GB2088037A

GB2088037A - Fuel Nozzle for a Gas Turbine Engine

Info

Publication number: GB2088037A
Application number: GB8121834A
Authority: GB
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1980-11-25
Filing date: 1981-07-15
Publication date: 1982-06-03
Also published as: FR2494778A1; CA1176477A; JPS5792609A; DE3132352A1; IL63171A0; IT8123606A0

Abstract

A fuel nozzle 30 includes a primary flowpath 26 and a secondary flowpath 32, each of which includes a pair of axially opposing input and output ends disposed along a common central longitudinal axis. The secondary path is circumferentially disposed around the primary path. A nozzle discharge portion 36 is circumferentially disposed around the primary and secondary output ends for receiving interacting output flows from the first and second paths and developing a nozzle output therefrom. The nozzle discharge portion includes a conical portion 38 having an input end of smaller diameter which increases along the longitudinal axis to an output end of relatively larger diameter. In a preferred embodiment, the conical portion defines an included solid angle of 60 degrees with respect to the central longitudinal axis. Other embodiments are disclosed. <IMAGE>

Description

SPECIFICATION Fuel Nozzle for a Gas Turbine Engine The present invention relates to a fuel nozzle for a gas turbine engine, and more particularly, to such a nozzle which exhibits reduced carbon formation without requiring an air shroud.

In a conventional gas turbine engine, a combustor section is utilized to provide a zone in which fuel and compressor discharge air may be burned with the resultant energy release employed to drive other operating parts of the engine. The combuster includes at least one fuel nozzle located therein for supplying fuel to the combustor section. One conventional type of fuel nozzle is often referred to as a fuel pressure atomizing nozzle indicating that fuel pressure utilized to provide an atomized fuel flow from an orifice in the output tip portion of the nozzle into the combustor for desirable combustor operation.

To provide desirable engine starting performance, it is often necessary to provide a dual fuel flowpath, i.e., primary and secondary paths, from the fuel nozzle to the combustor.

Although such dual flowpath nozzles are satisfactory for many applications, it is known that conventional dual path nozzles are likely to develop undesirable carbon deposits on the nozzle surfaces adjacent to the output portion thereof. Accordingly, a present solution to the formation of such undesirable carbon deposits is to provide the nozzle with an air shroud structure which encircles the output portion of the nozzle.

The air shroud functions to direct airflow entering the combustor section from the compressor section through a sweeping motion which tends to reduce the formation of the undesirable carbon deposits. A problem with this solution, however, is that additional structure, i.e., an air shroud, is required. The air shroud adds weight and cost to the nozzle assembly. This added weight is particularly undesirable as it is well known that reduced nozzle tip weight resuits in improved vibratory patterns, e.g., reduced tip mass reduces the possibility of resonance in the fundamental bending frequency, and hence, improved part life.

In addition, for many applications, additional swirler and venturi components are provided at the output of the nozzle for improving the fuel and air mixing in the primary zone of the combustor.

Typically, such swirler and venturi components are circumferentially disposed around the output portion of the fuel nozzle. When such swirler and venturi components are employed in combination with the conventional fuel nozzle having an air shroud, the result is an undesirably large outer diameter structure.

In one form of our invention, we provide a dual fuel'path fuel nozzle for use in a combustor section of a gas turbine engine. The nozzle includes primary path means with a central longitudinal axis. The primary path means has an input end for receiving a primary flow of fuel and an opposing output end for developing a primary output flow having a predetermined rotational motion at the output end. The nozzle includes secondary path means having an input end for receiving a secondary flow of fuel and an opposing output end for developing a secondary output flow. The secondary output flow has a rotational motion which generally corresponds in direction to the predetermined rotational motion of the primary output flow.The secondary path means is circumferentially disposed in fixed relation around the primary path means with the secondary path means output end being circumferentially disposed around the primary path means output end, thereby forming an interacting nozzle output flow. Nozzle discharge means is circumferentially disposed around the primary and secondary path means output ends for receiving the interacting output flow and developing a processed nozzle output therefrom for use in subsequent ignition in the combustor section. The nozzle discharge means includes a conical portion having an input end of relatively smaller diameter which increases along the central longitudinal axis to an output end of relatively larger diameter. The conical portion defines an included solid angle therein of at least 45 degrees with respect to the central longitudinal axis of the primary path.

Figure 1 is a partially broken away schematic representation of an exemplary gas turbine engine to which the present invention relates.

Figure 2 is a sectional view showing a fuel nozzle of the Prior Art.

Figure 3 is a sectional view, taken as in Figure 2, showing one form of the fuel nozzle of the present invention. For purposes of clarity, the fuel nozzle of Figure 3 is illustrated as a larger structure than the fuel nozzle of Figure 2.

Referring initially to Figure 1, one form of exemplary gas turbine engine to which the present invention relates is generally designated 1 0. The gas turbine engine 10 includes a fan section 12, a compressor section 14, a combustor section 16, a high pressure turbine section 18, a low pressure turbine section 20, and an exhaust section 22. The combustor section 1 6 includes a plurality of nozzles 1 9 which receive the fuel flow to the engine and develop an atomized fuel flow for ignition in the combustor 1 6. The nozzle 1 9 is coupled through a fuel stem 21 to a fuel injector inlet 23.The fuel injector inlet 23 is coupled to receive the engine fuel and controllably pass the engine fuel to the nozzle 1 9 for subsequent atomization and ignition.

Referring now to Figure 2, a typical Prior Art dual fuel path fuel pressure atomizing nozzle 19 is shown in further detail. The fuel nozzle 19 of Figure 2 includes an input end 1 9A and an output end 1 9B. The nozzle 19 includes a primary fuel path 26 having an input end 26A for receiving the primary fuel flow from the fuel stem 21 (not shown in Figure 2). The primary path 26 also includes an axially opposing output end 26B.

Slots 28 are coupled to the primary path 26 at a location between the input end 26A and the output end 26B thereof. The slots 28 function to direct the primary fuel flow (see arrows) through additional spin slots 29. After passing through the slots 28 and 29, the primary fuel flow is passed through a primary spin chamber 30 before being directed out of primary output 26B. As is well known in the art, the slots 28 and 29, and spin chamber 30, function to impart a predetermined rotational motion of the primary fuel flow as it is directed from the output 26B.

The Prior Art fuel nozzle 19 includes a secondary fuel path 32 for receiving the secondary fuel flow from the fuel stem 21. The secondary path 32 includes an input end 32A and an output end 32B. The secondary path 32 is circumferentially disposed in fixed relation around the primary path 26. The output end 32B of the secondary path 32 is circumferentially disposed around the primary path output 268. The secondary path 32 also includes a number of swirl vanes 33 through which the secondary fuel flow passes before entering a secondary spin chamber 34. As a result of its passage through secondary path 32, the secondary fuel flow output at 32B is provided with a rotational motion which generally corresponds in direction to the rotaional motion of the primary flow at output 26B.

The nozzle 1 9 includes a nozzle discharge portion 36 which is circumferentially disposed around the primary and secondary outputs 268 and 32B. The nozzle discharge portion 36 functions to receive the interacting output flow from outputs 26B and 32B and to develop an output therefrom for use in subsequent ignition in the combustor section (not shown in Figure 2).

The nozzle discharge portion 36 includes a conical portion 38. The conical portion 38 has an input end 39 of relatively smaller inside diameter (d), e.g. typically about .15 inches, which increases along the longitudinal central axis to an output end 41 of relatively larger inside diameter (D), e.g., typically about .44 inches. The conical portion 38 includes an interior surface 40 which typically defines an included solid angle a therein of less than 36 degrees with respect to the central longitudinal axis of the primary path 26. The longitudinal length (1) of the interior surface 40 is typically about .150 inches.

As noted previously, the Prior Art nozzle 1 9 is typically provided with a conventional air shroud structure 42 having slots 43. The air shroud 42 is disposed circumferentially around the fuel nozzle 19 and functions to receive and direct air entering (see arrows) the combustor section (not shown in Figure 2) through the slots 43 in a manner so as to reduce the carbon formations on the interior conical surface 40.

Referring now to Figure 3, one form of fuel nozzle of the present invention is generally designated 50. The fuel nozzle 50 of Figure 3 is similar in many respects to the Prior Art fuel nozzle 1 9 of Figure 2 so that, whereever possible, like reference numbers have been used to represent like elements. The fuel nozzle 50 of Figure 3, however, differs from the Prior Art fuel nozzle 1 9 of Figure 2 in at least two significant respects. The fuel nozzle 50 is provided with a modified nozzle discharge portion and includes no air shroud structure.

More particularly, the nozzle discharge portion 36 of the fuel nozzle 50 of the present invention is provided with a conical portion 38 thereof having an interior surface 40 which defines a solid angle a of at least 45 degrees with respect to the central longitudinal axis thereof. The solid angle a is preferably in the range of from about 50 degrees to about 65 degrees with about 60 degrees being a particularly preferred value. The longitudinal length (1) of the interior surface 40 5 typically about .080 inches. In addition, typical inside diameters (d) and (D) of the nozzle 50 are .18 inches and .40 inches, respectively.The fuel nozzle 50 is preferably provided with a wear coating 52 along its exposed exterior for protecting the fuel nozzle 50 from the harsh rubbing action between itself and the combustor part in which it is inserted. Typically, the wear coating 52 comprises a conventional high temperature-resistant material. An exemplary wear coating 52 may comprise, for example, .015 inches of chromium carbide. Although, for purposes of illustration, the fuel nozzle of the present invention has been described as being of certain exemplary dimensions, other dimensions may be appropriate for certain applications.

Referring now to the operation of the nozzle 50 of Figure 3, the primary flow through primary path 26 and its output end 268 is shown as resulting in a primary spray 60 which does not impinge on the interior conical surface portion 40. The secondary fuel flow through the secondary path 32 and its secondary output end 328 is shown as resulting in a secondary spray 62. An outer portion 62A of the secondary spray 62 passes on and along the conical surface portion 40.

However, as mentioned previously, the particular configuration of the discharge portion 36, i.e., the solid angle a of at least 45 degrees, results in reduced carbon formation along the surface portion 40. Indeed, the configuration shown in the fuel nozzle 50 of Figure 3 obviates the need for an additional air shroud structure, such as the air shroud 42 shown in the Prior Art fuel nozzle of Figure 2. In this connection, the outer diameter of the fuel nozzle 50 of Figure 3 may be about the same as the outer diameter of the fuel nozzle 1 9 of Figure 2, without the air shroud 42.

For some applications, it may be desirable to employ the fuel nozzle of the present invention in combination with additional components for providing highly desirable ignition in the combustor section. In this connection, conventional structures, including airblast discs, venturi shrouds, and secondary swirlers, may be employed. Such conventional structures are shown in U.S. Patent 4,198,815, issued April22, 1980, to Bobo, et al., entitled, "Central Injection Fuel Carburetor." This patent is assigned to the assignee of the present invention and is incorporated by reference in the present application.

Although the fuel nozzle of the present invention has been illustrated as having a linear central longitudinal axis with axially opposing input and output ends, other nozzle configurations may be appropriate for certain nozzle applications. For example, for certain applications, the central longitudinal axis may be curvilinear. In addition, it is to be appreciated that the fuel nozzle of the present invention is suitable for engine applications other than the previouslydiscussed exemplary gas turbing engine. Indeed, the fuel nozzle of the present invention is applicable to any gas turbine engine, such as one which includes only a compressor section, a combustor section and an exhaust section.

Thus, there is provided by the present invention a fuel nozzle which exhibits reduced carbon formation without requiring an air shroud. The fuel nozzle of the present invention is relatively simple to manufacture. Further, the fuel nozzle of the present invention can be conveniently inserted into and removed from its operating position in the combustor section without the need to remove other associated parts in the combustor section. Also, the fuel nozzle of the present invention, as a result of its relatively low weight, provides a desirable operational part life.

Claims

1. A dual fuel path fuel nozzle for use in a combustor section in a gas turbine engine, which comprises: (a) primary path means having an input end for receiving a primary flow of fuel and an opposing output end for developing a primary output flow having a predetermined rotational motion at said output end, said primary path means having a central longitudinal axis;; (b) secondary path means having an input end for receiving a secondary flow of fuel and an opposing output end for developing a secondary output flow having a rotational motion which generally corresponds in direction to said predetermined rotational motion, said secondary path means being circumferentially disposed in fixed relation around said primary path means with said secondary path means output end being circumferentially disposed around said primary path means output end, thereby forming an interacting output flow; and (c) nozzle discharge means circumferentially disposed around said primary and secondary path means output ends for receiving said interacting output flow and developing a processed nozzle output therefrom for use in subsequent ignition in the combustor section, said nozzle discharge means including a conical portion having an input end of relatively smaller diameter which increases along the longitudinal central axis to an output end of relatively larger diameter, said conical portion defining an included solid angle therein of at least 45 degrees with respect to the central longitudinal axis of said primary path means.

2. A fuel nozzle in accordance with claim 1 in which said included solid angle is in the range of from about 50 degrees to about 65 degrees.

3. A fuel nozzle in accordance with claim 2 in which said included solid angle is about 60 degrees.

4. A fuel nozzle in accordance with claim 2 in which the longitudinal central axis is linear.

5. A fuel nozzle in accordance with claim 2 in which the longitudinal central axis is curvilinear.

6. A fuel nozzle in accordance with claim 2 in which said primary path means, said secondary path means, and said nozzle discharge means are disposed within a nozzle housing and in which said nozzle housing includes an exterior surface having a wear coating disposed thereon.

7. A fuel nozzle in accordance with claim 6 in which said wear coating comprises chromium carbide.

8. A fuel nozzle in accordance with claim 6 which includes no air shroud structure disposed circumferentially around said nozzle housing.

9. A fuel nozzle substantially as hereinbefore described with reference to and as illustrated in the drawings.