The present invention relates to exhaust thrust vectoring for aircraft and, more particularly, pertains to the fluidic control of pitch/yaw thrust vectoring of the jet engine exhaust.

Future aircraft will be required to possess the capability of being able to vector the thrust of their jet engines for the attainment of the improved attitude control. A primary need which must be met is to improve the aircraft maneuverability via simultaneous pitch/yaw thrust vectoring of the engine exhaust. A specific application of thrust vectoring is already being used to provide aircraft with Short Ta e-Off and Landing (STOL) characteristics. An improvement in thrust vectoring technology has the potential of improving (shortening) the take-off requirements of conventional aircraft. The greatest potential benefit of thrust vectoring resides in the development of future generations of attack and fighter aircraft, with increased emphasis being placed on stealth characteristics. Such aircraft have increased requirements for low weight, reduced optical signatures and high maneuverability at low to moderate speeds in order to ensure their survival. Thrust vectoring may be substituted for stability and aerodynamic control surfaces for reasons of low observability, with additional benefits derived through a decrease in mechanical complexities and structure, cost and savings in weight.

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Traditionally, thrust vectoring is performed by the employment of mechanical systems, in connection with which different types of systems have been utilized. Some of these systems are subject to severe transition problems and must carry or incorporate auxiliary structure, ducting, nozzles and control systems, all of which add to the weight of the exhaust nozzle. Most of these systems rely upon impinging the high temperature exhaust flow against a solid surface. The resulting surface heating necessitates the use of active nozzle cooling and/or the provision of advanced materials. Finally, some of these systems are unable to provide independent or simultaneous pitch and yaw control. U.S. Patent No. 2,702,986 discloses a system using moving and solid blockage to create deflection, the exhaust nozzle is of a convergent-divergent type with a blockage located in the throat.

U.S. Patent No. 2,763,984 relates to a tangential injection system where the injection is implemented upstream into the flow in order to control the cross-section of the discharge nozzle. Consequently, this system is not a vectoring system.

U.S. Patent No. 2,793,493 illustrates a device for deflecting fluid jets without any discussion of offsets and curve type of the deflection or Coanda surface, or the positioning of the injection jet.

U.S. Patent No. 2,812,636 discloses a tangential injection system with injection into the boundary layer and not therethrough.

U.S. Patent No. 3,016,699 shows a modification of a normal injection system for a rectangular nozzle. Vectoring is controlled by jet injection angle to primary flow and not by strength. , U.S. Patent No. 3,740,003 pertains to a bistable fluid amplifier for a missile application. Reaction control jets are not fluid obstacles and no Coanda type surface is shown.

U.S. Patent No. 3,795,367 discloses an ejector which uses Coanda wall jet flow to induce a small additional amount of low energy flow through the device by entrainment.

Finally, U.S. Patent No. 4,069,977 discloses a system using injected flow through the boundary layer to separate the primary flow from the Coanda surface. Control is the reverse of the present invention and injection is on the same side as the deflection.

The present invention relates to a fluidic control thrust vectoring system that does not require any movable mechanical parts and which provides control of the exhaust thrust vector without significant weight, volume and cost increase.

The fluidic control thrust vectoring system of the present invention operates efficiently, effectively and reliably.

The system of the present invention is survivable to electrical power surges and electromagnetic interference. The present invention further relates to a fluidic control thrust vectoring system capable of

performing in an adverse environment that includes environmental insensitivity to radiation, temperature, shock and vibration.

More specifically, the present invention is directed to a fluidic control thrust vectoring exhaust nozzle connected to an engine discharging an exhaust stream, the exhaust stream having a thrust vector direction, the fluidic control nozzle comprising: an exhaust nozzle having an input end connected to the engine, a spaced output end for discharging the exhaust stream, an enclosed cavity connecting said input end to said output end, and a Coanda surface connected to said output end, said Coanda surface extending from said output end; and at least one fluidic control injector having an input connected to a control gas source, and an output disposed near said output of said exhaust nozzle and being in communication with said enclosed cavity of said exhaust nozzle, said control injector selectively altering the exhaust stream thrust vector direction by injecting a control gas into said exhaust stream via said enclosed cavity.

The present invention is further directed to a fluidic control thrust vectoring nozzle comprising: an exhaust nozzle having an input end connected to an engine, a spaced output end for discharging an exhaust stream from the engine, and an enclosed cavity connecting said input end to said output end, said exhaust stream having a thrust vector direction, said output end having a Coanda surface; at least one fluidic control injector having an input connected to

a control gas source, and an output disposed near said output of said exhaust nozzle and being in communication with said enclosed cavity of said exhaust nozzle, said fluidic control injector selectively altering the exhaust stream thrust vector direction by injecting a control gas into said exhaust stream via said enclosed cavity, said injection of control gas causing said exhaust stream to adhere to the Coanda surface at the output end of said exhaust nozzle.

Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings which disclose three embodiments of the present invention. It should be understood, however, that the drawings are intended for purposes of illustration only and not as a definition of the limits of the invention.

Reference is now had to the drawings, wherein similar reference characters denote similar elements throughout the several views; and in which:

Figure la is a schematic diagram of a normal jet exhaust through from a jet engine;

Figure lb is a schematic diagram of the controlled jet flow of the fluidic control thrust vectoring nozzle of the invention;

Figure 2 is a block diagram of an entire fluidic control system of the invention;

Figure 3a is an embodiment of a boundary layer fluidic control thrust vectoring system of the invention;

Figure 3b is a schematic diagram of the various separation points of the boundary layer control system of Figure 3a;

Figures 4a and 4b show two views of a rectangular cross-section exhaust nozzle with multi- axis deflectors;

Figures 5a and 5b show two views of an elliptical cross-section exhaust nozzle with multiple injectors; Figures 6a and 6b, respectively, are schematic diagrams of exhaust nozzles with symmetric Coanda surfaces;

Figure 6c is a schematic diagram of an exhaust nozzle with straight Coanda surfaces on one side of the nozzle;

Figure 7 is a schematic diagram of an exhaust nozzle with asymmetric Coanda surfaces;

Figure 8 is a schematic diagram of an exhaust nozzle with a tangential injection; and Figures 9 and 10 are graphical representations of the offset versus the deflection angle due to the Coanda surfaces.

Referring now in specific detail to the drawings, Figure la shows a normal exhaust jet 14 as it exits the exhaust nozzle 12. The exhaust nozzle 12 is connected to the engine 16 and has Coanda surfaces 20 and 22 at the exit portion thereof. A pair of fluidic control injectors 18a and 18b are disposed opposite each other and extend perpendicular to the normal exhaust flow near the exit portion of exhaust nozzle 12. Figure lb shows the flow of a controlled

exhaust jet 24 when fluidic control gas 26 is injected through control injector 18b. Thus, when fluidic control gas 26 is injected through control injector 18b, the injected flow becomes an aerodynamic obstacle which separates the primary flow from that surface and diverts exhaust flow 24 attaching it to the Coanda surface 20 so as to vector the net force component for aircraft attitude control.

The exhaust flow will "stick" to the desired opposite Coanda surface due to the Coanda effect.

That is, a combination of the radial pressure gradient resulting from the streamline curvature and the entrained flow. The amount of deflection of the exhaust jet 24 is controlled by the amount of injected flow 26.

Control injector 18a would be the control for diverting the exhaust flow to the opposite Coanda surface 22.

The most practical and logical method for obtaining the control gas would be directly from the engine combustors or by diverting some of the exhaust flow. Figure 2 shows a fluidic control bypass 26 connected to the engine 16 at one side and to control injector 18b at the other side. Fluidic control bypass 26 receives the fluidic control gas 27 and uses a diverted engine exhaust flow to inject the control gas 27 into the nozzle 12.

Figures 3a and 3b show another manifestation of this invention. They show a boundary layer control system 30 of the present invention where the control injector 34 injects the secondary fluid tangent to and

along the Coanda surface 32. The amount and strength of the injection fluid from control injector 34 can control the separation point of the exhaust flow. Exhaust flows 36a, 36b and 36c show examples of different separation points from the Coanda surface 32. A stronger injection will cause the flow to travel farther along the Coanda surface and separate later, as shown by flow 36a, whereas a weaker injection will cause the flow to travel less along the Coanda surface and separate sooner therefrom, as shown in flow 36c. thus, the strength and amount of the injection will change the angle at which the flow leaves the Coanda surface and thereby change the thrust vector angle imparted to the aircraft. The shape of the exhaust nozzle is preferably rectangular but may be any shape of suitable known type. Figures 4a and 4b shown a rectangular exhaust nozzle 40 with control injector slots 42a and 42b for injecting fluidic control gas into the exhaust flow. Figures 5a and 5b show an embodiment of an elliptical exhaust nozzle 50 with control injector slots 52a and 52b.

Figures 6a-6c shown the normal injection embodiment of the invention with the output of injector 62 perpendicular to the exhaust flow and symmetrical offsets of the Coanda surfaces. Figure 6b shows Coanda surfaces 66a and 66b symmetrically offset from exhaust nozzle 60. Offset 67 is the distance of the Coanda surface from exhaust nozzle 60. This step or offset 67 on the Coanda surface side of the nozzle

creates a trapped vortex that assists the coanda flow formation.

Figure 6c shows an alternative embodiment with different configurations of Coanda surfaces as shown by dotted lines 65 and 69. Curved Coanda surfaces have been tested and proven to be most efficient because straight wall Coanda surfaces limit the maximum angle to the physical angle at which they are mounted to the exhaust nozzle. Figure 7 shows an example of asymmetric offsets of the control Coanda surfaces 72a and 72b with respect to the exhaust nozzle 70. The backward facing offset step 73 assists in the Coanda flow formation along Coanda surface 72b. A trapped vortex flow results from the primary flow over the backward facing step. As in the case of the normal fluidic injection, the result is a fluid obstacle that separates the primary flow from the wall. This method relies only on the movement of the Coanda surfaces perpendicular to the primary jet flow. The offset is created on the wall opposite the direction that the deflection is desired. As the step is increased, the flow is deflected increasingly towards the opposite wall. There is a definite value where there is significant deflection and another value beyond which there is no additional deflection. As shown in Figure 9, the value at which there is significant deflection is 7% of the primary jet width, and the value beyond which there is no additional deflection is 15% of the primary jet width (Figure 10) .

Figure 8 shows an alternative embodiment of the invention with the output of control injector 84 disposed tangentially to the exhaust stream and Coanda surface 82b. This configuration is similar to the blow boundary control system shown in Figure 3.

Thus, the injection of the fluidic control gas tangent to the axial exhaust stream causes the exhaust flow stream from nozzle 80 to attach to Coanda surface 82b. The injected wall jet from injector 84 produces a low pressure region that deflects the primary jet by suction. Once the primary jet is deflected, it remains attached to the Coanda surface 82b as in the normal injection flow. Because the injection is along the Coanda wall, a backward facing step offset 85 is mandatory. The low pressure created by the presence of the vortex behind the backward facing step 85 is lost, because the vortex is washed away by the injection flow. Because the main flow is held in place by a pressure effect, a slight decrease in the control jet flow releases the main flow back to its original undeflected position as a hysteresis effect. However, for a device of given length, tangential injection requires much more control flow to create the deflection than for the normal injection case. Thus, if the supply of control flow is not of concern, there is also a viable method for the deflection of the main exhaust flow.

While there has been shown and described what are considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail

could readily be made without departing from the spirit of the invention. It is, therefore, intended that the invention be not limited to the exact form and detail herein shown and described, nor to anything less^ than the whole of the invention herein disclosed as hereinafter claimed.