Patent Application
20200248904
The disclosure relates generally to gas turbine engines, and more particularly, to fuel nozzle insulation.
Fuel nozzles for gas turbine engines are supplied with fluid fuel under pressure and compressed air. The fuel and air are conveyed axially and radially through flow channels within the fuel nozzle to spray, swirl, atomize and mix together on exit in preparation for fuel ignition and combustion.
The flow channels within fuel nozzles are defined between inward and outward surfaces of various concentric components that are brazed or welded together. Flow channels can also be machined into a component. The outermost component of the concentric assembly of components is exposed to hot combustion gas flowing within the combustion chamber and around exterior surfaces of the fuel nozzle.
Air flow bores communicate with the air flow channels to convey compressed air radially inward from the outward flow channels to the outer surface of the innermost component of the fuel nozzle that is exposed to hot gases. The outer surface of the outermost component of the fuel nozzle can absorb heat from the surrounding hot gases. Via convection and conduction, the outer surface of the outermost component can convey heat to the inner concentric components of the fuel nozzle.
Although the temperature of the inner concentric components during operation is moderated by the continuous flow of cooler fuel through the flow channels in the fuel nozzle, avoiding heat transfer by convection and conduction from hot air is desirable to reduce thermal stress, extend the service life of the components, and reduce or eliminate coke build up in fuel passage. Improvement is thus desirable.
In one aspect, the disclosure describes a fuel nozzle for injecting fuel and air into a combustor of a gas turbine engine, the fuel nozzle comprising: an outer component having an outward surface adapted for exposure to a flow of hot gas within the combustor; an inner component concentrically disposed within the outer component, the inner component defining an axially extending air flow channel; an air passage bore extending from the outward surface of the outer component to the air flow channel; and a sleeve disposed at least within a portion of the air passage bore, the sleeve having a sleeve body spaced apart from the outer component by an air gap.
In another aspect, the disclosure describes a gas turbine engine with a fuel nozzle as described above. Embodiments can include combinations of the above features.
Further details of these and other aspects of the subject matter of this application will be apparent from the detailed description included below and the drawings.
The inner component 13 defines an axially extending air flow channel 15. In the example shown an inward facing groove 16 is formed opposite a concentric core component 17 to define the air flow channel 15. The air flow channel 15 can also be formed by other means such as by conventional (casting, machine from solid, etc.) or advanced manufacturing (additive, MIM, chemical etching, etc.) methods. For example the inner component 13 can have an outward surface defining the air flow channel 15 with the inward surface of the outer component 12.
A radial air passage bore 18 extends through the outward surface of the outer component 12 and communicates with the air flow channel 15. An intermediate component may be disposed concentrically between the inner component 13 and the outer component 12. Multiple layers of intermediate components 19 is also possible. The air passage bore 18 passes through the intermediate component(s) as well as the inner component 13 and the outer component 12 to convey air from the air flow channel 15 to the interior of the combustor 8.
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The air gap 24 can be in the range of 0.003 inches to 0.010 inches (0.076 mm to 0.254 mm). The concentric core component 17 is inward of the inner component 13. The air passage bore 18 and sleeve 21 extend through the inner component 13 but not through the core component 17. If any intermediate component is provided between outer component 12 and inner component 13, the intermediate component may be spaced apart from the thermal insulating sleeve 21 by the air gap 24. Alternatively, if the sleeve body 23 requires further structural support (other than the connection of the annular flange 22) further discrete points of connection between the sleeve body 23 and the intermediate component or the inner component 13 can be provided by brazing.
The above description is meant to be exemplary only, and one skilled in the relevant arts will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. The present disclosure may be embodied in other specific forms without departing from the subject matter of the claims. The present disclosure is intended to cover and embrace all suitable changes in technology. Modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims. Also, the scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.
