Exhaust nozzle

Abstract

The present invention relates to an exhaust nozzle for fluid thrust vectoring comprising an elongated channel for directing exhaust gases having first and second ends. The elongated channel has an inlet at the first end with a continuously curved cross-sectional shape and an outlet at the second end with a polygonal cross-sectional shape. In a preferred embodiment, the exhaust nozzle has an outlet of rectangular cross-section. A jet engine and an aircraft having the exhaust nozzle are also provided.

Description

Technical Field

[0001] The present invention relates to an exhaust nozzle for channelling the thrust generated by a jet engine or a rocket. Specifically, the present invention relates to an exhaust nozzle for use in a jet engine or an aircraft, but is not limited thereto.

Background Art

[0002] The nozzle is the rearmost part of the exhaust pipe (i.e., duct), which directs the thrust from the engine.

[0003] Fluidic thrust vectoring using two-dimensional (2D) nozzles (i.e., slits) is currently well known. Three-dimensional (3D) nozzles are also generally known, but it has been difficult to make them function in fluidic thrust vectoring. Various exhaust pipe geometry parameters, such as nozzle shape and bypass duct diameter, have been studied in the past. Rectangular nozzles, such as those found on the Lockheed Martin F-22 Raptor, are preferred. Circular nozzles are also known as axisymmetric nozzles.

[0004] Thrust vectoring is the ability of a vehicle, such as an aircraft or a rocket, to manipulate the direction of the exhaust flow from its engine(s) or motor(s) in order to control the attitude or angular velocity of the vehicle. Thrust vectoring flight control is obtained through the deflection of the thrust generated by the vehicle's engine in the pitch direction and / or the yaw direction. This can be achieved by mechanical means such as pivoting the nozzle by a hinge. Fluidic thrust vectoring is the manipulation or control of the exhaust flow using a secondary air source, typically bleed air from an engine compressor or fan.

[0005] The Dual Throat Nozzle (DTN) concept was developed in 2003 by NASA Langley Research Centre based on the thrust shifting method. This is shown in Figure 1. The concave cavity section 3 is located between the minimum upstream area (conventional nozzle throat) and the minimum downstream area (outlet throat). Fluid thrust 1 is introduced at the minimum upstream area location. This concept combines the thrust efficiency of the throat skewing thrust vectoring method with the increased thrust vector efficiency obtained by maximizing the pressure difference in the separated cavity flow 2 located downstream of the first nozzle throat.

[0006] The thrust vectoring efficiency of DTNs has been shown to be higher than that of shock vector control (SVC) and throat-shift methods, and has been the subject of numerous research studies conducted by NASA. These studies cover a wide range of nozzle designs and operating conditions. Configurations range from those with rectangular cross-sections to those with circular cross-sections, and the nozzles operate in uniaxial and biaxial modes.

[0007] Further design enhancements to the DTN nozzle concept to enable use in supersonic aircraft include varying the nozzle area and adopting a “bypass DTN” approach in which throat bypass is injected into the cavity between the two throats. The latter bypass approach is shown in Figure 2. Changing the divergence and convergence angles of cavity 3, combined with the curvature of the walls, resulted in a significant increase in the achievable thrust vector angle and thrust vectoring efficiency.

[0008] The bypass DTN uses exhaust gas from upstream of the throat convergence for secondary injection 5, rather than independent bleed gas from the engine compressor. The bypass duct 4, including a control valve, is used to controllably supply exhaust gas 1 from the primary nozzle upstream of the throat contraction into the injection nozzle in the throat.

[0009] By eliminating oblique shock, it is possible to prevent the flow from changing direction prematurely and generate greater vectoring in the subsonic flow region downstream of normal shock.

[0010] This approach, using a primary nozzle bypass 4, avoids the complexity and cost of providing dedicated compressor bleed outlets and transfer ducts, and eliminates the influence of the bleed outlet on engine performance and stability.

[0011] Known prior art exhaust ducts have one of the following: 1) an axisymmetric nozzle, in which the entire exhaust duct has an axisymmetric (circular) cross-section along its length (from the turbine outlet through the throat to the nozzle outlet), or 2) a rectangular nozzle, in which the entire exhaust duct has a rectangular / square cross-section along its length (from the turbine outlet through the throat to the nozzle outlet).

[0012] The inventors have designed a 3D exhaust nozzle geometry that enables nearly monotonous pitch and yaw vectoring of the exhaust jet passing through a rectangular nozzle outlet. This avoids the tendency for the jet to vectorize only in two orthogonal directions defined by the nozzle outlet geometry. This problem is not solved by known prior art designs. [Overview of the project]

[0013] According to a first aspect of the present invention, An elongated channel for directing exhaust gas, having a first end and a second end, wherein the elongated channel has an inlet at the first end having a continuous curved cross-sectional shape and an outlet at the second end having a polygonal cross-sectional shape. An exhaust nozzle for fluid thrust vectoring is provided, which includes the following features.

[0014] Advantageously, the present invention provides a three-dimensional exhaust nozzle that transitions directly from the shape of a turbine outlet to a shape that offers several advantages for fluid thrust vectoring. While rectangular outlets are known, they are not provided in three-dimensional nozzles, and since the transition from a circular cross-sectional shape to a polygonal cross-sectional shape in the same nozzle is not known, complexity tends to be reduced.

[0015] The exhaust nozzle is An expanded region having an inlet, wherein the cross-sectional area of ​​the discharge nozzle increases with the distance from the inlet toward the contracted region, A contraction region having an outlet and connected to the expansion region at the end of the expansion region opposite to the inlet, wherein the cross-sectional area of ​​the exhaust nozzle decreases with distance from the contraction region toward the outlet, and the expansion region and the contraction region together define a channel, It is equipped with.

[0016] The contraction region can form 15% to 40% of the exhaust nozzle length. Preferably, the contraction region forms 20% to 30% of the exhaust nozzle length. More preferably, the contraction region forms about 25% of the exhaust nozzle length.

[0017] The entrance may have a circular cross-sectional shape. Alternatively, the entrance may have an elliptical cross-sectional shape.

[0018] The outlet may have a rectangular cross-sectional shape. Alternatively, the outlet may have a square cross-sectional shape. Alternatively, the outlet may have a triangular cross-sectional shape.

[0019] The channel may not have corners. In other words, the channel may have surfaces that intersect at an angle of 120° to 180°. Preferably, the channel may have surfaces that intersect at an angle of 140° to 180°.

[0020] The contraction region may include a plurality of joined mosaic panels in order to change the cross-sectional shape of the channel from a continuous curve to an intermediate cross-sectional shape before the cross-sectional shape of the outlet is formed. Each panel may be triangular and may be arranged such that adjacent panels are inverted with respect to each other to form a uniform outlet surface.

[0021] The cross-sectional shape of the nozzle may transition from a continuous curve to the cross-sectional shape of the outlet between the second end and 20% of the length of the exhaust nozzle as measured from the second end. Alternatively, the cross-sectional shape of the nozzle may transition from a continuous curve to the cross-sectional shape of the outlet between the second end and 15% of the length of the exhaust nozzle as measured from the second end. Alternatively, the cross-sectional shape of the nozzle may transition from a continuous curve to the cross-sectional shape of the outlet between the second end and 10% of the length of the exhaust nozzle as measured from the second end. Alternatively, the cross-sectional shape of the nozzle may transition from a continuous curve to the cross-sectional shape of the outlet between the second end and 5% of the length of the exhaust nozzle as measured from the second end.

[0022] According to a second aspect of the present invention, a jet engine comprising an exhaust nozzle according to the first aspect is provided.

[0023] According to a third aspect of the present invention, an aircraft comprising an exhaust nozzle according to the first aspect is provided.

Brief Description of the Drawings

[0024] Next, embodiments of the present invention will be described by way of example only with reference to the drawings. [Figure 1] FIG. 1 shows a schematic view of a DTN according to the prior art. [Figure 2] FIG. 2 shows a schematic view of an improved DTN according to the prior art. [Figure 3a]FIG. 3a shows a cross-sectional view through a nozzle according to one embodiment. [Figure 3b] FIG. 3b shows a longitudinal cross-sectional view through the nozzle according to one embodiment, taken along line AA of FIG. 3a. [Figure 4a] FIGS. 4a and 4b show perspective views of a nozzle according to one embodiment, looking from the outlet towards the inlet. [Figure 4b] FIGS. 4a and 4b show perspective views of a nozzle according to one embodiment, looking from the outlet towards the inlet. [Figure 5a] FIG. 5a shows a perspective view of an end portion of a nozzle according to one embodiment. [Figure 5b] FIG. 5b shows a perspective view of the end portion of the nozzle of FIG. 5a, looking from the inside towards the rear (nearby surfaces are removed). DETAILED DESCRIPTION OF THE INVENTION

[0025] Generally, embodiments relate to an exhaust nozzle that transitions from a circular or elliptical cross-section at its inlet (throat) to an outlet (outlet) having a rectangular cross-section. The outlet having a rectangular cross-section is beneficial, but the turbine and consequently the outlet are necessarily circular. Thus, the described embodiments provide an optimal way to transition the cross-section of the exhaust nozzle from circular to rectangular in order to maximize the overall propulsion efficiency along with the vectoring efficiency and effectiveness (especially when it is necessary to achieve combined two-axis vectoring for pitch and yaw control).

[0026] Figures 3a and 3b show a cross-sectional view through an exhaust nozzle 100 according to one embodiment. The exhaust nozzle 100 defines a cavity. The exhaust nozzle 100 comprises an expansion region 12 and a contraction region 10. The expansion region 12 comprises a throat 20 for receiving exhaust gases from the turbine outlet. The throat 20 is the region into which compressed gas injection used for vectoring control is introduced to the exhaust nozzle 100. The throat 20 has a circular cross-section to coincide with the cross-section of the turbine outlet. In other embodiments, the throat 20 has an elliptical cross-section to coincide with the turbine outlet. The throat 20 is where the exhaust nozzle 100 reaches its first minimum cross-sectional area downstream of the turbine outlet.

[0027] The cross-section of the expanded region 12 increases in area between the throat 20 and the point where it intersects with the contracted region 10. If the aspect ratio of the nozzle outlet 18 is not 1:1 (i.e., not square), the internal cross-section of the expanded region 12 transitions from a circular shape in the throat 20 to an ellipse at the point where it intersects with the contracted region 10. In other words, the inner wall of the expanded portion 12 is smooth and curved, maintaining continuity of curvature.

[0028] An outlet 18 is provided in the contraction region 10, through which exhaust gas is released from the nozzle 100 and mixed with the atmosphere. The outlet 18 is an opening (or orifice) on the outer surface of the nozzle 100, providing access to the cavity within the nozzle 100 for channeling the exhaust gas. The outlet 18 has a rectangular cross-section. In alternative embodiments, the outlet 18 has a square, triangular, pentagonal, or hexagonal cross-section. Generally, the outlet 18 has a non-circular cross-section.

[0029] The contraction region 10 transitions from its maximum axial cross-sectional area (i.e., diameter) at the point where it intersects with the expansion region 12 to its minimum axial cross-sectional area (i.e., diameter) at the exit 18.

[0030] The contraction region 10 typically accounts for 15% to 25% of the length of the nozzle 100 (i.e., between the throat 20 and the outlet 18).

[0031] The transition from a circular cross-section to a rectangular nozzle outlet 18 is best achieved during the final short contraction region 10 of the nozzle 100. The final transition from an elliptical to a rectangular cross-section is best realized using a mathematical surface geometry approach that avoids the formation of strong corners until reaching the surface of the outlet 18. The surface of the outlet 18 is an artificial plane that contacts all parts of the nozzle that form the lip of the outlet 18. If corners (i.e., internal panels intersecting at angles less than 120 degrees) are formed far ahead of the surface of the outlet 18, the ability to achieve uniform and monotonically varying biaxial (pitch and yaw combination) vectoring of the exhaust jet is impaired.

[0032] Introducing sharp corners into the nozzle 100 tends to bias the vectoring to "snap" toward either of the orthogonal directions of the outlet 18. In other words, the geometry inside the shrinking region 10 is designed so that corners are not formed along the vertices 24 that lead to the outlet 18. Here, a corner is defined as a vertex of a panel that intersects at an angle of less than 110 degrees, preferably less than 110 degrees, more preferably less than 120 degrees, and even more preferably less than 130 degrees. In other words, most preferably, the panel 22 is positioned or designed to intersect at an angle of 130 degrees or more in the shrinking region 10. These vertices 24 are clearly illustrated by Figures 3b, 5a, and 5b. Figures 5a and 5b illustrate different perspective views of the shrinking region 10 as described above.

[0033] Figure 3b is a cross-sectional view passing through line A to A in Figure 3a. Figure 3b shows that one panel 22a forming the inner surface of the contraction region 10 is planar, while the adjacent panel (22b) can be curved. This allows for a gradual transition from the throat 20, which has a cross-section with continuity of curvature, to the outlet 18, which has a completely straight side surface. As the nozzle approaches the outlet 18, the panel 22 becomes more linear until the cross-sectional shape of the nozzle is completely deformed to the cross-sectional shape of the outlet 18. The panel 22 is positioned to optimize the transition from a curved cross-section to a straight cross-section, while ensuring that no corners (i.e., angles less than 120 degrees) are formed between the panels 22.

[0034] One solution to this problem, namely avoiding the formation of corners, is to use triangular panels 22 to form the inner surface of the contraction region 10. Other, more complex mathematical surface generation methods can achieve transition surfaces with even better performance. For example, the panels 22 may not be perfectly planar or curved, but a combination thereof. The panels 22 may have irregular shapes as they progress from a wide base to a narrow tip. The panels 22 may be mosaic-like to one another.

[0035] The transition from a smoothly curved cross-section (e.g., a circle or ellipse) to a rectangular duct outlet 18 occurs during the final contraction of the nozzle 100. Preferably, the final transition occurs in the last 5% to 15% of the length of the nozzle 100, measured from the throat 20 to the surface of the outlet 18. In other words, the cross-sectional area of ​​the nozzle 100 decreases throughout the contraction region 10, but in the last 5% to 15% of the length of the nozzle 100, the cross-sectional shape gradually changes to the cross-sectional shape of the outlet 18. The function of this final contraction is to change the shape of the internal nozzle structure, control the outlet area, and provide a final turning of the jet to achieve vectoring.

[0036] Experimental data show that the above approach tends to enable thrust vectoring angles up to approximately 15 degrees in a 45-degree combined pitch / yaw plane. Nozzle 100, where the transition surface is generated using a corner funneling directly into the corner of the exit 18 (i.e., the edge along the vertex 24), can only achieve 2-4 degrees of vectoring in a 45-degree combined pitch / yaw plane, and the exhaust jet tends to flip to either the pitch or yaw plane when operated to achieve a combined pitch / yaw vector angle.

[0037] This approach is applicable to all fluid thrust vectoring schemes that use fluid injection in the nozzle throat 20 to achieve vectoring of the jet discharged through a rectangular (or optionally any non-elliptical) outlet 18. For example, the nozzle 100 described herein is applicable to DTN and bypass DTN exhaust ducts.

[0038] The exhaust nozzle 100 can be mounted on the rear of an aircraft to direct thrust from a jet engine or rocket motor. Here, the jet engine may be a ramjet, scramjet, turboprop, turbofan, turbojet, or turboshaft engine. The exhaust nozzle 100 is further applicable to water jets. Therefore, instead of an aircraft, the exhaust nozzle 100 can be applied to a ship or spacecraft. The following is a direct reproduction of the claims as originally filed. [C1] An exhaust nozzle for fluid thrust vectoring, An elongated channel for directing exhaust gas having a first end and a second end, wherein the elongated channel has an inlet at the first end having a continuous curved cross-sectional shape and an outlet at the second end having a polygonal cross-sectional shape. An exhaust nozzle equipped with the following features. [C2] An expanded region having the aforementioned inlet, wherein in the expanded region, the cross-sectional area of ​​the discharge nozzle increases with the distance from the inlet toward the contracted region. Having the aforementioned outlet, a contracted region is connected to the expanded region at the end of the expanded region opposite to the inlet, and in this region, the cross-sectional area of ​​the exhaust nozzle decreases with distance from the contracted region toward the outlet. The expanded region and the contracted region together define the channel. An exhaust nozzle as described in C1, comprising the features described above. [C3] The exhaust nozzle according to C2, wherein the contraction region forms 15% to 40% of the length of the exhaust nozzle. [C4] The inlet is an exhaust nozzle according to any one of C1 to 3, having a circular cross-section. [C5] The outlet is an exhaust nozzle according to any one of C1 to 4, having a rectangular cross-section. [C6] The exhaust nozzle according to any one of C1 to 5, wherein the channel has surfaces that intersect at an angle of 120 to 180 degrees. [C7] The exhaust nozzle according to any one of C1 to 6, wherein the contraction region comprises a plurality of joined mosaic panels to change the cross-sectional shape of the channel from a continuous curve to an intermediate cross-sectional shape before the cross-sectional shape of the outlet is formed. [C8] The exhaust nozzle described in C7, wherein each panel is triangular and adjacent panels are inverted relative to each other to form a uniform outlet surface. [C9] The exhaust nozzle according to any one of C1 to 8, wherein the cross-sectional shape of the nozzle transitions from a continuous curve to the cross-sectional shape of the outlet between the second end and 20% of the length of the exhaust nozzle measured from the second end. [C10] A jet engine comprising the exhaust nozzle described in any one of C1 to C9. [C11] An aircraft comprising the exhaust nozzle described in any one of C1 to C9.

Claims

1. An exhaust nozzle for fluid thrust vectoring, An elongated channel for directing exhaust gas having a first end and a second end, wherein the elongated channel has an inlet at the first end having a continuous curved cross-sectional shape and an outlet at the second end having a polygonal cross-sectional shape, An expanded region having the aforementioned inlet, wherein in the expanded region, the cross-sectional area of ​​the exhaust nozzle increases with the distance from the inlet toward the contracted region, A contraction region having the outlet, and connected to the expansion region at the end of the expansion region opposite to the inlet, wherein the cross-sectional area of ​​the exhaust nozzle decreases with distance from the contraction region toward the outlet, and transitions from a continuously curved cross-sectional shape at the end of the expansion region to a polygonal cross-sectional shape at the outlet, and the expansion region and the contraction region together define the elongated channel, An exhaust nozzle equipped with the following features.

2. The exhaust nozzle according to claim 1, wherein the contracted region forms 15% to 40% of the length of the exhaust nozzle.

3. The exhaust nozzle according to claim 1, wherein the inlet has a circular cross-section.

4. The exhaust nozzle according to claim 1, wherein the outlet has a rectangular cross-section.

5. The exhaust nozzle according to claim 1, wherein the elongated channel has surfaces that intersect at an angle of 120 to 180 degrees.

6. The exhaust nozzle according to claim 1, wherein the contraction region comprises a plurality of joined mosaic-like panels to change the cross-sectional shape of the elongated channel from a continuous curve to an intermediate cross-sectional shape before the cross-sectional shape of the outlet is formed.

7. The exhaust nozzle according to claim 6, wherein each panel is triangular and adjacent panels are inverted relative to each other to form a uniform outlet surface.

8. The exhaust nozzle according to claim 1, wherein the cross-sectional shape of the nozzle transitions from a continuous curve to the cross-sectional shape of the outlet between the second end and 20% of the length of the exhaust nozzle measured from the second end.

9. A jet engine comprising the exhaust nozzle described in claim 1.

10. An aircraft comprising the exhaust nozzle described in claim 1.

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