Air turbine starter one-piece air exit port baffle

A one-piece air exit port baffle for containment for an air start turbine includes a circular arc section with a circumferentially corrugated circular arc section and a flange section. The circumferentially corrugated circular arc section has a plurality of openings. The flange section is axially adjacent to the circumferentially corrugated circular arc section and configured for attachment adjacent to an air exit port of an air turbine starter.

BACKGROUND

The present invention relates to gas turbine engines. In particular, the invention relates to air exit port containment systems for air turbine starters.

Gas turbine engines require a starter component to rotate the core of the gas turbine to provide sufficient speed and compression to facilitate igniting the engine. An air turbine starter (ATS) is commonly employed in such applications. The ATS is powered by compressed air from an external source. The compressed air passes over blades of an air turbine in the ATS and exits the ATS through an air exit port. As the air turbine rotates, it rotates a shaft connected to the compressor in the gas turbine engine, providing sufficient torque to start the engine.

As with any powerful, high speed rotary system, such as an ATS, there is a risk that internal failure of a component, such as an air turbine, can result in high energy fragments escaping the rotary system and damaging nearby systems. Primary containment systems are employed in positions directly radially outward of rotating components, such as air turbine blades, to prevent large fragments from escaping the system. In the case of an ATS, with its large flow path and volume of compressed air moving past the air turbine blades, it is also possible for midsize and smaller fragments to be carried out of the ATS through an air exit port with sufficient energy to damage nearby components. For example, aircraft often have an ATS physically attached to each engine and proximate fuel pumps, fuel lines, and other important systems. Fragments escaping the ATS through the air exit port have the potential to damage such systems. Generally, an ATS will have a separate containment system, such as a baffle system, positioned at the ATS air exit port to contain such fragments within the ATS or, at least absorb and reduce the kinetic energy of any fragments that do escape through the air exit port.

SUMMARY

The present invention includes a one-piece air exit port baffle for containing or deflecting fragments within an air turbine starter with an annular air exit port. The one-piece baffle includes a circumferentially corrugated circular arc section and a flange section. The circumferentially corrugated circular arc section has a plurality of openings. The flange section is axially adjacent to the circumferentially corrugated circular arc section and configured for attachment adjacent to an air exit port of an air turbine starter.

DETAILED DESCRIPTION

Conventionally, an ATS exit port baffle comprises series of flat or slightly dished stamped steel rings around the ATS partially covering an annular air exit port. The flat rings are commonly positioned at an angle relative to air exiting the air exit port to inhibit the direct escape of fragments from the ATS through the air exit port. An ATS air exit port baffle must permit air to exit the port as freely as possible to ensure efficient air turbine operation while also inhibiting the escape of fragments in the event of sudden air turbine failure. These requirements are conflicting—the more open the path through the ATS air exit port baffle the more likely fragments may pass thru and not be contained or deflected. An effective ATS air exit port baffle must balance these requirements.

The conventional series of flat rings for an ATS air exit port baffle is comprised of a high number of individual components—baffle rings, spacers between rings, bolts, washers, nuts, etc. It is not uncommon for the part count to reach fifty separate components—all of which must be tracked, counted, inventoried, etc. In addition, assembling such a system is labor intensive. The present invention relieves these problems by replacing the rings, spacers, washers, nuts, etc. with a one-piece baffle. The one-piece baffle has openings to accommodate the air flow needs of the ATS. The one-piece baffle is corrugated to provide the radial strength necessary to inhibit the high energy fragments from escaping the ATS through the air exit port. The baffle has a circular arc section shape to match the annular shape of the air exit port.

ConsideringFIGS. 1 and 2together,FIG. 1is a partial cross-section of an air turbine starter illustrating an embodiment of the one-piece air exit port baffle of the present invention.FIG. 1shows ATS10, primary casing12, air input port14, annular air exit port16, air exit port baffle18, and output power shaft20.FIG. 2is an expanded view of a portion of the air turbine starter illustrated inFIG. 1. As shown inFIG. 2, ATS10further comprises annular air flow channel22, air turbine24, turbine containment system26, and retaining plate28, and mid-housing30. Internal annular air flow channel22comprises stator vanes34and36. Air turbine24comprises turbine blades38, turbine wheel hub40, and turbine shaft42. Retaining plate28comprises attachment block sections44and channel sections46.

Primary casing12surrounds the bulk of ATS10and attaches to mid-housing30. Annular air flow channel22extends from air input port14, past stator vanes34, turbine blades38, and stator vanes36to annular air exit port16. Turbine blades38are attached to turbine wheel hub40which is attached to turbine shaft42. Turbine shaft42drives thru a reduction gear train to output shaft20. Turbine containment system26is positioned radially outward from air turbine24to prevent the escape of large, high-energy fragments from air turbine24in the even of a catastrophic failure of air turbine24. Attachment block sections44are connected by channel sections46to form retaining plate28. Retaining plate28is attached to mid-housing30at each of attachment block sections44by a bolt (not shown) passing from primary casing12through mid-housing30and terminating in a threaded connection (not shown) in attachment block sections44. Air exit port baffle18is attached to retaining plate28at attachment block sections44such that it covers annular air exit port16.

In operation, compressed air enters air input port14and flows into annular flow channel22, past stator vanes34which direct the air flow to turbine blades38. Air flows are indicated by arrows marked F. The air flow continues past stator vanes36and out through annular air exit port16and air exit port baffle18. Stator vanes34and36are positioned to direct air flow past turbine blades38to enhance the interaction between the air flow and turbine blades38to improve the efficiency of ATS10. As the compressed air flows past turbine blades38, the air flow causes turbine wheel hub40to rotate about centerline axis CL, rotating turbine shaft42and causing rotation in output shaft20. The rotation of output shaft20provides the torque necessary to start an attached engine (not shown).

In the event of catastrophic failure of air turbine24, air exit port baffle18prevents smaller fragments of air turbine24that may follow the flow path from exiting annular air exit port16from escaping ATS10. Air exit port baffle18provides this protection while still permitting air to exit ATS10in an efficient manner.

FIGS. 3A,3B, and3C are perspective and cross-section views of an embodiment of the one-piece air exit port baffle18of the present invention.FIG. 3Ais a perspective view of air exit port baffle18attached to retaining plate28illustrating that air exit port baffle18is a one-piece, circular arc section comprising plurality of openings50, flange section52and corrugation54. Flange section52and corrugation54run in a circumferential direction, defining a circular arc section. In this embodiment, plurality of openings50is a series of perforations or holes through flange section52and corrugation54. As shown inFIG. 3A, air exit port baffle18attaches to retaining plate28at interface56between attachment block sections44and flange section52. The attachment at interface56is accomplished by, for example, welding or brazing.

FIG. 3Bis a cross-section of a portion of air exit port baffle18and attachment block section44showing an alternative to welding or brazing for the attachment at interface56. Alternatively, attachment block section44further comprises threaded receiver57, flange section52comprises bolt holes58corresponding to attachment block section44. The attachment at interface56is accomplished by inserting threaded fastener59through bolt hole58and threading threaded fastener59into threaded receiver57. Another alternative for attachment at interface56is the combination of welding or brazing with the previously described attachment by threaded fastener59.

Corrugation54of air exit port baffle18provides the radial strength needed to prevent fragments from escaping air exit port16in addition to increased surface area for plurality of openings50for efficient air flow through air exit port baffle18.FIG. 3Cillustrates further details of air exit port baffle18.FIG. 3Cis a cross-section of air exit port baffle18illustrating flange section52and corrugation54. Corrugation54comprises circumferential valley section60, first axial edge62, second axial edge64, first circumferential peak section66, and second circumferential peak section68. Openings50are omitted for clarity.

Flange section52and corrugation54are a one-piece shape that forms air exit port baffle18. Corrugation54has a generally wave-like shape, for example, a sinusoidal wave shape or a triangular wave shape, of about one wave length. Circumferential valley section60extends in an inward radial direction, bounded by first axial edge62and second axial edge64. First circumferential peak section66is radially and axially adjacent first axial edge62and extends away from circumferential valley section60in an axial direction and in an increasing radial direction. Similarly, second circumferential peak section68is radially and axially adjacent second axial edge64and extends away from circumferential valley section60in an axial direction opposite that of first circumferential peak section66and in an increasing radial direction. Flange section52extends in an axial direction away from circumferential valley section60and is axially adjacent first circumferential peak section66opposite first axial edge62.

Air exit port baffle18is a one-piece baffle replacing the many rings, spacers, washers, nuts, etc. used in the prior art, thus saving costs associated with tracking, counting, and inventorying components. Significant labor savings in assembling and servicing are also realized with air exit port baffle18. The circular arc section shape of air exit port baffle18permits it to be easily attached by welding or brazing to retaining plate28. Alternatively, by accepting a relatively small increase in components, air exit port baffle18is attached to retaining plate28by threaded fasteners. Openings50are sized and spaced as necessary to achieve the desired air flow through air turbine24, while limiting the escape of high-energy fragments from ATS10. Corrugation54provides mechanical strength to withstand high-energy impacts and, once impacted, corrugation54will tend to compress, closing up plurality of openings50to automatically provide additional protection against escaping fragments under conditions where efficient air flow through ATS10is no longer a concern. Finally, air exit port baffle18provides for safer and more robust handling of ATS10by eliminating the rings, which have sharp outer edges and are prone to bending.

Air exit port baffle18is made of a material with good formability and ductility, for example, corrosion-resistant steel, to better absorb the energy from high-energy fragments. Air exit port baffle18is made by starting with a sheet of such material and forming plurality of openings50into the sheet by a process appropriate to the nature of openings50, for example, punching, drilling, cutting, mill-slotting, and stamping. At the same time, bolt holes, if desired, are also formed. The sheet with plurality of openings50undergoes a stamping operation to form corrugation54and flange section52. The corrugated sheet then undergoes a bending or rolling operation to create a circular arc section shape to properly fit over air exit port16. The processing sequence may be tailored to the equipment and skills of the producer.

FIGS. 4A and 4Bare perspective and cross-section views of another embodiment of the one-piece air exit port baffle of the present invention.FIG. 4Ais a perspective view of air exit port baffle118attached to retaining plate28illustrating that air exit port baffle118is a one-piece, circular arc section comprising plurality of openings150, flange section152, corrugation154, and, unlike the previous embodiment, baffle extension section155. In this embodiment, plurality of openings150is a series of perforations or holes through flange section152, corrugation154, and baffle extension section155. As shown inFIG. 4A, air exit port baffle118attaches to retaining plate28at interface158between attachment block sections44and flange section152. The attachment at interface158is accomplished by, for example, welding or brazing. Alternatively, the attachment at interface158is accomplished by a threaded fastener (not shown) through flange section152into attachment block sections44. As shown inFIG. 4A, flange section152, corrugation154, and baffle extension section155run in a circumferential direction, defining a circular arc section.

Corrugation154of air exit port baffle118provides the strength needed to prevent fragments from escaping air exit port16in addition to increased surface area for the plurality of openings150for efficient air flow through air exit port baffle118.FIG. 4Billustrates further aspects of air exit port baffle118.FIG. 4Bis a cross-section of air exit port baffle118of the present invention illustrating flange section152, corrugation154, and baffle extension section155. Corrugation154comprises circumferential valley section160, first axial edge162, second axial edge164, first circumferential peak section166, second circumferential peak section168, and, unlike the previous embodiment, third circumferential peak section170. Openings150are omitted for clarity.

Flange section152, corrugation154, and baffle extension155form a one-piece shape comprising air exit port baffle118. Corrugation154has a generally wave-like shape, for example, a sinusoidal wave shape or a triangular wave shape, of about 1¼ wave lengths. Circumferential valley section160extends in an inward radial direction, bounded by first axial edge162and second axial edge164. First circumferential peak section166is radially and axially adjacent first axial edge162and extends away from circumferential valley section160in an axial direction and in an increasing radial direction. Similarly, second circumferential peak section168is radially and axially adjacent second axial edge164and extends away from circumferential valley section160in an axial direction opposite that of first circumferential peak section166and in an increasing radial direction. Flange section152extends in an axial direction away from circumferential valley section160and is axially adjacent first circumferential peak section166opposite first axial edge162. Third circumferential peak section170is axially adjacent second circumferential peak section168opposite second axial edge164and extends away from second circumferential peak section168in an axial direction and in a decreasing radial direction. Baffle extension section155extends in an axial direction away from circumferential valley section160and is axially adjacent third circumferential peak section170opposite second circumferential peak section168.

Air exit port baffle118retains all of the advantages described above for the previous embodiment. In addition, air exit port baffle118, with baffle extension155properly positioned by third circumferential peak section170, provides termination of form, corresponding to adjacent housing features, and provides improved coverage of exit port16. Finally, because third circumferential peak section170turns inward by extending in a decreasing radial direction, it forms a “pocket” to capture debris, further improving the ability of air exit port baffle118to contain fragments within ATS10.

While the previous embodiments employed perforations or holes, other shapes may be employed.FIG. 5is a perspective view of another embodiment of air exit port baffle218of the present invention. Air exit port baffle218shown inFIG. 5is identical to the embodiment discussed in reference toFIGS. 4A and 4Bexcept that plurality of openings250is a series of slots cut in corrugation254.

In the previous embodiments, the air exit port baffle is illustrated as a one-piece, circular arc section that is not a complete circle. Multiple air exit port baffles attached to the retaining plate and positioned end to end form a complete circle covering the entirety of the air exit port.FIG. 6is a perspective view of another embodiment of air exit port baffle318of the present invention. Air exit port baffle318shown inFIG. 6is identical to the embodiment discussed in reference toFIGS. 4A and 4B, except that the one-piece, circular arc section forms a complete circle. With this embodiment, air exit port baffle318covers the full circumference of air exit port16.

The embodiments described above employ corrugations of either 1 or 1¼ wave lengths. It is understood that embodiments of the present invention may employ additional whole or fractional wave lengths to extend the corrugation of the one-piece air exit port baffle of the present invention to as many wave lengths as desired to cover an air exit port with a wider axial dimension.