Fuel nozzle heat shield
An aft heat shield for a fuel nozzle tip includes: an annular shield wall; an annular shield flange extending radially outward from an aft end of the shield wall; an annular baffle flange surrounding the conical section, and disposed such that an axial gap is defined between the shield flange and the baffle flange, the baffle flange including a radially outer rim extending axially forward therefrom; and a plurality of impingement cooling holes passing through the baffle flange and oriented to as to direct air flow towards the shield wall.
1. A fuel nozzle apparatus for a gas turbine engine, the fuel nozzle apparatus comprising:
an annular pilot housing, the pilot housing including a conical wall section having a diverging conical aft end;
an annular main fuel injector surrounding the pilot housing;
an annular fuel nozzle casing surrounding the annular main fuel injector; and
a heat shield comprising:
an annular shield wall having a forward cylindrical section with a counterbore formed therein, the diverging conical aft end of the pilot housing being attached to the counterbore through a slip fit;
an annular shield flange extending radially outward from an aft end of the shield wall;
an annular baffle flange surrounding the shield wall, and disposed such that an axial gap is defined between the shield flange and the baffle flange, the baffle flange including a radially outer rim extending axially forward from a radially outer extent of the baffle flange; and
a plurality of impingement cooling holes passing through the baffle flange and oriented so as to direct air flow towards the shield flange.
2. The apparatus of claim 1 , wherein:
the annular shield wall includes an aft conical section;
an aft end of the annular fuel nozzle casing is bonded to the radially outer rim of the baffle flange through a metallurgical bond.
3. A method of repairing the apparatus of claim 1 after field use, the method comprising:
separating the heat shield from the pilot housing and the fuel nozzle casing; and
metallurgically bonding a replacement heat shield to the pilot housing and the fuel nozzle casing.
4. A method of assembling the fuel nozzle apparatus of claim 1 , comprising:
engaging the conical wall section of the pilot housing to the counterbore of the forward cylindrical section of the heat shield using the slip fit; and
metallurgically bonding an aft end of the annular fuel nozzle casing to the radially outer rim of the baffle flange thereby forming a metallurgical bond.
5. The method of claim 4 , wherein the metallurgical bond is formed by fusion welding.
6. A method of repairing a fuel nozzle apparatus for a gas turbine engine after field use, wherein the fuel nozzle apparatus includes an annular pilot housing, the pilot housing including a conical wall section having a diverging conical aft end, an annular main fuel injector surrounding the pilot housing, an annular fuel nozzle casing surrounding the annular main fuel injector, and a heat shield having an annular shield wall having a forward cylindrical section with a counterbore formed therein, the diverging conical aft end of the pilot housing being attached to the counterbore through a slip fit, an annular shield flange extending radially outward from an aft end of the shield wall, an annular baffle flange surrounding the shield wall, and disposed such that an axial gap is defined between the shield flange and the baffle flange, the baffle flange including a radially outer rim extending axially forward from a radially outer extent of the baffle flange, and a plurality of impingement cooling holes passing through the baffle flange and oriented so as to direct air flow towards the shield flange, the method comprising:
separating the heat shield from the pilot housing and the fuel nozzle casing;
assembling the conical wall section of the pilot housing to a counterbore formed in the cylindrical section of a replacement heat shield through a slip fit; and
metallurgically bonding an aft end of the annular fuel nozzle casing to a radially outer rim of a baffle flange of the replacement heat shield.
7. The method of repairing the fuel nozzle apparatus after field use of claim 6 , the method further comprising:
machining an aft end of the conical wall section of the pilot housing to include a cylindrical outer surface.