FR2927673A1 - 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 following description, 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 vanes 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 fan 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 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 the main axis when the turbomachine is in operation) and the heads 14 of the blades 10 do not touch the casing 90. The noise certification standards of an aircraft, especially during the take-off and landing phases, impose further restrictions. more severe on the noise generated by the engines (turbomachine) 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 fan has two components: a first component is the noise specific to the fan, 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 vortices generated at the top of the fan blades with the boundary layer at the surface of the crankcase.

90 and 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 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 root of the blade on the first face, and at its other end by orifices. at the head of the blade, the at least one chimney being intended to convey from the inlet orifices to the outlet orifices exclusively a small percentage of the air entering the turbomachine along its main axis and running along the dawn of the blower in normal operation. Thanks to these provisions, the centrifugal force generated by the rotation of the fan causes air through each blade by the chimney or chimneys, from the foot of the blade to the head of the blade. Thus, the vortices at the top of the fan blade are partially destroyed by the air ejected by the outlets. The interaction of these vortices with the blades 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 40010 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 route the air more easily along the chimney or chimneys from the inlet ports to the outlets. 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 the line BB of Figure 3 of a fan blade according to the invention at its central region, Figure 3C shows a cross section along the line CC of Figure 3 of a fan blade according to the invention at its head, Figure 4 is a front view of the foot 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 face (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 orifices 20 which open into one or more chimneys dug in the blade 10. These inlet orifices 20 do not open on the second In FIG. 3A there is shown the case where the blade 10 comprises two chimneys 31 and 32. The inlet orifices 20 are located in the region of the blade 10 which is closer to 12. The chimneys 31, 32 extend from substantially the root of the blade to the head 14 of the blade 10. The chimneys 31, 32 open at the head 14 through outlets 40 The outlet orifices 40 are distributed at the most radially outer end of the blade 10, that is to say on the portion of the head 14 of the blade 10 which connects the radially outer ends of the edge of the blade. 15 and the trailing edge 16. The chimneys 31, 32 are completely embedded in the volume of the blade 10, and do not The centrifugal force to which a point of a body rotates 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 head 14 of the blade 10 is subjected to a centrifugal force approximately twice as large centrifugal force to which is subjected the foot 12 of the blade 10. This difference in centrifugal force between the foot and the head of the blade is sufficient so that it is not necessary to use a pumping device for routing the air from the inlet ports 20 to the outlet ports 40. The inlet ports 20, the chimneys 31, 32 and the outlet ports 40 therefore constitute a self-suction system which allows a flow to be conveyed. foot air 12 from the blade 10 to the head 14 of the blade 10 only by using the 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

dawn 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 greater than its thickness (distance between his first face 17 and his 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 top of the blade 10 by 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 sections of the inlet ports 40 is less than the sum of the area of the section of the first chimney 31 and the area of the section of the second chimney 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 40 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. 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.

The section of each chimney 31, 32 is substantially constant from the inlet ports 20 over the entire height of this chimney. Thus, 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 the first chimney 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 is due to the decrease in the thickness of the blade 10 between its foot 12 and its head 14. In the case where the blade 10 has two chimneys, the first chimney 31 opens with the half of the outlets 40 which are the most upstream on the head 14 of the blade 10, while the second chimney 32 (situated further downstream than the first chimney 31) opens out by half of the outlets which are the further downstream on the head 14. This geometry chimneys 31, 32 can minimize the amount of material removed in the dawn to form these chimneys.

For example, the first chimney 31 connects at least a portion of the inlet ports 20 to a first group 41 of outlet ports 40, and a second chimney 32 connects at least a portion of the inlet ports 20 to a second group 42 of outlets 40 which are located downstream of the first group 41.

This situation is illustrated in FIG. 3A, the outlet orifices 40 being distributed between a first group 41 consisting of the outlet orifices situated between the leading edge 15 and substantially the middle of the head 14, and a second group 42 consisting of outlet ports located between the middle of the head 14 and the trailing edge 16. 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 ports 20 are distributed in the 40% of the height of the blade 10 closest to the foot 12. For example the inlet ports 20 are distributed between 5% and 40% of the height of the blade. dawn 10 closest to the foot 12. In fact, the calculations made by the inventors have shown that if the inlet ports 20 are not sufficiently far apart

outlets 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 outlet ports 40. The percentage of the incoming air in 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 dawn adjacent to the dawn 10 which is opposite this first face 17. It is important that this percentage of air taken remains low, because if the air flow in the chimneys 31, 32 is too large, less air passes through the blower, and its performance is decreased detrimentally. 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 outlet orifices 40 are distributed along the head 14 of the blade 10 between 5 ° and 95% of the length of the head 14 from the leading edge 15 of the blade 10. small width of the head 14 of the blade 10, the outlet ports 40 are aligned on a single line. The outlet orifices 40 are oriented substantially in the radial direction, so that the air emerging from the outlet orifices 40 is directed radially outwards. Alternatively, the outlet orifices 40 may be further directed upstream, so that the air emerging from these outlet orifices 40 is directed both radially outwards and towards the leading edge 15 of the dawn 10. This configuration potentially amplifies the aerodynamic blocking effect which limits the undesirable recirculation of air from the intrados (second face 18) to the extrados (first face 17) at the head of the blade. 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 nearest 40% and 20% of the surface of the blade 10 from 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, reduction of the blade root boundary layer 12 results in improved blower efficiency. 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 10 is taken and enters the chimneys 31, 32. At the same time, these inlet orifices 20 must not be too much numerous, in order to minimize the costs of manufacture of the blade 10. The inlet ports 20 are for example divided into several columns C (a column being oriented in the direction of the foot 12 towards the head 14 of the dawn) . 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 top of the boxes of a checkerboard. To minimize the concentration of stresses 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 from each other. These two adjacent inlet ports 20 will therefore generate a lower stress concentration. It is also preferable that the inlet ports are 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 only 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 ports 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 ports 20. Description above was made in the case where the dawn 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 fan of this turbomachine is a blade 10 as described above.

Claims (9)

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 by outlet orifices (40) located at said head (14), said at least one chimney (31, 32) being intended to convey from said inlet orifices (20) to said orifices outlet (40) exclusively a small percentage of the air entering said turbomachine along its main axis and along said blade (10) of the blower in fo 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. fan blade (10) according to any one of claims 1 to 5 characterized in that said outlet orifices (40) are distributed along said head (14) of the blade between 5% and 95% of the length of said head (14) from said leading edge (15) of the blade. 7. Fan blade (10) according to any one of claims 1 to 6 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 that a second chimney (32) connects at least a portion of the inlet ports to a second group (42) of outlet ports which are located downstream of said first group ( 41). 8. fan blade (10) according to any one of claims 1 to 7 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 . 9. A turbomachine whose blower comprises a blade (10) according to any one of the preceding claims.