Fluid intake system

Abstract

A fluid intake system including a fluid collector scoop designed to be fastened on an inside surface of a wall in order to collect the fluid flowing on the outside of the wall; and an extraction duct suitable for directing the fluid from an inlet orifice into the duct to at least one outlet orifice from the duct, is provided. The scoop is arranged so as to direct the collected fluid towards the inlet orifice of the extraction duct. In this system, at least one outlet orifice is of substantially elliptical section with a ratio of the major diameter of the ellipse over its minor diameter being greater than 1.5.

Claims

1. A fluid intake system comprising: a fluid collector scoop designed to be fastened on an inside side of an opening arranged in an outer wall of a gas turbine engine in order to collect a fluid including ambient air flowing on an outside of the outer wall; and an extraction duct suitable for directing the fluid from an inlet orifice into said extraction duct to an outlet orifice from said extraction duct, wherein the fluid collector scoop is arranged so as to direct the fluid towards the inlet orifice of the extraction duct, wherein the outlet orifice comprises an elliptical section with a ratio of a major diameter of the elliptical section over a minor diameter of the elliptical section being between 1.5 and 8.0, wherein the extraction duct includes: a transfer portion having a first cross-sectional area that is constant or that increases in a linear manner as a first function of a curvilinear abscissa position along a neutral axis of the extraction duct, the first cross-sectional area of the transfer portion being rectangular, and a diffuser extending from a transition section of the extraction duct to an outlet section, the diffuser having a second cross-sectional area that increases in a convex manner from an upstream end to a downstream end as a second function of the curvilinear abscissa position along the neutral axis of the extraction duct, the second cross-sectional area of the diffuser being rectangular at the upstream end and elliptical at the downstream end.

2. The fluid intake system according to claim 1, wherein the transfer portion extends from the inlet orifice.

3. The fluid intake system according to claim 1, wherein the outlet orifice of the extraction duct is singular, wherein a first width L.sub.t of the transition section satisfies:
0.95*L.sub.iL.sub.t1.05*L.sub.i where L.sub.i is a second width of the inlet orifice.

4. The fluid intake system according to claim 1, wherein the outlet orifice of the extraction duct is singular, wherein a third cross-sectional area A.sub.t of the transition section perpendicular to the neutral axis of the extraction duct satisfies:
A.sub.t1.09*A.sub.i where A.sub.i is a fourth cross-sectional area of the inlet orifice perpendicular to the neutral axis of the extraction duct.

5. The fluid intake system according to claim 1, wherein a third cross-sectional area A.sub.o of the outlet orifice of the diffuser perpendicular to the neutral axis of the extraction duct satisfies:
A.sub.o10*A.sub.t where A.sub.t is a fourth cross-sectional area of the transition section perpendicular to the neutral axis of the extraction duct.

6. The fluid intake system according to claim 1, wherein an angle of divergence formed between two straight lines passing respectively on either side of the neutral axis of the extraction duct via outer limit points of the transition section and of the outlet orifice of the diffuser lies in a range of 25 to 90.

7. The fluid intake system according to claim 1, wherein a third cross-sectional area A.sub.so of a total section of said outlet orifice perpendicular to the neutral axis of the extraction duct satisfies:
A.sub.so10*A.sub.i where A.sub.i is a fourth cross-sectional area of the inlet orifice perpendicular to the neutral axis of the extraction duct.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention can be well understood and its advantages appear better on reading the following detailed description of embodiments given as non-limiting examples. The description refers to the accompanying drawings, in which:

(2) FIG. 1 is a diagrammatic perspective view of an intake system of the invention;

(3) FIG. 2 is another diagrammatic perspective view of the FIG. 1 intake system;

(4) FIG. 3 is a diagrammatic side view of the FIG. 1 intake system;

(5) FIG. 4 is a diagrammatic plan view of the FIG. 1 intake system; and

(6) FIG. 5 is a graph plotting a curve showing variation in the distance between the limit of the section of the duct and the neutral axis of the duct as a function of curvilinear abscissa position along the duct.

DETAILED DESCRIPTION OF THE INVENTION

(7) The fluid intake system 10 of the invention is described with reference to FIGS. 1 to 5.

(8) The system 10 comprises a fluid collector or scoop 12 and a fluid extraction duct 14.

(9) The collector or scoop 12 is fastened to the inside surface of a wall 16. In the example shown, this wall is the wall of an airplane engine nacelle. The scoop 12 is a flush scoop of the National Advisory Committee for Aeronautics (NACA) shape that is conventional in aviation. It comprises an upstream fluid collection portion 18 and an air inlet orifice 20 of section presenting an area A.sub.i.

(10) The fluid collection portion 18 is in the form of a groove of increasing width formed in the wall 16.

(11) At its downstream end (opposite end in the direction of arrow B), this groove 18 is defined: at the surface of the wall 16 by the wall 16 itself which forms a leading edge 21; below this leading edge 21, the groove opens out into the inlet orifice 20 of the fluid extraction duct 14, via which it feeds the duct with fluid.

(12) The scoop 12 faces upstream in the direction B in which the engine advances through the air. Because of its shape, when the airplane is in flight, it collects ambient air and directs it to the air inlet orifice 20.

(13) The duct 14 is arranged immediately downstream from the orifice 20. It receives the air collected by the scoop 12 and directs it towards the inside of the nacelle via a component that is to be cooled (not shown).

(14) In a plane perpendicular to the travel direction of the airplane (axis X, FIG. 2), the air inlet orifice 20 has a section of rectangular shape and of area A.sub.i, of height equal to about 20 millimeters (mm), and of width Li equal to about 70 mm in the example shown. Its height may lie in the range 10 mm to 50 mm, and its width in the range 40 mm to 300 mm, for example. Conventionally, the width of the air inlet orifice is equal to about four times its height. The area of the section 20 is dimensioned in particular as a function of the flow rate of air that it is desired to cause to pass through this section.

(15) The duct 14 comprises two portions: at its upstream end, a so-called transfer portion 22; and downstream therefrom, a diffusion portion or diffuser 24. The section of the duct 14 at the upstream limit of the diffuser 24 is referred to as the transition section 30; it presents a width L.sub.t and an area A.sub.t.

(16) In the example shown, the transition section 30 is the downstream limit of the transfer portion 22.

(17) Variations in the area A of the section of the duct 14 are plotted in FIG. 5, in association with FIG. 4. The area A is a function of curvilinear abscissa position X measured along the neutral axis F of the duct 14. In this embodiment, and moving in the fluid flow direction along the duct 14 from upstream to downstream, the abscissa position X conventionally decreases: the fluid begins by passing via the air inlet orifice 20 of section at abscissa position X.sub.i; it then passes through the transition section 30 at abscissa position X.sub.t and is ejected from the air intake system at the outlet from the diffuser 24 at abscissa position X=0.

(18) The following inequality thus applies:
X.sub.i>X.sub.t>0

(19) The transfer portion 22 serves to transport the fluid collected by the scoop 12 from the air inlet orifice to the diffuser 24; it may possibly be relatively long. It may also have one or more bifurcations, i.e. portions where the duct in the upstream to downstream direction splits into two or more ducts.

(20) The area A of the section of the transfer portion 22 is generally relatively constant, and preferably increases slightly going from upstream to downstream. In the example shown, the area A is constant in the transfer portion 22 from abscissa position X.sub.i to abscissa position X.sub.t.

(21) The transfer portion 22 is rectangular in section. In the transfer portion 22, the area A of the duct increases linearly and very progressively from the area A.sub.i of the inlet orifice to the area A.sub.t of the transition section 30, which constitutes the downstream outlet from the transfer portion. The area of the transition section 30 preferably lies in the range 1.03 A.sub.i to 1.09 A.sub.i.

(22) Furthermore, the width L.sub.t of the transition section 30 is equal to the width L.sub.i of the inlet orifice, so:
L.sub.t=L.sub.i

(23) After the transition section 30, the fluid penetrates into the diffuser 24, which is situated immediately downstream from the transfer portion 22. In the diffuser 24, the area A of the section of the duct 14 increases convexly as a function of curvilinear abscissa position X. It thus increases considerably more quickly than in the transfer portion 22.

(24) The diffuser 24 extends downstream from the transfer portion 22. It is in the form of a flared horn and serves to diffuse the jet of fluid over a relatively large solid angle, given the relatively small section of the extraction duct.

(25) The diffuser has a section that varies from an upstream end that is rectangular in shape (i.e. having the shape of the transition section 30), to an outlet orifice 25 that has a section that is elliptical in shape.

(26) In the example shown, the outlet orifice is elliptical in shape with a large ratio of the major diameter Lo over the minor diameter Ho of the ellipse (FIG. 1), this ratio being about 6.

(27) The area A of the diffuser expressed as a function of curvilinear abscissa position along a neutral axis of the duct increases continuously from upstream to downstream from the area A.sub.t of the transition section 30 to the area A.sub.o of the section of the outlet orifice.

(28) The area A(x) of the section of the diffuser is a convex function. The curve representing it thus presents an upwardly rounded portion on the right-hand side of FIG. 5 between the curvilinear abscissa position X.sub.t (abscissa position of the transition section 30) and X.sub.o (abscissa position of the outlet orifice). This upwardly rounded shape differs from the straight shape (i.e. formed by a straight line segment) of the linearly curved portion presented by the transfer portion between abscissa position X.sub.i at the inlet orifice and abscissa position X.sub.t.

(29) Because the area increases in convex manner within the diffuser 24, the increase in section takes place more slowly upstream than it does downstream, thereby enabling the pressure gradient to remain constant along the channel, and thus reducing head losses by about 40% compared with a diffuser having straight walls.

(30) Furthermore, the angle of divergence is defined in a meridian plane as being the angle formed between the two straight lines (D1 and D2 in FIG. 4) passing via the limit points on the outsides of the transition section 30 and of the outlet orifice, respectively on either side of the neutral axis of the duct.

(31) Whatever the meridian plane, within the diffuser 24 the angle of divergence between the lines D1 and D2 remains within the range 25 to 90.

(32) Furthermore, the shape of the wall of the diffuser 24 is defined as follows.

(33) The distance in the direction perpendicular to the neutral axis of the duct between the wall and the neutral axis of the duct, as a function of curvilinear abscissa position X is governed substantially by the following equation:

(34) $y=\frac{y1}{\sqrt[3]{1+\frac{x}{d}.Math.\left[{\left(\frac{y1}{y0}\right)}^3-1\right]}}$
where:

(35) x is the curvilinear abscissa position along the neutral axis of the duct, having the value d at the upstream section of the diffuser and 0 at the outlet orifice;

(36) y is the radial distance in the meridian plane under consideration relative to the neutral axis; and

(37) y0 and y1 are the radial distances respectively at the transition section 30 at the upstream end of the diffuser (x=X.sub.t) and at the outlet orifice of the diffuser (x=0).

(38) At the transition section 30, the shape of the duct 14 is arranged so as to ensure tangent and curvature continuity between the walls of the transfer portion and the walls of the diffuser.

(39) The value y1 is selected so that the area A.sub.o of the outlet orifice 25 remains in the preferred range 1.1 A.sub.t to 10 A.sub.t. This makes it possible to avoid the ejection stream becoming separated, i.e. to avoid it being highly turbulent in the vicinity of the walls of the diffuser 24.

(40) The term ejection angle is used to designate the limiting angle made between the neutral axis of the diffuser at the outlet orifice of the duct relative to the wall on which the intake system is fastened.

(41) Preferably, the ejection angle is small, and in particular less than 30. Consequently, the neutral axis F of the duct also forms an angle that is small relative to the wall in which the intake system is arranged. The bottom 13 of the scoop 12 conventionally presents an angle close to 7 relative to the wall in which the intake system is fastened (FIG. 3).

(42) Although in the example shown the extraction duct 14 presents only one outlet orifice, the present invention may be performed with an extraction duct 14 that presents one or more branches and consequently a plurality of outlet orifices.

(43) Under such circumstances, the relationships between the area of the outlet section and the area of the inlet section of the duct 14 apply to the sum A.sub.so of the areas of the various outlet orifices (as contrasted with the area of any one of the various outlet orifices). The area A.sub.so of the total section of the outlet orifices thus preferably satisfies the following relationships:
A.sub.so1.1*A.sub.i
and/or
A.sub.so10*A.sub.i