AERODYNAMIC MEASUREMENT PROBE

Abstract

An aerodynamic measurement probe intended to measure a local angle of attack of an air stream flowing along the fuselage of an aircraft, includes a support and a shaft that is able to rotate about a longitudinal axis with respect to the support, the support and the shaft being configured to form between them a gap, passing around an annular tab at the end of the shaft in the support, making it possible to maintain a functional clearance to allow one end of the shaft to pivot freely in the support, and communicating with an impurity discharge circuit, the gap comprising an inner annular groove about the axis of rotation, made in the support, and opening out away from the axis directly onto the end part of the annular tab, the profile of the inner groove being rounded.

Claims

1. An aerodynamic measurement probe intended to measure a local angle of attack of an air stream flowing along the fuselage of an aircraft, comprising a support and a shaft that is able to rotate about a longitudinal axis with respect to the support, the support and the shaft being configured to form between them a gap, passing around an annular tab at the end of the shaft in the support, making it possible to maintain a functional clearance to allow one end of the shaft to pivot freely in the support, and communicating with an impurity discharge circuit, the gap comprising an inner annular groove about the axis of rotation, made in the support, and opening out away from the axis directly onto the end part of the annular tab, the profile of the inner groove being rounded.

2. The probe as claimed in claim 1, wherein the gap further comprises an outer annular groove, about the axis of rotation, made in the support, and opening out toward the axis, so that the annular tab is positioned directly between the inner and outer grooves.

3. The probe as claimed in claim 2, wherein the profile of the outer groove is rectangular.

4. The probe as claimed in claim 3, wherein the rectangular profile of the outer groove has a height (a) of between 1.5 mm and 4 mm.

5. The probe as claimed in claim 4, wherein the rectangular profile of the outer groove has a height (a) of 3 mm.

6. The probe as claimed in claim 3, wherein the rectangular profile of the outer groove (7) has a depth (b) of between 3 mm and 7 mm.

7. The probe as claimed in claim 6, wherein the rectangular profile of the outer groove has a depth (b) of 4.5 mm.

8. The probe as claimed in claim 7, wherein the rounded profile of the inner groove has a diameter (d) of between 2 and 5 mm.

9. The probe as claimed in claim 8, wherein the rounded profile of the inner groove has a diameter (d) of 3.2 mm.

10. The probe as claimed in claim 1, wherein the profile of the inner groove is rectangular.

11. The probe as claimed in claim 10, wherein the profile of the rectangular inner groove has a height of between 2 mm and 5 mm.

12. The probe as claimed in claim 1, wherein the gap comprises a substantially straight first part, having a width (f) of between 1 mm and 5 mm, between the part of the gap emerging into the open air and the outer groove.

13. The probe as claimed in claim 12, wherein the first part of the gap has a width (f) of 1.2 mm.

14. The probe as claimed in claim 1, wherein the gap comprises a substantially straight second part, between the outer groove and the inner groove, having a width (c) of between 0.5 mm and 1 mm.

15. The probe as claimed in claim 14, wherein the second part of the gap has a width (c) of 0.65 mm.

16. The probe as claimed in claim 1, wherein the gap comprises a substantially straight third part, positioned between the inner groove and a fourth part of the gap in contact with mechanical elements of the movable shaft allowing the rotation thereof, having a width (e) of between 0.5 mm and 1 mm.

17. The probe as claimed in claim 16, wherein the third part of the gap has a width (e) of 0.65 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention will be better understood on examining various embodiments described by way of non-limiting example and illustrated by the appended drawings, in which:

[0043] FIG. 1 schematically illustrates an exterior view of the aerodynamic measurement probe, according to one aspect of the invention;

[0044] FIG. 2 schematically illustrates a cross-sectional view of the aerodynamic measurement probe that does not pass through the drain holes of the impurity discharge circuit, according to one aspect of the invention;

[0045] FIG. 3 schematically illustrates a cross-sectional view of the aerodynamic measurement probe that passes through the drain holes of the impurity discharge circuit, according to one aspect of the invention;

[0046] FIG. 4 schematically illustrates a cross-sectional view of the aerodynamic measurement probe in line with the gap between the support and the rotating shaft with velocity fields projected in the section plane, according to one aspect of the invention;

[0047] FIG. 5a schematically illustrates an exterior view of the streamlines of the air flow leaving the drain holes of the impurity discharge circuit, according to one aspect of the invention;

[0048] FIG. 5b schematically illustrates an exterior view of the streamlines of the air flow leaving the rear part of the gap, according to one aspect of the invention;

[0049] FIG. 6a schematically illustrates an interior view of the streamlines of the air flow leaving the drain holes of the impurity discharge circuit, according to one aspect of the invention; and

[0050] FIG. 6b schematically illustrates an interior view of the streamlines of the air flow leaving the rear part of the gap, according to one aspect of the invention. In all of the figures, elements with identical reference signs are similar.

DETAILED DESCRIPTION

[0051] In the present description, the embodiments described are non-limiting, and the features and functions well known to a person skilled in the art are not described in detail.

[0052] FIG. 1 schematically shows an aerodynamic measurement probe intended to measure a local angle of attack of an air stream flowing along the fuselage of an aircraft, comprising a support 1, in this instance circular in shape, and a shaft 2 that is able to rotate about a longitudinal axis 3 with respect to the support 1.

[0053] The solution proposed for managing the ingestion of impurities by an aerodynamic measurement probe is based on the design of the functional clearance between the movable shaft or vane 2 and the heating body, and of the drain holes. The proposed design makes it possible to simultaneously manage the ingestion of ice crystals, water droplets and solid particles such as volcanic ash, dust or grains of sand, etc. (defined by DO-160, which defines the test procedures for equipment on board an aircraft).

[0054] FIG. 1 shows the exterior of an aerodynamic measurement probe and highlights the gap 4 between the support 1 and the movable shaft 2, which passes around an annular tab 2a at the end of the shaft 2 in the support 1. When the probe is placed in an air flow, the air enters through the front part of the gap 4 and leaves through the drain holes of an impurity discharge circuit 5, in this case two drain holes 5a and 5b, and through the rear part of the gap 4.

[0055] For example, the drain holes 5a and 5b are positioned so that one of the two can always be situated toward the bottom (direction of gravity), whether the probe is mounted on the right or left of the aircraft. FIG. 1 shows a situation in which the drain hole 5b is situated toward the bottom. This makes it possible to discharge by gravity the impurities that enter the probe when the aircraft is stopped or taxiing.

[0056] FIG. 2 shows a cross-sectional view of the aerodynamic measurement probe, which does not pass through the drain holes 5a, 5b of the impurity discharge circuit, and FIG. 3 shows a cross-sectional view of the aerodynamic measurement probe, which does not pass through the drain holes 5a, 5b of the impurity discharge circuit, according to one aspect of the invention. These cross-sections pass through the plane of symmetry of the movable shaft or vane 2.

[0057] The gap 4 comprises an inner annular groove 6 about the axis of rotation, made in the support 1 and opening out away from the axis.

[0058] FIG. 4 shows the gap 4 in greater detail.

[0059] As illustrated in FIGS. 2, 3 and 4, the start of the gap 4 between the foot of the rotating shaft 2 and the fixed support 1 is substantially straight, having a constant width that makes it possible to avoid air being sucked in through the drain holes.

[0060] Optionally, the gap 4 can further comprise an outer annular groove 7, about the axis of rotation 3, made in the support and opening out toward the axis. In a non-limiting manner, the figures described in the present description comprise such an outer annular groove 7.

[0061] The end of the shaft 2 in the support can further comprise an annular tab 2a positioned between the inner 6 and outer 7 grooves.

[0062] The ingestion of airborne sand through the gap 1 must not jam the rotation of the movable shaft 2. It must therefore let through the largest grains of sand. Standard DO-160 states a maximum grain size of the order of 1 mm. The minimum width of the gap 4 must thus be slightly greater than 1 mm. On the other hand, for thermal protection reasons, the width of the gap 4 must be as small as possible. A maximum acceptable value for this width is 5 mm.

[0063] Considering the direction of flow, the gap 4 comprises a substantially straight first part, upstream of the first groove, having a width of between 1 mm and 5 mm, and preferably having a width of 1.2 mm.

[0064] This substantially straight first part emerges into the outer groove 7.

[0065] The outer annular groove 7 can have a rectangular profile, having a height of between 1.5 mm and 4 mm, preferably 3 mm, and a depth of between 3 mm and 7 mm, preferably 4.5 mm.

[0066] There is then a substantially straight second part 4b, between the outer groove 7 and the inner groove 6, having a width of between 0.5 mm and 1 mm, preferably 0.65 mm.

[0067] The gap 4 comprises a substantially straight third part 4c, positioned downstream of the inner groove 6, and upstream of a fourth part 4d in contact with mechanical elements of the movable shaft 2 allowing the rotation thereof, having a width of between 0.5 mm and 1 mm, and preferably having a width of 0.65 mm.

[0068] The first part of the gap 4 communicates directly with the outer groove 7. This is a cylindrical groove that makes a complete turn around the heating body (symmetry of revolution), not shown in the figures.

[0069] The profile of the inner groove 6 is for example rounded or rectangular.

[0070] If it is rounded, the profile of the inner groove 6 has a diameter of between 2 and 5 mm, and preferably a diameter of 3.2 mm.

[0071] If it is rectangular, the profile of the inner groove 6 has a height of between 2 mm and 5 mm.

[0072] The sudden change in cross-section between the gap 4 and the outer groove 7 results in the formation of a recirculation vortex T7 inside the outer groove 7, as illustrated in FIG. 4. It originates inside the outer groove 7 directly below the leading edge of the movable shaft 2 along its axis of rotation and then develops on either side of this element to the drain holes 5a and 5b. This vortex T7 therefore guides any impurities that enter through the upstream part of the gap 4 toward the drain holes 5a, 5b.

[0073] The rounded (teardrop shaped) or rectangular profile of the inner groove 6 generates another vortex T6, counter-rotating with respect to the vortex T7 of the outer groove 7. Like the vortex T7, the vortex T6 originates at the furthest upstream point of the geometry. It develops to the downstream part of the probe where the flow, and the impurities it is carrying, are discharged.

[0074] Some impurities might not be guided toward a drain hole 5a, 5b by the vortex T7, and so continue on their path under the shaft 2. They then meet the upper chicane or inner groove 6, which is the last obstacle preventing the intrusion of impurities into the mechanism of the shaft 2, and therefore the jamming thereof. It must be as high as possible, without however hindering the rotation of the movable shaft 2 of the probe.

[0075] The foot of the shaft 2 extends slightly beyond the fixed support so that a stopping point of the flow is situated on the probe foot. As a result, the flow enters under the probe foot through the upstream half-portion of the gap 4 and exits through the downstream half-portion of the gap and through the drain holes 5a, 5b.

[0076] The connection between the drain holes and the rest of the impurity discharge system is shown in FIG. 5a and FIG. 5b, as well as in FIG. 6a and FIG. 6b.

[0077] FIG. 5a shows the streamlines of the flow passing through the drain holes 5a, 5b. Before exiting the holes, the flow arrives from the bottom left of FIG. 5a and follows the direction of the arrows. It enters through the upstream part of the gap 4 and then flows in the grooves 7 and/or 6 before exiting through the drain hole 5a and/or through the drain hole 5b.

[0078] FIG. 5b supplements FIG. 5a, as showing everything in the same figure would be illegible. FIG. 5b shows the streamlines of the flow passing through the rear part of the gap 4.

[0079] FIG. 6a shows in interior view of the streamlines of the air flow passing through the drain holes of the impurity discharge circuit.

[0080] FIG. 6b supplements FIG. 6a, as showing everything in the same figure would be illegible. FIG. 6b shows an interior view of the streamlines of the air flow passing through the rear part of the gap 4.