US3020713A - Thrust spoiling device for jet propulsion units - Google Patents

Description

Feb. 13, 1962 J. H. BERTIN ETAL 3,020,713

THRUST SPOILING DEVICE FOR JET PROPULSIQN UNITS Filed Dec. 9, 1953 United States Patent Qfiice 3,020,713 Patented Feb. 13, 1962 3,020,713 THRUST SPOILING DEVICE FOR JET PROPULSION UNITS Jean H. Bertin, Neuilly-sur-Seine, and Marcel Kadosch,

Paris, France, assignors to Societe Nationale dEtude et de Construction de Moteurs dAviation, Paris,

France, a French company Filed Dec. 9, 1953, Ser. No. 397,228 Claims priority, application France Dec. 12, 1952 1 Claim. (Cl. 60-3554) It is known to provide reaction propulsion units with a device for deflecting the jet, whereby in particular a braking effect is obtained or by reversal of the direction of the thrust.

The applicants have themselves proposed, deflection arrangements which operate by means of a solid or fluid obstacl (in the latter case, a jet of auxiliary gas is injected into the jet with a component at right angles to the direction of flow of the jet) which by modifying the forces which act on the jet, produce the desired change in direction. Means for guiding the jet thus deflected, constituted in most cases by a grid of blades, serve to re-enforce the deflection created by the obstacle.

These deflection devices have been most frequently placed at the end of the discharge nozzle, thus increasing the maximum overall cross-section at this point, which gives rise to the necessity of a supplementary fairing, extends the length of the casing and has generally an adverse effect on the performance of the aircraft.

It would be of great advantage to be able to house the deflection device in the space within the propulsion unit, forward of the exhaust discharge nozzle, in a portion of the casing in which there is in general a large amount of room available, and this would avoid any increase in the maximum overall cross-section as compared with a propulsion unit which is not provided with a deflection device, and which also avoids any increase in the length of the casing, while enabling the provision of grids of blades which are more developed in the radial direction, thus increasing the effectiveness of these blades. In order to achieve this, it is necessary to form openings for the passage of the deflected jet, both in the wall of the propulsion unit and also in the casing, at a point forward of the exhaust discharge nozzle. Since, however, in this zone, the expansion of the gases is not completed, the gases thus having a static pressure higher than atmospheric pressure, the problem arises of closing these openings during normal operation and only causing them to open at the moment when it is desired to deflect the jet. The provision of movable mechanical shutters leads to great complication and difliculties because of the necessity of causing these shutters to operate in the center of gases at a high temperature.

The object of the present invention is to solve this hitherto unsolved problem.

In accordance with the invention, the openings formed in the wall of a jet propulsion unit, and in the casing in front of the exhaust discharge nozzle, for the exit of the gases during the deflection period, are combined with an arrangement of slots or orifices formed in the wall of the jet propulsion unit forward of the said openings, and which are themselves connected to a source of auxiliary gas at a suitable pressure, in particular to the delivery side of the air compressor of the unit, the said orifices having a direction such that the auxiliary gas under pressure, injected into the center of the gases of the stream with a velocity component at right angles to the direction of flow of this stream, forms a kind of marginal fluid screen which masks the openings and displaces the stream away from them.

The'said discharge openings for the deflected jet may thus remain constantly open to the interior of the propulsion unit, and it will suffice that the auxiliary gas under pressure is blown permanently through the blowing orifice or orifices during the periods when there is no deflection; the deflection is produced by stopping the auxiliary injection and may be furthered by the use of a mobile obstacle which may itself be either solid or fluid. It should furthermore be noted that the deflection is facilitated by the fact that the static pressure of the gases of the stream at a point level with the openings tends to produce naurally a flow through these openings as soon as the auxiliary fluid screen is suppressed.

The description which follows below in respect of the attached drawings (which are given by way of example only, and not in any way in a limiting sense) will make it quite clear how the invention is to be carried into effect.

FIG. 1 shows diagrammatically one form of embodiment of the invention. The upper half and the lower half of this figure are two axial cross-sections of the rear portion of a jet propulsion unit taken in two planes at right angles to each other.

FIG. 2 is a transverse cross-section along the line IIII of FIG. 1. In this figure, the lines 01 and Ola represent respectively the outlines of the cross-sectional planes of the upper half and of the lower half of FIG. 1.

FIG. 3 is a diagrammatic view of an alternative embodiment.

In the drawing, there is shown at 1, the tubular rear portion of a reaction propulsion unit.

This tubular portion receives the gases coming from the turbine 2. At 3, there is located the exhaust discharge nozzle having a shape adapted for the expansion of the gases and the formation of the propulsive jet at high speed. This discharge nozzle is generally mounted by the aircraft manufacturer immediately after the tube 1 of the reaction propulsion unit, at the same time as the cowling 4 which surrounds the unit. This cowling being adapted to the shape of the propulsion unit and of the discharge nozzle in order that it shall have a minimumaerodynamic drag, it will be seen that the arrangement of a deflection device aft of the discharge nozzle has an adverse effect by varying the aerodynamic .qualities of the casing.

In carrying out the invention, the openings for the deflected jet are formed at a point forward of the discharge nozzle 3. In the form of embodiment shown in the drawing, these openings are formed by two indentations which are diametrically opposite and extend parallel to the axis of the propulsion unit, the said indentations being formed both at 5 on the internal Wall of the gas conduit forward of the discharge nozzle, and also at 6 in the wall of the cowling of the unit. Between the wall of the propulsion unit and the wall of the cowling, they are closed in by two parallel partitions 7, 8 (see FIG. 2). They form with these partitions and the walls 9, 10, which are joined to the casing, two channels through which the gases of the jet may escape in the direction shown by the arrows F with a component of speed directed towards the front of the unit in order to give a braking effect.

In these channels, there are arranged grids of blades 11, suitably curved from the interior of the propulsion unit towards the exterior and forming as many individual channels which assist in directing the deflected jet in the direction F Forward of each of the grids of blades, there is provided a curved surface 12 which is connected tangentially both to the internal wall of the gas conduit and to the external wall of the cowling, and which may have an ejector-shaped cross-section as shown in the drawing. Forward of this point, the surface 12 is separated from the internal wall of the gas conduit by a slot 13, the function of which will be explained in the description below.

Two diametrically opposite holes 14, 15, formed on the wall of the propulsion unit in the plane Ola, perpendicular to the median plane OI of the grids of blades, are connected by pipes 16 provided with a valve 17 to the delivery side of the air compressor (not shown) of the propulsion unit. The holes 14, 15, have an extended shape in the direction of the periphery of the propulsion unit. On the internal wall of the gas conduit, and immediately forward of the surface 12 respectively, of the orifices 13 which precede these surfaces, there is formed a continuous annular slot 18 which connects the interior of the propulsion unit with an annular collector 19, the latter being in turn connected to the delivery side of the air compressor through a pipe 20 with a wave 21.

The operation is as follows:

It is first of all supposed that the valves 17 are closed, so that the orifices 14, 15, are not supplied with air. The gases issuing from the tube 1 of the propulsion unit and proceeding towards the discharge nozzle 3 pass in front of the passages 5. Since at that point, the gases have a high static pressure, they would have a tendency to escape to the exterior if nothing were provided to prevent this. The valve 21 is open and a jet of air passes through the annular slot 18 and penetrates into the interior of the propulsion unit with a component of speed at right angles to the direction of flow of the gases. This auxiliary jet compresses the jet of gases flowing through the tube. It forms around this jet a kind of convergentdivergent fluid wall which prevents the gases from escaping through the notches and the channels of the grids of blades. The gases are thus led into the discharge nozzle 3 without losses, in spite of the absence of any mechanical shutter on the notches 5.

In this phase of the operation, the orifices 13 serve to supply the low-pressure zones, or wake zones which tend to be formed on the outside of the fluid screen. The orifices 13 may be supplied with air by the cooling circuit of the jet propulsion unit or by the special air inlet openings 22 formed in the cowling.

The operation described naturally supposes that the auxiliary jet is discharged from the annular slot 18 with a suitable total pressure. This pressure must be suflicient for the fluid screen formed around the gases to ensure a balance between the high pressure of the gases and the ambient atmospheric pressure, until the jet of gas again reaches the full wall of the discharge nozzle. On the other hand, it must not be too high, since in this case, the excessive contraction of the jet of gas would lead to an aspiration of the exterior air through the channels of the grids of blades. As, at the delivery of the compressor of the jet propulsion unit there is available a pressure very much higher than the pressure of the gases in the portion 1, the gases having passed through their first expansion in the turbine, it will be possible to vary the pressure and/or the output of the gases passing through the slot 18 in order to achieve the desired effect.

If now it is desired to deflect the jet, the valve 21 is first closed in order that the fluid screen shall cease to exist and the gases already have a tendency to pass out to the exterior through the channels of the grids of blades. The valves 17 of the conduits 16 are opened. Two jets of air thus pass out through the opposed orifices 14 and in the diametrical plane at right angles to the median plane of the grids of blades. These jets tend to form an obstacle to the flow of the jet of gas towards the discharge nozzle, and the jet is thus deflected into the channels of the grids of blades, which cause it to escape to the exterior in the direction of the arrows P In order to ensure the maximum elfect of the deflecting jets which are discharged through the orifices '14, 15, it is an advantage to provide holes such as 1 341, 15a in the wall of the gas conduit aft of the orifices 14, 15; these holes enable air to enter and supply the wake created by the deflecting jets.

In order to close-in the channels on each side of the grids of blades, the form of embodiment described includes the walls 7, 8, which are parallel to each other. This has the advantage that all the portions of the deflected jet are directed parallel to these walls, without any lateral component of speed at right angles to the plane of the upper half of FIG. 1. The detachment of the jet from the walls is thus avoided and the jet retains the maximum of kinetic energy whilst producing a powerful counter-thrust.

Other arrangements of the outlet channel of the defleoted jet may, however, be adopted.

The fluid obstacle formed by the jets of air escaping through the orifices 14, 15, could be replaced by a solid obstacle. There could, for example, be provided a diametrical support with an aerodynamic profile which could extend into the discharge nozzle between the points occupied on the drawing by the orifices 14, 15 and which would carry movable screens which could be withdrawn into this support, or be caused to project from it; the said solid screens could, furthermore, be replaced by jets of auxiliary gas escaping from slots in the said support. There could also be provided a diametrical obstacle 25 turning about a diametrical axis 26 as shown in FIG. 3, the said obstacle occupying either the position shown in full lines for which it presents a profiled form to the jet of gas, or the position shown in dotted lines, for which it produces a symmetrical deflection through the oppositely-disposed notches in the gas conduit, or any intermediate position giving rise to an asymmetrical deflection through the said notches and, in consequence, to a variation in the direction of the thrust.

The arrangement of the channels for the passage of the deflected jet may be varied. For example the two diametricallyopposed channels described, could be replaced by a single annular channel.

Externally, the continuity of the cowling 4, or at least a part of that continuity, may be restored by' a grid of cross stays in the form of a honeycomb for example, following the line 6 outlined in chain-dotted lines in FIG. 1. There could also be provided along this line 6, a movable hood which would only be opened during the deflection periods; during periods of no deflection, this hood could not be subjected to the action of the hot gases by virtue of the interposition of the screen formed by the constrictive jet.

What we claim is:

In a jet propulsion unit ending with a propulsive nozzle designed for expanding motive gas and having a pipe conmeeting said propulsive nozzle for conducting thereto a stream of motive gas, a thrust spoiling device comprising passage means at the periphery of said pipe upstream of said propulsive nozzle, said passage means extending laterally of the normal axial flow path of said stream and opening into the atmosphere at a substantial angle with the axis of said nozzle, to provide an auxiliary deflected exhaust path for said stream, blowing means extending at the periphery of said pipe and opening thereinto upstream of said passage means, said blowing means being designed for forming a screen-like fluid partition about the motive gas stream past the passage means, means for supplying pressure fluid to said blowing means, controllable means for cutting off the supply of pressure fluid, means for collecting ambient air and means for leading said ambient air to a point of the pipe located between the blowing 3,020,713 5 means and the passage means, whereby the low-pressure wake zone which tends to arise at the side of the fluid partition opposite to the screen is filled with air.

Thompson April. 18, 1947 Nichols et a1 Oct. 26, 1954 8 Kadosch et a1. Mar. 1, 1955 Kadosch et a1. May 28, 1957 FOREIGN PATENTS France Nov. 12, 1952 OTHER REFERENCES Anti-Bomber Rocket Missiles, by Chandler Aero Digest, April 1950, pages 100102.

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