Patent Publication Number: US-6983602-B2

Title: Ejector cooled nozzle

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to aircraft gas turbine engines and, particularly, to ejector cooling of flaps and/or seals of the exhaust nozzle. 
   2. Description of Related Art 
   Hot aircraft gas turbine engine exhaust nozzles emit infrared radiation (IR) which is highly undesirable for military combat aircraft. Such aircraft engines include variable area axisymmetric, axisymmetric vectoring, and two dimensional convergent/divergent (CD) nozzles. Convergent and divergent flaps and seals confine hot exhaust flow and typically are used to provide variable throat area and exit area nozzles. These flow confining elements get hot and the divergent flaps and seals provide an unwanted infrared radiation (IR) signature for the engine and aircraft. Infrared radiation from gas turbine engines is conventionally suppressed by shielding and cooling the hot metal structures of the engine. Nozzles may also require or make use of cooling for structural reasons. Cooling air is conventionally drawn from the fan section or a compressor section of the gas turbine engine which is expensive in terms of fuel and power consumption. Nozzles including cooling air ejectors, such as the type used on some General Electric J79 engine models, have employed slot type ejectors to induct ambient cooling air from the atmosphere to supplement the engine supplied cooling air in order to reduce the use of the more expensive engine air. 
   Such ejecting nozzles provided cooling for variable nozzle throats but often require expensive compressor air for cooling or have trouble providing sufficiently pressurized air for cooling. Thus, it is highly desirable to provide a nozzle having ejector cooling that is inexpensive to use from an engine power perspective and operates effectively over a wide range of engine operating conditions. 
   SUMMARY OF THE INVENTION 
   An aircraft gas turbine engine convergent/divergent (CD) exhaust nozzle circumscribing a nozzle centerline includes a divergent section located aft of a convergent section and a throat therebetween. An exterior fairing surrounds and is spaced radially outwardly of at least the divergent section. An ejector cooling air flowpath leads from an ejector cooling air inlet in an aft portion of the fairing to a cooling air ejector in the nozzle. An exemplary embodiment of the nozzle further includes an annular nozzle plenum radially bounded by the divergent section of the nozzle and the external fairing. The ejector cooling air flowpath further includes the nozzle plenum between the ejector cooling air inlet and the ejector. 
   The exemplary embodiment of the nozzle further includes a plurality of circumferentially adjacent convergent flaps and convergent seals in the convergent section, pivotably mounted to an outer engine casing, and being pivotable relative to the centerline axis. A plurality of divergent flaps and divergent seals are in the divergent section and circumferentially disposed aft of and pivotably connected to the convergent section. The ejector is operable to cool the divergent flaps and seals. The ejector may include cooling air passages in the divergent flaps and seals, and the cooling air passages may be slots. 
   The exterior fairing in the exemplary embodiment of the nozzle further includes a plurality of circumferentially adjacent exterior flaps and exterior seals. Aft ends of the exterior flaps are pivotally attached to aft ends of the divergent flaps and forward ends of the exterior flaps and seals of exterior fairing are pivotally attached to the outer casing. The exterior fairing includes truncated ends of the exterior seals serving as the ejector cooling air inlet. Each of the truncated ends is located radially inwardly of and between circumferentially adjacent ones of the exterior flaps. 
   The exterior fairing in one alternative embodiment of the nozzle includes apertures in the exterior seals serving as the ejector cooling air inlet. Each of the apertures being located radially inwardly of and circumferentially between adjacent ones of the exterior flaps. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and other features of the invention are explained in the following description, taken in connection with the accompanying drawings where: 
       FIG. 1  is a longitudinal sectional view illustration of an aircraft gas turbine engine convergent/divergent nozzle with an ejector and a cooling air flowpath on an outer side of a fairing surrounding the nozzle. 
       FIG. 2  is a longitudinal sectional view illustration of an alternative embodiment of the nozzle illustrated in  FIG. 1 . 
       FIG. 3  is a perspective view illustration of the nozzle illustrated in  FIG. 1  in a closed position. 
       FIG. 4  is a perspective view illustration of the nozzle illustrated in  FIG. 1  in an open position. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Illustrated in  FIG. 1  is an exemplary axisymmetric aftwardly extending variable area aircraft gas turbine engine convergent/divergent (CD) exhaust nozzle  10  circumscribing a nozzle centerline  8 . The nozzle  10  includes a divergent section  14  located aft of a convergent section  16  and a throat  13  therebetween circumscribing the nozzle centerline  8 . An exterior fairing  18  surrounds and is spaced radially outwardly of at least the divergent section  14  of the nozzle  10 . An annular region radially bounded by the divergent section  14  and the external fairing  18  is referred to as a nozzle plenum  24 . 
   The convergent section  16  of the nozzle  10  includes a plurality of circumferentially adjacent convergent flaps  26  and convergent seals  27  pivotably mounted to an outer engine casing  12 . The convergent flaps  26  and convergent seals  27  are operable to pivot relative to the centerline axis  8 . The divergent section  14  includes a plurality of divergent flaps  36  and divergent seals  38  circumferentially disposed aft of and pivotably connected to the convergent section  16 . 
   The divergent flaps and seals  36  and  38  each includes a cooling air passage  40  which is illustrated in the form of a slot. The cooling air passages  40  are designed to operate together as an ejector  41  located aft of the convergent section  16  to cool the divergent flaps and seals  36  and  38 . The exterior fairing  18  includes a plurality of circumferentially adjacent exterior flaps  42  and exterior seals  43 . Aft ends  45  of the exterior flaps and seals  42  and  43  are pivotally attached to aft ends  39  of the divergent flaps and/or seals  36  and  38 , respectively. The exterior seals  43  may be carried and supported by the exterior flaps  42  and not pivotally attached to aft ends  39  of the divergent seals  38 . Forward ends  49  of the exterior flaps and seals  42  and  43  of exterior fairing  18  are pivotally attached to the outer casing  12 . 
   The ejector cooling air inlet  50  is located in an aft portion  52  of the fairing  18  and permits pressurized cooling air  56  to flow from outside of the fairing  18  into the nozzle plenum  24  and then into the slots or cooling air passages  40  of the ejector  41 . Thus, the ejector cooling air inlet  50  together with the nozzle plenum  24  provides an ejector cooling air flowpath  54  for the pressurized cooling air  56  to flow from the outside of the fairing  18  into the nozzle plenum  24  and then into the slots or cooling air passages  40  of the ejector  41 . Pressurized air  55  outside of the fairing  18  generally has higher pressure than that of the cooling air  56  through the divergent slot  40  of the nozzle  10  because internal airflow  58  expands and drives the static pressure of the external airflow  60  up. Furthermore, static pressure near the aft end of the nozzle  10  is increased due to high pressures of an expanding exhaust plume that emanates from the nozzle during engine operation. Thus, sufficient static pressure exists at the ejector cooling air inlet  50  to drive the pressurized cooling air  56  from outside of the fairing  18  into the nozzle plenum  24  when the nozzle  10  is open as illustrated in  FIG. 4  as well as when the nozzle  10  is closed as illustrated in  FIG. 3  and when the nozzle  10  is partially opened. 
   The ejector cooling air inlet  50  illustrated in  FIG. 1  is formed from truncated ends  62  of the exterior seals  43 . Each of the truncated ends  62  of the exterior seals  43  is located radially inwardly of and between circumferentially adjacent ones  64  of the exterior flaps  42  as further illustrated in  FIG. 3 . Opening and closing of the nozzle  10  spreads the circumferentially adjacent ones  64  of the exterior flaps  42  apart and together, respectively. This provides the ejector cooling air inlet  50  with a variable inlet area  68  as is illustrated by a comparison of a first area A 1  of the ejector cooling air inlet  50  in the closed nozzle  10  illustrated in  FIG. 3  to a second area A 2  of the ejector cooling air inlet  50  in the fully opened nozzle  10  illustrated in  FIG. 4 . 
   One alternative ejector cooling air inlet  50 , illustrated in  FIG. 2 , is formed from apertures  66  in the exterior seals  43  and because they are located radially inwardly of and between circumferentially adjacent ones  64  of the exterior flaps  42  the ejector cooling air inlet  50  in this design also has a variable inlet area  68 . The nozzle  10  is designed such that the variable inlet area  68  of the ejector cooling air inlet  50  increases in size as the nozzle  10  is opened from a closed position to a partially opened position. The nozzle  10  is also designed such that the variable inlet area  68  remains substantially constant when the nozzle  10  is opened from a partially opened position to a fully opened position. 
   The exemplary variable area aircraft gas turbine engine convergent/divergent (CD) nozzle  10  described above is illustrated as an axisymmetrical nozzle. However, the variable area aircraft gas turbine engine convergent/divergent (CD) nozzle  10  engine may also be a non axisymmetric nozzle such as a two dimensional nozzle and may also be a axisymmetric vectoring exhaust nozzle. 
   While there have been described herein what are considered to be preferred and exemplary embodiments of the present invention, other modifications of the invention shall be apparent to those skilled in the art from the teachings herein and, it is therefore, desired to be secured in the appended claims all such modifications as fall within the true spirit and scope of the invention. Accordingly, what is desired to be secured by Letters Patent of the United States is the invention as defined and differentiated in the following claims.