EP3018359A1 - Automotive fan with blades optimised for high flow rates - Google Patents

Abstract

The invention relates to a ventilation fan (1) comprising a hub (2) and blades (3) extending radially outwardly from the hub (2) between a blade root (3a) and a blade head (2). blade (3b), which is characterized in that said blades (3) have, in the last twenty percent of their wingspan, at least one rope whose length is at least 1.5 times the shortest rope length on the full span of the blade. Advantageously, in the last twenty percent span of the blade, the blade advantageously comprises at least a portion of its mid-rope line having a rear curvature and a setting which changes by at least +5 °.

Description

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

The vehicles with thermal engine need to evacuate the calories that generates their operation and for that they are equipped with heat exchangers, in particular cooling radiators, placed at the front of the vehicle and crossed by outside air. To force the circulation of this air through the exchanger or exchangers, a fan is placed upstream or downstream. The ventilation fan which serves to force the flow of air has an axially oriented flow. It comprises blades connected by their foot to a central hub, and generally held together in their heads by a rotating shell (as illustrated in FIG. figure 1 ).

Some uses require that the propeller produce a large flow rate with respect to its diameter and speed of rotation, while operating with low pressure rises. Because of this operating point characteristic, it is necessary to design the propeller with large blades. For this purpose, a central hub (sometimes called a bowl) of small diameter is used, to which are added blades extending towards the outer radius. The diameters of the central bowl and the blades are typically in a ratio of 1 to 3. This gives the propeller a large passage section, which is delimited by the bowl at its center and by the blade end (or by the ferrule) in its outer circumference. This section of passage corresponds to what is called the vein. The span of the blade, that is to say its height from its foot to its end, corresponds to the height of the vein.

The designers of these propellers are regularly confronted with difficulties balancing the aerodynamic load between the foot and the blade heads, otherwise the vein does not fill properly; indeed, for the efficiency to be optimal, it is necessary to minimize the secondary flows, the recirculations and the zones not working from an aerodynamic point of view. For this, it is necessary that the blades are loaded as homogeneously possible from the foot to the head, which allows to communicate maximum energy to the fluid by printing a gyration movement over the entire span of the blade. This gyration is at the origin of the speed of the fluid that the fan produces, and the flow rate that it imposes on it.

A properly configured blade must therefore produce at its downstream a total pressure (or dynamic pressure) relatively constant so that no secondary flow is established.

However, it is found that under certain operating conditions, particularly when looking for high flows, side effects occur, mainly at the head, which affect the efficiency of the propeller when part of the span of the blade does not work. This is reflected, as can be seen on the figure 2 , by a total pressure P downstream of the helix, which decreases strongly and therefore by a work delivered by the head which is very weak. The yield R also decreases sharply. This is all the more detrimental as the area of the head is the one where the speed due to the rotation is the largest (large radius) and should therefore contribute mainly to the work of turning produced on the air.

There is therefore a need to design propellers that are capable of delivering high flow rates, while maintaining high efficiency and homogeneity of downstream pressure.

For this purpose, the subject of the invention is a ventilation fan comprising a hub and blades extending radially outwardly from the hub between a blade root and a blade head, characterized in that said blades present , in the last twenty percent of their wingspan, at least, a rope whose length is at least 1.5 times the shortest rope length on the whole span of the blade. By last twenty percents, we mean the portion of the blade being between 80 and 100% of the span of the blade, from the blade root. In other words, on this distal part of the blade, the length of the rope is at least 1.5 times the shortest rope length on the entire span of the blade, without necessarily being constant. Such a condition may optionally be filled on a larger fraction and / or on another fraction of the span of the blade without departing from the scope of the invention. Advantageously, however, such a condition will be fulfilled only on this distal part of the blade.

The evolution of the rope to a great length over the last twenty percent of its span allows to produce ventilation propellers that are optimized for aerodynamics and, among other things, for an effective filling of the vein at the head.

Preferably said rope over the last twenty percent is at least equal to 2 times said shorter rope length.

Advantageously, said smaller length of rope is between 50 and 80% of the span of the blade.

In a particular embodiment, the rope is constantly decreasing from the blade root to said rope of shorter length and then constantly increasing from this point to the blade head.

According to another aspect of the invention, which may or may not be combined with the preceding one, the invention also relates to a ventilation propeller in which the blade comprises, in the last twenty percent, at least a portion of its line. mid-rope having a rear curvature. In other words, on this distal portion of the blade, a portion of its mid-rope line has a rear curvature. Such a condition may optionally be filled on a larger fraction and / or on another fraction of the span of the blade without departing from the scope of the invention.

Advantageously, the blade comprises a maximum curvature, oriented towards the front, which is located between 50 and 80% of the span of the blade.

In a particular embodiment, the curvature is constantly growing from the blade root to a maximum forward curvature and then constantly decreasing from this point to the blade head. More particularly, this decrease is greater than or equal to 7 °.

According to another aspect of the invention, which may or may not be combined with the one or more of the preceding aspects, the invention also relates to a ventilation propeller in which the setting changes by at least +5 ° on said twenty c inq, or even the last twenty percent span of the blade. In other words, between the point located at 80% of the span of the blade and its end, the setting changes by at least +5 °.

Advantageously the setting changes by at least + 10 ° between 33 and 75% of the span of the blade.

Preferably the wedging is less than 65 ° in the first third of the span.

In a particular embodiment, the wedging is in constant decay of the blade root to a minimum setting located on the first third of the span then in constant growth from this point to the blade head.

According to another aspect of the invention, which may or may not be combined with the one or more of the preceding aspects, the invention also relates to a ventilation propeller in which the blade comprises, in said last twenty percent, a superior camber or equal to 8%, in at least one point of its half-rope line. In other words, on this distal part of the blade, the camber of the blade is greater than or equal to 8%, in at least one point of its mid-string line, without necessarily being constant. Such a condition may optionally be filled on a larger fraction and / or on another fraction of the span of the blade without departing from the scope of the invention.

Advantageously the camber is between 8 and 10% throughout the last twenty percent.

In a particular embodiment the camber is constant over the entire span of the blade.

The invention also relates to a motor-fan unit comprising a propeller as described above and a cooling system comprising such a motor-fan unit. Such a system may include one or more heat exchangers traversed by the air flow generated by the propeller.

The invention will be better understood, and other objects, details, features and advantages thereof will appear more clearly in the following detailed explanatory description of an embodiment of the invention given as a 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 les évolutions, en fonction du débit, de la pression en aval et du rendement de l'hélice de la figure 1,
• la figure 3 est une vue en coupe d'une pale d'une hélice de ventilateur automobile,
• la figure 4 est une vue de face d'une hélice selon l'invention,
• la figure 5 est une vue en perspective d'une pale de l'hélice de la figure 4,
• la figure 6 est un graphique donnant l'évolution du calage de la pale de la figure 5 le long de son envergure,
• la figure 7 est un graphique donnant l'évolution de la corde de la pale de la figure 5 le long de son envergure,
• la figure 8 est un graphique donnant l'évolution de la cambrure de la pale de la figure 5 le long de son envergure,
• la figure 9 est un graphique donnant l'évolution de la courbure de la pale de la figure 5 le long de son envergure,
• la figure 10 est un graphique donnant l'évolution de la pression en aval de l'hélice, le long de l'envergure de la pale, et
• la figure 11 un graphique donnant les évolutions, en fonction du débit, de la pression en aval et du rendement de l'hélice de la figure 4.

On these drawings:

• the figure 1 is a front view of a helix, according to the prior art,
• the figure 2 is a schematic view giving the evolutions, as a function of the flow rate, of the downstream pressure and the efficiency of the propeller of the figure 1 ,
• the figure 3 is a sectional view of a blade of an automobile fan propeller,
• the figure 4 is a front view of a propeller according to the invention,
• the figure 5 is a perspective view of a blade from the propeller of the figure 4 ,
• the figure 6 is a graph giving the evolution of the wedging of the blade of the figure 5 along its wingspan,
• the figure 7 is a graph giving the evolution of the rope of the blade of the figure 5 along its wingspan,
• the figure 8 is a graph giving the evolution of the camber of the blade of the figure 5 along its wingspan,
• the figure 9 is a graph giving the evolution of the curvature of the blade of the figure 5 along its wingspan,
• the figure 10 is a graph showing the evolution of the pressure downstream of the propeller, along the span of the blade, and
• the figure 11 a graph showing the evolutions, as a function of the flow rate, of the downstream pressure and the efficiency of the propeller of the figure 4 .

The figure 1 shows a propeller 1, of the prior art, which is rotatably mounted about an axis passing through its center O and here oriented orthogonally to the plane of the figure. The direction of rotation of the helix 1 is designated by the arrow F. When the propeller 1 is rotated, for example by an electric motor (not visible), the propeller 1 brews the air which the crosses. 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 themselves used with reference to the axis of rotation of the helix.

• 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 3a, fixées sur le moyeu 2, 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 3b des pales 3.

This helix 1, comprises:

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

As regards the blades 3, they are generally identical to each other and may have a substantially airfoil cross section, with an upper surface 3E and a lower surface 3I, as illustrated by FIG. figure 3 . They thus extend transversely between, respectively, a leading edge 31 which first comes into contact with the air flow during the rotation of the propeller 1, and a trailing edge 32 which is opposite to it.

The figure 2 gives the performance of a propeller according to the prior art as a function of the flow that passes through it, the latter being modulated by its rotational speed. The curve P gives the pressure differences between the upstream and downstream of the helix 1 as a function of the flow rate passing through the helix, while the curve R gives the values of the yield of this helix under the same conditions. It is noted that the yields are of the order of 30 to 40% for the flow rates currently sought (between 1500 and 3000 m ³ / h) and that they collapse, as well as the pressure difference, as soon as the flow implemented rises, and in particular exceeds 2500 m ³ / h. The pressure difference would even become negative at very high flows (above 3000 m ³ / h), which results from recirculations and, therefore, from areas of the propeller that do not work from an aerodynamic point of view.

• sa corde qui est la longueur de la ligne de corde C, exprimée en mm,
• sa cambrure qui est la valeur maximale d de la distance entre la ligne de corde C et la ligne de cambrure A, 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 C 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).

The figure 3 represents a section of the blade 3 in a plane parallel to the axis of rotation, perpendicular to the line connecting the mid-rope points. In this plane, the line C connecting the leading edge 31 to the trailing edge 32 is called a rope line, while the line connecting the equidistant points of the extrados 3E and 3I intrados of the blade is called the line of camber A. aerodynamic characteristics of the blade are defined by the following parameters, which are possibly evolutive all along the blade:

• its rope which is the length of the rope line C, expressed in mm,
• its camber, which is the maximum value d of the distance between the chord line C and the camber line A, referred to the length of the chord line and expressed in percents,
• its wedging which is the angle that makes the line of rope C with the axis of rotation of the propeller.
  (Note: by convention in this text, the angle of rigging is the angle complementary to the angle of setting 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 mid-rope points of the blade. The curvature of the blade is said before if, for the rope considered, the tangent to this line is oriented, moving from the foot to the head, in the direction of rotation F; it is said to be backwards in the opposite direction. The curvature, at each mid-cord point along the span, is expressed by the value in degrees of the angle made by the radius at this point with the radius of the half-rope point at the foot of the blade.

The figure 4 shows, in plan, an automobile fan propeller according to the invention. It comprises, here, seven blades and a ferrule, without these specific characteristics being essential for the realization of the invention.

The figure 5 gives a frontal view of a blade of such a helix. The particular characteristics of this propeller are given by the Figures 6 to 9 , with respect to the evolution, respectively, of its rigging, its rope, its arch and its curvature, along its span.

The propeller that is represented on the Figures 4 and 5 integrates the particular features that are defined by the invention for these four parameters, but the invention relates to any of the possible combinations between the mentioned parameters, the latter may vary independently of each other. It nevertheless relates more particularly to the values that these parameters take in the last twenty percent of the span of the blade and the combinations between them in this range.

First of all, as regards the wedging of the blade, the figure 6 gives the optimal evolution, along the span of the blade, the angle of the rope with respect to the axial direction. To optimize the aerodynamic performance of the propeller, the value used according to the invention for setting is different from that which is usually used, namely that which is simply based on the velocity triangle. In the prior art, the wedging given to the rope of the blade is defined by an aerodynamic incidence which is added to the direction resulting from the vector sum of the tangential and axial speeds of the fluid.

In contrast to the invention, as illustrated here and without all the characteristics represented being essential for the realization of the invention, the setting locally takes a low value, which remains lower than 65 ° over the entire first third of the invention. span of the blade (from 0 to 33%). It has a minimum value on this range, which is referred to as reference Pt1. Then, it increases overall, between this first third and 75% of the blade span, with a Pt2 value at the end of the range (ie at 75%) which is at least + 10 ° greater than the minimum value Pt1 retained on the first third. Finally, compared to the Pt2 value obtained at 75%, the wedging still increases over the last 25 percent span of the blade, with an increase in this segment that is greater than or equal to + 5 °, while remaining lower than 90 °. In the end we observe a growth on the last two thirds which is at least 15 ° compared to the point of weakest wedging, the latter being positioned in the first third of the span of the blade.

Then the figure 7 gives the optimal evolution, according to the invention, for the value of the rope, along the span of the blade.

As illustrated, the rope is globally decreasing from the blade root to the first half of its span. It then has a minimum that is placed in the range of 50 to 80% of the span, then it grows towards the blade head. It then takes a maximum value at a point beyond 80% wingspan. The maximum value on the segment of the last twenty percent is, according to the invention, greater than one and a half times and, preferably, twice the minimum value of rope which has been found between 50 and 80% of span.

The figure 8 illustrates, then, the evolution according to the invention for the camber of the blade, along its wingspan.

As illustrated, the camber takes a value that is greater than 8% beyond 80% wingspan. In the mode illustrated in the figure, without this configuration is essential for the realization of the invention, the camber remains the same over the entire span, being greater than these 8%; the value used in this particular case, which corresponds to an optimum, is 9.5%.

Finally, figure 9 gives the evolution according to the invention for the curvature of the blade, along its span.

As illustrated in the figure, and without all the features shown being, again, essential for the realization of the invention, the curvature is zero at the foot, which means that the blade extends perpendicular to the hub 2. The curvature gradually increases towards a curvature before becoming more pronounced, to reach a maximum value which is situated between 50 and 80% of the span. It then goes down again by at least 7 ° with respect to this maximum value to reach its value at the top of the blade.

In a more general way, according to the invention, the curvature passes in rear curvature in the zone of 80 to 100% of the blade. This results in the fact that the evolution of the angular position of the leading edge, translates a more retracted position of the blade head compared to the most advanced angular position between 0 and 80% span.

The minimum value of the curvature of the blade, at the head, is moreover advantageously lower by at least 7 ° to the maximum value of the curvature noted between 50 and 80% of span, with an overall decrease between this point and the head of the blade.

The Figures 10 and 11 give the aerodynamic results obtained with a propeller that includes the four proposed improvements.

We see on the figure 10 that the pressure downstream of the propeller, for a given flow, remains globally high and, in particular, that it does not weaken when approaching the blade head.

This is confirmed by reading the figure 11 where it can be seen that the pressure difference between upstream and downstream of the propeller remains high, even at high flow rates up to 3500 m ³ / h, which was not the case with the propeller of the prior art illustrated by the figure 2 .

Similarly the yields reach values that can even exceed 50% at 2500 m ³ / h and, in any case, they remain higher than those obtained with the state of the art for a flow rate of 3500 m ³ / h.

The combination of the parameters resulting in the blade shape described in the figures above, and, in particular, associating a strong variation of the rope in the zone greater than 80% of the span with maximum rope lengths in this zone, results in the production of optimized ventilation propellers for aerodynamics and, among other things, for an effective filling of the vein at the head.

In addition, it is found that significant head camber (height of camber between 8 and 10% of the rope) and a rear curvature of the blade, combined with the increase of rope at the head, are effective for loading the blade head and improve the efficiency of the propeller.

The invention has been described in the case of a helix having a ferrule connecting the end of the blades. It is obvious that it can just as well be carried out in the absence of ferrule, provided that the shape given to the blades 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 helix rotates about 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 cooling system or module of a motor vehicle engine block. It then includes, in particular, the fan-motor group 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 helix.

Claims (15)

Ventilation propeller (1) comprising a hub (2) and blades (3) extending radially outwardly from the hub (2) between a blade root (3a) and a blade head (3b),
characterized in that said blades (3) have, in the last twenty percent of their wingspan, at least one rope the length of which is at least 1.5 times the shortest rope length on the entire span of the blade. A ventilation propeller according to claim 1, wherein said rope over the last twenty percent is at least 2 times said shorter rope length. A fan propeller according to any one of claims 1 or 2, wherein said smaller string length is between 50 and 80% of the blade span. Ventilation propeller according to any one of claims 1 to 3, wherein the rope is in constant decay of the blade root (3a) to said rope of shorter length and then constantly increasing from this point to the head of blade (3b). A fan propeller according to any one of claims 1 to 4, wherein the blade has, in said last twenty percent, at least a portion of its mid-rope line having a rear curvature. A ventilation propeller according to claim 5, wherein the blade has a maximum curvature, facing forward, which is between 50 and 80% of the span of the blade. Ventilation propeller according to any one of claims 5 or 6, wherein the curvature is in constant growth of the blade root (3a) to a maximum forward curvature and then constantly decreasing from this point to the blade head ( 3b), this decrease being greater than or equal to 7 °. Fan propeller according to any one of claims 1 to 7, wherein the setting evolves by at least +5 ° said last 20 percent last percent span of the blade. Ventilation propeller according to the preceding claim wherein the setting changes by at least + 10 ° between 33 and 75% of the span of the blade Ventilation propeller according to any one of claims 8 or 9, wherein the wedging is in constant decay of the blade root (3a) to a minimum pitch (Pt1) located on the first third of the span then in constant growth from this point to the blade head (3b) Ventilation propeller according to any one of claims 1 to 10, wherein the blade has, in said last twenty percent, a camber greater than or equal to 8%, at least one point of its mid-rope line. Ventilation propeller according to claim 11 wherein the camber is between 8 and 10% throughout the last twenty percent. Fan propeller according to claim 11 wherein the camber is constant over the entire span of the blade. Motor-fan unit comprising a propeller (1) according to any one of the preceding claims. Motor vehicle cooling system comprising a motor-fan unit according to the preceding claim and one or more heat exchangers traversed by the air flow generated by said propeller.

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