Flow inlet

An apparatus is formed of a cowl and a flow inlet formed on an interior surface of the cowl. The flow inlet has a supersonic compression section attached to a subsonic diffusion section at a throat. The supersonic compression section includes an at least partially elliptical compression ramp which extends along an approximately 180 degree arc along the interior surface. The flow inlet may form part of an aircraft. A method of air flow using the flow inlet is also disclosed.

FIELD OF THE DISCLOSURE

The disclosure relates to flow inlets, and particularly to flow inlets for aircraft engines.

BACKGROUND OF THE DISCLOSURE

Existing 2-D flow inlets, such as in the F-15 and the F-14, for diffusing supersonic airflow to subsonic airflow entering an engine typically experience higher weight and drag than comparable axisymmetric flow inlets due to pressure loads on flat panels and overall larger surface area. They also may experience undesirable pressure distortion and inadequate total pressure recovery associated with the real flow physics of their corners. Bump inlet designs, such as in the F-22, may improve weight and drag, but often experience poor recoveries. Existing axisymmetric inlets, such as in the MiG-21, typically do not provide the same stability margins and tolerance to changes in the onset flow angle as 2-D flow inlets. Existing half-round inlets, such as in the Mirage III, often create integration issues for podded nacelle installations because the inlet aperture is wider than the engine cowl at the fan face. Typically, in the design of aircraft, one of the above-referenced designs is used which may add weight or reduce performance.

There is a need for a flow inlet which will improve upon one or more issues experienced by one or more of the existing flow inlets.

SUMMARY OF THE DISCLOSURE

In one embodiment, a flow inlet is disclosed. The flow inlet is formed on an interior surface of a cowl. The flow inlet has a supersonic compression section attached to a subsonic diffusion section at a throat. The supersonic compression section includes an at least partially elliptical compression ramp which extends along an approximately 180 degree arc along the interior surface. The flow inlet may form part of an aircraft.

In another embodiment, an aircraft is disclosed. The aircraft includes a flow inlet formed on an interior surface of a cowl. The flow inlet has a supersonic compression section attached to a subsonic diffusion section at a throat. The supersonic compression section includes an at least partially elliptical compression ramp which extends along an approximately 180 degree arc along the interior surface. The flow inlet may form part of an aircraft. A method of air flow using the flow inlet is also disclosed.

In still another embodiment, a method of diffusing airflow is disclosed. In one step, airflow is flowed into a supersonic compression section of a flow inlet formed on an interior surface of a cowl. The supersonic compression section is formed of an at least partially elliptical compression ramp which extends along an approximately 180 degree arc along the interior surface. In another step, the airflow is compressed as it flows through the flow inlet.

These and other features, aspects and advantages of the disclosure will become better understood with reference to the following drawings, description and claims. This summary is provided merely for purposes of summarizing some example embodiments so as to provide a basic understanding of some aspects of the disclosure. Accordingly, it will be appreciated that the above described example embodiments are merely examples and should not be construed to narrow the scope or spirit of the disclosure in any way. Other embodiments, aspects, and advantages of various disclosed embodiments will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments.

DETAILED DESCRIPTION OF THE DISCLOSURE

While the disclosure may be susceptible to embodiment in different forms, there is shown in the drawings, and herein will be described in detail, a specific embodiment with the understanding that the present disclosure is to be considered an exemplification of the principles of the disclosure, and is not intended to limit the disclosure to that as illustrated and described herein. Therefore, unless otherwise noted, features disclosed herein may be combined together to form additional combinations that were not otherwise shown for purposes of brevity. It will be further appreciated that in some embodiments, one or more elements illustrated by way of example in a drawing(s) may be eliminated and/or substituted with alternative elements within the scope of the disclosure. The following detailed description is of the best currently contemplated modes of carrying out the disclosure. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the disclosure, since the scope of the disclosure is best defined by the appended claims.

FIGS. 1 and 2illustrate perspective views of an embodiment of a supersonic flow inlet10. The supersonic flow inlet10forms an interior surface of a cowl28. The supersonic flow inlet10may comprise an external-compression supersonic inlet. In another embodiment the supersonic flow inlet10may comprise a mixed-compression supersonic inlet. The supersonic flow inlet10may comprise a portion of an aircraft12.

The cowl28may be made of composite materials. In other embodiments, the cowl28may be made of other materials such as titanium, steel, aluminum, or other types of materials. The cowl28is at least partially elliptical as viewed in the stream-wise direction. The cowl28comprises a first surface32defining a crown, a second surface33defining a keel, and side surfaces34and36attached to and extending between opposed ends of the first surface32and opposed ends of the second surface33. The side surfaces34,36define maximum half breadths of the cowl28which are defined at the maximum width of the cowl28. A highlight46is defined at the forward end of the cowl28, and an aft end47is defined at the rearward end of the cowl28. The highlight46angles rearwardly from the keel to the crown. A diffuser35may be attached to the second surface33of the cowl28.

FIGS. 4 and 6illustrate side elevation views of the supersonic flow inlet10ofFIGS. 1 and 2. InFIG. 4, the supersonic flow inlet10is shown in a 2 degree toed out position along axis A ofFIG. 3, which is the position the supersonic flow inlet10is positioned during use on parts of the aircraft12. The supersonic flow inlet10may also be positioned in a 2 degree toed in position during use on parts of the aircraft12. The supersonic flow inlet10is also scarfed during use.FIG. 6illustrates a side elevation view of the supersonic flow inlet10along the X-Z plane, axis B, ofFIG. 3.

As shown inFIG. 1, the supersonic flow inlet10comprises a supersonic compression section14attached to a subsonic diffusion section16at a throat18(seeFIG. 6). The throat18is located at the aft most point of the highlight46. The throat18is planar as shown inFIG. 6. The supersonic flow inlet10has a curved upper duct26which extends from the highlight46to the aft end47of the cowl28. As shown inFIG. 2, the supersonic compression section14is configured to compress a free stream airflow22, when the airflow22is in a supersonic condition, as it flows from a beginning entrance24of the supersonic compression section14, through the supersonic compression section14, and to the throat18(seeFIG. 6) at which the subsonic diffusion section16begins. The subsonic diffusion section16is connected to an engine20. The engine20may comprises a gas turbine engine with a BPR (bypass ratio) value of 3.5, an OPR (overall pressure ratio) of 24, and a RIT (burner exit temperature) of 2900 degrees F. In other embodiments, the engine20may comprise a gas turbine engine with a range of BPR values of 1 to 16, OPR values of 14 to 80 and RIT values of 2,000 to 3,500 F, or a ramjet, ducted rocket, scramjet, or other type of air-breathing engine.

The supersonic compression section14is formed by a forward portion26aof the curved upper duct26and a supersonic compression ramp30. The forward portion26aand the supersonic compression ramp30form a continuous perimeter around the supersonic compression section14of the flow inlet10. The supersonic compression section14is at least partially elliptical as viewed in the stream-wise direction. The supersonic compression ramp30is divided into a first compression ramp section30aand a second compression ramp section30b(seeFIGS. 4-6). The first compression ramp section30aextends between the highlight46and the second ramp compression section30b. The second compression ramp section30bextends between the first compression ramp section30aand the throat18. A first turn48is provided between the first compression ramp section30aand the second compression ramp section30b. A second turn49is provided between the second compression ramp section30band the throat18. The first and second turns48and49, respectively, are configured to provide oblique shock waves in the airflow22as the airflow22flows through supersonic compression section14to compress the airflow22. The cross-section area (defined as the stream-wise cross-section area between the upper duct26and the supersonic compression ramp30) is smallest at the throat18(seeFIG. 6).

The first compression ramp section30aextends along an approximately 180 degree arc along the supersonic flow inlet10, and extends continuously from an interior point aligned with the maximum half breadth of the side surface34, along the interior of the second surface33of the cowl28, to an interior point aligned with the maximum half breadth of the side surface36. The first compression ramp section30amay extend past the interior point aligned with the maximum half breadth of each side surface34,36. The first compression ramp section30ais partially elliptical, having a radius of curvature. As shown in the cross-sectional views ofFIGS. 7-9, at all points around the perimeter of the first compression ramp section30a, the first compression ramp section30aextends linearly from the highlight46to the second compression ramp section30b. The second compression ramp section30bextends along an approximately 180 degree arc along the supersonic flow inlet10, and extends continuously from an interior point aligned with the maximum half breadth of the side surface34, along the interior of the second surface33of the cowl28, to an interior point aligned with the maximum half breadth of the side surface36. The second compression ramp section30bmay extend past the interior point aligned with maximum half breadth of each side surface34,36. The second compression ramp section30bis partially elliptical, having a radius of curvature. As shown in the cross-sectional view ofFIGS. 7-9, at all points around the perimeter of the second compression ramp section30b, the second compression ramp section30bextends linearly from the first compression ramp section30ato the throat18.

As shown inFIG. 6, the first compression ramp section30ais angled at an angle α relative to a centerline37of the cowl28; the second compression ramp section30bis angled at an angle β relative to the centerline37. Angle α is different than angle β, and angle α is less than angle β. Angle α may be within the range of about 2 degrees to about 4 degrees; angle β may be within the range of about 3 degrees to about 7 degrees; however, angle α is always less than angle β.

The length of the supersonic compression ramp30varies as the supersonic compression ramp30extends around the perimeter of the supersonic flow inlet10. The length is defined as the distance from the highlight46to the throat18. The supersonic compression ramp30preferably has a length over height of 1 to 3. The supersonic compression ramp30is longer at the second surface33than at the maximum half breadth. The first compression ramp section30ahas a length which is shorter than the length of the second compression ramp section30b. The length of the first compression ramp section30ais defined as the distance between the highlight46and the second compression ramp section30balong the various points of the first compression ramp section30a. The length of the second compression ramp section30bis defined as the distance between the first compression ramp section30aand the throat18along the various points of the second compression ramp section30b. The compression ramp sections30a,30bhave a length ratio (the absolute length in the X direction) of approximately 1.7 to 1. This length ratio is substantially consistent around the curvature of the supersonic compression ramp30around the supersonic flow inlet10. For example, at the keel of the supersonic compression ramp30, the first compression ramp section30amay have a length of 27 inches and the second compression ramp section30bmay have a length of 45 inches.

As a result, the supersonic flow inlet10effectively has more compression area than prior art ramps because the supersonic compression ramp30extends over an approximately 180 degree arc along the supersonic flow inlet10. Since the supersonic compression ramp30does not include any flat panels, this results in reduced pressure loads and reduced circumferential area at the supersonic flow inlet10. As a result, this supersonic flow inlet10has lower drag than typical supersonic inlets.

Since the supersonic compression ramp30wraps around an approximately 180 degree arc along the supersonic flow inlet10, this results in a crown height, that is the minimum distance between the supersonic compression ramp30and the highlight46, which is less than a conventional flat ramp. This enables a simpler subsonic diffusion section16.

The subsonic diffusion section16is configured to receive the airflow22which has been compressed by the supersonic compression section14and is configured to diffuse the airflow22into a subsonic condition prior to entering the engine20. The subsonic diffusion section16comprises a rearward portion26bof the upper duct26and a subsonic diffusion ramp31. The rearward portion26band subsonic diffusion ramp31form a continuous perimeter around the supersonic flow inlet10. The subsonic diffusion section16extends from the throat18to the aft end70of the cowl28. The supersonic flow inlet10may be at least partially elliptical in the subsonic diffusion section16. The subsonic diffusion ramp31may be at least partially elliptical comprising 50% of an ellipse. In other embodiments, the subsonic diffusion ramp31may comprise any percentage of an ellipse, or may be in varying shapes. In still other embodiments, the upper arcuate duct26and the subsonic diffusion ramp31may vary in shape. In yet other embodiments, the diffusion ramp31may be eliminated.

The cross-section of the supersonic compression section14is largest at the beginning entrance24and is smallest at the throat18. The cross-section of the subsonic diffusion section16is smallest at the throat18and is largest at the end70.

At the interior points aligned with the maximum half breadths, the second compression ramp section30bmerges smoothly with the upper arcuate duct26which forms part of the subsonic diffusion section16. Along a width of the subsonic diffusion ramp31, the second compression ramp section30bmerges smoothly with the subsonic diffusion ramp31. As a result, the supersonic compression ramp30merges smoothly with the upper arcuate duct26and with the subsonic diffusion ramp31.

The configuration of the supersonic flow inlet10provides many benefits over one or more of the existing supersonic inlets such as providing high performance, providing high efficiency, providing low distortion, providing high recovery, providing low external drag, and being of low weight allowing for a reduction in size of the aircraft12or an increase in range of the aircraft12over one or more existing aircraft which utilize one or more of the existing supersonic inlets. The airflow22uniformly flows in the cross-section area of the supersonic compression section14, and the airflow22uniformly flows in the cross-section area of the subsonic diffusion section16, and the airflow22remains near-uniform at the end70of the subsonic diffusion section16. The supersonic flow inlet10provides a low external drag due to the reduction in external surface area of the supersonic flow inlet10. Use of the supersonic flow inlet10allows for an improvement in range of the aircraft12.

FIG. 10is a flowchart of one embodiment of a method72of compressing and diffusing the airflow22. In step74, the airflow22is flowed into the supersonic compression section14. In step76, the airflow22is compressed as it flows through the supersonic compression section14. The airflow22flows over the compression ramp sections30a,30bas it flows through the supersonic compression section14with the turn48providing a shock to the airflow22. In step78, the airflow22flows from the supersonic compression section14through the throat18and into and through the subsonic diffusion section16. The airflow22flows through the throat18with the turn49providing a shock to the airflow22. In step80, the airflow22is diffused into subsonic airflow within the subsonic diffusion section16and subsequently flows into the engine20.

While a particular embodiment is illustrated in and described with respect to the drawings, it is envisioned that those skilled in the art may devise various modifications without departing from the spirit and scope of the appended claims. It will therefore be appreciated that the scope of the disclosure and the appended claims is not limited to the specific embodiments illustrated in and discussed with respect to the drawings and that modifications and other embodiments are intended to be included within the scope of the disclosure and appended drawings. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the disclosure and the appended claims.