Patent Publication Number: US-2009217643-A1

Title: Gas discharge device for a vehicle engine

Description:
BACKGROUND 
     The present invention relates generally to gas discharge techniques for vehicle engines, and more particularly, but not exclusively, to signature suppression for gas turbine engines of airborne vehicles. 
     Signature suppression remains an area of significant interest for both homeland security and military purposes. Unfortunately, some existing systems have various shortcomings relative to certain applications. Accordingly, there remains a need for further contributions in this area of technology. 
     SUMMARY 
     One embodiment of the present application is a unique discharge technique for a vehicle engine. Other embodiments include unique apparatus, systems, devices, hardware, methods, and combinations for signature suppression. Further embodiments, forms, objects, features, advantages, aspects, and benefits of the present invention shall become apparent from the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial schematic side view of a turboprop powered aircraft having a suppression device including an ejector. 
         FIG. 2  is a side view of an s-shaped conduit in another type of a suppression device shown from the side opposite that depicted in  FIG. 1  that may be used in place of the suppression device of  FIG. 1 . 
         FIG. 3  is a diagrammatic end view of an exhaust segment of the suppression device taken along the  3 - 3  view line of  FIG. 2 . 
         FIG. 4  is a diagrammatic end view of an exhaust segment opposite the end view of  FIG. 3  as taken along the  4 - 4  view line of  FIG. 2 . 
         FIG. 5  is a side view of yet another type of suppression device with an s-shaped conduit that can be used in place of the suppression device of  FIG. 1 . 
         FIG. 6  is a partially diagrammatic, cut away side view of an s-shaped conduit of still another type of suppression device that can be used in place of the suppression device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS 
     For purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the illustrated device, and any further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
     One embodiment of the present application is a gas turbine engine that includes an s-shaped conduit having an ejector formed therein. The s-shaped conduit is configured downstream of the outlet of the gas turbine engine and serves to radially displace an exhaust flow generated by the engine to alter the line of sight angles from which infrared radiation may be detected. The ejector additionally serves to reduce total emitted infrared radiation by entraining non-exhaust flow air into the exhaust flow to create a cooled flow mixture. The ejector may be located at a point upstream of an inflection point in the s-shaped conduit. As used herein, the term “inflection point” means a point where a tangent line to such point reverses direction. A nacelle may be attached near the gas turbine engine to house the s-shaped conduit and may have an inlet that is in fluid communication with the ejector. 
     For another embodiment,  FIG. 1  illustrates a turboprop aircraft  55  having a nozzle system  50  including a suppression device  51 . The nozzle system  50  is installed on the aircraft  55  which includes a gas turbine engine  60  located beneath and somewhat fore of a wing  65  of the aircraft  55 ; however, in other embodiments the position of the nozzle system  50  to the wing, aircraft, or other application may differ. The aircraft  55  further includes the gas turbine engine  60  that provides power to turn the propeller  70  and comprises at least one compressor  75 , combustor  80 , and two turbines  85  in a free turbine arrangement; however, it should be appreciated that other forms may include more or fewer gas turbine engine components with correspondingly different arrangements. A cowling  87  encloses the gas turbine engine  60  to create an aerodynamic fairing for reduced drag. In the depicted embodiments, the gas turbine engine  60  is of a turboprop type, and the aircraft  55  is of a fixed wing type. Nonetheless, in other embodiments a different engine and/or aircraft type may be utilized; where the term aircraft includes, but is not limited to, helicopters, airplanes, unmanned space vehicles, fixed wing vehicles, variable wing vehicles, rotary wing vehicles, hover crafts, and others. Further, in various embodiments of the present application, other applications are contemplated that may not include an aircraft such as, for example, industrial applications, power generation, pumping sets, naval propulsion and other applications known to one of ordinary skill in the art. 
     In this nonlimiting example, the nozzle system  50  is shown located beneath the wing  65  of the aircraft  55  downstream of the gas turbine engine  60 . The nozzle system  50  includes an s-shaped discharge duct  90  (alternatively designated an s-shaped conduit  95 ) as well as a nacelle  100 . The system  50  is structured to suppress the infrared (IR) signature that would otherwise result from the discharge of hot exhaust therethrough. In operation, hot exhaust from the gas turbine engine  60  is routed through the s-shaped duct  90  and out the downstream end of the nacelle  100 . The s-shaped character of the s-shaped duct  90  forces the exhaust flow to be radially displaced while still preserving the axial direction of the exhaust flow that existed prior to entering the s-shaped duct  90 . However, in other forms, the axial flow direction may not be entirely or substantially preserved. The s-shaped duct  90  has a sinuous shape  105 , the nature of which is described further hereinbelow. 
     The S-shaped duct  90  includes a first segment  110  and a second segment  115  and further includes an ejector  120  formed by the relative orientation between the first segment  110  and the second segment  115 . The s-shaped duct  90  is shaped to reduce, if not eliminate any line of sight to the turbines  85  by an external observer looking through the discharge end thereof; thus reducing the detectable emitted infrared radiation from gas turbine engine  60 . In addition, external air, as represented by the arrow designated with reference numeral  121 , is provided to the s-shaped duct  90  through the action of the ejector  120  and thereafter mixed with hot exhaust flow. Mixing exhaust flow with external flow reduces the temperature of the flow traveling through the s-shaped duct  90  and therefore further reduces the signature of emitted radiation. As used herein, the terms “external flow” or “external air” means air flow that is external to the flow path through the gas turbine engine core, i.e. the air flow along a path through compressor  75 , combustor  80  and turbines  85 ; that is typically cooler in temperature than the core flow. As an example, air flow downstream of the propeller  70  is one form of “external air.” In addition, air flow at ambient conditions upstream of the propeller  70  is also included in the meaning of such terms. 
     The first segment  110  of the s-shaped duct  90  is attached to an outlet  122  of the gas turbine engine  60  to receive hot exhaust flow. In one form, the first segment  110  is permanently attached to the gas turbine engine  60 , but in other forms may be releasably attached. In yet other forms, the first segment  110  may be an integral part of the gas turbine engine  60 . The first segment  110  defines a first segment inlet opening  125  and a first segment exit opening  130  in fluid communication with one another to via first segment passage  111  to provide a first segment flow path therethrough. As exhaust flow exits the gas turbine engine  60 , it is substantially captured by the first segment  110  through the opening  125  so that it may be conveyed further downstream through the passage  111 . As the exhaust flow is conveyed downstream through passage  111 , it is radially displaced by the geometry of the first segment  110 . In the illustrated embodiment, the first segment  110  only partially provides for the final radial displacement of exhaust flow downstream of the nozzle system  50 , but in other embodiments the first segment  110  may be configured to provide all or none of the final radial displacement. In addition to radial displacement, in some implementations the first segment  110  may be oriented at an angle relative to the longitudinal axis of the gas turbine engine  60 . The first segment opening  125  substantially conforms in shape to the outlet  122  and may provide for an efficient flow path transition from the gas turbine engine  60  to the first segment  110 . The opening  125  can be approximately circular in shape, but other shapes are also contemplated. Although not depicted in the illustrated embodiment, the interface between the first segment  110  and the outlet  122  of gas turbine engine  60  may or may not have an additional seal to prevent the escape of hot exhaust flow. 
     The second segment  115  is positioned downstream of the first segment  110  and is configured to receive exhaust flow traveling out of an exit opening  130  from first segment  110 . The second segment  115  defines a second segment inlet opening  135  and a second segment exit opening  140  in fluid communication with one another via second segment passage  115  to provide a second segment flow path therethrough. The inlet opening  135  of the second segment  115  can be larger in size but typically conforms in shape to the exit opening  130  of the first segment  110 . In some forms, the inlet opening  135  may not conform in shape to the exit  130 . The inlet opening  135  may be approximately circular in some forms, but other shapes are also contemplated. The second segment  115  provides for the final radial displacement of the exhaust flow from the gas turbine engine  60 . In some forms, the second segment  115  may provide none or all of the radial displacement of the s-shaped duct  90 . A vector angle in the exhaust flow aft of the second segment  115  may be provided in some implementations. 
     The ejector  120  is formed when the inlet opening  135  receives the exit opening  130 . Although the second segment  115  is shown oriented symmetrically from top to bottom about the first segment  110 , other forms contemplate offsets in the configuration. For example, the inlet opening  135  may be oriented such that its top edge is coincident with the top edge of the exit opening  130 , thus leaving a large and asymmetric gap created between the bottom of the inlet opening  135  and exit opening  130 . The ejector  120  is configured to entrain an external flow of air with the exhaust flow traversing through s-shaped duct and is sized to accommodate a broad range of mass flows both in the internal hot exhaust flow and the pumped external air. 
     The nacelle  100  includes a nacelle inlet  145  opposite a nacelle outlet  150 , a nacelle flow director  155 , and a nacelle connector  160 . The nacelle  100  is configured to substantially enclose the conduit  95 , but in some implementations nacelle  100  may only partially enclose it. An outer surface  165  of the nacelle  100  provides an aerodynamic fairing for the nozzle system  50  such that aerodynamic drag is reduced. The nacelle  100  is connected to the wing  65  by the nacelle connector  160  and may be permanently or releasably connected. The nacelle flow director  155  is configured to be in fluid communication with the nacelle inlet  145  and the ejector  120 , and may be configured as a ramp or other suitable structure for directing airflow. In some implementations, the flow director  155  may not be included such as when a nacelle is not provided, to name one possibility. During operation of the nozzle system  50 , the airflow that is channeled to the ejector  120  by the flow director  155  is thereafter entrained with exhaust flow traversing the conduit  95 . Mixed exhaust flow and external air flow are discharged from the nacelle outlet  150 . In some implementations, the nacelle outlet  150  may be coincident with the second segment exit opening  140  such as when the outer surface  165  of the nacelle  100  converges at the second segment exit opening  140 . Correspondingly, the outlet  150  is not defined separately from the opening  140 . In other implementations, the nacelle outlet  150  may be axially and/or radially displaced from the second segment exit  140 . 
     The duct segment support  175  is used to connect at least part of the s-shaped duct  90  to the nacelle  100 , and may be permanently or releasably connected to either or both the s-shaped duct  90  and the nacelle  100 . In the illustrated embodiment, the duct segment support  175  is configured to support the second segment  115  and suspend it aft of the first segment  110 . The second segment  115  is not supported by the first segment  110 , but in other forms the second segment  115  may be supported solely by the first segment  110  or via a combination of the first segment  110  and the duct segment support  175 . 
       FIG. 2  depicts another embodiment of an ejector-assisted conduit for a suppression device including an s-shaped conduit  180 ; where like reference numerals refer to like features. The s-shaped conduit  180  is shown attached to the outlet  185  of the gas turbine engine  60  and comprises three segments. A first segment  190  may be attached to the outlet  185  of the turbine  85  as previously described in connection with the aircraft  55 . A second segment  195  is located aft of the first segment  190  with a margin  200  of the second segment  195  receiving a margin  205  of the first segment  190 . The spacing between the margin  200  and the margin  205  defines an axial overlap that is depicted as radially symmetric in  FIG. 2 , but it should be understood that any variety of configurations are contemplated, such as a larger overlap at the bottom of s-shaped conduit than at the top. 
     An ejector  215  is formed by the relative orientation of the second segment  195  and the first segment  190  and includes an ejector lip  220  that defines an inlet  225  of the ejector  215  in cooperation with the second segment  195 . Airflow, as represented by the arrow designated by reference numeral  230 , enters the inlet  225  at the bottom of the s-shaped conduit  180 , but in other forms may also enter the ejector  215  substantially around the entire circumferential periphery of the s-shaped conduit  180 . In other forms, the airflow  230  may enter at the top or sides of the ejector  215 . In still other forms, the airflow  230  may be bifurcated into two streams or further divided into multiple streams before entering the ejector  215 . The airflow  230  entering the ejector  215  is entrained in the exhaust flow  235  traversing from the first segment  190  thus creating a mixed flow. 
     A third segment  240  is provided and is oriented aft of the second segment  195  to also form an ejector  250 . Airflow, as represented by the arrow designated by reference numeral  245 , enters the bottom of the ejector  250 , but may also enter around the entire circumferential periphery of the s-shaped conduit  180 . In other forms, the airflow  245  may enter at the top or sides of the ejector  250 , or be divided into two or more streams. The airflow  245  entering the ejector  250  is entrained in the mixed flow traversing from the second segment  195 . 
     The relative orientation of the first segment  190 , the second segment  195 , and the third segment  240  creates an s-shaped pathway  255  that includes two reversals of curvatures denoted by the inflection points  260  and  265 . It will be understood that the first segment  190 , the second segment  195 , and the third segment  240  may be arranged to provide any number of inflection points, including only one as would be defined by a literal s-shaped. In this way, the term “s-shaped” includes a sinuous shape of a conduit that has at least one inflection point, and also includes a sinuous shape that has more than one inflection point such that it defines more than a single s-shaped portion. It will also be understood that either or both ejectors may be located upstream or downstream of an inflection point as suits a particular application. 
       FIGS. 3 and 4  depict cross-sectional views taken of the s-shaped conduit  180  illustrated in  FIG. 2  taken along view lines  3 - 3  and  4 - 4 , respectively.  FIG. 3  shows a projected exhaust inlet  270  having a substantially circular shape  272 , but other shapes are also contemplated. The projected exhaust inlet  270  has a projected exhaust inlet width  275  and a projected exhaust inlet height  280 , both of which may be transverse to the flow path through an s-shaped conduit  180 . The ratio of the projected exhaust inlet width  275  to the projected exhaust inlet height  280  may be referred to as inlet aspect ratio of projected exhaust inlet  270 . Inlet aspect ratio is approximately 1:1 (approximately unity), but may have other values in other implementations. 
       FIG. 4  shows a projected outlet  285  having a rounded rectangular shape  286 , but other shapes are also contemplated. Similar to the projected exhaust inlet  270  discussed above, the projected exhaust outlet  285  has a projected outlet width  290  and a projected outlet height  300 . The ratio of the projected outlet width  290  to the projected outlet height  300  may be referred to as outlet aspect ratio of the projected exhaust outlet  285 . In one form, the inlet aspect ratio and the outlet aspect ratio differ, preferably the outlet aspect ratio is greater than the inlet aspect ratio, and more preferably the outlet aspect ratio is greater than the inlet aspect ratio and is greater than unity. 
     The s-shaped conduit  180  may vary smoothly between the shapes of the projected exhaust inlet  270  and the projected exhaust outlet  285 , or may be discontinuous at some point along the length of the duct. For example, the cross section of the s-shaped duct  180  may be held substantially circular for the length of the first segment  190  and then abruptly change to a different cross sectional shape for the length of the second segment  195 . In another form, the cross section may change along one segment but be held substantially constant across another. In yet another form the cross section of both segments may be substantially the same. 
     Referring to  FIG. 5 , another form of an ejector-assisted suppression device is illustrated in the form of s-shaped conduit  305 ; where like reference numerals refer to like features. Conduit  305  is structured for attachment to an outlet of a gas turbine engine (not shown) in place of one of the embodiments previously described and comprises two segments. A first segment  310  is composed of a forward section  315  and an aft section  320  that are coupled together. The forward section  315  can be attached to an existing turbine frame section of a gas turbine engine by a primary mount flange  325 . Though the first segment  310  is comprised of two sections in  FIG. 5 , it will be understood that more or fewer sections may be included in the first segment  310 . Furthermore, the sections in other forms may be capable of receiving each other axially, radially, or in any other configuration. A cooling slot  330  is formed between the forward section  315  and the aft section  320  and serves to provide cooling air for the s-shaped conduit  305 . The cooling slot  330  is z-shaped in the illustrative embodiment and also serves to maintain the spacing between the forward section  315  and second section  320 . The cooling slot  330  may be configured to permit cooling air to enter the entire periphery of the s-shaped conduit  305  or may be configured to limit cooling air exposure/entry to a certain region or regions. Also included are stiffening bands  335  and  337  used on the aft section  320  of the first segment  310  to provide structural support. 
     A second segment  340  is located aft of the first segment  310  and includes support channels  345  and  350  and mount bosses  355  and  360 . The second segment  340  also includes a forward flow blocker  365  that extends in the space defined between the s-shaped conduit  305 , the nacelle  100 , and a bottom surface  367  of the wing  65 . The forward flow blocker  365  impedes airflow from flowing in the nacelle  100  from one side of the forward flow blocker  365  to the other side. The forward flow blocker  365  substantially surrounds the s-shaped conduit  305  in the illustrative embodiment, but in other embodiments may only partially surround the conduit s-shaped conduit  305 . A heat shield  370  is located between the first segment  310  and the second segment  340  to provide for thermal management of the s-shaped conduit  305 . An ejector  375  is formed by the relative orientation of the second segment  340  and the heat shield  370 . In addition, an ejector  377  is also formed between the first segment  310  and heat shield  370 . Both ejectors  375  and  377  operate in the same manner as the previously described ejectors. 
       FIG. 6  represents yet another embodiment of a multisegment s-shaped conduit of a suppression device. It includes a first segment  380  capable of being permanently or releasably attached to the outlet of a gas turbine engine (not shown), and a second segment  385  structured to receive at least a part of the first segment  380 . The relative orientation of the segments  380  and  385  forms an ejector  390  that operates like the various forms of ejectors described previously. Airflow, as indicated by an arrow designated by reference numeral  395 , enters an ejector inlet  400  and is thereafter entrained in an exhaust flow  405  as designated by the like labeled arrow. An inflection point  410  is formed downstream of the inlet  400 . An outlet  415  of the second segment  385  is flared, and in other embodiments may comprise any number of shapes such as circular or rectangular. 
     Many different embodiments are envisioned, for example in some embodiments the nacelle and second segment may be formed as an integrated suppression apparatus. In still other implementations, the nacelle second segment, and first segment may be formed in an integrated assembly that may be capable of attachment directly to the wing. Additionally and/or alternatively, an integrated assembly may be mounted to the exhaust outlet of gas turbine engine. 
     In one particular form, a suppression device is provided to that can be retrofit to the engines of pre-existing aircraft. This form may include a nacelle that carries a multisegment s-shaped conduit that can be connected to the pre-existing exhaust outlet of an engine. One implementation of such form is used to retrofit underwing turboprop engines, such as those of a C-130 fixed wing aircraft. 
     In another embodiment, an ejector formed by a third segment and second segment can have a configuration independent of the configuration of an ejector formed by a first segment and second segment. For example, a bifurcated stream may be configured to enter a first ejector and a peripheral stream may enter a second ejector. 
     Still another embodiment of the present application includes a nozzle system having an s-shaped duct. Two segments comprise the s-shaped duct wherein a margin of one segment is at least partially nested in the margin of another segment. The relative orientation of the two segments defines an ejector configured to mix a secondary flow stream with a primary flow stream. 
     In still another embodiment, a fixed wing aircraft powered by a gas turbine engine includes an s-shaped duct to receive and discharge an exhaust flow. An ejector is formed along the length of the s-shaped duct to mix air with the exhaust flow before being discharged through the outlet. 
     In yet another embodiment, an s-shaped duct is provided having an inlet with a first aspect ratio and an outlet with a second aspect ratio. The first aspect ratio is taken from a cross section of the duct near the inlet end and the second aspect ratio is taken from a cross section of the duct near the outlet. Both aspect ratios are determined by dividing a maximum distance by a minimum distance of the cross section. The cross sections may be transverse to a flow from a gas turbine engine. The first cross section may be circular in shape thus having a near unity aspect ratio while the outlet aspect ratio may be rectangular in shape, thus resulting in a greater than unity aspect ratio. 
     Another embodiment includes: providing a gas turbine powered aircraft having a turbine exhaust, connecting a first duct segment to the turbine exhaust, and installing a nacelle having a second duct segment such that the relative orientation of the first duct segment and the second duct segment create an s-shaped conduit having an ejector with an ejector lip. 
     In a further embodiment, the present invention provides means for ducting an exhaust flow in an s-shape and providing an ejector therein. The ducting is comprised of two segments wherein one segment nestingly receives another segment. An ejector means is formed by the relative orientation of the first segment to the second segment wherein a secondary flow stream is entrained in a primary flow stream. The relative orientation of the two segments provides at least one inflection point. 
     In a still further embodiment, means for ducting the exhaust from a gas turbine powered aircraft are provided, including an s-shaped means and an ejector means. The ejector means is capable of mixing air with an exhaust flow from the gas turbine engine. 
     In a still another embodiment, means for ducting the exhaust from a gas turbine powered aircraft are provided, including an s-shaped means and an ejector means. The s-shaped means having an inlet aspect ratio less than an outlet aspect ratio. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected. It should be understood that while the use of the word preferable, preferably or preferred in the description above indicates that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, that scope being defined by the claims that follow. In reading the claims it is intended that when words such as “a,” “an,” “at least one,” “at least a portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. Further, when the language “at least a portion” and/or “a portion” is used the item may include a portion and/or the entire item unless specifically stated to the contrary.