GB2073400A

GB2073400A - Fuel injector

Info

Publication number: GB2073400A
Application number: GB8110152A
Authority: GB
Original assignee: United Technologies Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1980-04-02
Filing date: 1981-04-01
Publication date: 1981-10-14
Also published as: GB2073400B; JPS56168037A

Abstract

A fuel injector 16 for the main fuel system for a two-stage combustor 18 of a gas turbine engine is modified so that the swirling air 24 mixing with the fuel is injected into a fuel passage 22 prior to the mixture being injected into the combustion zone for reduced smoke emissions. <IMAGE>

Description

SPECIFICATION Fuel injector Technical Field This invention relates to combustors for gas turbine engines and particularly to the main fuel nozzles for two-stage combustors.

Background Art This invention constitutes an improvement over the vorbix combustor described in U.S.

Patent 3,788,065 entitled ANNULAR COM BUSTION CHAMBER FOR DISSIMILAR FLU IDS IN SWIRLING FLOW RELATIONSHIP, granted to S.. J. Markowski on January 29, 1 974 and assigned to the same assignee. As disclosed in this patent, fuel is injected into the combustion zone where it is engulfed by a field of swirling air in proximity to the point of combustion. While the heretofore known vorbix type of combustors have shown to reduce certain unwanted emissions, there remained a problem owing to the fact that such combustors emitted an unacceptable amount of smoke.

We have found that by inserting the fuel emitting orifice in a tube upstream of the plane where it enters the combustion chamber in the main burning zone and by premixing the fuel with the swirling air prior to its egression into the combustion chamber the smoke emitted from the combustor has been considerably reduced. In tests with this configuration we have operated the combustor without evidencing any measurable smoke emissions and without adversely affecting the other emission characteristics of the combustor.

This invention contemplates introducing main zone air in the fuel injector port radial inflow swirlers in the outer liner so as to achieve improved performance and emission reduction characteristics. Substantially all main zone air supplied through the outer liner is introduced through the fuel injector ports, thus eliminating the need for the outer liner swirlers used in the heretofore known vorbix combustors. The radial swirlers will centrifuge the fuel to the outer wall of the fuel injector port where a fuel film will be established. At the downstream lip of the port, the fuel film will be sheared into droplets by interaction with the combustion gases. Fuel/air distribution will be improved over the case of direct injection from pressure atomized nozzles located between swirling air jets which is the vorbix combustor configuration heretofore investigated.Additional air can be provided at the outer perimeter of the fuel injector port downstream lip in a co- or counter-swirling fashion in order to achieve an added measure of control of the fuel atomization and distribution process in the main burner.

Fuel injector port contour lends itself to being designed to provide accelerating flow downstream of the fuel injector plane to avoid flow separations and to maintain fuel/air mixture residence times below auto-ignition limits.

Disclosure of the Invention An object of this invention is to provide for a two-stage combustor of a gas turbine engine an improved main combustion zone fuel injector system.

A feature of this invention is to recess the tip of the fuel nozzle away from the main combustion zone and premix fuel with swirling air prior to it being injected into the main combustion zone. Additional air may be added to the swirling fuel/air mixture at the point of injection into the combustion zone to enhance fuel atomization and distribution.

Other features and advantages will be apparent from the specification and claims and from the accompanying drawings which illustrate an embodiment of the invention.

Brief Description of the Drawings The sole Figure is a partial view partly in schematic and partly in section showing a combustor with the improved main fuel injector.

Best Mode For Carrying Out The Invention For purposes of this invention, main fuel nozzle and main combustion zone refer to the secondary nozzle and zone in a two-stage combustor and is utilized solely in the high thrust regimes of the combustor operating envelope.

It is to be understood, and as one skilled in the art will appreciate, this invention can be employed in all types of combustors such as annular, can or a combination thereof. However, as will be apparent from the description to follow hereinbelow, the invention is intended for smoke emission problems that are insidious in a two-stage burner and applies to the modification of the fuel injection system in the main zone.

As shown in the sole Figure which typifies a two-stage burner having a pilot or primary burner zone 10 with its attendant fuel injection system 1 2 and the main burner zone 1 4 with its attendant main injection system 1 6 for the combustor generally indicated by reference numeral 1 8. The fuel nozzle 20, which may be either a high pressure or low pressure type, injects fuel into the premix tube 22 where it premixes with the swirling air issuing from the suitable type of radial inflow swirler 24. Air is received from the compressor (nit shown) of which a portion surrounds the combustor either in a typical diffuser shroud or cavity.The fuel nozzle is retained in position by the seal and retainer member 28 that slidably fits into slot 31 to allow nozzle movement to adjust for thermal expansion.

The fuel and air mixture is injected into the main zone of the combustor. It may be desirable to give an additional amount of control to the atomizing and distribution of the fuel which can be achieved by adding an additional airflow at the point of injecting the fuel/air mixture into the main burning zone.

The annular ring 30 surrounds the tube 22 at the discharge end 32. Fingers 34 supporting the ring 30 in space relationship may be contoured to impart a counter or co-swirling moment to the additional air which is taken from the surrounding cavity filled with compressor discharge air. As noted, fingers 34 merely bear against the inner diameter of ring 30 to allow it to thermally expand without any constraints and eliminate undue stresses imparted to the tube 22.

As is apparent from the-foregoing, the tip of the fuel nozzle 20 is spaced or recessed from the main combustion zone which minimizes overheating of the tip and contributes to its longevity. The fuel injector port lends itself to being contoured to provide accelerating flow downstream of the fuel injector plane to avoid flow separation and this feature together with tube length selected to maintain fuel/air mixture residence times below auto-ignition limits.

It should be understood that the invention is not limited to the particular embodiments shown and described herein, but that various changes and modifications may be made without departing from the spirit and scope of this novel concept as defined by the following

Claims

claims. CLAIMS

1. A fuel injection system for a main burning zone in a two-stage combustor having a tube having a discharge port at the combustion zone, a fuel nozzle in said tube having a tip at the end remote from said discharge port, and means for applying a swirling air from a cavity surrounding said combustor to the fuel issuing from said fuel nozzle in said tube whereby said fuel and air is injected into said main burning zone in a mixture selected to reduce the smoke emissions from said combustor.

2. A fuel injection system of claim 1 including a radial inflow swirler disposed concentric with said fuel nozzle.

3. A fuel nozzle injection system including an annular ring defining a discharge port for air from said cavity surrounding said discharge port for adding additional air to the fuel/air mixture in said main burning zone.