front of the vehicle and through which the outside air passes. . To force the circulation of this air through the exchanger (s), a fan is placed upstream or downstream. The ventilator, which serves to force the air circulation, has an axially oriented flow. It comprises blades which are connected by their foot to a central hub, and generally held together at their head by a rotating ferrule (as illustrated on figure 1 ).

It is also customary to give curvature effects to the blades in order to improve their acoustics. The curvature is said to be forward if the blade is curved in the direction of rotation, considering the plane perpendicular to the axis of rotation; it is said to be rear in the opposite case. Using the curvature effects, the sound sources that are located along the span of the blade are out of phase with each other, and tonal noise reductions of several decibels can be noted.

While curvature has beneficial effects for acoustics, it also modifies aerodynamic properties because it produces forces perpendicular to the blade surface, these forces in turn creating radial flows. In general, for the same operating point, a rear curvature will produce a flow extending radially outwards, while a front curvature will produce an effect of contraction of the flow (as will be explained in more detail below). detail in relation to the figure 2 ). Thus, a rear curvature will work more at the head, and will promote performance at high flow, while a front curvature will promote low flows by working more at the foot.

But from an aeroacoustic point of view, the benefits are reversed and the rear curvature will be noisier at high speed because of the more important work at the head, while the front curvature will be noisier at low speed because of the more important work in front. foot. It is therefore noted that the benefits of a curvature effect (front or rear) are antagonistic and that, by this effect, it is not possible to satisfy both the aerodynamic efficiency and the acoustic quality for the same operating range ( low or high speed).

Mixed solutions between rear curvature and front curvature then constitute a compromise which is frequently used. These mixed back-front curvatures produce a flow contraction effect, which centers at about mid-span (see figure 2 ). A ventilation propeller with blades exhibiting a rear-to-front curvature is disclosed in EP 0 933 534 A2 . But, due to these particular mid-span flow conditions, the pressure gradient between the trailing edge and the leading edge is modified and a marked separation is observed on the upper surface of the blade, which begins at the level of this mid-span.

There is therefore a need to design improved propellers which are capable of producing high aerodynamic efficiencies without their aeroacoustic performance thereby being degraded.

To this end, the invention relates to a ventilation propeller comprising a hub and blades extending radially outwards from the hub between a blade root and a blade head, the blades of said propeller having a rear-front curvature due to an inversion of curvature on their wingspan.

According to the invention, said blades comprise at least one sudden variation in their pitch extending over a limited span deviation, said pitch variation being located near a point of reversal of curvature of the blades. The term “abrupt” variation is understood to mean at least 2 ° more or less with respect to a linear setting on said difference in scope. The term “limited” span deviation is understood to mean a maximum span deviation of 25% of the total span of the blade. By variation situated “close to” a point of inversion of the curvature of the blades, is meant situated between 20 and 80% of their span. Advantageously, the setting variation is between 3 and 5 °.

This setting inflection, with respect to a blade exhibiting a continuous evolution of its setting along the span, makes it possible to avoid detachment of the air flow on the blade and therefore to avoid both noise pollution and losses. performance caused by these detachments.

Preferably, a peak of the variation in timing is positioned, relative to the point of inversion of curvature, at a distance less than or equal to 30% of the wingspan of the blade. The proximity of this peak to the point of inversion of the curvature allows it to act as close as possible to the place where the detachments occur, and therefore improves its efficiency.

More preferably, said distance is less than or equal to 10% of the span of the blade.

In a particular embodiment, the variation in setting is said to be positive, the value of the setting being greater than said linear setting over the entire span deviation.

In another particular embodiment, the variation in setting is said to be negative, the value of the setting being less than said linear setting over the entire span deviation.

Advantageously, the setting variation has a positive slope, respectively negative, up to its peak, followed by a negative slope, respectively positive. This pointed shape represents an optimum in terms of efficiency for the suppression of flow detachments which are generally observed on the upper surface.

Preferably, at least one of the slopes of the variation in setting has, in absolute value, a value greater than 1 ° per 10% of variation in span. And, more preferably, the other slope has, in absolute value, a value of less than 1 ° per 10% of span variation.

Advantageously, the curvature of the blades at the point of inversion of its curvature is between -4 and -25 °.

In a particular embodiment, the variation in curvature between the point of inversion and the head of the blades is between 4 and 25 °.

Preferably, the curvatures of the blades at the base and at the head differ by less than 10 °. And more preferably, said curvatures are both less than 10 °.

The invention also relates to a motor-fan unit comprising a propeller as described above as well as a cooling system comprising such a motor-fan unit. Such a system could include one or more heat exchangers through which the air flow generated by the propeller passes.

The invention will be better understood, and other aims, details, characteristics and advantages thereof will emerge more clearly during the detailed explanatory description which follows, of an embodiment of the invention, given by way of reference. purely illustrative and non-limiting example, with reference to the accompanying schematic drawings.

• la figure 1 est une vue de face d'une hélice, selon l'art antérieur,
• la figure 2 est une vue schématique donnant la forme de l'écoulement de l'air traversant une l'hélice selon la figure 1, dans les cas, respectivement, d'une courbure arrière, d'une courbure avant et d'une courbure mixte arrière-avant de ses pales,
• la figure 3 est une vue de face d'une hélice à courbure mixte arrière-avant,
• la figure 4 est une vue en perspective d'une pale de l'hélice de la figure 3, selon l'art antérieur,
• la figure 5 est une vue en perspective d'une pale de l'hélice de la figure 3, modifiée selon l'invention,
• la figure 6 est une vue schématique donnant l'évolution de la courbure de la pale de la figure 5 le long de son envergure,
• la figure 7 est une vue schématique donnant l'évolution du calage de la pale de la figure 5 le long de son envergure, respectivement selon un premier mode de réalisation de l'invention et selon un mode de réalisation de référence,
• la figure 8 est une vue schématique donnant l'évolution du calage de la pale de la figure 5 le long de son envergure, respectivement selon un second mode de réalisation et selon un mode de réalisation de référence,
• la figure 9 est une vue de face d'une hélice, dans une première mise en œuvre de l'invention,
• la figure 10 est une vue de face d'une hélice, dans une seconde mise en œuvre de l'invention, et
• la figure 11 une vue de face d'une hélice, dans une troisième mise en œuvre de l'invention.

On these drawings:

• the figure 1 is a front view of a propeller, according to the prior art,
• the figure 2 is a schematic view showing the shape of the air flow passing through a propeller according to the figure 1 , in the cases, respectively, of a rear curvature, a front curvature and a rear-front mixed curvature of its blades,
• the figure 3 is a front view of a rear-front mixed curvature propeller,
• the figure 4 is a perspective view of a propeller blade of the figure 3 , according to the prior art,
• the figure 5 is a perspective view of a propeller blade of the figure 3 , modified according to the invention,
• the figure 6 is a schematic view showing the evolution of the curvature of the blade of the figure 5 along its span,
• the figure 7 is a schematic view showing the evolution of the pitch of the blade of the figure 5 along its span, respectively according to a first embodiment of the invention and according to a reference embodiment,
• the figure 8 is a schematic view showing the evolution of the pitch of the blade of the figure 5 along its span, respectively according to a second embodiment and according to a reference embodiment,
• the figure 9 is a front view of a propeller, in a first implementation of the invention,
• the figure 10 is a front view of a propeller, in a second implementation of the invention, and
• the figure 11 a front view of a propeller, in a third implementation of the invention.

The figure 1 shows a propeller 1, of the prior art, which is mounted in rotation about an axis passing through its center O and here oriented orthogonally to the plane of the figure. The direction of rotation of the propeller 1 is designated by the arrow F. When the propeller 1 is driven in rotation, for example by an electric motor (not visible), the propeller 1 stirs the air which passes through it. The air flow then flows in a direction of flow oriented substantially axially.

In the remainder of the description, the terms “upstream” and “downstream” are understood with reference to the direction of flow of the air flow. The terms “axial”, “radial” or “tangential” are used in reference to the axis of rotation of the propeller.

• un moyeu central 2, avantageusement destiné à coiffer le moteur d'entrainement de l'hélice,
• une pluralité de pales 3 (ici au nombre de six), avec leurs premières extrémités, ou pieds 3a, qui sont fixées sur le moyeu 2 et qui s'étendent radialement à partir de ce moyeu,
• et, bien que cet élément ne soit pas impératif, une virole périphérique 4, de forme annulaire cylindrique, à laquelle se raccordent les deuxièmes extrémités, ou têtes 3b, des pales 3.

This propeller 1, includes:

• a central hub 2, advantageously intended to cover the propeller drive motor,
• a plurality of blades 3 (here six in number), with their first ends, or feet 3a, which are fixed to the hub 2 and which extend radially from this hub,
• and, although this element is not imperative, a peripheral ring 4, of cylindrical annular shape, to which are connected the second ends, or heads 3b, of the blades 3.

As regards the blades 3, they are generally identical to each other and may have a cross section substantially in the form of an airplane wing, with an upper surface and an lower surface. They thus extend transversely between, respectively, a leading edge which first comes into contact with the air flow during the rotation of the propeller 1, and a trailing edge which is opposite to it.

• sa corde, qui est la longueur de la ligne de corde, exprimée en mm,
• sa cambrure, qui est la valeur maximale de la distance entre la ligne de corde et la ligne de cambrure, rapportée à la longueur de la ligne de corde et exprimée en pourcents,
• son calage, qui est l'angle que fait la ligne de corde avec l'axe de rotation de l'hélice. (Nota : par convention dans ce texte, l'angle de calage est l'angle complémentaire de l'angle de calage habituellement défini en aérodynamique).

Une quatrième caractéristique, qui influe sur ses performances aérodynamiques est la courbure de la ligne qui relie, en projection sur un plan radial, les points à mi-corde de la pale. La courbure de la pale est dite avant si, pour la corde considérée, la tangente à cette ligne est orientée, en se déplaçant du pied vers la tête, dans le sens de rotation F ; elle est dite arrière dans le sens contraire. La courbure, en chaque point à mi-corde le long de l'envergure, est exprimée par la valeur en degrés de l'angle que fait le rayon en ce point avec le rayon du point à mi-corde en pied de pale.In a section of the blade along a plane parallel to the axis of rotation, perpendicular to the line connecting the points at mid-chord, the line connecting the leading edge to the trailing edge is called the chord line, while the line connecting the points equidistant from the upper and lower surfaces of the blade is called the camber line. The aerodynamic characteristics of a blade are defined by the following parameters, which change throughout the blade:

• its chord, which is the length of the chord line, expressed in mm,
• its camber, which is the maximum value of the distance between the chord line and the camber line, related to the length of the chord line and expressed in percent,
• its setting, which is the angle that the chord line makes with the axis of rotation of the propeller. (Note: by convention in this text, the setting angle is the angle complementary to the setting angle usually defined in aerodynamics).

A fourth characteristic, which influences its aerodynamic performance is the curvature of the line which connects, in projection on a radial plane, the points at the mid-chord of the blade. The curvature of the blade is said to be forward if, for the chord considered, the tangent to this line is oriented, moving from the foot towards the head, in the direction of rotation F; it is said to be rear in the opposite direction. The curvature, at each point at mid-chord along the span, is expressed by the value in degrees of the angle that the radius makes at this point with the radius of the point at mid-chord at the root of the blade.

The figure 2 shows the deflection that a fluid undergoes while passing through the propeller 1 in the case, respectively, of a rear curvature, a front curvature and a mixed rear-front curvature of its blades 3.

In the left figure the back curvature produces a flow which extends radially outward while the central figure shows that a forward curvature produces a centripetal deflection of the flow. In the figure on the right, which corresponds to a mixed back-front curvature, the two previous effects neutralize each other and together produce a maintenance of an axial direction, with a contraction of the flow which centers at about mid-span. On the other hand, due to these particular mid-span flow conditions, the pressure gradient between the trailing edge and the leading edge is modified and a marked separation can be observed on the upper surface of the blade 3, which then arises substantially at mid-span. It is this detachment effect that the invention proposes to reduce, in particular by adjusting the distribution of the setting along the span of the blade, and in particular around this point at mid-span.

The figure 3 shows a propeller 1 whose blades 3 have a mixed curvature, rear at the foot 3a then front from the mid-wingspan up to the head 3b.

The figure 4 shows, for its part, a blade, according to the prior art, of the propeller of the figure 3 . The timing of the blade 3 varies continuously along the span, without abrupt variation thereof.

On the other hand the figure 5 shows a propeller blade 3 according to the invention which has an inflection peak 5 for its setting at the point of the wingspan where the curvature is reversed, that is to say where the flow contraction effect. The positioning, shape and intensity of this peak 5 are given by the figures 6 to 8 .

The figure 6 shows the evolution of the curvature in the case of a mixed rear-front curvature. The curvature is zero at the root of the blade 3a, which means that the line of points located at mid-chord moves away from the hub 2 while being perpendicular to it. The curvature increases, in the rear direction, until it reaches a maximum rear value equal, in the example shown, to -13 ° and positioned at mid-span. From this point, the blade 3 resumes a forward curvature, reducing its curvature gradually, from -13 ° to 0 ° which it reaches, by way of example, at the head of the blade 3b. The curve which is represented in the figure corresponds to the simplest form conceivable for a blade with mixed curvature, for the purpose of illustration of the invention; on the other hand, this is not limited to these simple geometric shapes.

The figures 7 and 8 show the evolution of the setting along the span of a blade 3, in a reference propeller version (so-called initial setting) and, respectively, in two embodiments of the invention (said modified timing). The invention is characterized by an inflection of the wedging forming a wedging peak; this peak is located here at 50% of the span, that is to say precisely around the point of inversion of the curvature. This inflection is either positive ( figure 7 ) or negative ( figure 8 ). But in both cases its amplitude is significant, the slope of the inflection being greater than or equal, in absolute value, to 1 ° per 10% of variation in curvature. The preferred values retained in the version shown in the figures and provided by way of example are 3 and 5 ° for 10% variation in setting, depending on whether the slope is ascending or descending and depending on whether the initial setting curve is it. - even decreasing or increasing around the point of inversion of the curvature. By way of example, the curvature may have slopes of the same absolute value on either side of the point of inversion.

The figures 9 to 11 show three cases of implementation of the invention on mixed curvature propellers.

On the figure 9 the curvature is rear-front with zero curvatures at the foot 3a and at the head 3b and a curvature inversion located at 75% of the span. At this point the curvature is equal to -4 °.

On the figure 10 the curvature is rear-front with zero curvatures at the foot 3a and at the head 3b and a curvature inversion located at 50% of the span. At this point the curvature is equal to -25 °

On the figure 11 the curvature is rear-front with zero curvatures at the foot 3a and equal to 7 ° at the head 3b. The curvature inversion is located at 20% of the span, and at this point the curvature is equal to -30 °.

It can therefore be seen that the invention, namely the positioning of an inversion, or peak, of setting 5, can be implemented on any type of propeller with mixed rear-front curvature, with a wide range of possible values for the curvature at the foot, the curvature at the head and for the position of the inversion of curvature along the span.

• dont l'inversion se situe entre 20 et 80% de l'envergure de la pale,
• dont la courbure a, en ce point d'inversion, une valeur comprise entre -4 et -25°,
• et dont la variation de courbure entre le point d'inversion et la tête est comprise entre 4 et 25°.

Preferably, the invention relates to a rear-to-front curvature:

• the inversion of which is between 20 and 80% of the wingspan,
• whose curvature has, at this point of inversion, a value between -4 and -25 °,
• and of which the variation in curvature between the point of inversion and the head is between 4 and 25 °.

Advantageously, the curvature at the foot and at the head are close to each other, that is to say with a difference less than or equal to 10 °, and more preferably they are both close to zero. , that is to say less than 10 °.

Associated with this curvature, the setting of the blade 3 exhibits a sudden variation, and limited in scope, in its value. This results in a setting which deviates, over a given wing span segment, from the linear timing existing between the two end points of this segment. This variation in timing is defined, according to the invention, advantageously as follows.

The pitch variation is in wingspan in an area close to the point of maximum rear curvature. The span difference between the point of maximum curvature and the inflection peak 5 is less than or equal to 30% of the span, more preferably less than or equal to 10%.

The inflection peak 5 is constituted by a sudden variation in the setting, of at least 2 ° over a variation of at most 25% of the wingspan. Preferably, this variation is between 3 and 5 °.

Preferably, the wedging is located on the same side with respect to said linear wedging, over the entire span deviation, whether above or below.

In a first embodiment, the sudden change in setting has a positive slope greater than 1 ° per 10% of change in setting, until an inflection peak 5 is reached, then, from this peak , a negative slope of less than -1 ° by 10% of the setting variation. In a second mode, it has, first of all, a negative slope of less than -1 ° per 10% variation of the setting, then a positive slope greater than 1 ° per 10% of the variation of the setting.

Finally, the invention has been illustrated by blades 3 having only one inflection peak 5; in alternative versions, several peaks may be present along the span of the blade 3, at least one of them having the minimum characteristics described above.

In terms of performance, the geometry proposed for the blade 3 by the present patent application tends to find an optimum both from an aerodynamic and aeroacoustic point of view. The objectives pursued are good efficiency, minimization of the acoustic effects and minimization of the deflection at the head of the blade 3b.

The geometry is based first of all on a mixed rear-front curvature, and on a law of timing distribution along the span which is adapted to the three-dimensional nature of the flow. Improved performance is achieved by a shape inflection that is positioned close to the span where the curvature reverses. This inflection has the effect of locally modifying the angle of attack of the flow incident on the aerodynamic profile and thus improving the flow on its upper surface and minimizing detachments. Thanks to this improved design, the drag of the profile is reduced for the same lift, and the elimination of detachments improves the acoustics by minimizing the noises of interaction of the propeller with its support. In terms of aerodynamic performance, there is an improvement with, in the example of the propeller of the figure 3 , an efficiency which goes from 43.8 to 45.2%, at the same speed of rotation and same flow.

In the end, the use of the timing variations described in the present patent application makes it possible to obtain automobile ventilation propellers producing a very good compromise between aerodynamics, acoustics and structural deflection effects.

The invention has been described in the case of a propeller having a ferrule 4 connecting the outer end 3b of the blades. It is obvious that it can just as well be produced in the absence of a ferrule, provided that the shape given to the blades 3 is that described above.

The invention also relates to a motor-fan unit comprising such a propeller, and its drive motor. Said group may comprise a nozzle provided with an air passage orifice inside which the propeller rotates around its axis, said drive motor being carried by the nozzle by means of radial arms advantageously forming stator blades.

The invention also relates to a system or module for cooling an engine block of a motor vehicle. It then comprises, in particular, the motor-fan unit mentioned above and a cooling radiator. The propeller may be located between the cooling radiator and the engine block or upstream of said radiator. These elements are, for example, substantially aligned along the axis of rotation of the propeller.

Claims (15)

1. Ventilation blower wheel (1) comprising a hub (2) and blades (3) extending radially outwards from the hub (2) between a blade root (3a) and a blade tip (3b), the blades of said blower wheel having a backward/forward curvature as a result of a reversal in curvature along their span,
   characterized in that said blades (3) comprise, between 20% and 80% along their span, at least one variation in their pitch, extending over a maximum span distance of 25%, of at least 2° more or less than a linear pitch existing between the two end points of said span distance.
2. Ventilation blower wheel according to Claim 1, in which the pitch variation is between 3° and 5°.
3. Ventilation blower wheel according to either of Claims 1 and 2, in which a peak (5) in the pitch variation is positioned at a distance less than or equal to 30% of the span of the blade (3), relative to a curvature reversal point.
4. Ventilation blower wheel according to Claim 3, in which said distance is less than or equal to 10% of the span of the blade (3).
5. Ventilation blower wheel according to any one of Claims 1 to 4, in which the pitch variation is referred to as positive, the pitch value being greater than said linear pitch over the whole span distance.
6. Ventilation blower wheel according to any one of Claims 1 to 4, in which the pitch variation is referred to as negative, the pitch value being less than said linear pitch over the whole span distance.
7. Ventilation blower wheel according to Claim 5 or respectively 6, in which the pitch variation has a positive or respectively negative slope, until its peak (5), followed by a negative or respectively positive slope.
8. Ventilation blower wheel according to Claim 7, in which at least one of the pitch variation slopes has, as an absolute value, a value of more than 1° per 10% span variation.
9. Ventilation blower wheel according to Claim 8, in which the other slope has, as an absolute value, a value less than 1° per 10% span variation.
10. Ventilation blower wheel according to any one of Claims 1 to 9, in which the curvature of the blades (3) at the curvature reversal point is between -4° and -25°.
11. Ventilation blower wheel according to one of Claims 1 to 10, in which the variation in curvature between the reversal point and the tip (3b) of the blades is between 4° and 25°.
12. Ventilation blower wheel according to any one of Claims 1 to 11, in which the curvatures of the blades at the root (3a) and at the tip (3b) differ by less than 10°.
13. Ventilation blower wheel according to Claim 12, in which said curvatures are both less than 10°.
14. Engine fan comprising a blower wheel (1) according to any one of the preceding claims.
15. Car cooling system comprising an engine fan according to the preceding claim and one or more heat exchangers through which the air flow generated by said blower wheel passes.

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