FR2927674A1 - Fan blade for turbine engine of airplane, has two vents exclusively transporting less percentages of air, which enters into turbine engine along main axis and runs along blade during normal operation, from inlet orifices to outlet orifices - Google Patents

Abstract

The blade (10) has a convex face (17) that is a low pressure face or wing upper surface in normal operation of a turbine engine. The face is radially extended from a foot (12) to a head (14) and axially extended from a leading edge (15) to a trailing edge (16). Two vents exclusively transport less percentages of air, which enters into the engine along a main axis of the engine and runs along the blade during normal operation, from inlet orifices (20) e.g. oblong holes, to outlet orifices (40) e.g. circular holes. The vents are opened at its ends by the inlet and outlet orifices, respectively.

Description

The present invention relates to a turbomachine fan blade having a first face which is in normal operation of the turbomachine a low pressure face, a foot, a head, a leading edge and a trailing edge, the first face extending radially from the foot to the head of the dawn, and axially from the leading edge to the trailing edge of the dawn. In the description which follows, the terms "upstream" and "downstream" are defined with respect to the direction of normal circulation of the air through the turbomachine. FIG. 1 represents the upstream part of a turbomachine. At the upstream end of this turbomachine is a conical nose centered on the main axis of the turbomachine, and which flares from upstream to downstream. This conical nose is extended by an annular platform 80 on which are mounted blades 10 which extend substantially radially outwardly from the platform 80 to near the annular housing 90 centered on the main axis of the turbomachine. The blades 10 are distributed over the circumference of the platform 80. The blower is the assembly comprising the blades 10 and the platform 80. The foot 12 of a blade 10 is the radially inner portion of the blade 10, at its end. intersection with the platform 80 supporting the blade 10. The head 14 of a blade 10 is its radially outer end, near the housing 90. The blades 10 are movable (they rotate with the platform 80 and the conical nose around 25 the main axis when the turbomachine is in operation) and the heads 14 of the vanes 10 do not touch the casing 90. The standards of acoustic certification of an aircraft, especially during the take-off and landing phases, impose restrictions of more and more severe on the noise generated by the engines (turbomachine) 30 equipping the aircraft. The noise generated by the turbomachines is largely due to the rotation of the blowers. The noise caused by the high speed rotation of the blower includes the following two components: a first component is the noise specific to the blower, which is due to the development of turbulent structures in the boundary layers on the fan blades. The second component is the noise caused by

the interaction of the wakes generated at the trailing edge (called base) of the blades of the fan with the blades 100 of the rectifier located downstream of the fan (see Figure 1). It is therefore necessary to act on these two components in order to obtain a sufficient reduction of the noise generated by a turbomachine. A technique adopted to date to produce less noise-generating blades is to take acoustic criteria into account right from the design phase of the dawn to optimize the 3-dimensional shape of the dawn. However, the constraints imposed by the performance requirements of the turbomachine can limit the possibilities of noise reduction by this method. The invention aims to provide a fan blade that reduces the noise generated by the fan without affecting its performance.

This object is achieved by virtue of the fact that the blade is pierced by at least one chimney opening at one end through inlet orifices situated towards the foot of the blade on its first face, and at its other end by orifices. at the end of the trailing edge along one half of the trailing edge closest to the head of the blade, the at least one chimney being intended to convey from the inlet ports to the output only a small percentage of the air entering the turbomachine along its main axis and along the blade of the fan in normal operation. Thanks to these provisions, the centrifugal force generated by the rotation of the fan causes air through each blade through the chimney or chimneys, from the root of the blade to the outlet ports located towards the head of the fan. dawn. Thus, the wakes at the trailing edge of the fan blade are partially destroyed by the air ejected by the outlets located just at the end of the trailing edge. The interaction of these wakes with the blades located downstream is therefore reduced, and the noise generated by this interaction is minimized. In addition, the boundary layers at the bottom of the blade are sucked by the air entering the chimney or chimneys through the inlet ports. These boundary layers are therefore reduced, and the noise generated by these boundary layers is reduced.

Advantageously, the inlet ports are distributed in the 40% of the surface of the blade closest to the root of the blade.

The inlet orifices are thus further radially away from the outlet orifices, and the centrifugal force between these inlet and outlet orifices, being higher, is able to convey the air more easily along the chimney or chimneys. the inlet ports to the outlet ports.

The invention will be better understood and its advantages will appear better on reading the detailed description which follows, of an embodiment shown by way of non-limiting example. The description refers to the accompanying drawings, in which: FIG. 1 is a longitudinal section of a turbomachine fan according to the prior art, FIG. 2 is a perspective view of a fan blade according to the invention, FIG. 3A is a longitudinal section along the line III-III of Figure 2 of a fan blade according to the invention, Figure 3B shows a cross section along line BB of Figure 3 of a fan blade according to the invention at its central region, Figure 3C shows a partial section along the line C-C of Figure 3 of a fan blade according to the invention near its trailing edge, Figure 4 is a view of 5A is a perspective and cross-sectional view of the trailing edge of a fan blade according to the invention showing the outlet orifices of a fan blade according to another embodiment of the invention; FIG. 5B is a perspective view in co upe of the trailing edge of a fan blade according to another embodiment of the invention. FIG. 2 represents a fan blade 10 according to the invention.

This blade 10 is carried by a platform 80. The blade has a leading edge 15 upstream, a trailing edge 16 downstream. The blade 10 extends radially from its foot 12, which is its radially lower end where it is fixed on the platform 80, to its head 14, which is its radially outer end. The blade 10 has a curved shape in three dimensions, and thus has a first convex face 17, and a second concave face 18. The first face 17 is the low pressure side

in normal operation of the turbomachine (this face is also called extrados), and the second face 18 is the high pressure side (this face is also called intrados). The first face 17 and the second face 18 is therefore each bordered by the foot 12, the head 14, the leading edge 15 and the trailing edge 16 of the blade 10. In normal operation of the fan, the air circulates between the blades 10 according to the arrow F, from the leading edge 15 to the trailing edge 16 of each blade 10. The low-pressure face (or first face) 17 of the blade 10 is pierced with several inlet ports 20 which open into one or more chimneys dug in the blade 10. These inlet orifices 20 do not open on the second face 18 of the blade 10. In FIG. 3A is shown the case where the blade 10 comprises two chimneys 31 and 32. The inlet ports 20 are located in the region of the blade 10 which is closer to its foot 12. The chimneys 31, 32 extend from substantially the foot of the blade to trailing edge 16 of the blade 10. The chimneys 31, 32 open at the trailing edge 16 by outlet orifices 40 situated in the trough. 16 of the blade 16 which is closer to the blade head 14 than to its foot 12. The outlet orifices 40 are located exactly on the trailing edge 16, so that the air emerging through them Exit ports 40 bridge the relative air speed deficit immediately downstream of the trailing edge 16 from the adjacent air layers. The chimneys 31, 32 are entirely embedded in the volume of the blade 10, and open only through the inlet orifices 20 and the outlet orifices 40. The centrifugal force to which a point of a body is subjected in rotation about an axis is proportional to the distance from this point to this axis. Thus, in the case of the fan blade 10 which rotates about the main axis of the turbomachine (visible in FIG. 1), the part of the blade 10 closest to its head 14 (this is in this part that is located the outlet ports 40) is subjected to a centrifugal force substantially greater than the centrifugal force to which the foot 12 of the blade 10 is subjected. This difference in centrifugal force between the root of the blade and the portion of the blade near its head is sufficient so that it is not necessary to use a pumping device to route air from the inlet ports 20 to the outlet ports 40.

20, the chimneys 31, 32 and the outlet orifices 40 therefore constitute a self-suction system which allows a foot air flow 12 to be conveyed from the blade 10 to the part of the trailing edge 16 close to the head 14 of the blade 10 only by use of centrifugal force. If the blade 10 comprises a single chimney, the section of this chimney must be large enough so that the flow of air sucked through the inlet ports 20 is sufficient. The size of this section is however limited by the volume of the blade 10. In fact, if the digging of this chimney removes too much material at dawn 10, the mechanical strength of the blade 10 will be insufficient. This mechanical strength also decreases as the size of the chimney increases, given the flattened shape of this chimney. This flattened shape is due to the fact that the blade 10 itself has a flattened shape, its axial dimensions (from the leading edge 15 to the trailing edge 16) and radial (from the foot 12 to the head 14) being larger. that its thickness (distance between its first face 17 and its second face 18). It is therefore preferable that several chimneys connect the inlet orifices and the outlet orifices. For example the blade has two chimneys, namely a first chimney 31 and a second chimney 32, as shown in Figures 3A, 3B, 3C. In this case, one half of the inlet ports 20 opens into the first chimney 31, and the other half of the inlet ports opens into the second chimney 32. From the outside of the blade 10 to the interior of the blade (that is to say in the chimneys 31, 32) through the inlet orifices 20, the speed of the air increases (passage of a flow of a region with a surface section important to a region with a smaller surface area). But the aerodynamic losses of the air increase with its speed. The area of the section of each of the chimneys 31, 32 must not be too small, so that the speed of the air flowing in each stack 31, 32 is not too high. It is therefore preferable that the dawn 10 is not pierced by more than three chimneys. Alternatively, the blade 10 may be pierced by a double chimney, that is to say a chimney which has a single initial channel at the inlet ports 20, and which, in its central part, splits into two channels, each channel opening at the trailing edge 16 of the dawn

10 through one half of the outlet ports 40. Each channel has a section substantially equal to half the section of the initial channel. Preferably, the sum of the surfaces of the inlet port sections 20 is less than the sum of the area of the section of the first stack 31 and the area of the section of the second stack 32 (or alternatively to the section of the the chimney if the blade 10 is only one), so that the air flow in each inlet port 20 is not too low. More generally, the sum of the surfaces of the sections of the inlet ports 40 is smaller than the area of the section of the at least one chimney. This prevents aerodynamic blockage. At the same time, maximize the size of the chimney (s) to obtain the lowest possible Mach numbers in the chimneys. Preferably, the sum of the surfaces of the sections of the inlet orifices 20 is substantially equal to the sum of the surfaces of the sections of the outlet orifices 40. This configuration makes it possible to ensure a sufficient flow rate at the outlet of the chimney. Preferably, the section of each stack 31, 32 increases slightly from the inlet ports 20 to the outlet ports 40, in order to maintain a suction flow. But overall, the thickness of the first chimney 31 (that is to say its dimension perpendicular to the first face 17 and second face 18 of the blade 10) near the outlet orifices 40 (where this first chimney s' widens) is smaller than the thickness of the first chimney 31 over the remainder of its length, as shown in Figures 3B and 3C. Similarly, the thickness of the second chimney 32 near the outlets 40 (where the second chimney widens) is smaller than the thickness of the second chimney 32 over the rest of its length. This reduction in the thickness of the chimneys 31, 32 results from the decrease in thickness of the blade 10 as one approaches its trailing edge 16. In the case where the blade 10 possesses two chimneys, the first chimney 31 opens out by half of the outlet orifices 40 which are closest to the head 14 of the vane 10, whereas the second chimney 32 (situated further downstream than the first chimney 31) emerges by half of the outlets that are closest to the foot 12. For example, the first chimney 31 connects at least a portion of the orifices

20 to a first group 41 of outlets 40, and the second chimney 32 connects at least a portion of the inlet ports 20 to a second group 42 of outlets 40 which are located further from the head 14 of dawn as the first group 41.

This situation is illustrated in FIG. 3A, the outlet orifices 40 being distributed between a first group 41 consisting of half of the outlet orifices situated close to the head 14, and a second group 42 consisting of the other half of the orifices of outlet, those located closer to the foot 12. The first chimney 31 opens through the first group 41 of orifices, and the second chimney 32 opens through the second group 42 of orifices. The inlet orifices 20 are for example distributed between the 5% and 40% of the height of the blade 10 closest to the foot 12. The outlet orifices 40 are distributed along the trailing edge 16 of the vane between 60% and 95% of the length of the trailing edge 16 measured from the foot 12. All the outlet orifices 40 are therefore further than the inlet ports of the axis of rotation of the fan. Indeed, the calculations made by the inventors have shown that if the inlet ports 20 are not sufficiently far from the outlet orifices 40, then the difference in centrifugal force between the inlet and outlet ports 40 does not generate a sufficient flow between these inlet ports 20 and these outlet ports 40. Given the small thickness of the blade 10 at its trailing edge 16, the outlet ports 40 are aligned on a single line along 16. Ideally, the outlet orifices 40 open exactly on the trailing edge 16. The outlet orifices 40 are oriented substantially perpendicularly to the trailing edge 16 in the mean plane of the blade 10 at its edge. 16, so that the air emerging from the outlet orifices 40 is directed substantially perpendicularly to the trailing edge 16 in this mean plane.

The percentage of the air entering the chimney or chimneys is less than 2%, preferably less than 1% of the air along the blade 10. This air along the blade 10 is the air passing between the first face 17 of the blade 10 and the blade adjacent to the blade 10 which is opposite this first face 17. It is important that this percentage of air drawn remains low, because if the air flow in the chimneys 31, 32 are too large, less air passes through the blower, and its efficiency is reduced so

detrimental. In addition, the friction losses in the chimneys being proportional to the flow of air that is conveyed there, the overall efficiency of the fan is affected if too much air enters the chimneys. The air flow taken is proportional to the speed of rotation of the blower.

The inlet ports are distributed over half the surface of the blade 10 closest to the trailing edge, that is to say, considering ropes connecting the leading edge 15 to the trailing edge 16 along the half of each of these cords which is closest to the trailing edge 16. The inlet ports 20 are preferably distributed between the 40010 and 20% of the surface of the blade 10 closest to the trailing edge 16 of the dawn 10. Indeed, it is in this region that the boundary layer at the foot 12 of the blade 10 is the thickest. The inlet ports 20 thus located are therefore more effective for sucking the bottom edge layer 12 of blade 10, which improves the aerodynamic efficiency of the blade 10, and decreases the noise of the blower. In addition, the reduction of the limiting layer 12 at the bottom of blade 10 results in an improvement of the efficiency of the blower. The inlet ports 20 are small enough to minimize the stress concentrations that can lead to blade rupture under the effect of centrifugal force. The inlet orifices 20 must therefore be sufficiently numerous so that, in total, the desired air flow rate is taken and enters the chimneys 31, 32. At the same time, these inlet orifices 20 must therefore not be too numerous. , in order to minimize the manufacturing costs of dawn 10.

The inlet ports 20 are for example divided into several columns C (a column being oriented in the direction of the foot 12 to the head 14 of the blade). These inlet orifices 20 thus also form lines L which are substantially perpendicular to the columns C. The inlet orifices 20 are thus distributed at the tops of the cells of a checkerboard. To minimize the stress concentration resulting from the gathering of all these inlet ports 20 in the same area, it is preferred that the C columns be spaced from each other. Indeed, the centrifugal force, which is the main force acting on the blade 10, is parallel to the inlet port columns 20. The more the columns C are spaced from each other, plus two inlet ports 20 located on the same line L in two adjacent columns C will be distant one

others. These two adjacent inlet ports 20 will therefore generate a lower stress concentration. It is also preferable for the inlet ports to be staggered between two adjacent columns, as shown in FIG. 2. Thus, the distance between two inlet ports 20 of the same line L is greater. In the same column C, the inlet orifices 20 can be brought closer to each other, because it is known that when two holes are aligned with the direction of the main force, the stress concentration generated at the edge of one of these holes is less than the stress concentration generated by just one of these holes. Alternatively, the inlet orifices 20 may be oblong holes oriented from the foot to the head of the blade, as shown in FIG. 4. The shape and orientation of these oblong holes allows easier penetration of the air in the chimneys. In FIG. 4, the inlet orifices 20 between two adjacent columns C are not arranged in staggered rows, so that the inlet orifices 20 are distributed in lines L which are perpendicular to the columns C. Alternatively, the orifices C 20 between two adjacent columns C may be arranged in staggered rows. Through the thickness of the wall of the first face 17 through which they pass, the inlet orifices 20 are perpendicular to this wall. Alternatively the inlet ports 20 may be oriented in part towards the leading edge 16 of the blade 10, that is to say that the axis of an inlet orifice 20 is oriented, since the outside the wall of the first face 17 to the chimney, substantially from upstream to downstream. Thus, the inlet orifices 20 are oriented substantially in the direction of the flow of air along the wall of the first face 17, so that this air penetrates more naturally into these inlet orifices 20.

The outlets 40 may have several shapes. For example, the outlets 40 are selected from an assembly comprising substantially circular holes, oblong holes elongate in the direction of the trailing edge 16, or one or more slots. FIGS. 5A and 5B illustrate the cases where the blade 10 comprises two chimneys 31, 32.

FIG. 5A shows the part of the trailing edge 16 carrying exit orifices 40 in the form of substantially circular holes, the first chimney 31 opening into the first group 41 of these holes, and the second chimney 32 (situated further downstream than the first chimney 31) opening into the second group 42 of these holes, those located closer to the foot 12. Figure 5B shows the portion of the trailing edge 16 having outlet orifices 40 consist of two slots. The first chimney 31 opens into a first slot 41, and the second chimney 32 opens into the second slot 42. Alternatively, the outlet orifices 40 may form a single slot in which opens the chimney or chimneys. The description above was made in the case where the blade 10 is pierced with two chimneys. This description is also valid in the case where this blade is pierced by a single chimney, or more than two chimneys. The present invention also relates to a turbomachine whose blower comprises a blade 10 as described above. For example, each blade of the blower of this turbomachine is a blade 10 as described above.

Claims (10)

1. A turbomachine fan blade (10) having a first face (17) which is in normal operation of the turbomachine a low pressure side, a foot (12), a head (14), a leading edge (15) and a trailing edge (16), said first face (17) extending radially from said foot (12) to said head (14), and axially from said leading edge (15) to said trailing edge (16), said blade (10) being characterized in that it is pierced by at least one chimney (31, 32) opening at one end through inlet orifices (20) located towards said foot (12) on said first face (17). ), and at its other end through outlets (40) at the end of said trailing edge (16) along the half of the trailing edge (16) closest to said head (14), said at least one chimney (31, 32) for conveying from said inlet ports (20) to said outlet ports (40) exclusively a small percentage of the incoming air in said turbomachine along its main axis and along said blade (10) of the fan in normal operation. 2. Fan blade (10) according to claim 1 characterized in that the percentage of air entering said at least one chimney (31, 32) is less than 2%, preferably less than 1% of the air following said dawn (10). Blower blade (10) according to claim 1 or 2, characterized in that said inlet orifices (20) are distributed between the 40% and 20% of the surface of said blade closest to said trailing edge (16). ) of dawn. 4. blade (10) of a fan according to any one of claims 1 to 3 characterized in that said inlet ports (20) are distributed in the 40% of the surface of said blade closest to said foot (12) of dawn. 5. Fan blade (10) according to any one of claims 1 to 4 characterized in that said inlet ports (20) are distributed in several columns (C) oriented in the direction of said foot (12) to said head (14) of the blade, and that said inlet ports (20) are staggered between two adjacent columns. 6. blade (10) of a fan according to any one of claims 1 to 5 characterized in that said outlet orifices (40) are distributed along said trailing edge (16) of the blade between 60% and 95% the length of said trailing edge (16) measured from said root (12) of the blade. Blower blade (10) according to one of Claims 1 to 6, characterized in that the outlet openings (40) are chosen from a set comprising substantially circular holes, oblong holes elongated in the direction of the edge of the groove. leak (16), or one or more slots. 8. fan blade (10) according to any one of claims 1 to 7 characterized in that a first chimney (31) connects at least a portion of said inlet ports (20) to a first group (41) d outlets (40), and in that a second chimney (32) connects at least a portion of the inlet ports to a second group (42) of outlet ports which are further from said head ( 14) of the blade as said first group (41). 9. fan blade (10) according to any one of claims 1 to 8 characterized in that the sum of the surfaces of the sections of said inlet ports (20) is smaller than the surface of the section of said at least one chimney . 10. Turbomachine whose blower comprises a blade (10) according to any one of the preceding claims.