Air intake guide

Abstract

An air intake guide for a jet propulsion power plant for a supersonic aircraft comprises an intake aperture, an intake center body and an intake adjustment device. The intake aperture has an intake lip, an intake center body is positioned within the aperture, and an intake adjustment device is positioned on a radially inwardly facing surface of the air intake guide downstream of the intake lip. The intake adjustment device comprises a flexible panel and an actuator with the actuator being adapted to deflect the flexible panel in a radially inwardly direction so as to reduce a cross-sectional area of the intake aperture and thereby to position a shock wave at the intake lip.

Claims

1. An air intake guide for a jet propulsion power plant for a supersonic aircraft, the air intake guide comprising: an intake aperture having an intake lip; and an intake adjustment device positioned on a radially inwardly facing surface of the air intake guide downstream of the intake lip, wherein the intake adjustment device comprises a flexible panel and an actuator, the actuator being adapted to deflect the flexible panel in a radially inwardly direction so as to reduce a cross-sectional area of the intake aperture, wherein the air intake guide further comprises a flexible fairing positioned downstream of, and contiguous with, the flexible panel, and wherein the actuator comprises a first, high rate response actuator and a second, low rate response actuator.

2. The air intake guide as claimed in claim 1, further comprising an intake center body positioned within the aperture.

3. The air intake guide as claimed in claim 1, wherein the intake aperture is circular in cross-section.

4. The air intake guide as claimed in claim 1, wherein the actuator is one or more of a hydraulic, pneumatic, electric and piezo-electric actuator.

5. The air intake guide as claimed in claim 1, wherein the actuator provides a radially inwardly directed force on the flexible panel.

6. The air intake guide as claimed in claim 1, wherein the actuator provides an axially directed force on the flexible panel.

7. The air intake guide as claimed in claim 6, further comprising a slipper interposed between the actuator and the flexible panel, the slipper comprising a first ramp surface, the flexible panel comprising a second ramp surface, the first and second ramp surfaces being in sliding contact with one another, wherein axial movement of the actuator causes a corresponding radially inward movement of the flexible panel.

8. The air intake guide as claimed in claim 1, further comprising one or more pressure sensors positioned on a radially inwardly facing surface of the intake lip.

9. The air intake guide as claimed in claim 1, further comprising one or more pressure sensors positioned on a radially outwardly facing surface of the intake lip.

10. The air intake guide as claimed in claim 1, wherein the flexible panel is formed from an elastomeric material.

11. The air intake guide as claimed in claim 1, wherein the flexible panel is formed from a fibre-reinforced composite material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) There now follows a description of an embodiment of the invention, by way of non-limiting example, with reference being made to the accompanying drawings in which:

(2) FIG. 1 shows a schematic partial sectional view of a jet engine having an air intake guide according to a first embodiment of the invention;

(3) FIG. 2 shows a schematic partial sectional view of the air intake guide of FIG. 1, in its inactive position;

(4) FIG. 3 shows a schematic partial sectional view of the air intake guide of FIG. 1, in its activated position;

(5) FIG. 4 shows schematic partial sectional view of an air intake guide according to a second embodiment of the invention;

(6) FIG. 5 shows a schematic arrangement of an engine of a supersonic aircraft in a critical shock arrangement;

(7) FIG. 6 shows a schematic arrangement of the engine of FIG. 5 in a supercritical operation; and

(8) FIG. 7 shows a schematic arrangement of the engine of FIG. 5 in a subcritical operation.

(9) It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION

(10) Referring to FIGS. 1 to 3, an air intake guide according to a first embodiment of the invention is designated generally by the reference numeral 100. The air intake guide 100 is positioned at the air inlet, or air intake, of the nacelle 102 of a jet propulsion power plant (not shown) for a supersonic aircraft (also not shown).

(11) In the following disclosure, the following definitions are adopted. The terms upstream and downstream are considered to be relative to the air flow through the engine, which in all of the figures is from left to right. The term radially inwardly is considered to relate to a direction relative to the axis of the engine and corresponds to a downward direction in each of FIGS. 1 to 4. The terms axial and axially are considered to relate to the direction of the axis of the engine, which in all of the figures is from left to right.

(12) The air intake guide 100 comprises an intake aperture 120 having an intake lip 130, and an intake adjustment device 140 positioned on a radially inwardly facing surface 104 of the air intake guide 100 and downstream of the intake lip 130.

(13) The intake lip 130 encircles and thereby defines the intake aperture 120. In the present embodiment, the intake aperture 120 is circular. However, in other embodiments of the invention the intake aperture may take other geometric forms such as, for example, an ellipse or an oval.

(14) In the present embodiment, an intake centre body 110 is positioned within the intake aperture 120. The function of the intake centre body 110 is to generate a system of shock waves 190 and so to optimise the efficiency of the intake of air into the engine.

(15) The intake lip 130 has a radially inwardly facing surface 132 and a radially outwardly facing surface 134. A plurality of pressure sensors 180 are provided in each of the inwardly and outwardly facing surfaces 132,134, at first sensing positions represented by arrow 182 in FIG. 3.

(16) Additionally, further pressure sensors 180 are provided at second sensing positions represented by arrow 184 in FIG. 3. The second sensing positions are arranged on a radially inwardly facing surface of the nacelle 102 downstream of the air intake guide.

(17) The intake adjustment device 140 comprises a flexible panel 144 and an actuator 150 configured to press against the flexible panel 144 and so to deflect the flexible panel 144 in a radially inwardly direction.

(18) The flexible panel 144 is formed as an annular ring and projects into the intake aperture 120. The above-mentioned deflection of the flexible panel 144 results in a cross-sectional area of the intake aperture 120 being reduced.

(19) In the present embodiment, the flexible panel 144 is formed from a thin sheet of spring steel. In alternative arrangements, the flexible panel 144 may be provided with thin slots in its surface to increase the range of deflection.

(20) In the present embodiment of the invention, the actuator 150 comprises a first, high rate response actuator 152 and a second, low rate response actuator 154 arranged in series with one another. In other words, the second actuator 154 is configured to provide an axial force against the first actuator 152.

(21) The second, low rate response actuator 154 is arranged to provide a slow, steady state axial force while the first, high rate response actuator 152 provides for a rapidly variable tuning axial force to supplement the steady state force provided by the second actuator 154.

(22) The first actuator 152 and the second actuator 154 are each formed as a plurality of individual piezo-electric actuating elements (not shown) that are uniformly circumferentially distributed around a circumference of the air intake guide 100.

(23) In other embodiments of the invention, the second actuator 154 may take the form of memory metal alloys, hydraulic, electro-hydraulic or electro-mechanical means. Similarly, in other arrangements, the first actuator 152 may comprise hydraulic, electro-hydraulic or electro-mechanical means.

(24) A slipper 170 is interposed between the first actuator 152 and the flexible panel 144. The first actuator 152 therefore exerts an axial force against the slipper 170. The slipper 170 comprises a first ramp surface 172 which is configured to transmit the axial force to the flexible panel 144.

(25) The flexible panel 144 is formed in a hook or U shape. A first leg of the U forms the radially inwardly facing surface 104 of the air intake guide 100 and extends upstream to join the radially inwardly facing surface 132 of the intake lip 130. A second leg of the U is provided with a second ramp surface 174 which slidingly contacts the first ramp surface 172 of the slipper 170 to thereby receive the axial force generated by the first and second actuators 152,154.

(26) Referring to FIG. 4, an air intake guide according to a second embodiment of the invention is designated generally by the reference numeral 200. Features of the air intake guide 200 which correspond to those of apparatus 100 have been given corresponding reference numerals for ease of reference.

(27) In this second embodiment, the intake adjustment device 240 comprises a flexible panel 244 and an actuator 250 configured to press against the flexible panel 244 and thereby to deflect the flexible panel 244 in a radially inwardly direction

(28) The actuator 250 comprises a first, high rate response actuator 252 and a second, low rate response actuator 254.

(29) The first actuator 252 is an electro-mechanical actuator and presses in an axial direction against an edge 246 of the flexible panel 244 thereby causing the flexible panel 244 to bow and thereby deflect in a radially inwardly direction. The second actuator 254 is an electro-mechanical actuator and presses in a radially inward direction against a radially outwardly facing surface 248 of the flexible panel 244.

(30) In other arrangements of the second embodiment, the second actuator 254 may comprise a electro-hydraulic actuator, for example using a circumferentially arranged cable which may be variably tensioned.

(31) In use, pressure measurements are taken from the pressure sensors 180 and transmitted to the engine control unit (ECU). The ECU (not shown) uses this data together with other information relating to the engine's operating condition and the aircraft's flight envelope to determine an actuation strategy for the actuator 150; 250.

(32) FIG. 5 shows the ideal scenario which facilitates a minimum (critical) size nacelle and thus minimum drag. The shock is axially aligned with the intake lip which is an unstable scenario with a high risk of shock ingestion into the engine.

(33) With reference to FIG. 6, if the shock is ingested into the intake aperture 120, then the flow will accelerate in the diverging section of the intake normally provided for subsonic diffusion to the first compressor and will thus accelerate to exceed the flight Mach number (i.e. the Mach number corresponding to the aircraft's speed). This will result in a higher pressure ratio terminal shock with increased pressure loss and a risk of the engine entering a compressor surge condition. This reduces the efficiency of the engine and may cause damage to the engine.

(34) The actuation strategy is intended to actively respond to variations in the flow presented to the intake that would have otherwise caused shock ingestion. The present invention thus allows a design of engine and nacelle to approach the ideal scenario in FIG. 5 closer than is currently possible with a passive fixed structure. Operation of the engine with the shock wave 190 at this closer position minimises the aerodynamic drag and so maximises the efficiency of the installed engine.

(35) If the shock moves too close to the intake as determined by processing pressure data from sensors 180 (thus threatening shock ingestion and supercritical operation) the actuator 150; 250 will be actuated by the ECU and will deflect the flexible panel 144; 244 radially inwardly to thereby constrict the flow through the intake aperture 120. This causes the shock wave 190 to move away from the intake lip 130.

(36) The active nature of the air intake guide of the present invention allows subcritcal operation to be maintained at smaller nacelle diameters than is currently possible. This corresponds to a shock system lying closer to the intake lip 130 than currently possible for a passive intake

(37) The foregoing description of various aspects of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously, many modifications and variations are possible. Such modifications and variations that may be apparent to a person of skill in the art are included within the scope of the invention as defined by the accompanying claims.