US2944631A - Retractable guards for air intakes - Google Patents

Description

y 1 ,1950 1'. H. KERRY ETAL 2,944,631

I I RETRACTABLE GUARDS FOR AIR INTAKES Filed-mamas, 195s Z-Sheets-Sheet 1 4 i l ri gv Inventors Attorney! July 12, 1960 'r. H. KERRY L 2,944,631

RETRACTABLE GUARDS FOR AIR INTAKES Fi led Dec. 26, 1956 2 Sheets-Sheet 2 FIG.'4.

Inventors) y M M- Attorneys United es Patent Office 2,944,631 Patented July 12,1960

, 2,944,631 RETRACTABLE GUARDS ro AIR INTAKES Thomas Henry Kerry,

Littleover, England, assignors to Rolls-Royce Limited, 7. Derby, England, a British company Filed Dec. 26,1956, Ser, No. 630,643 I Claims priority, application Great Britain Jan. 6,1956

3"Claims. (Cl. 183-62) This invention relates" to retractable guards for air intakes such as are used, for example, in conjunctionwith gas-turbine power plants. g It has preyiou'sl been proposed to provide in an annular air intake a'debris guard arrangement comprising a number of 'gridvp'ortions' each formed substantially as a sector of the annulus and arranged to swing about circumferentially-extending axes adjacent the outer edges of the respective grid portions between an operative position in which the grid portions together extend across the whole of the path of a fluid flowing in the air intake,

Derby, and Peter Arthur Ward,

The guard'portions may be in the'form of grids composed of a number of bars, the spacing of which will be such as to catch debris entrained in the fluid, and the bars may be in the form ofstrips which are fiat in one plane and are arranged in two sets, those of one set lying in planes parallel to the axis of the intake duct and extending substantially lengthwise of the duct when the guard portion is in its inoperative position, and-those of the otherset being curved and lying in planes which are at right-angles to the abovementioned-planes and are parallel to the axis of the duct when the guard grid is in its operative position.

thereby to catch debris entrained in the 'fluid, and an inoperative position in which the grid'portions lie out of the path of the fluid and are accommodated within an outer wall of the annular air intake duct.

The present. inventionis applicable to air intake ducts which are of non-annular form, for example, 'of full 'cir- 3 cular form or of rectangular form, and has for anobject to provide an improved construction of retractable guard arrangement.

According to the present invention a retractable guard comprises two guard portions each of which is mounted to pivot, about an axis extending across the duct, between an operative position in which the guard portions together extend, across the whole of the path of fluid flowing in the duct, one edge of each guard portion cooperates with a corresponding edge of the other guard portion and another edge of each guard portion co-operates with a wall of the duct, and an inoperative position in which the guard portions are substantially out of the path of fluid flowing through the duct, the guard portions being so shaped as to conform with the wall of the duct against a a which they lie in the retracted position.

Where the intake duct is of full circular form the two guard portions may be pivoted about a diameter of the duct, and in this case each guard portion will be of part-cylindrical form, where the duct is of constant diameter in the length swept by the guard portions, or of partconical form, where'the duct is varying, for example, of gradually increasing diameter in that length, so'thatthe guard portions conform with the correspondingly-shaped wall of the duct; i I

By a guard of full circular-form is meant one in which the cross section of the intake where the guard is fitted is circular.

According to a feature of the invention, the retractable guard comprises a pair of guard portions which are mounted to pivot about a common axis extending centrally across the duct, and the guard portions meet when in ,-In an'alternative arrangement the guard portions may be 'imperforate, being provided: in this case to prevent a flow of air through the engine when the latter is shut down, and thus to prevent windmilling of the engine.

In yet another arrangement there may be provided two guard portions in accordance with the invention formed as grids, and there may be provided in addition two imperforate panels which substantially conform to the shape of the grid portions and which are arranged to move from an inoperative position, in which they are out of the path of the fluid, to an operative position in which they lie against the guard grid portions when these are in their operative position. I

,One' embodiment of this invention will now be described with reference to the accompanying drawings of which 7 Figure Us 'a perspective view showing the guard grid in the operative position, v

Figure 2 is a view corresponding to Figure lwith the guard grid in the inoperative position, and

I Figure 3 is a longitudinal section. Figure 4 is a view looking downwardly in Figure 3 with the top half of the nacelle removed. 1 1 Referring; to Figure ,l the guard grid arrangement is shown as applied to an air'intake for a gas-turbine engine in a nacelle.

The nacelle 10 has inner and outer walls 11, 12, the inner wall forming the boundary of a fully circular crosssection air intake, duct 1'3 and the outer wall 12 forming Ward end which faces in the direction of flight of the aircraft of which the nacelle is to form part and leads at its rear end to the air entry of an axial-flow compressor 16 of ages-turbine engine. 1

As is well known, it is desirable to prevent birds'a'nd other foreign'bodies from passing down the air intake entrained in the entering air andstri-kin'g the inlet vanes or blades of the compressor 16, and for thispurpose there is provided a guard grid arrangement which will now be described. V I

The guard grid arrangement comprises a pair of guard grid portions 17, each of which comprises a number of bars arranged in two sets 18, 19. Each bar is of a'flat, substantially rectangular cross-section, of which the length issay 12 times \the width, and the ends of the cross-section i.e. the edges of the bars may be rounded. The

bars 18 of one set lie in parallel planes and extend,'when-- the guard-grid portions are in theinoperative position, as

shown in Figure 2; parallel to the axis 20 of the air intake 13. The bars 19 of-the other setextend in planes which are at right angles'to the-planes in which the =bars 18 of the first set lie, the bars of the two sets thus being in planes at right-angles to one another, and both set's of planes when the guard grid portions are in their operative positions (as seen in Figure 1), being parallel tothe axis 20 of the intake. Forexample, as shown in Figure 1, the

bars of the first set 18 may lie in parallel vertical planes and the bars 19 of the second set in parallel horizontal planes. The bars 19 of the second set are curved in the planes in which they lie, and are interconnected with the bars 18 of the first set; for example, each bar of one set may be formed with a slot which extends half-way through its cross-section and the bars of the other set may be formed with a co-operating slot, the bars interengaging so that the remainder of the cross-section of one bar lies in the slot in the other bar.

The edges of the guard grid portions 17 are formed of parts 21, 22 of increased cross-section area for strengthening purposes, one 21 of these parts lying parallel to the bars'19 of the second set, and the other 22 being at an angle which is somewhat less than a right angle to the bars 18 of the first set.

Thus each of the guard grid portions 17 has the form of part of the surface of a cylinder, and accordingly when they are in the inoperative position as shown in Figure 2 they substantially conform with the cylindrical inner wall 11 of the nacelle.

There may be provided a recess 23 in the wall 11 of the nacelle, which extends over that part of the wall adjacent to which the guard grid portions 17 lie when in the inoperative position, for the purpose of receiving debris accumulated by the grid portions. It has been found that owing to the force of the impact of the debris on the grip portions, the debris tends to be retained on these portions. It may, however, be arranged that the frame 21' of each guard grid portion '17 co-operates closely with the edge 24 of the recess 23 in the inner wall 11 when the guard grid portions are in the inoperative position, in order to prevent such debris from becoming loose during flight and entering the air intake of the compressor 16.

The guard grid portions 17 are mounted, as shown, to pivot about an axis 25 which is a diameter of the circular-section air intake duct 13, and this diameter may conveniently be horizontal. Each guard could be individually mounted to pivot on an axis which is a chord of the duct, the two axes being parallel or even coincident. Each guard grid portion 17 will be provided with a pair of sockets 26 at the intersections of the two frame members 21, 22, the sockets 26 of one guard grid portion 17 lying within those of the other portion with respect to the intake duct, and engaging with t-runnions 27 which may be spigot members carried by the nacelle wall 11.

Suitable operating mechanism will be provided for the guard grid portions 17, and this may comprise a ram, which may be, for example, pneumatically or hydraulically operated, and comprises a cylinder 28, of which one end is secured to the nacelle wall structure, and a piston which is connected by the rod 2% to a lever arm 30 attached to the frame member 22 of the guard grid portion 17. A separate ram may be provided for each grid portion, in which case stops will be provided to ensure that each grid portion moves to its appropriate positions, shown in Figures 1 and 2, or alternatively, as shown in the figures, a single ram may be provided and the guard grid portions 17 may be interlinked by means of pairs of links 31, one end of the links of each pair being connected one to each of the frame members 22 of the grid portions and the other end of the links being interconnected and carrying a roller 32 which co-operates with a corresponding track 33 afforded by the inner wall 11 of the nacelle structure. In this way symmetry of movement of the grid portions may be ensured during opening and closing. It will be arranged that the frame member 22 of each grid portion co-operates with a part-spherical surface 34 onthe wall 11 of the intake duct, the frame member 22 moving over the part-spherical surface 34 during movement of the guard grid portion 17 from the operative to the inoperative position. This sealing arrangement ensures that debris is not carried around the guard grid portions into the air intake of the compressor.

In addition to the guard grid portions 17 there may be provided a pair of imperforate panels 35 (see Figures 3 and 4) one of which co-operates with and lies radially outside each of the guard grid portions when the latter are in their inoperative position. (In the full line position of the panels 35 in Figure 3.) The rear part 36 of each of these panels 35 is of part-spherical form and lies immediately outside the part-spherical portion 34 of the inner wall 11 of the nacelle, and each panel is preferably of dished form to afford the recess 23 above-mentioned in which debris is trapped when the guard grid portions 17 are moved to their inoperative position. The imperforate panels 35 are also formed with socket members to engage the trunnions 27 carried by the nacelle inner wall 11 and are thus mounted to pivot about the horizontal diameter of the intake duct. It may be arranged that the imperforate panels 35 are held in their inoperative position by a latch mechanism 37 which engages their forward edges, and it may be arranged that the aerodynamic forces on the panels 35 are such that when the latches 37 are released the panelsmove into their operative position in which they lie over theguard grid portions and abut one another on a horizontal plane I through the intake. (In the dotted line position of the panels 35 in Figure 3.)

In moving to the operative position the part-spherical rear part 36 of each imperforate panel 35 travels over and is in sealing engagement with the external surface of the part-spherical portion 34 of the inner wall 11, and

thus no gap occurs between the outer edge of the imperforate panels 35 and the stationary wall structure 11 when the panels move to the operative position.

Means similar to links 31 and track and roller 32, 33 may be provided attached to and outside the panels 35, if desired, to ensure simultaneous operation. 7

it will be appreciated that the panels 35 may be moved to the operative position simultaneously with, or later than the grid portions 17.

In a further modification, instead of the guard portions being formed as grids to catch debris entrained in air passing into the engine, the guard portions may be made imperfor-ate so that when they are in the operative position, flow of air into the air intake of the engine is prevented. It will be appreciated that under certain circumstances, :for example, when damage has been caused to an engine, it is desirable to prevent rotation of the engine due to windmilling and this may be effected by preventing the flow of air through the engine.

We claim:

1. A two section, retractable guard for the full crosssection of a non-annular air intake duct of an aircraft gas turbine having a continuous substantially cylindrical wall, said guard sections being complementary when mated to extend across the whole path of fluid flowing in the duct and shaped to conform throughout their areas to thecylindrical configuration of the duct walls when retracted, means pivoting the downstream edges of said guard sections to said duct wall near a diameter thereof, the downstream edge of each guard portion interfitting closely with a portion of the wall of the duct to prevent the passage of debris therebetween when the guard is extended, a pocket in the duct wall in the area covered by each guard section when retracted to accommodate the debris which accumulated on the section when extended, and means out of the path of the fluid at all times to actuate the guard sections from retracted position to extended mating position and vice versa.

2. An air intake duct and retractable guard system,

said duct having a wall'of full circular form for feeding "s the duct with the guard leading edges other and the trailing edges substantially engaging said wall to prevent the passage (:5 particles therebetween, and an inoperative position in which the portions are substantially out of the path of fluid flowing through the duct, the cylindrical shaped portions having substantially the same radius as the duct so as to conform throughout with the wall thereof against which they are retracted, and operating means wholly out of the path of fluid flowing through the duct being connected to move the guard portions between the said two positions.

3. A duct and guard system as claimed in claim 2 which the guard portions are in the form of grids composed of a number of bars in the form of strips which are fiat at least transversely and are arranged in two sets, those of one set being straight and lying in planes engaging with each parallel to axis of the intakeduet and extending substantially lengthwise of the duct when the guard portion is in its inoperative positio 1, and those of the other set being'curve'd and lying in parallel planes which are at right-angles to the above-mentioned planes and are parallel to the axis of the duct when the guard grid is in its operative position.

References Cited in the file of this patent

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