Late lean injection injector

A fuel injector is provided and includes an outer body, a converging tubular body including a converging section, defining a converging annular passage therein and being disposed within the outer body to define an outer annular passage between an interior surface of the outer body and an exterior surface of the converging tubular body, the annular passages each being receptive of a fluid at respective inlets thereof such that the fluid is directed to flow toward respective outlets thereof and a fuel line to deliver fuel through at least the converging tubular body at the converging section to the converging annular passage in a substantially tangential direction relative to a circumferential curvature of the converging tubular body.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to a combustor having a premixed injector.

In turbine engines and, in particular, gas turbine engines, fuels, such as gas and compressed air, are fed to a combustor where combustion thereof occurs. High temperature fluids generated from this combustion are then directed through a transition piece and into a turbine for power and/or electricity generation. Generally, the compressed air is fed to the combustor from a compressor and travels upstream toward the head end where it is mixed with the other fuels.

When the fuel/air mixture is combusted certain pollutants, such as Nitrous Oxides (NOx), are produced. Since NOx production is generally undesirable, recent efforts have been undertaken to reduce NOx production and emission. In some cases, these efforts have centered on encouraging more complete mixing of the air and fuel. In these and/or other cases, late lean injection (LLI) has also been employed.

The purpose of LLI is to reduce NOx formation by reducing the residence time of fuel and air within the combustor. This is achieved by injecting a portion of the fuel and air into the combustor at an axial location downstream from the main combustion zone. In this way, the LLI fuel and air are combusted but do not travel as far through the combustor as they otherwise would. As such, as long as sufficient fuel and air mixing occurs, the LLI fuel and air generally do not form as much NOx as would otherwise be produced.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a fuel injector is provided and includes an outer body, a converging tubular body including a converging section, defining a converging annular passage therein and being disposed within the outer body to define an outer annular passage between an interior surface of the outer body and an exterior surface of the converging tubular body, the annular passages each being receptive of a fluid at respective inlets thereof such that the fluid is directed to flow toward respective outlets thereof and a fuel line to deliver fuel through at least the converging tubular body at the converging section to the converging annular passage in a substantially tangential direction relative to a circumferential curvature of the converging tubular body.

According to another aspect of the invention, a fuel injector is provided and includes an outer body, a converging tubular body having a length that is similar to or longer than that of the outer body, the converging tubular body including a converging section, defining a converging annular passage therein and being disposed within the outer body to define an outer annular passage between an interior surface of the outer body and an exterior surface of the converging tubular body, the annular passages each being receptive of a fluid at respective inlets thereof such that the fluid is directed to flow toward respective outlets thereof and a fuel line to deliver fuel through at least the converging tubular body at the converging section to the converging annular passage in a substantially tangential direction relative to a circumferential curvature of the converging tubular body.

According to yet another aspect of the invention, a late lean injection (LLI) combustor is provided and includes a liner defining a passage along which a main flow proceeds from an upstream section at which combustion producing the main flow occurs and a fuel injector coupled to the liner downstream from the upstream section. The fuel injector includes an outer body, a converging tubular body including a converging section, defining a converging annular passage therein and being disposed within the outer body to define an outer annular passage between an interior surface of the outer body and an exterior surface of the converging tubular body, the annular passages each being receptive of a fluid at respective inlets thereof such that the fluid is directed to flow toward respective outlets thereof, which are respectively disposed within the liner and a fuel line to deliver fuel through at least the converging tubular body at the converging section to the converging annular passage in a substantially tangential direction relative to a circumferential curvature of the converging tubular body.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIGS. 1-3, in order to increase the degree to which fuel and air mix within a combustor or, more particularly, a late lean injection (LLI) combustor, a fuel injector10is provided and is fluidly coupled to a combustor lining20. The combustor lining20is formed to define an interior21along which a main fluid flow proceeds from an upstream section25, which may be, in the case of the LLI combustor, a combustion zone.

The fuel injector10includes an outer body30having an interior annular surface31and an exterior annular surface32, a converging tubular body40having an interior annular surface41and an exterior annular surface42and a fuel line100. The converging tubular body40includes a converging section401, which has a decreasing cross-sectional area from a first end thereof to a second end thereof, and which is formed to define a converging annular passage50therein. The converging tubular body40is disposed within the outer body30and, as such, the converging tubular body40and the outer body30cooperatively define an outer annular passage60between the interior surface31of the outer body30and the exterior surface42of the converging tubular body40.

Both of the converging annular passage50and the outer annular passage60are receptive of a fluid70, such as compressed air extracted from a compressor, at respective inlets81and80thereof such that the fluid70is directed to flow toward respective outlets91and90thereof The inlets81and80may be substantially coplanar with one another or otherwise disposed at substantially similar radial locations relative to the main flow through the combustor liner20.

The outlet90of the outer annular passage60penetrates the combustor liner20to a predefined depth into the main flow. The outlet91of the converging annular passage50penetrates the combustor liner20to at least the predefined depth into the main flow of the outlet90. In some cases, the outlet91extends even further into the main flow through the combustor liner20. That is, the converging tubular body40may have a length L1, which is similar to or longer than a length L2of the outer annular body30.

The fuel line100delivers fuel101, such as one or more of natural gas, synthetic gas and oil, through at least the converging tubular body40at the converging section401to the converging annular passage50. The fuel101is delivered in a direction that is, as shown inFIG. 3, substantially tangential relative to a circumferential curvature of the converging tubular body40. By being delivered in the substantially tangential direction, the fuel101and the fluid70mix with one another. This mixing is due at least in part to shear forces generated between the fuel101and the fluid70, which result in a cyclonic flow of fuel101and fluid70within the converging annular passage50. A pressure of the cyclonic flow is maintained by the convergence of the converging tubular body40.

Where the converging annular passage50is longer than the outer annular passage60, the mixture of fluid70and fuel101may be injected into the main flow at a relatively low radial position of the combustor liner20as compared to the relatively high radial position of the injection of fluid70from the outer annular passage60. As such, the fluid70injected from the outer annular passage60may serve as a barrier layer interposed between the fluid70/fuel101mixture and an interior surface of the combustor liner20downstream from the fuel injector10. This barrier layer may shield the interior surface of the combustor liner20from high temperature fluids and may, in some cases, extend downstream into a transition piece (TP) disposed in fluid communication with the combustor liner20.

A terminal102of the fuel line100may be coplanar with the interior surface41of the converging tubular body40such that the interior surface41is substantially smooth even at the terminal102.

The substantially tangential direction may be oriented transversely in relation to a predominant direction of fluid flow through the converging annular passage50and the outer annular passage60. In some embodiments, the substantially tangential direction is oriented substantially perpendicularly relative to the predominant direction of the fluid flow through the converging annular passage50and the outer annular passage60. In other embodiments, the fuel line100may be directed such that fuel101enters the converging annular passage50at either an incline or a decline relative to the predominant direction of the fluid flow through the converging annular passage50and the outer annular passage60.

The fuel line100may be formed of piping extending from an exterior of the outer body30, through the outer annular passage60and through the converging tubular body40and may include a plurality of individual fuel lines110,111and112. The number of these individual fuel lines may be two, three or more with each being separated by a constant or irregular interval. The individual fuel lines110,111and112are oriented transversely relative to one another and may be coplanar or staggered. The individual fuel lines110,111and112may also be substantially straight and in-line with the direction of fuel delivery to the converging annular passage50.